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MATERIALS TRANSACTIONS Vol. 63 (2022), No. 3

ISIJ International
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ONLINE ISSN: 1347-5320
PRINT ISSN: 1345-9678
Publisher: The Japan Institute of Metals and Materials

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MATERIALS TRANSACTIONS Vol. 63 (2022), No. 3

Application of Grain Boundary Segregation Prediction Using a Nano-Polycrystalline Grain Boundary Model to Transition Metal Solute Elements: Prediction of Grain Boundary Segregation of Mn and Cr in bcc-Fe Polycrystals

Kazuma Ito, Yuta Tanaka, Hideaki Sawada

pp. 269-277

DOI:

10.2320/matertrans.MT-M2021205

Abstract

A prediction method for grain boundary segregation using a nano-polycrystalline grain boundary model is applied to the grain boundary segregation of Cr and Mn in bcc-Fe polycrystals for which experimental results exist, and the validity of the prediction method is verified. In this prediction method, focusing on the fact that the atomic structure of grain boundaries is almost independent of grain size, grain boundaries of polycrystals with grain sizes of the order of micrometers are modeled as grain boundaries of nano-polycrystals, for which structural relaxation calculations by molecular dynamics calculations are possible. For this grain boundary model, the grain boundary segregation energy of each site is calculated exhaustively using the interatomic potential. In addition, the average amount of grain boundary segregation in the polycrystal is calculated from the obtained grain boundary segregation energy. With this prediction method, the average amounts of grain boundary segregation and segregation energies of Cr and Mn in bcc-Fe polycrystals can be calculated and compared with the experimental results. Calculated results for both elements reproduced the experimental results well, suggesting that this prediction method is also effective in predicting the grain boundary segregation of other solute elements. This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 85 (2021) 421–429.

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Application of Grain Boundary Segregation Prediction Using a Nano-Polycrystalline Grain Boundary Model to Transition Metal Solute Elements: Prediction of Grain Boundary Segregation of Mn and Cr in bcc-Fe Polycrystals

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A Comparison Study of Electrical Resistivity, Vickers Hardness, and Microstructures of Alloy 625 Prior and Posterior to Rolling

Tomohiro Nagata, Kohei Takeda, Hiroki Adachi, Kazuhiro Ishikawa, Yoji Miyajima

pp. 278-285

DOI:

10.2320/matertrans.MT-M2021204

Abstract

Electrical resistivity and Vickers hardness of Alloy 625 due to cold rolling were measured, and, discussed with the microstructural change obtained using electron backscattered diffraction and X-ray diffraction. Both increase in dislocation density and grain subdivision due to rolling was observed. Although the electrical resistivity of the normal pure metals increases with increasing the rolling reduction, that of Alloy 625 initially decreased with increasing the rolling reduction of 70%. Then, the electrical resistivity slightly increased with increasing the rolling reduction of 80%. Up to the rolling reduction of 70%, the reduction of electrical resistivity is associated with K-effect, which is the destroy of the short-range ordered domain due to the plastic deformation. On the other hand, Vickers hardness increased with increasing the rolling reduction. It was associated with the contribution of grain refinement, dislocation, solid solution, and sort-range order strengthening. This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 85 (2021) 391–398. Section 2.2 was slightly modified.

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A Comparison Study of Electrical Resistivity, Vickers Hardness, and Microstructures of Alloy 625 Prior and Posterior to Rolling

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Effect of Reheating after Low Temperature Pre-Aging on Microstructure of 6061 Aluminum Alloy

Naohiro Saruwatari, Kohki Yasue, Yoshihiro Nakayama

pp. 286-293

DOI:

