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Tetsu-to-Hagané Vol. 110 (2024), No. 3

ISIJ International
belloff

Grid List Abstracts
ONLINE ISSN: 1883-2954
PRINT ISSN: 0021-1575
Publisher: The Iron and Steel Institute of Japan

Backnumber

  1. Vol. 110 (2024)

    1. No.15
    2. No.14
    3. No.13
    4. No.12
    5. No.11
    6. No.10
    7. No.9
    8. No.8
    9. No.7
    10. No.6
    11. No.5
    12. No.4
    13. No.3
    14. No.2
    15. No.1

  2. Vol. 109 (2023)

    1. No.12
    2. No.11
    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
    9. No.4
    10. No.3
    11. No.2
    12. No.1

  3. Vol. 108 (2022)

    1. No.12
    2. No.11
    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
    9. No.4
    10. No.3
    11. No.2
    12. No.1

  4. Vol. 107 (2021)

    1. No.12
    2. No.11
    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
    9. No.4
    10. No.3
    11. No.2
    12. No.1

  5. Vol. 106 (2020)

    1. No.12
    2. No.11
    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
    9. No.4
    10. No.3
    11. No.2
    12. No.1

  6. Vol. 105 (2019)

    1. No.12
    2. No.11
    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
    9. No.4
    10. No.3
    11. No.2
    12. No.1

  7. Vol. 104 (2018)

    1. No.12
    2. No.11
    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
    9. No.4
    10. No.3
    11. No.2
    12. No.1

  8. Vol. 103 (2017)

    1. No.12
    2. No.11
    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
    9. No.4
    10. No.3
    11. No.2
    12. No.1

  9. Vol. 102 (2016)

    1. No.12
    2. No.11
    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
    9. No.4
    10. No.3
    11. No.2
    12. No.1

  10. Vol. 101 (2015)

    1. No.12
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    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
    9. No.4
    10. No.3
    11. No.2
    12. No.1

  11. Vol. 100 (2014)

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    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
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    10. No.3
    11. No.2
    12. No.1

  12. Vol. 99 (2013)

    1. No.12
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    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
    9. No.4
    10. No.3
    11. No.2
    12. No.1

  13. Vol. 98 (2012)

    1. No.12
    2. No.11
    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
    9. No.4
    10. No.3
    11. No.2
    12. No.1

  14. Vol. 97 (2011)

    1. No.12
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    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
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    10. No.3
    11. No.2
    12. No.1

  15. Vol. 96 (2010)

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    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
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    10. No.3
    11. No.2
    12. No.1

  16. Vol. 95 (2009)

    1. No.12
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    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
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    10. No.3
    11. No.2
    12. No.1

  17. Vol. 94 (2008)

    1. No.12
    2. No.11
    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
    9. No.4
    10. No.3
    11. No.2
    12. No.1

  18. Vol. 93 (2007)

    1. No.12
    2. No.11
    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
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    10. No.3
    11. No.2
    12. No.1

  19. Vol. 92 (2006)

    1. No.12
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    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
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    10. No.3
    11. No.2
    12. No.1

  20. Vol. 91 (2005)

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    4. No.9
    5. No.8
    6. No.7
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  21. Vol. 90 (2004)

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    4. No.9
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    6. No.7
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    11. No.2
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  22. Vol. 89 (2003)

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    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
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    10. No.3
    11. No.2
    12. No.1

  23. Vol. 88 (2002)

    1. No.12
    2. No.11
    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
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    10. No.3
    11. No.2
    12. No.1

  24. Vol. 87 (2001)

    1. No.12
    2. No.11
    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
    9. No.4
    10. No.3
    11. No.2
    12. No.1

  25. Vol. 86 (2000)

    1. No.12
    2. No.11
    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
    9. No.4
    10. No.3
    11. No.2
    12. No.1

  26. Vol. 85 (1999)

    1. No.12
    2. No.11
    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
    9. No.4
    10. No.3
    11. No.2
    12. No.1

  27. Vol. 84 (1998)

    1. No.12
    2. No.11
    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
    9. No.4
    10. No.3
    11. No.2
    12. No.1

  28. Vol. 83 (1997)

    1. No.12
    2. No.11
    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
    9. No.4
    10. No.3
    11. No.2
    12. No.1

  29. Vol. 82 (1996)

    1. No.12
    2. No.11
    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
    9. No.4
    10. No.3
    11. No.2
    12. No.1

  30. Vol. 81 (1995)

    1. No.12
    2. No.11
    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
    9. No.4
    10. No.3
    11. No.2
    12. No.1

  31. Vol. 80 (1994)

    1. No.12
    2. No.11
    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
    9. No.4
    10. No.3
    11. No.2
    12. No.1

  32. Vol. 79 (1993)

    1. No.12
    2. No.11
    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
    9. No.4
    10. No.3
    11. No.2
    12. No.1

  33. Vol. 78 (1992)

    1. No.12
    2. No.11
    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
    9. No.4
    10. No.3
    11. No.2
    12. No.1

  34. Vol. 77 (1991)

    1. No.12
    2. No.11
    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
    9. No.4
    10. No.3
    11. No.2
    12. No.1

  35. Vol. 76 (1990)

    1. No.12
    2. No.11
    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
    9. No.4
    10. No.3
    11. No.2
    12. No.1

  36. Vol. 75 (1989)

    1. No.12
    2. No.11
    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
    9. No.4
    10. No.3
    11. No.2
    12. No.1

  37. Vol. 74 (1988)

    1. No.12
    2. No.11
    3. No.10
    4. No.9
    5. No.8
    6. No.7
    7. No.6
    8. No.5
    9. No.4
    10. No.3
    11. No.2
    12. No.1

  38. Vol. 73 (1987)

    1. No.16
    2. No.15
    3. No.14
    4. No.13
    5. No.12
    6. No.11
    7. No.10
    8. No.9
    9. No.8
    10. No.7
    11. No.6
    12. No.5
    13. No.4
    14. No.3
    15. No.2
    16. No.1

  39. Vol. 72 (1986)

    1. No.16
    2. No.15
    3. No.14
    4. No.13
    5. No.12
    6. No.11
    7. No.10
    8. No.9
    9. No.8
    10. No.7
    11. No.6
    12. No.5
    13. No.4
    14. No.3
    15. No.2
    16. No.1

