This article reviews the interactions between hydrogen and lattice defects produced by high-pressure torsion (HPT) process in ferritic iron and austenitic steels, and it shows the direction of development of hydrogen-resistant high-strength steels. In ferritic iron, grain boundaries as well as dislocations participate in hydrogen trapping. For austenitic steels, the contribution of grain boundaries to hydrogen trapping is negligible, while short-circuit diffusion occurs through them. Hydrogen trapping on precipitates caused by annealing after HPT processing depends on the affinity of hydrogen with constituting elements. In metastable austenitic steels, the presence of hydrogen suppresses deformation-induced martensitic transformation through enhanced slip planarity. If hydrogen-containing austenite transforms to martensite, excess hydrogen corresponding to a difference in the solubility between both phases is generated and diffuses out of the martensite, resulting in hydrogen concentration at the interphase. Deformation-induced martensite generated from ultrafine-grained austenite is used to simultaneously enhance strength and ductility without suffering from hydrogen embrittlement.

This paper reviews the recent developments of hydroforming technology in China. Limited corner radius, ring hoop tension test and tube bulging test were introduced on fundamentals of hydroforming. New hydroforming and hydro-bending process of ultra-thin tubes were investigated. Ultra-thin Y-shaped parts and complex section components were manufactured and applied in aerospace and aviation industry. Applications of tube hydroforming in automotive industry in China are also presented, including the hydroforming machines and production lines, typical automotive parts and potential market. New sheet hydroforming process with controllable radial pressure was proposed to increase the formability of sheets metals. Warm tube and sheet hydroforming were analyzed and discussed.

Bursting at the corner during calibration stage is a popular failure mode in hydroforming process of tubular part with polygonal sections. Bending of thin-walled tube is also a big obstacle for hydroforming process, especially for aluminum alloy tube. In this paper, a thin-walled aluminum alloy tubular part with polygonal sections was hydroformed with the step of hydro-bending, preforming and hydroforming. The influence of internal pressure during bending was discussed. Corner filling process of a symbol section was analyzed, such as filling sequence, corner shape changing and thickness distribution. The corner with less expansion ratio contacted the die first and thickness reduction is smaller. Bursting occurred in the corner with big expansion ratio. If the corner is located in the outer side of bending arc, danger of bursting is more severe. The key factor is to maintain a sound shape for the section before calibration to keep the expansion distribution evenly.

Hydroforming has certain advantages, for example integration of components and weight reduction, but it also has some disadvantages. One disadvantage is the difficulty in joining a hydroformed component to another part. Therefore hydro-burring after hydro-piercing in a hydroforming die has been investigated. The internal pressure during hydro-burring is found to have a large effect on the burring limit. The hydroformed component can be joined to another part with the thread tapped at the hydro-burring portion. However, it is difficult to tap thin-walled tubes. Therefore a new technique, a nut-inlaying method in a hydroformed component, has been developed. As a result, thin-walled hydroformed components can also be joined to other parts using this nut-inlaying method.

In this study, a free bulge test simulation was performed with conditions corresponding to experiments for a cobalt-alloy tube hydroforming. A 3D strain measurement scheme was introduced to obtain strain data after free bulge tests, and the measured strain values were used in the evaluation of ductile fracture criteria. Cockcroft ductile fracture criterion, Oyane ductile fracture criterion and the modified Cockcroft criterion were adopted for establishing the material constants by simple tensile test and notched tensile test. Experimental data from free bulge tests were used for fracture prediction with these criteria. The results revealed that for the purpose of tube hydrofoming, the modified Cockcroft criterion with strain paths is more accurate than either the Cockcroft ductile fracture criterion or the Oyane ductile fracture criterion.