10.2320/matertrans.MT-L2021014

Abstract

This study aimed to understand the microstructural changes with reversion treatment in a 6061 aluminum alloy, such as dissolution of clusters formed during low temperature pre-aging. The specimens subjected to a solution treatment for 1.8 ks at 803 K and then pre-aged at 283 K for 604.8 ks were reheated under various temperature and time conditions. When reheated at 423 K, the hardness of the alloy specimen after reheating increased compared with that immediately after low temperature pre-aging. It was suggested that while the cluster dissolution hardly occurred during the reheating at 423 K, the formation of a strengthening phase from the supersaturated solid solution and transformation of some of the Mg–Si clusters formed during the low temperature pre-aging into the strengthening phase have occurred. In the case of reheating for 1 and 10 s at 523 K, which is commonly used as the reversion treatment temperature, the hardness of the final-aged specimen increased to the same level as that without low temperature pre-aging, indicating that the negative effect of two-step aging was mitigated. The mitigation of the negative effect was considered to be owing to microstructural changes, such as cluster dissolution, transformation of the Si-rich clusters, and precipitation of the strengthening phase during reheating at 523 K. Reheating above 573 K reduced the amount of age-hardening in the final-aging owing to the precipitation during the reheating. From these results, it is suggested that the adequate amount of solute atoms concentration in the matrix corresponding to that after a solution treatment could not be realized by the conventional reversion treatment.

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Effect of Reheating after Low Temperature Pre-Aging on Microstructure of 6061 Aluminum Alloy

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Wear and Degradation of Drilling Performance of Polycrystalline Diamond Compact Bit in Laboratory Test

Kuniyuki Miyazaki, Tetsuji Ohno, Takashi Takehara, Hiroyuki Imaizumi

pp. 294-303

DOI:

10.2320/matertrans.M-M2021825

Abstract

Polycrystalline diamond compact (PDC) bits have been widely used in oil and gas well drilling and have recently also begun to be used in geothermal well drilling. In the present study, the drilling performance and wear of a PDC bit were assessed by laboratory drilling tests. The correlation between the progress of bit wear and some indexes of rock abrasivity was discussed referring to the test results. The rate of penetration was formulated as a function of weight on the bit using the drilling test results for other PDC bits with the same geometric design as that used in the present study and introducing a parameter that represents the drilling performance of the bit. The parameter was found to be exponentially reduced with the wear volume of the polycrystalline diamond layer. The parameter was also found to be associated with the drilled rock type.

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Wear and Degradation of Drilling Performance of Polycrystalline Diamond Compact Bit in Laboratory Test

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Suppression of Springback for Longitudinally Curved Part by Imparting In-Plane Compression Stress in Press Forming

Toyohisa Shinmiya, Yuji Yamasaki, Hiroto Miyake, Jiro Hiramoto

pp. 304-310

DOI:

10.2320/matertrans.P-M2021856

Abstract

Dimensional accuracy defects caused by springback behavior are one of the serious problems in press forming for automobile parts using ultrahigh-strength steel sheets. In particular, in hat-shaped parts curved in the longitudinal direction, camber back, which is a kind of springback behavior, occurs. In this study, in order to suppress camber back, a new press-forming method that can impart in-plane compression stress was investigated using parts with a simple hat-shaped section and a W-shaped section simulating automotive parts. As a result, it was found that the amount of camber back decreases on applying compression stress in the longitudinal direction, because the bending moment caused by the difference between stress in the punch bottom area and that in the flange area was reduced. It was also clarified that the sensitivity of the amount of camber back to tensile strength was lowered when this forming method was used. Furthermore, a forming method in which buckling in both ends under a high compression condition can be prevented was developed. This Paper was Originally Published in Japanese in J. JSTP 60 (2019) 161–166.