  40. Vol. 71 (1985)

    1. No.16
    2. No.15
    3. No.14
    4. No.13
    5. No.12
    6. No.11
    7. No.10
    8. No.9
    9. No.8
    10. No.7
    11. No.6
    12. No.5
    13. No.4
    14. No.3
    15. No.2
    16. No.1

  41. Vol. 70 (1984)

    1. No.16
    2. No.15
    3. No.14
    4. No.13
    5. No.12
    6. No.11
    7. No.10
    8. No.9
    9. No.8
    10. No.7
    11. No.6
    12. No.5
    13. No.4
    14. No.3
    15. No.2
    16. No.1

  42. Vol. 69 (1983)

    1. No.16
    2. No.15
    3. No.14
    4. No.13
    5. No.12
    6. No.11
    7. No.10
    8. No.9
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    10. No.7
    11. No.6
    12. No.5
    13. No.4
    14. No.3
    15. No.2
    16. No.1

  43. Vol. 68 (1982)

    1. No.16
    2. No.15
    3. No.14
    4. No.13
    5. No.12
    6. No.11
    7. No.10
    8. No.9
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    10. No.7
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    16. No.1

  44. Vol. 67 (1981)

    1. No.16
    2. No.15
    3. No.14
    4. No.13
    5. No.12
    6. No.11
    7. No.10
    8. No.9
    9. No.8
    10. No.7
    11. No.6
    12. No.5
    13. No.4
    14. No.3
    15. No.2
    16. No.1

  45. Vol. 66 (1980)

    1. No.14
    2. No.13
    3. No.12
    4. No.11
    5. No.10
    6. No.9
    7. No.8
    8. No.7
    9. No.6
    10. No.5
    11. No.4
    12. No.3
    13. No.2
    14. No.1

  46. Vol. 65 (1979)

    1. No.14
    2. No.13
    3. No.12
    4. No.11
    5. No.10
    6. No.9
    7. No.8
    8. No.7
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    10. No.5
    11. No.4
    12. No.3
    13. No.2
    14. No.1

  47. Vol. 64 (1978)

    1. No.14
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    3. No.12
    4. No.11
    5. No.10
    6. No.9
    7. No.8
    8. No.7
    9. No.6
    10. No.5
    11. No.4
    12. No.3
    13. No.2
    14. No.1

  48. Vol. 63 (1977)

    1. No.14
    2. No.13
    3. No.12
    4. No.11
    5. No.10
    6. No.9
    7. No.8
    8. No.7
    9. No.6
    10. No.5
    11. No.4
    12. No.3
    13. No.2
    14. No.1

  49. Vol. 62 (1976)

    1. No.14
    2. No.13
    3. No.12
    4. No.11
    5. No.10
    6. No.9
    7. No.8
    8. No.7
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    10. No.5
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    14. No.1

  50. Vol. 61 (1975)

    1. No.15
    2. No.14
    3. No.13
    4. No.12
    5. No.11
    6. No.10
    7. No.9
    8. No.8
    9. No.7
    10. No.6
    11. No.5
    12. No.4
    13. No.3
    14. No.2
    15. No.1

  51. Vol. 60 (1974)

    1. No.14
    2. No.13
    3. No.12
    4. No.11
    5. No.10
    6. No.9
    7. No.8
    8. No.7
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    10. No.5
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    12. No.3
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  52. Vol. 59 (1973)

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    3. No.12
    4. No.11
    5. No.10
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  53. Vol. 58 (1972)

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    5. No.10
    6. No.9
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    8. No.7
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  54. Vol. 57 (1971)

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    3. No.12
    4. No.11
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    7. No.8
    8. No.7
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    10. No.5
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    14. No.1

  55. Vol. 56 (1970)

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  56. Vol. 55 (1969)

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  57. Vol. 54 (1968)

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    3. No.12
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  58. Vol. 53 (1967)

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  59. Vol. 52 (1966)

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  60. Vol. 51 (1965)

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    6. No.8
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  61. Vol. 50 (1964)

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  62. Vol. 49 (1963)

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  63. Vol. 48 (1962)

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    4. No.11
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  64. Vol. 47 (1961)

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  65. Vol. 46 (1960)

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  66. Vol. 45 (1959)

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  67. Vol. 44 (1958)

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  68. Vol. 43 (1957)

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  69. Vol. 42 (1956)

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  70. Vol. 41 (1955)

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21 Nov. (Last 30 Days)

Tetsu-to-Hagané Vol. 110 (2024), No. 3

Preface to the Special Issue “Heterogeneous Deformation Microstructure and Related Mechanical Properties”

Toshihiro Tsuchiyama

pp. 89-89

DOI:

10.2355/tetsutohagane.110.89
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Preface to the Special Issue “Heterogeneous Deformation Microstructure and Related Mechanical Properties”

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Bridging between Heterogeneous Local Strain Distribution and Macroscopic Stress-strain Curves

Manabu Takahashi, Kotaro Ueno, Kenta Sakaguchi, Kohtaro Hayashi, Hiroyuki Kawata, Shigeto Yamasaki

pp. 90-100

DOI:

10.2355/tetsutohagane.TETSU-2023-063

Abstract

A modified continuum composite model was utilized to analyze the stress–strain behavior of as-quenched steels with a fully martensitic microstructure. The model was employed to express the stress–strain curves obtained by a simple tensile test and those obtained by forward and backward loading using a simple shear test machine. The study confirmed that the model can represent the stress–strain behavior under both forward and backward deformation. In addition, the evolution of local strain distributions during plastic deformation was investigated using a digital image correlation method. The strain distributions and their evolution during deformation were qualitatively represented using this model. The discrepancies between the model calculations and experiments are due to the limitations of the iso-work assumption and the impact of slip deformation on the macroscopic work-hardening behavior of martensitic steels. Highly strain-concentrated regions aligned along the longitudinal direction of the lath and block, known as in-lath-plane slips, may not play an important role in the work-hardening behavior of as-quenched martensitic steels. However, the other slips, namely the out-of-lath slip, may play a significant role in the work hardening of as-quenched martensitic steels.