In order to numerically evaluate hydroformed DP-steel tubes on crash performance while considering weld-heat effects, finite element simulations of the crash were performed for hydroformed tubes with and without considering heat treatment effects. Also, finite element simulations were carried out for sequential procedures of bending and hydro-forming of tubes in order to evaluate formability and spring-back for process parameters: boost condition and axial feeding. As for the constitutive law, the isotropic hardening law was used along with non-quadratic anisotropic yield functions Yld2000-2d. Forming limit diagrams were calculated based on Hill’s bifurcation theory and the M–K theory. In order to characterize the material properties of the base material (BM) sheet, tensile tests were performed with various strain rates. Tensile tests were conducted also for tensile specimens that were cut out from tubes for the measurement of material properties of the base material (BM) tube and electric resistance weld (ERW) zone. The mechanical properties of the metal inert gas (MAG) arc-weld zone as well as those of the heat affected zone (HAZ) were also obtained by using the continuous indentation method. Based on the determined material characteristics, crash performance evaluations were then numerically carried out for the tube, formed with optimized process parameters, with and without welding heat effects. With this work, numerical methods to properly implement the welding heat effects on the tube crash performance were established, which will be useful to evaluate the welding heat effects on the tube crash performance under realistic crash conditions.

Eccentric shaft parts, such as crankshaft and camshaft, fabricated by thick-wall tube hydroforming are increasingly used in industries, especially air-conditioner and automotive industry. In hydroforming those thick-wall components, the very high internal pressure and incomplete filling of the die corner make the forming process become difficult. In this paper, a new less-loading hydroforming die with movable sleeve is introduced to form the tube-like eccentric shaft workpiece. The characteristic of less loading hydroforming is illustrated by comparing with the conventional one by using FE simulation. Some typical loading paths and defects in the new hydroforming process are also investigated. The results obtained from this paper demonstrated the internal pressure, die closing force and die stress can be significantly decreased, as well as the qualified tube-like eccentric shaft workpiece can be formed by using the new movable die hydroforming.

The effect of the outflow volume of the pressure medium on the fluid-lubrication effect during the sheet hydroforming was investigated experimentally. The hydraulic pressures in the flange area obtained for the sheet hydroforming during which the hydraulic pressure was pressurized using pump were higher than those of the sheet hydroforming during which the pump was not utilized. This might be owing to the difference in the outflow volume of the pressure medium. On the other hand, the drawability of the sheet was almost independent of with or without using pump. Examining the so-called effective punch force, we found that the effect of the difference in the outflow volume of the pressure medium on the fluid-lubrication effect was negligible. We concluded from these results that the fluid-lubrication effect was affected significantly by the existence or non-existence of the outflow of the pressure medium, i.e. the lubricant oil, but it was almost independent of the outflow volume of the pressure medium. Furthermore we also found that the hydraulic pressure distribution in the flange area would not affect the fluid-lubrication effect.

A low-carbon TRIP seamless steel tube, which is expected to be used in the hydroforming process, was successfully fabricated using piercing, cold-drawing and two-stage heat treatment process. In this study, to maximize the volume fraction and stability of retained austenite as well as to obtain a TRIP seamless steel tube with good combination of strength and ductility, the optimal heat treatment conditions (intercritical annealing “IA” and isothermal bainite treatment “IBT”) were investigated. The influence of heat treatment on the microstructure of the TRIP seamless steel tube was studied via optical microscopy, TEM and XRD. The mechanical properties in axial and circumferential directions of TRIP seamless steel tube were also evaluated by conventional tensile test and the ring tensile test developed by the author, respectively. The results show that for a particular set of IA and IBT temperature, the volume fraction of retained austenite increased with increasing IA holding time but decreased with the increase of IBT holding time in the set of time range in this study. As a result, the high retained austenite volume fraction of 10.26% was obtained with IA holding time of 5 min at IA temperature of 810°C, IBT holding time of 6 min at temperature of 410°C. And this sample possessed a UTS of 542 MPa, YS of 355 MPa and EL of 35% in the circumferential direction obtained by the ring tensile test.