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Suppression of Springback for Longitudinally Curved Part by Imparting In-Plane Compression Stress in Press Forming

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Influence of 1st Step Shape on Formability of Circular Truncated Cone Stretch Forming in Two-Step Forming

Kinya Nakagawa, Yuji Yamasaki, Yoshikiyo Tamai, Jiro Hiramoto

pp. 311-318

DOI:

10.2320/matertrans.MT-P2021004

Abstract

The formability of steel sheets must be improved in order to form complicated car parts. Multistep forming is one way to improve formability. Although the shape after preforming can influence formability in the main step of multistep forming, no relationship has been reported between the shape after preforming and the final shape in stretch forming.In this study, circular truncated cones were formed by a two-step forming process consisting of preforming and main forming with combinations of various shapes after preforming and final shapes in order to investigate the effect of the shape after preforming on the forming limit in main forming. The results confirmed that the forming limit height in main forming is affected by the preforming shape. It was also found that the forming limit height in main forming is determined by the central cross-sectional line length of the shape after preforming. This Paper was Originally Published in Japanese in J. JSTP 61 (2020) 87–92. Abstract was slightly modified.

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Influence of 1st Step Shape on Formability of Circular Truncated Cone Stretch Forming in Two-Step Forming

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Clustering Analysis of Acoustic Emission Signals during Compression Tests in Mille-Feuille Structure Materials

Hanqing Liu, Fabien Briffod, Takayuki Shiraiwa, Manabu Enoki, Satoshi Emura

pp. 319-328

DOI:

10.2320/matertrans.MT-M2021105

Abstract

Acoustic emission (AE) methods with supervised and unsupervised machine learning were applied to investigate deformation behaviors of Mg–Y–Zn alloys and Ti–12Mo alloy with mille-feuille-like structure. In the supervised learning process, AE signals received from compression tests with pure magnesium and directionally solidified (DS) Mg85Zn6Y9 alloy with long-period stacking ordered (LPSO) structure were used as the training data to build a classification model for classifying AE sources from α-Mg phase and LPSO phase in Mg–Y–Zn alloys. In the unsupervised learning process, AE signals data from Ti–12Mo alloy were divided into two clusters according to the frequency spectrum features, and digital image correlation (DIC) was carried out to study those clusters and deformation behaviors. Deformation behavior of Mg–Y–Zn alloys and Ti–12Mo alloy were compared and discussed, and the method of applying AE with supervised and unsupervised machine learning was evaluated.

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Clustering Analysis of Acoustic Emission Signals during Compression Tests in Mille-Feuille Structure Materials

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Adhesive and Frictional Properties of Solid Lubricants for Powder Metallurgy Evaluated by Surface Force Apparatus

Hanako Shimamoto, Shigeru Unami, Masashi Mizukami, Kazue Kurihara

pp. 329-334

DOI:

10.2320/matertrans.MT-Y2021004

Abstract

Iron-based powder mixtures for the powder metallurgy process commonly contain solid lubricants. Both zinc stearate (ZnSt) and N,N′-ethylenebis(stearamide) (EBS), which are conventional lubricants in this field, exhibit similarly adequate lubrication performance. However, their effects on powder mixture flowability are different; that is, powder mixtures containing ZnSt exhibit better flowability than ones containing EBS. In this study, the adhesive and frictional properties of five surface combinations (iron–iron, iron–EBS, iron–ZnSt, EBS–EBS, and ZnSt–ZnSt) were investigated using surface force and resonance shear measurements. The adhesive forces obtained for all combinations were almost the same. On the other hand, the frictional forces for the iron–EBS and EBS–EBS combinations obtained from resonance shear measurement were larger than the others under low applied loads (<ca. 1.0 mN). This result suggests that the frictional properties of lubricants under low applied loads determine the powder mixture flowability. This Paper was Originally Published in Japanese in J. Jpn. Soc. Powder Metallurgy 66 (2019) 554–559.

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Adhesive and Frictional Properties of Solid Lubricants for Powder Metallurgy Evaluated by Surface Force Apparatus

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The Role of Micro Pits in the Initiation Process of Crevice Corrosion of SUS304 Stainless Steel in an Aqueous Chloride Solution

Akira Nagaoka, Kiyomi Nose, Kana Nokami, Haruhiko Kajimura

pp. 335-342

DOI:

10.2320/matertrans.MT-C2021007

Abstract

On free surfaces without crevice structures, micro pits of several micrometers in diameter that are repassivated immediately are called metastable pits. The role of the micro pit as an initiation site of crevice corrosion was examined by comparing the metastable pitting corrosion potential (V′cMS) of SUS304 stainless steel measured on the free surface with the critical potential for crevice corrosion (VCREV). VCREV presented the similar value to V′cMS. It was also revealed that micro pits, as well as SUS304 stainless steel surface, were hard to be repassivated at pH ≤ 2.0, meaning that micro pits can be initiation sites of crevice corrosions. Investigating Cl− concentration and pH dependencies on each potential, the influences of these factors were also examined in terms of the contribution to a crevice corrosion initiation. Cl− ions, which have V′cMS and VCREV less noble, will directly contribute to a crevice corrosion initiation by facilitating micro pit initiations. pH decrease accelerating passive dissolution would promote a crevice corrosion initiation indirectly by increasing Cl− migration into a crevice structure. This Paper was Originally Published in Zairyo-to-Kankyo 70 (2021) 32–39. The captions of Figs. 4, 7 are slightly modified.

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The Role of Micro Pits in the Initiation Process of Crevice Corrosion of SUS304 Stainless Steel in an Aqueous Chloride Solution

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Catalytic Hydrogenation of C2H2 over Amorphous CeNi2Hx and Crystalline CeNi2: Effects of Hydrogen-Induced Amorphization and Oxidation

Ryota Tsukuda, Satoshi Ohhashi, Ya Xu, Chikashi Nishimura, Satoshi Kameoka

pp. 343-350

DOI:

10.2320/matertrans.MT-M2021202

Abstract

The catalytic hydrogenation of acetylene over crystalline CeNi2 and amorphous CeNi2Hx was investigated. CeNi2 was found to undergo a transformation to an amorphous phase after exposure to 0.35 MPa hydrogen at 25°C. Both crystalline CeNi2 and amorphous CeNi2Hx without exposure to air showed minimal catalytic activity. These results indicated that the hydrogen-induced amorphization of CeNi2Hx does not result in an increase of catalytic activity and that the absorbed hydrogen in CeNi2Hx was minimally active. After exposure to air, both materials were found to catalyze the hydrogenation of acetylene, suggesting that surface oxidation was a prerequisite. Amorphous CeNi2Hx also exhibited higher catalytic activity than crystalline CeNi2 and provided complete conversion of acetylene at 125°C. Both the crystalline CeNi2 and amorphous CeNi2Hx were characterized by X-ray photoelectron spectroscopy, thermogravimetry-differential thermal analysis and transmission electron microscopy. Amorphous CeNi2Hx was more readily oxidized and formed a dense surface nanostructure that provided superior catalytic activity. Amorphous CeNi2Hx is evidently a better catalytic precursor for acetylene hydrogenation than crystalline CeNi2.

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Catalytic Hydrogenation of C2H2 over Amorphous CeNi2Hx and Crystalline CeNi2: Effects of Hydrogen-Induced Amorphization and Oxidation

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Investigation of the Effect of Hydrogen Gas as Raw Material for DLC Film Preparation

Koki Okada, Akio Nishimoto

pp. 351-356

DOI:

10.2320/matertrans.MT-M2021213

Abstract

For reducing the frictional losses on the sliding surfaces of mounting parts and improving the wear resistance in order to extend the life of the component, diamond-like carbon (DLC) film coating has been considered, in recent years. However, reduction of the long processing time involved is desirable for mass production. For achieving this, the effect of mixing hydrocarbon gas and hydrogen gas in the deposition process is compared, and the differences in the resulting DLC films are determined in this study. DLC films are deposited on Si wafers through radio frequency plasma chemical vapor deposition (RF-PECVD), with a mixture of methane gas and hydrogen (dilution gas) as the raw material. In addition, DLC films are prepared by mixing acetylene gas with hydrogen gas for comparison, and the effect of the hydrogen gas mixture on the deposition rate, composition, and hardness of the films is confirmed. When hydrogen gas is mixed with methane gas, the deposition rate increases with the increase in the ratio of hydrogen gas in the raw material, and the percentage of sp3 bonds increases; however, the hardness and elastic modulus decrease. Furthermore, the adhesiveness deteriorates with the increase in the hydrogen gas ratio.