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Bridging between Heterogeneous Local Strain Distribution and Macroscopic Stress-strain Curves

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Relation between Low Elastic Limit and Mobile Dislocation Density in Ultra-low Carbon Martensitic Steel

Yushi Takenouchi, Shuhei Wada, Takuro Masumura, Toshihiro Tsuchiyama, Hiroshi Okano, Shusaku Takagi

pp. 101-109

DOI:

10.2355/tetsutohagane.TETSU-2023-057

Abstract

Stress relaxation tests were conducted in the elastic region of an ultralow carbon martensitic steel (Fe-18%Ni alloy) to quantitatively analyze the effect of mobile dislocations on the low elastic limit of the steel. The elastic limit of the as-quenched material was measured at 255 MPa, although its tensile strength was as high as 720 MPa. The stress relaxation tests, which were performed at 255 MPa, revealed a remarkable stress reduction due to the movement of the mobile dislocations present in the as-quenched material. The total dislocation density barely changed during the test, while the distribution parameter (M-value) decreased significantly, indicating that the mobile dislocations exhibited stable arrangements. The 5% cold rolling before the relaxation tests suppressed the relaxation and simultaneously increased the elastic limit to a maximum, 435 MPa. By estimating the mobile dislocation density by relating the stress reduction in the stress relaxation tests to the distance of the dislocation movement evaluated via transmission electron microscopy (TEM) observations, it was estimated that the mobile dislocation density of the 5%-cold-rolled material was lowered to ~1/10 of that of the as-quenched material.

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Relation between Low Elastic Limit and Mobile Dislocation Density in Ultra-low Carbon Martensitic Steel

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Effect of Prior Austenite Grain Size on Strain Distribution of As-Quenched Martensitic Steel

Kosuke Shibata, Motoki Fujita, Shigenobu Nanba, Norimitsu Koga

pp. 110-117

DOI:

10.2355/tetsutohagane.TETSU-2023-058

Abstract

Strain distribution developed during tensile deformation in as quenched martensitic steels with various prior austenite grain sizes (PAGS) was visualized by using digital image correlation method, and then the effect of PAGS on strain distribution was discussed based on the results obtained from SEM/EBSD measurements. The martensitic steels with PAGS ranging from 8 to 110 μm were fabricated by controlling the solution-treated temperature. Carbides were observed in all specimens, suggesting that the auto-tempering occurred during the water quenching. The amount and size of carbide increased with increasing the PAGS. Inhomogeneous microscopic strain distribution in a unit of block was developed by tensile deformation in all specimens, and the strain distribution became rather inhomogeneous with increasing the PAGS. The blocks with the high Schmid factor of habit plane slip system tended to exhibit high strain. It was observed that there were blocks with low Schmid factor but high strain, and such blocks had numerous carbide precipitates, indicating that those blocks were well-tempered by auto-tempering. The nano-indentation hardness in the blocks with well-tempered blocks tended to be lower than that in the less-tempered blocks. The well-tempered blocks exhibited high strain independent of Schmid factor of habit plane slip system. Thus, the auto-tempering is one of the influential factors on the inhomogeneous strain distribution in as quenched martensitic steel. It could be reasonably understood that the increase of PAGS led to the increase of Ms temperature and the promotion of auto-tempering, resulting in rather inhomogeneous strain distribution in coarse-PAGS specimen.

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Effect of Prior Austenite Grain Size on Strain Distribution of As-Quenched Martensitic Steel

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Characteristics of Microstructure and Mechanical Properties in Al-bearing Medium Carbon Martensitic Steels

Yusaku Shirakami, Takuro Masumura, Shigenobu Nanba, Toshihiro Tsuchiyama

pp. 118-129

DOI:

10.2355/tetsutohagane.TETSU-2023-095

Abstract

As-quenched α'-martensitic structure and its mechanical properties of Fe-1.5%Mn-0.5%C-Al alloys containing various concentrations of Al were investigated. Microstructural observations of specimens heat-treated under various conditions confirmed that a austenite single-phase region can be obtained in the temperature range from 1373 K to 1473 K when Al is increased up to 3%. Dilatometry tests showed that the Ms temperature increases at a rate of 25 K/mass% with increasing Al content. The hardness of α' tended to decrease due to the decrease in the concentration of carbon in solid solution by auto-tempering and the formation of coarse blocks near the prior austenite grain boundaries. The coarse blocks had a butterfly shape, and there were no lath structures or transformation twins inside them, but rather high-density dislocations and carbides. Tensile tests on the 2%Al steel showed that the above coarse blocks can produce a large strain, which suppresses early rupture, resulting in a significant increase in ductility without any loss of strength.

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Characteristics of Microstructure and Mechanical Properties in Al-bearing Medium Carbon Martensitic Steels

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Effect of Carbon Content on Microstructure and Deformation of Quenched and Tempered Martensite

Takahisa Suzuki

pp. 130-142

DOI:

10.2355/tetsutohagane.TETSU-2023-067

Abstract

Microstructure of martensite has variety in size of martensite blocks and mechanical properties, depending on transformation temperature in sequential martensite transformation. Transformation temperature and type of martensite (lath or butterfly) are known to depend on chemical composition, mainly carbon content of steels. In this paper, we used 0.2~0.8 mass%C steel to prepare two grade tensile strength steel (1500 MPa and 2000 MPa) after quenching and tempering. After tensile test of these steels, we investigated the microstructure, nano hardness distribution and deformation property by Kernel Average Misorientation (KAM) map of Electron Back Scattered Diffraction pattern analysis (EBSD). In microstructure, lath martensite size was refined by the increase of carbon content. But course butterfly martensite was also formed around the former austenite grain boundary in high carbon steel. Nano hardness was lower at the course lath martensite in low carbon steel and course butterfly martensite in high carbon steel. Deformation properties were evaluated by comparing KAM map at not deformed region and uniform elongation deformed region. In 1500 MPa grade steel, 0.2%C and 0.4%C steel deformed uniformly, but strain was concentrated at low KAM grains in 0.6%C carbon steel. In 2000 MPa grade steel, deformation was concentrated at low KAM grains even in 0.4%C steel. These results shows that mechanical properties and deformation properties of martensite is not uniform at the level of martensite blocks, even if macro strength is similar among steels with different chemical composition.