Due to the recent needs for weight reduction in automotive industry, the hot stamping became a promising process to replace the classical press forming technology to form complex, high strength components. In the hot stamping process, the mechanical properties and accuracy of the final products are strongly dependent on temperature, cooling rate, time and so on. In this paper, the cooling time was selected as a key process parameter for the stamping of Coupled Torsion Beam Axle (CTBA) part and it was optimized using the finite element analysis which takes the deformation and strengthening induced by the cooling and phase transformation into account. Finally, the developed FE procedure was applied to the optimization of new cooling channel design of CTBA with different gage thickness, but maintaining cooling capacity with already manufactured CTBA as a reference.

It is advantageous for industrial pipes to have small bending radii because of several advantages such as smaller space and less costs. However, the mechanical properties of such bent pipes often deteriorate, especially at the outer sections, due to the smaller thickness; in general, the properties worsen as the pipe bending radii decrease. Therefore, it is important to investigate the mechanical properties of bent pipes having smaller radii than is conventional. In this study, to verify the applicability of such bent pipes with small bending radii, the fatigue properties for a small radius of curvature from 1.5–2.0 diameter ratio (DR) have been investigated. Our pipe material was low carbon steel (SA106Gr-B) having the chemical compositions of 0.3C, 0.29Mn, 0.4Cr, and 0.4Cu (mass%). The high cycle fatigue, microstructure, hardness, and residual stress of two bent sections — extrados and intrados regions — were compared with those of the raw material section. Low carbon steel pipes have better fatigue characteristics at the bent section than at the raw material section. The improvements in the fatigue strength of specimen resulted from grain refinement and phase transformation, while compressive residual stress at surface of bent pipe remained by thermo-mechanical processing can give better fatigue properties in fields.

Manufacturing of thin tube with a large diameter could be a target of tube spinning. This kind of tube could be used as a casting mould for optical films and laminate films which protect IC cards. In the present research, a new machine has been developed in order to manufacture stainless steel tubes with a thin thickness of 0.2 mm and a very large diameter of 500 mm. Deformation in tube spinning for a small diameter of 30 mm was examined using a conventional spinning machine for thin tubes with small diameters. The examined characteristics of deformation include effect of initial thickness deviation and indentation on dimensional precision of formed tubes. Based on the examination in the conventional machine, a new tube-spinning machine was designed and the spinning conditions were determined, and the machine has successfully deformed parent tubes into thin tubes with a large diameter.

Dieless tube drawing is one of the advanced material forming technologies to reduce cross section area of a tube with the absence of dies, mandrel and lubricant. However, this promising technique has technological challenges to improve dimensional stability and accuracy. Machine vision based on image processing technique was selected to monitor deformation behavior on dieless drawing process. The present paper describes real-time monitoring using image processing approach in order to achieve real-time process control of dimensional profile and temperature distribution during dieless drawing process. The results show that machine vision is effective and efficient to monitor dieless drawing process.

The author is studying side compressive processing to compress two sides of a cross-sectional circular tube by dies during bending in order to suppress flatness. In the present research, the experiments were performed by changing the initial thickness of a 5056 aluminum tube with a diameter of 27.2 mm from 2.0 to 3.2 mm. The bending radius R₀ is equal to 3 times the diameter d₀. The experimental results clarified that it is possible to suppress the flatness ratio to 1.6% when the side-compressive displacement is set as δ_c = 1.0 mm. Higher circularity is obtained by side compression with this method. In addition, the forming limit is clarified in terms of side compressive displacement and initial tube thickness.

Aluminum alloy sections are widely utilized in many applications such as in general structures and automotive components. Owing to the increasing complexity of these components there is an increasing demand for highly curved thin wall sections. Therefore, reliable bending processes are required to manufacture such components without undesirable deformations such as wrinkling and folding occurring during bending. To prevent undesirable deformations and predict when they might occur, it is necessary to generate much data from various forming configurations in which process parameters are varied. In this paper, the authors concentrate on the problem of bending square-section thin-walled tubes and use finite element analysis to generate the data required to predict working limits. Two different tube materials (A6063S-O and A6063S-T5) were used to investigate the relationship between deformation behavior and material properties. Moreover, the effect of using a wiper die on the working limit of the extruded aluminum sections was investigated.