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Investigation of the Effect of Hydrogen Gas as Raw Material for DLC Film Preparation

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Fabrication of Nanoprotrusion Surface on AISI 316 Stainless Steel via Ar–N2 Plasma Etching

Mitsuhiro Hirano, Shinya Takeda, Naofumi Ohtsu

pp. 357-362

DOI:

10.2320/matertrans.MT-M2021102

Abstract

Argon (Ar) plasma etching of stainless steel is known to form a unique surface texture consisting of nanopillars of several hundred nanometers due to the use of carbide precipitates as a template. The present study demonstrates that adding a small amount of nitrogen (N2) gas to Ar plasma discharge gas reduces the pillar size and enhances the pillar density, thereby resulting in a densely arranged nanoprotrusion surface. Admixing 1% N2 to the discharge gas decreased the height of each nanopillar to approximately a quarter of its original height. A further increase in N2 gas hardly changed the size of the nanoprotrusions, yet its number density increased up to 5% N2 addition. Admixed N2 gas generates N2+ species in the plasma, which form tiny chromium nitride (CrN) precipitates on a stainless steel surface. These CrN precipitates have become an alternative template for plasma etching. Nanoprotrusion surfaces are expected to improve the tribological properties of stainless steel surfaces; thus, the introduced process has potential for industrial applications.

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Fabrication of Nanoprotrusion Surface on AISI 316 Stainless Steel via Ar–N2 Plasma Etching

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Microstructural Changes during Interfacial Diffusion at the Sm2Fe17–Zn Interface

Masashi Matsuura, Kuniko Yamamoto, Satoshi Sugimoto, Noritsugu Sakuma, Masaaki Ito

pp. 363-372

DOI:

10.2320/matertrans.MT-M2021184

Abstract

The microstructural changes and interdiffusion coefficients at the Sm2Fe17–Zn interface were investigated in this study. Sm2Fe17–Zn diffusion couples were annealed for 10 min at 320, 350, and 400°C, which are below the melting temperature of Zn (419°C), resulting in the interdiffusion of Zn, Fe, and Sm. At the interface annealed at 400°C, three diffusion regions were identified between the Sm2Fe17 and Zn phases. The thickest region was a Zn-rich region composed of polycrystalline δ- and ζ-Zn–Fe binary alloy phases and a ThMn12-type Sm(Zn,Fe)12 ternary alloy phase. The annealing time dependence of the thickness of the Zn-rich region at 400°C was measured, and the interdiffusion coefficient was evaluated as 7.3 × 10−13 m2s−1 using the Einstein–Smoluchowski equation. At the surface of the Sm2Fe17 phase, a region with a fiber-like microstructure was observed that consisted of two phases, α-(Zn,Fe) and Sm(Zn,Fe)12. Interestingly, these two phases exhibited a specific crystal orientational relationship of α-FeZn(10-1)[111]//Sm(Zn,Fe)12(01-1)[011]. Between these two diffusion regions, a third region composed of nanosized polycrystalline grains of Γ-FeZn, α-FeZn, and Sm(Zn,Fe)12 was observed.The temperature dependence of the microstructural changes at the Sm2Fe17–Zn interface indicated that the microstructural changes proceed as follows. In the initial stage of diffusion, interdiffusion of Zn, Fe, and Sm lead to the formation of the Zn-rich region. As the interdiffusion progresses, Zn diffuses into the Sm2Fe17 phase, which decomposes to Sm(Zn,Fe)12 and α-FeZn phases with a fiber-like microstructure. Upon further Zn diffusion into the fiber-like region, Zn reacts with the α-FeZn phase to generate a polycrystalline region composed of Γ-FeZn, α-FeZn, and Sm(Zn,Fe)12 phases. To the best our knowledge, this is the first paper to report on the interdiffusion and detailed microstructural changes at the Sm2Fe17–Zn interface.