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Effect of Carbon Content on Microstructure and Deformation of Quenched and Tempered Martensite

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Characterization of Strain Distribution and Microstructure at Crack Nucleation Sites in Martensitic Steel Subjected to Tensile Deformation

Norimitsu Koga, Motoki Fujita, Kosuke Shibata, Shigenobu Nanba

pp. 143-149

DOI:

10.2355/tetsutohagane.TETSU-2023-055

Abstract

The strain distribution and microstructure at the crack nucleation sites in martensitic steel with fine- and coarse-prior austenite grains subjected to tensile deformation were characterized using the digital image correlation method on replica films. Although the tensile properties of the fine- and coarse-prior austenite grain specimens were approximately identical, the total strain was certainly improved in the coarse-prior austenite grain specimen. The crack size increased with the coarsening prior austenite grains, whereas the number of cracks decreased. An inhomogeneous strain was introduced in both the specimens by tensile deformation. The accumulated strain when crack nucleates was approximately the same in both specimens, independent of the prior austenite grain size. In low-strain regions, there were no cracks even though the accumulated strain was comparable to that when crack nucleates in high-strain regions. The strain at the crack nucleation sites was high even before crack nucleation occurred. Cracks primarily nucleated on packet and prior austenite grain boundaries, even in the coarse-prior austenite grain specimen, which confirmed that the prior austenite grain boundary should be a preferential crack nucleation site. It can be concluded that the high local strain and the presence of packet or prior austenite grain boundaries are responsible for crack nucleation in martensitic steel subjected to tensile deformation.

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Characterization of Strain Distribution and Microstructure at Crack Nucleation Sites in Martensitic Steel Subjected to Tensile Deformation

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Deformation Behavior at Low Temperature in 9 mass%Ni Steel

Norimitsu Koga, Seiji Kumon, Chihiro Watanabe

pp. 150-159

DOI:

10.2355/tetsutohagane.TETSU-2023-060

Abstract

The strain distribution in the 9 mass%Ni steel introduced by tensile deformation at cryogenic temperature was visualized using a digital image correlation method, and the relationship between the strain distribution and the microstructure of the steel was systematically investigated. Based on the obtained results, the factors that influence the strain distribution were discussed. In the present 9mass%Ni steel, regions consisting of tempered- and fresh-martensite and austenite (TFMA) were embedded in the tempered martensite matrix. The volume fraction of the retained austenite varied along the normal direction of the hot-rolled plates, indicating that Ni segregation occurred during the manufacturing process. As the tensile stress increased, the total elongation remained constant with decreasing temperature. Strain was introduced inhomogeneously via tensile deformation at 77 K. The high- and low-strain regions tended to be distributed in a unit of the block, indicating that the deformability differed among the blocks. The average strain in the block (εblock) was strongly correlated with the Schmid factor of the slip system on the habit plane (SFhabit) and area fraction of TFMA in a block (AMA). The least absolute shrinkage and selection operator regression revealed that the contributions of SFhabit and AMA to εblock were nearly equal. Therefore, the deformability of the block in the 9 mass%Ni steel is dominated by SFhabit and ATFMA.

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Deformation Behavior at Low Temperature in 9 mass%Ni Steel

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Effect of Inhomogeneous Microstructure on Strength and Fracture Resistance in Sharp Edge of Japanese Swords

Kwangsik Kwak, Takateru Yamamuro, Yoji Mine, Shigekazu Morito, Kazuki Takashima

pp. 160-170

DOI:

10.2355/tetsutohagane.TETSU-2023-076

Abstract

Microtensile and microfracture tests were performed on the sharp-edge regions of Japanese swords fabricated in the Muromachi and Showa periods, which are called old sword (OS) and modern sword (MS), respectively, to correlate the mechanical properties with the inhomogeneous microstructures. The hardness of the sharp-edge regions was characterised by the distribution of fine pearlite mixed in martensite microstructures. The OS containing a large fraction of fine pearlite exhibited a low hardness compared to the MS. Microtensile tests using sharp-edge specimens revealed a positive correlation between their tensile strength and strain-to-failure, as opposed to the common tendency in conventional carbon steels made by modern iron-making technology. The fracture surfaces of the sharp-edge specimens were composed of intergranular and dimple fracture features. The tensile strength and dimple fracture area fraction were higher in the OS than in the MS. These findings suggest that the fine pearlite microstructure contributes to increased strength in the sharp-edge region through inhibiting the linkage of intergranular cracking owing to local plastic deformation. Microfracture tests using the sharp-edge specimens revealed that the intrinsic fracture resistance of both OS and MS was determined by the intergranular fracture, whereas the fine pearlite microstructure increased the resistance to crack propagation. The micromechanical testing study indicates that in the sharp-edge regions, their strength and fracture toughness are simultaneously enhanced by the presence of fine pearlite although depending on its distribution.

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Effect of Inhomogeneous Microstructure on Strength and Fracture Resistance in Sharp Edge of Japanese Swords

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Effect of Hydrogen on Tensile Shear Strength of Spot-Welded Ultrahigh-Strength TRIP-Aided Martensitic Steel Sheet

Tomohiko Hojo, Akihiko Nagasaka, Ryusei Wakabayashi, Chihaya Tabata, Yota Kondo, Kazuma Ogasawara, Yuki Shibayama, Eiji Akiyama

pp. 171-183

DOI:

10.2355/tetsutohagane.TETSU-2023-077

Abstract

In this study, the effect of hydrogen on the tensile shear strength of spot-welded transformation-induced plasticity (TRIP)-aided martensitic (TM) steel sheet was investigated. The tensile shear tests were carried out on a tensile testing machine using the spot-welded specimen which was spot-welded at the lapped portion of 30 mm×30 mm using specimen with dimensions of width of 30 mm and length of 170 mm at crosshead speeds of v=0.5 to 100 mm/min with and without hydrogen. The results were summarized as follows.

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Effect of Hydrogen on Tensile Shear Strength of Spot-Welded Ultrahigh-Strength TRIP-Aided Martensitic Steel Sheet

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Effect of Microalloying of V, Nb and Mo on Hydrogen Embrittlement Susceptibility of 2 GPa-grade Medium-carbon Si–Cr Spring Steel with Tempered Martensite Microstructure

Natsumi Morooka, Aya Matsushita, Masanori Sano, Takuya Yamaoka, Soichiro Yamaguchi, Kwangsik Kwak, Yoji Mine, Kazuki Takashima

pp. 184-196

DOI:

10.2355/tetsutohagane.TETSU-2023-081

Abstract

Hydrogen embrittlement (HE) susceptibility was evaluated on JIS-SUP12-based steel (SB), and V-, Nb- and (Nb+Mo)-added steels (SV, SNb and SNbMo, respectively) under uniaxial tension and high stress triaxiality conditions, to elucidate the roles of the microalloying elements in the HE mechanisms of 2 GPa-grade medium-carbon Si–Cr spring steels, which were obtained via low-temperature tempering. The SV steel contained solute V and undissolved V carbides, the SNb steel undissolved Nb carbides and the SNbMo steel solute Mo and undissolved Nb carbides. The microalloying of V, Nb and Mo decreased the apparent hydrogen diffusivity owing to strong hydrogen attraction by solute V and Mo, and reversible hydrogen trapping with V and Nb carbides. Although all the steels attained the 2 GPa tensile strength in an uncharged state, hydrogen significantly reduced the tensile strength through premature failure before the onset of yielding under uniaxial tension condition. In the hydrogen-charged specimens, the strength was strongly correlated with the shear fracture surface area. The HE susceptibility was increased in the following order: SNbMo ≈ SNb ＜ SB ＜ SV. This suggests that hydrogen-induced plasticity mitigates the HE susceptibility in the SNb and SNbMo steels, whereas the solute V facilitates the hydrogen-induced plastic inhomogeneity, which leads to premature fracture. Under high stress triaxiality condition in micro-cantilever specimens, hydrogen decreased the intrinsic fracture resistance to one third compared to the uncharged specimens, regardless of the steels. In the microalloyed specimens, hydrogen suppressed intergranular fracture, whereas the dependence of fracture resistance on the microalloying element was minor.

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Effect of Microalloying of V, Nb and Mo on Hydrogen Embrittlement Susceptibility of 2 GPa-grade Medium-carbon Si–Cr Spring Steel with Tempered Martensite Microstructure

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Microstructure and Plasticity Evolution During Lüders Deformation in an Fe-5Mn-0.1C Medium-Mn Steel

Motomichi Koyama, Takayuki Yamashita, Satoshi Morooka, Takahiro Sawaguchi, Zhipeng Yang, Tomohiko Hojo, Takuro Kawasaki, Stefanus Harjo

pp. 197-204

DOI:

10.2355/tetsutohagane.TETSU-2023-038

Abstract

The local plasticity and associated microstructure evolution in Fe-5Mn-0.1C medium-Mn steel (wt.%) were investigated in this study. Specifically, the micro-deformation mechanism during Lüders banding was characterized based on multi-scale electron backscatter diffraction measurements and electron channeling contrast imaging. Similar to other medium-Mn steels, the Fe-5Mn-0.1C steel showed discontinuous macroscopic deformation, preferential plastic deformation in austenite, and deformation-induced martensitic transformation during Lüders deformation. Hexagonal close-packed martensite was also observed as an intermediate phase. Furthermore, an in-situ neutron diffraction experiment revealed that the pre-existing body-centered cubic phase, which was mainly ferrite, was a minor deformation path, although ferrite was the major constituent phase.

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Microstructure and Plasticity Evolution During Lüders Deformation in an Fe-5Mn-0.1C Medium-Mn Steel

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Hierarchical Deformation Heterogeneity during Lüders Band Propagation in an Fe-5Mn-0.1C Medium Mn Steel Clarified through in situ Scanning Electron Microscopy

Motomichi Koyama, Takayuki Yamashita, Satoshi Morooka, Zhipeng Yang, Rama Srinivas Varanasi, Tomohiko Hojo, Takuro Kawasaki, Stefanus Harjo

pp. 205-216

DOI:

10.2355/tetsutohagane.TETSU-2023-052

Abstract

In-situ deformation experiments with cold-rolled and intercritically annealed Fe-5Mn-0.1C steel were carried out at ambient temperature to characterize the deformation heterogeneity during Lüders band propagation. Deformation band formation, which is a precursor phenomenon of Lüders band propagation, occurred even in the macroscopically elastic deformation stage. The deformation bands in the Lüders front grew from both the side edges to the center of the specimen. After macroscopic yielding, the thin deformation bands grew via band branching, thickening, multiple band initiation, and their coalescence, the behavior of which was heterogeneous. Thick deformation bands formed irregularly in front of the region where the thin deformation bands were densified. The thin deformation bands were not further densified when the spacing of the bands was below ~ 10 µm. Instead, the regions between the deformation bands showed a homogeneous plasticity evolution. The growth of the thin deformation bands was discontinuous, which may be due to the presence of ferrite groups in the propagation path of the deformation bands. Based on these observations, a model for discontinuous Lüders band propagation has been proposed.

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Hierarchical Deformation Heterogeneity during Lüders Band Propagation in an Fe-5Mn-0.1C Medium Mn Steel Clarified through in situ Scanning Electron Microscopy

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Local Yield Stress and its Unusual Independence on Multi-axial Stress States during Lüders Deformation of Medium-Mn, High-strength Steel

Takashi Matsuno, Koki Furukawa, Yoshitaka Okitsu, Motomichi Koyama, Toshihiro Tsuchiyama

pp. 217-226

DOI:

10.2355/tetsutohagane.TETSU-2023-049

Abstract

Medium-manganese steel that undergoes Lüders deformation exhibits good uniform elongation owing to large elongation with a yield plateau. To accurately predict the deformation behavior in engineering applications, the yield stresses of medium-manganese steel (5% Mn), exhibiting the transformation-induced plasticity (TRIP) effect were investigated during elongation under a multiaxial stress state (MSS). Compact tensile tests with real-time diameter measurements were conducted on smooth and notched, tiny round-bar specimens to evaluate the local yield stress and strain without the Lüders band propagation effect. Consequently, the true stress plateau was measured without the upper yield point for the smooth round-bar specimen, and the cross-sectional average true stress of the blunt notched round-bar specimens had the same plateau as the smooth round-bar specimen. The sharp-notched round-bar specimen exhibited a two-stage linear increase in true stress. The true stresses of the three specimens at the initial yield point were almost identical. Under the MSS, the hydrostatic stress typically increases the true stress at the initial yield point. The independence of the MSS indicates that the yield stress during elongation was independent of the shear-dominant crystal slip resistance. Finite element (FE) analysis using the Mises yield locus did not express the true stress plateau and its independence of the MSS. Additionally, the transformation rate of retained austenite was measured for mechanistic analysis; however, the TRIP effect did not contribute to this unusual independence because it started at the intermediate yield elongation stage. Thus, the stress criterion for the generation of mobile dislocations can determine yield stress.