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Microstructural Changes during Interfacial Diffusion at the Sm2Fe17–Zn Interface

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Titanium Culture Vessel Capable of Controlling Culture Temperature for Evaluation of Cell Thermotolerance

Chikahiro Imashiro, Yuta Ida, Shogo Miyata, Jun Komotori

pp. 373-378

DOI:

10.2320/matertrans.MT-Z2021018

Abstract

Surgery, radiation therapy, and chemical therapy have been reported as the main treatments for cancer, which is one of the deadliest reported diseases. However, because of the high invasiveness of patients, cancer hyperthermia has been studied as a non-invasive treatment. Hyperthermia uses a difference in thermal tolerance between normal and cancer cells and provides an affected part thermal stimulation to kill cancer cells selectively. To develop effective conditions for hyperthermia, an in vitro study to evaluate the thermal tolerance is required. However, because the existing cell culture vessels cannot control the culture temperature, genuine thermal tolerance of cells cannot be investigated appropriately. To reveal the critical temperature proper for hyperthermia, we developed a culture device controlling culture temperature. With the developed device, culture temperature was regulated considerably more quickly than the conventional method with the existing vessels, which enabled us to study the thermal tolerance of cells appropriately. For the control of culture temperature, the device has a titanium culture substrate, where a Peltier element is adhered. Because the biocompatibility of the device was confirmed, the difference in thermal tolerance between normal and cancer cells was investigated using the developed device as well as normal human dermal fibroblasts and Michigan Cancer Foundation-7 as model cell species. Therefore, it was confirmed that cancer cells were more sensitive to thermal stimulation than normal cells, which was qualitatively consistent with previous studies. Thus, our developed device can be used to investigate the thermal tolerance of each cell species, which will contribute to the development of cancer hyperthermia. This Paper was Originally Published in Japanese in J. Soc. Mater. Sci., Japan 70 (2021) 479–485.

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Titanium Culture Vessel Capable of Controlling Culture Temperature for Evaluation of Cell Thermotolerance

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Preparation of Mixed Metal Hydroxide Ash-Derived Adsorbent from Coal Fly Ash and Quicklime for Removal of Pb2+, NH4+, and PO43− from Aqueous Solution

Takaaki Wajima

pp. 379-388

DOI:

10.2320/matertrans.M-M2021853

Abstract

Preparation of a novel adsorbent, mainly composed of Si–(Al, Fe)–Ca mixed hydrous oxides, from a mixture of coal fly ash and quicklime (CaO) was attempted. Coal fly ash was mixed with NaOH powder and heated to 600°C for 6 h in an electric furnace, and after cooling to room temperature, the produced fused coal ash was mixed with quicklime. The mixture was then stirred in distilled water at room temperature for one day to prepare the adsorbent. With increase in CaO addition to the fused fly ash, the adsorbent changed from an amorphous material to a mixture of calcite [CaCO3] and amorphous phases, then a mixture of calcite and hydrocalumite [Ca4Al2O8(CO3)·11H2O], and finally that of calcite, hydrocalumite, and portlandite [Ca(OH)2]. The removal ability of the adsorbent for NH4+ is almost the same and that for Pb2+ and PO43− increases with increasing CaO addition. The removal of NH4+, PO43−, and Pb2+ depends on the pH of the solution. The adsorbent containing hydrocalumite without portlandite indicates good ability for multifunctional removal in neutral solution and fixation. Fly ash contents, Si and Al, in the adsorbent contribute to NH4+ removal by ion exchange of Si–Al amorphous gels, PO43− removal by synthesis of hydrocalumite to form hydroxyapatite, and Pb2+ removal by formation of PbSi2O5·1.6H2O. The kinetics of the removal of NH4+, PO43−, and Pb2+ using this adsorbent follows the pseudo-second-order kinetics model rather than the pseudo-first-order kinetics model, and the removal of Pb2+ is faster than that of NH4+ and PO43−. These results indicate that a novel adsorbent with removal abilities for NH4+, Pb2+, and PO43− can be prepared from coal fly ash and quicklime, and suggests a new recycling method for industrial wastes.

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Preparation of Mixed Metal Hydroxide Ash-Derived Adsorbent from Coal Fly Ash and Quicklime for Removal of Pb2+, NH4+, and PO43− from Aqueous Solution

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Fabrication of Foamed Porous Ceramics from Mixtures of Pork Bone and Incinerated Sewage Sludge Ash

Nobuyuki Takeuchi, Aya Yoshimura

pp. 389-393

DOI:

10.2320/matertrans.MT-Z2021010

Abstract

Ultra-lightweight ceramics were fabricated by firing the mixtures of pork bone (PB) and incinerated ash of sewage sludge. PB content in the mixtures was varied from 0 to 15 mass%. The mixtures were pressed in a discus body (4 cm in diameter) and the body was fired at the temperature range from 1000 to 1150°C for 1 h in air. Bloating behaviors were observed in the samples fired at the temperature over 1050°C. The remarkable lightweight ceramics, which have the apparent porosity less than 1.0 g cm−3, were obtained by the addition of 10–15 mass% PB and the firing at the temperature over 1050°C. Diffuse reflectance spectra revealed that ferric oxide in the samples fired at the temperature over 1050°C was reduced to ferrous oxide. It was considered that the large bloating in the PB added samples occurred due to both the evolution of oxygen from ferric oxide and the oxidation of residual carbon derived from PB inside the samples after melting of the surface at high temperatures.

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Fabrication of Foamed Porous Ceramics from Mixtures of Pork Bone and Incinerated Sewage Sludge Ash

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Recent Progress in Our Understanding of Phase Stability, Atomic Structures and Mechanical and Functional Properties of High-Entropy Alloys

Haruyuki Inui, Kyosuke Kishida, Zhenghao Chen

pp. 394-401

DOI:

10.2320/matertrans.MT-M2021234

Abstract

This paper reviews a current trend and recent progress in research on phase stability, atomic structures, mechanical and functional properties of high-entropy alloys. The survey is carried out based partly on the special issue published in April, 2020, in Materials Transactions (Vol. 61, No. 4). Research on high-entropy alloys has spread worldwide since the year of 2004, as many of them exhibit attractive properties for structural and functional applications, which have never been achieved in conventional alloys. Significant progress has been made in recent years in our understanding of high-entropy alloys in terms of processing, characterization, modeling and simulation, and so on. Some of them are briefly described in this paper.

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Recent Progress in Our Understanding of Phase Stability, Atomic Structures and Mechanical and Functional Properties of High-Entropy Alloys

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Statically Recrystallized Microstructure and Texture of Heterogeneous Nanostructured SUS316LN Austenite Stainless Steels

Hiromi Miura, Masakazu Kobayashi, Tomoki Tsuji, Takahiro Osuki, Takuya Hara, Naoki Yoshinaga

pp. 402-405

DOI:

10.2320/matertrans.MT-M2021231

Abstract

90% cold-rolled SUS316LN austenite stainless steels with different Mn content were annealed and the changes in the microstructure and texture after static recrystallization (SRX) were investigated. A typical heterogeneous nanostructure (HN), in which “eye”-shaped twin domains, shear bands and low-angle lamellae were main structural components, was developed by the heavy cold rolling. The formation of twin domains with crystallographical orientation of {111} // rolling plane effectively suppressed a sharp {101} texture evolution. However, preferential SRX nucleation at shear bands close to {101} orientation hindered the above {111} texture component and, then, a typical {101} one prevailed in whole area after full SRX. Dense nuclei in the HN led to homogeneous evolution of fine-grained structure. While the effects of Mn content on the microstructure and texture were not evident, superior mechanical properties appeared to be more emphasized with increasing Mn content.

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Statically Recrystallized Microstructure and Texture of Heterogeneous Nanostructured SUS316LN Austenite Stainless Steels

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