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Local Yield Stress and its Unusual Independence on Multi-axial Stress States during Lüders Deformation of Medium-Mn, High-strength Steel

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Stress and Plastic Strain Partitioning Behaviors and Those Contributions to Martensitic Transformation of Retained Austenite in Medium Manganese and Transformation-Induced Plasticity-Aided Bainitic Ferrite Steels

Tomohiko Hojo, Motomichi Koyama, Bakuya Kumai, Yutao Zhou, Yuki Shibayama, Ayumi Shiro, Takahisa Shobu, Hiroyuki Saitoh, Saya Ajito, Eiji Akiyama

pp. 227-240

DOI:

10.2355/tetsutohagane.TETSU-2023-062

Abstract

Stress and plastic strain distributions and those partitioning behaviors of ferrite and retained austenite were investigated in the medium manganese (Mn) and the transformation-induced plasticity-aided bainitic ferrite (TBF) steels, and the martensitic transformation behaviors of retained austenite during Lüders elongation and work hardening were analyzed using synchrotron X-ray diffraction at SPring-8. The stress and plastic strain of retained austenite and volume fraction of retained austenite were remarkably changed during Lüders deformation in the medium Mn steel, implying that the medium Mn steel possessed inhomogeneous deformation at the parallel part of the tensile specimen. On the other hand, the distributions of the stress, plastic strain and volume fraction of retained austenite were homogeneous and the homogeneous deformation occurred at the parallel part of the tensile specimen at the plastic deformation regime with work hardening in the medium Mn and TBF steels. The martensitic transformation of retained austenite at Lüders deformation in the medium Mn steel was possessed owing to the application of high stress and preferential deformation at retained austenite, resulting in a significant increase in the plastic deformation and reduction of stress in the retained austenite. The martensitic transformation of retained austenite at the plastic deformation regime with work hardening was induced by the high dislocation density and newly applied plastic deformation in retained austenite in the medium Mn steel whereas the TBF steel possessed gradual transformation of retained austenite which is applied high tensile stress and moderate plastic deformation.

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Stress and Plastic Strain Partitioning Behaviors and Those Contributions to Martensitic Transformation of Retained Austenite in Medium Manganese and Transformation-Induced Plasticity-Aided Bainitic Ferrite Steels

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Role of Retained Austenite and Deformation Induced Martensite in 0.15C-5Mn Steel Monitored by in-situ Neutron Diffraction Measurement during Tensile Deformation

Takayuki Yamashita, Satoshi Morooka, Wu Gong, Takuro Kawasaki, Stefanus Harjo, Tomohiko Hojo, Yoshitaka Okitsu, Hidetoshi Fujii

pp. 241-251

DOI:

10.2355/tetsutohagane.TETSU-2023-059

Abstract

A Fe-0.15C-5Mn-0.5Si-0.05Nb medium Mn steel annealed at 660°C and 685°C both exhibited inhomogeneous deformation with Lüders deformation and extremely high work hardening rates, but with different Lüders strain and work hardening behavior. In-situ neutron diffraction measurements during tensile test were performed to investigate changes in the phase stresses and in the contributed stresses to the strength of the constituent phases, and crystal orientation of austenite. The role of each constituent phase in the deformation and the effect of crystallographic orientation on austenite stability were discussed. Deformation induced martensite showed excellent phase stress and contributed to the strength approximately 1000 MPa, which is close to macroscopic tensile strength. Although austenite contributed less to the strength, but during Lüders deformation and work hardening stage, it continuously transformed to martensite as the deformation progressed, suggesting that it mainly contributed to the ductility of the steels through a transformation induced plasticity effect. Austenite transformed to martensite in all crystallographic orientations during Lüders deformation, but there was a tendency for more <311> austenite grains parallel to the tensile direction to remain.

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Role of Retained Austenite and Deformation Induced Martensite in 0.15C-5Mn Steel Monitored by in-situ Neutron Diffraction Measurement during Tensile Deformation

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Texture Development in Austenite during Tensile Deformation of 5%Mn Steel Accompanied by Deformation-Induced Martensite Transformation

Yusuke Onuki

pp. 252-259

DOI:

10.2355/tetsutohagane.TETSU-2023-079

Abstract

Medium manganese steels, containing 3~10 mass% of Mn, are considered promising as the 3rd generation high strength steel. In this study, in situ neutron diffraction experiments were conducted during uniaxial tensile deformation for Fe-4.91Mn-0.092C (mass%). The primary aim was to investigate the change of austenite texture accompanied with the deformation induced martensitic transformation (DIMT). It was observed that grains oriented <001> towards the tensile direction tend to persist during the deformation. Moreover, the fraction of <001> oriented grains increases due to crystal rotation caused by dislocation slip. Grains with <111> towards the tensile direction are consumed more rapidly than those with <001>. These observations are qualitatively reproduced by visco-plastic self-consistent model, additionally considering DIMT to ε martensite. Although ε martensite was not identified in the diffraction pattern obtained in this study, a previous microstructural study indicated the γ→ε→α’ type DIMT for the same material. In contrast, it is known that in low alloyed TRIP steels subjected to tensile deformation, grains with <111> tend to survive, where γ→α’ type DIMT occurs. Based on the results of this study, the orientation that persists after tensile deformation can distinguish between the DIMT mechanisms: γ→ε→α’ or γ→α’ type.

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Texture Development in Austenite during Tensile Deformation of 5%Mn Steel Accompanied by Deformation-Induced Martensite Transformation

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Dynamic Deformation Properties of Medium-Mn Multi-phase Steels Containing Retained Austenite

Yoshitaka Okitsu, Tomohiko Hojo, Satoshi Morooka, Goro Miyamoto

pp. 260-267

DOI:

10.2355/tetsutohagane.TETSU-2023-065

Abstract

We investigated the dynamic tensile properties of 4, 5, 6-mass%-Mn-containing low carbon steels with multi-phase microstructures containing retained austenite. The five materials used were classified into two groups. The first group of materials, with around 10% of retained austenite, showed normal strain rate dependence of yield strength (YS) and tensile strength (TS) as in conventional high strength steels. The second group of materials, containing 25-36% of retained austenite and exhibiting Lüders elongation, showed also normal strain rate dependence of YS and flow stress at Lüders deformation, but TS varied in a complex manner. Among the second group, in the 4 Mn steel, TS was nearly constant at strain rates below 1 s−1 and increased slightly at higher strain rates. In the 5 and 6 Mn steels, TS once decreased up to the strain rate of 1 or 10 s−1, and then began to increase at higher strain rates. These behaviors were discussed in terms of temperature rise during plastic deformation and thermal stability of retained austenite. In the 4 Mn steel with relatively unstable retained austenite, almost all the austenite transforms regardless of strain rate. In the 5 and 6 Mn steels, where the retained austenite is moderately stable, its martensitic transformation is suppressed due to temperature rise, resulting in the decrease in TS at relatively low strain rates. At higher strain rates, the increase in flow stress prevails and TS begins to increase.

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Dynamic Deformation Properties of Medium-Mn Multi-phase Steels Containing Retained Austenite

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Characteristics of Non-uniform Deformation Behavior in Fe-10%Mn-0.1%C Alloy with Ultrafine-grained Multi-phase Martensitic Structure

Takuya Maeda, Kyosuke Matsuda, Misa Takanashi, Takuro Masumura, Toshihiro Tsuchiyama, Hiroyuki Shirahata, Ryuji Uemori

pp. 268-278

DOI:

10.2355/tetsutohagane.TETSU-2023-069

Abstract

To clarify the characteristics of plastic deformation behavior in quenched Fe-10%Mn-0.1%C alloy (10Mn steel), the microstructure and tensile deformation behavior were investigated and the non-uniform deformation behavior was analyzed using digital image correlation (DIC) method. As a comparison material, Fe-5%Mn-0.1%C alloy with common lath martensitic structure (5Mn steel) was used. The 10Mn steel has an equiaxed ultrafine-grained (α'+ε+γ) three-phase microstructure formed through a two-step martensitic transformation of γ→ε→α' during quenching. Tensile testing of 10Mn steel results in a stress-strain curve characterized by a clear yield point and significant work hardening. The yielding of 10Mn steel can be explained by the generation of plastic strain due to the stress-induced martensitic transformations such as ε→α' and γ→α' transformations. Furthermore, the subsequent work hardening can be explained by the combined mechanism of the continuous ε→α' and γ→α' transformations responsible for plastic deformation and the hard α' martensite responsible for stress. In 5Mn steel with lath martensitic microstructure, strain is concentrated in specific blocks during tensile deformation due to the priority of habit plane slip system, and the plastic deformation proceeds non-uniformly, whereas in 10Mn steel with equiaxed ultrafine grain microstructure, although small strain bands are generated, relatively uniform deformation tends to occur. The ε martensite and retained γ dispersed in the microstructure are considered unlikely to be the cause of contributing to non-uniform deformation.

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Characteristics of Non-uniform Deformation Behavior in Fe-10%Mn-0.1%C Alloy with Ultrafine-grained Multi-phase Martensitic Structure

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Effect of Local Deformation Microstructure on Ductile Fracture Behavior of Ferrite-Bainite Duplex Steel

Kyono Yasuda, Nobuyuki Ishikawa, Hitoshi Sueyoshi, Tatsuya Morikawa, Masaki Tanaka, Kenji Higashida

pp. 279-288

DOI:

10.2355/tetsutohagane.TETSU-2023-066

Abstract

Microscopic deformation and fracture behavior of a ferrite-bainite dual phase steel was investigated by the micro-grid method and FE analysis to understand the inherent conditions of plastic instability and ductile fracture. The micro-grid method, which the microscopic strain is measured by the displacement of grids with 500 nm intervals drawn on the specimen surface, clearly revealed that the shear deformation along the lath structure in the bainite phase was seen before reaching the maximum loading point. Then, voids were observed in the ferrite phase adjacent to the ferrite/bainite boundary, where showing higher strain concentration. From the FE analysis with the model simulating actual ferrite-bainite microstructure, stress distribution was seen in the bainite phase, and high stressed regions could cause the shear deformation of the bainite phase. The local shear deformation in the bainite phase decreased strain hardenability and triggered the macroscopic plastic instability. It is considered that the macroscopic plastic instability accelerates the strain localization, and promotes the void nucleation and growth. Ductile fracture path was also visualized by the micro-grids in the ferrite phase along the shear deformation bands which is connecting the high strain regions. Development of shear deformation bands inside the ferrite phase was well simulated with the FE analysis, same as the development of high stressed region in the bainite phase in the early stage. It can be stated, therefore, that plastic instability and ductile fracture of dual phase steel is a structure dependent phenomenon which is strongly controlled by the morphologies of each constituent phases.

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Effect of Local Deformation Microstructure on Ductile Fracture Behavior of Ferrite-Bainite Duplex Steel

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Deformation and Fracture Behaviors of Spheroidized Pearlitic Steel under Tensile Loading

Norimitsu Koga, Yuto Yajima, Chihiro Watanabe

pp. 289-301

DOI:

10.2355/tetsutohagane.TETSU-2023-061

Abstract

The deformation and fracture behavior in spheroidized pearlitic steels were investigated using digital image correlation and the replica methods, and the origin of the inhomogeneous strain distribution and its effect on fracture were discussed. The cementite roundness increased while the area fraction within a colony decreased with increasing spheroidization time. Many coarse cementites were observed on the colony and block boundaries, which explains the decrease in the cementite area fraction within a colony. The strength–ductility balance deteriorated with cementite spheroidization. The inhomogeneous strain distribution in a unit of the colony was introduced by the tensile deformation in the spheroidized pearlitic steels. The numerous voids or cracks detected at low- and high-angle boundaries inside the cementite and in ferrite at the ferrite/cementite boundary tended to nucleate from the high-strain region. The deformability of the colony depended on the progress of cementite spheroidization, and the crystallographic orientation relationship between ferrite and cementite could affect the ease of cementite spheroidization in a colony. The strain gradient between the soft ferrite and hard cementite phases induced void or crack nucleation around the coarse cementite at the colony or block boundary; hence, voids or cracks tended to nucleate from the high-strain region. It can be concluded that inhomogeneous cementite spheroidization results in an inhomogeneous strain distribution, which causes the preferential nucleation of voids or cracks in the high-strain colony.

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Deformation and Fracture Behaviors of Spheroidized Pearlitic Steel under Tensile Loading

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Dependence of Carbon and Nitrogen Content on Grain Refinement Strengthening in Austenitic Stainless Steel

Yoshihiro Oka, Ayumi Morimatsu, Takuro Masumura, Takahito Ohmura, Toshihiro Tsuchiyama

pp. 302-310

DOI:

10.2355/tetsutohagane.TETSU-2023-072

Abstract

The effects of C and N on solid solution strengthening and grain refinement strengthening were quantitatively evaluated using various austenitic stainless steels in which C and N were added independently to Fe-18 mass%Cr-12 mass%Ni alloys. As a result of evaluating the amount of solid solution strengthening from the intercept value in the Hall-Petch relationship, it was confirmed that N has a stronger solid solution strengthening capacity than C. On the other hand, the addition of C and N increased the slope of the Hall-Petch relationship, the so-called Hall-Petch coefficient, and the amount of grain refinement strengthening increased. Comparing the effects of C and N, there was no significant difference in the effect of increasing the Hall-Petch coefficient between the two elements at the same amount of addition. The critical grain boundary shear stress measured by nanoindentation tests and the Hall-Petch coefficient corresponded well for both steels, demonstrating that the increase in critical shear stress due to the addition of C and N results in increased grain refinement strengthening. However, the amount of grain boundary segregation was calculated to be considerably higher for C than for N, suggesting that N is more effective than C in increasing the critical grain boundary shear stress.

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Dependence of Carbon and Nitrogen Content on Grain Refinement Strengthening in Austenitic Stainless Steel

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Quantitative Evaluation of the Relationship between Strain and Color Change in Opal Photonic Crystal Films and Application into Complex Specimen Geometries

Yutao Zhou, Zhipeng Yang, Motomichi Koyama, Saya Ajito, Tomohiko Hojo, Hiroshi Fudouzi, Eiji Akiyama

pp. 311-320

DOI:

10.2355/tetsutohagane.TETSU-2023-020

Abstract

The color change of opal photonic crystal films (OPCFs) due to deformation was quantitatively evaluated using digital image correlation (DIC) analysis. OPCFs were pasted on specimens of three different gauge geometries, and random patterns were formed on the opposite side of each specimen for DIC analysis. To assess the applicability of using OPCFs-based strain characterization for analyzing steel structural components and associated metallurgical analyses, smooth, width-gradient, and holed specimens were prepared in this study. As deformation increased in the smooth specimen, the color of the OPCFs changed significantly. The color change in the OPCFs could be quantitatively converted into strain values through Hue value analysis. Heterogeneous strain distributions could also be quantitatively analyzed using OPCFs-based analysis at the submillimeter or millimeter scale. When the strain gradient is too high, for example, near a stress concentration site such as a hole, local peeling of the OPCFs away from the specimen surface can occur. Consequently, for quantitative characterization, we must take proper care when measuring this upper limit of the “strain gradient” as well as strain, which would depend on the adhesion and surface condition of the specimen.

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Quantitative Evaluation of the Relationship between Strain and Color Change in Opal Photonic Crystal Films and Application into Complex Specimen Geometries

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Crystal Plasticity Analysis on the Fundamental Processes of Strain Localization and Damage Formation in Pure Iron Polycrystals under Cyclic Fatigue

Yelm Okuyama, Tetsuya Ohashi

pp. 321-332

DOI:

10.2355/tetsutohagane.TETSU-2023-094

Abstract

By using finite element method for crystal plasticity, we investigated the accumulation behavior of dislocation and atomic vacancies introduced by non-uniform deformation in pure iron polycrystals. Dislocation density was calculated from the increment of plastic shear strain and spatial gradient of the slip systems for SS and GN dislocation densities. Vacancy density was calculated from the edge component of SS dislocation density and the incremental plastic shear strain by expanding the theory of Essmann and Mughrabi, in which atomic vacancies are released by the annihilation of edge dislocations, for each slip system. The cyclic loading analysis was performed under strain-controlled with 10 cycles between a tensile process up to 0.5% nominal strain and a compressive process down to 0%. For comparison, a monotonic loading analysis was also performed. The macroscopic mechanical responses were significantly different under the two conditions, and the work hardening rate under cyclic loading was less than half that under monotonic loading. The localization of plastic strain was more pronounced in the cyclic loading deformation than in the monotonic one. The low work hardening rate for cyclic loading deformation was attributed to the low accumulation of GN dislocations due to the relaxation of the plastic shear strain gradient caused by the load reversal. The average vacancy density was twice higher for monotonic loading deformation than for cyclic loading deformation. On the other hand, the maximum value of vacancy density was almost the same in both conditions, indicating that the cyclic loading deformation was more localized.

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Crystal Plasticity Analysis on the Fundamental Processes of Strain Localization and Damage Formation in Pure Iron Polycrystals under Cyclic Fatigue

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Multiscale Finite Element Analysis of Yield-point Phenomenon in Ferrite–Pearlite Duplex Steels

Shinnosuke Yanagawa, Ikumu Watanabe

pp. 333-341

DOI:

10.2355/tetsutohagane.TETSU-2023-080

Abstract

Yield-point phenomena in Ferrite–Pearlite duplex steels were investigated using multi-scale computational simulations. In this multi-scale simulations, stress–strain relationship of Ferrite phase was characterized by an elastoplastic constitutive model considering yield-drop behavior and its material constants were determined by minimizing residual error between a computational simulation and experiment of tensile test, where yield-point phenomenon in a tensile test of Ferrite steel was reproduced. Using the determined material response of Ferrite phase, finite element analyses of Ferrite–Pearlite duplex microstructure were performed to examine its macroscopic material response and its microscopic deformation mechanism. Besides, finite element analyses of tensile test based on the numerical results of microscopic finite element analysis were conducted to reproduce yield-point phenomena in Ferrite–Pearlite duplex steels.

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Multiscale Finite Element Analysis of Yield-point Phenomenon in Ferrite–Pearlite Duplex Steels

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