Large-size of Zr₅₅Cu₃₀Al₁₀Ni₅ glassy alloy composites (GACs) containing TiNb particles were fabricated by spark plasma sintering (SPS) process. Large plasticity and high strength were obtained due to addition of TiNb particles. Two kinds of TiNb particles with different particle size were introduced into glassy matrix. The GACs samples reinforced by smaller particles showed higher strength and larger plasticity. The GACs with the addition of TiNb particles exhibit similar thermal properties in comparison with the glassy matrix alloy. No other crystalline phase besides TiNb was detected in the composites and good bonding state between TiNb and glassy matrix was observed.

Fe-intermetallic compounds are commonly detrimental for mechanical properties and formability of aluminum alloys. In this study, the refinement of Fe-intermetallic compounds and mechanical properties in high Fe-containing Al–Mg–Si alloys were studied by caliber rolling. The Al–(2.2–2.3) mass%Si–0.9 mass%Mg–(1, 1.5 and 2) mass%Fe alloys were severely deformed by the multi-pass caliber rolling at 573 and 723 K. Fe-intermetallic compounds were finely fragmented with the smallest size of around 200 nm. The morphologies of fragmented Fe compounds in the Al matrix depend on the as-cast microstructure and deformation behavior with better distribution in the outer area than in the center area. Good ultimate strength of 345–360 MPa and high elongation of 15–25% were achieved after 95% caliber rolling.

A Cu–3.0 mass%Co alloy was heat-treated by a method named “short-cut aging”. Incoherent fcc Co precipitates of about 200 nm in size formed in an fcc Cu matrix were observed with conventional and ultra-high-voltage transmission electron microscopes. Although the Co precipitates had shapes similar to a regular octahedron composed of {111} of the Cu matrix, small deviations from the regular octahedron were found. Most Co/Cu interfaces deviated from {111} of Cu and the average deviation angle δ was about 7 deg. Dislocations in the Cu matrix intersecting the Co precipitates were observed for those having deviated interfaces. Deviations of the orientation relationship from an exact cube-on-cube relationship were also found. Although the deviation angle θ of the orientation relationship was much smaller than δ, there was a linear relationship between θ and δ. The morphological and crystallographic characteristics of the octahedral Co precipitates are discussed by considering dislocations in the Cu matrix intersecting the Co precipitates.

The combination of the 10M martensite plate variants in Ni–Mn–Ga ferromagnetic shape memory alloy was investigated by conventional transmission electron microscopy (CTEM) and electron diffraction experiments. There were four plate variants commonly designated as A, B, C and D, and three fundamental plate combinations can be identified in a given plate group, namely A : B (C : D) of <\\bar{5}\\bar{5}1> Type II, A : C (B : D) of {1\\bar{2}\\bar{5}} Type I and A : D (B : C) of {105} compound twins in the martensites. The boundary structure of these twins was also observed in the edge-on state by high resolution electron microscopy (HREM). The boundary of the Type I and the compound twins was not sharp in comparison to that in other shape memory alloys. There were neither ledge nor step structures at the irrational boundary in the Type II twin.

The effect of pre-existing dislocations and interstitial carbon on the initiation of plastic deformation in interstitial free (IF) steel and ultra low carbon (ULC) steel were investigated by the nanoindentation technique. The critical load, P_c, of the pop-in phenomenon, which corresponds to plasticity initiation, appeared clearly on the loading curve. The P_c in high dislocation density materials was smaller than that in low dislocation density materials with no difference between IF and ULC while the P_c in low dislocation density materials was remarkably higher in ULC than in IF. These results indicate that the interstitial carbon in the matrix does not affect the pop-in phenomenon when there are pre-existing dislocations or dislocation sources, and we discuss the reason for their occurrence occurs in high dislocation density materials.

Irregular alumina (IAl₂O₃) is widely used in the procedure of sandblasting with large grit and acid-etching (SLA) which has been confirmed as a favorable surface treatment for implant to improve osseointegration. However, IAl₂O₃ with cytotoxic has been found residual on implant surfaces after modification and thought to be a potential threaten to implants’ long-term survival. Due to its similar shape and excellent biocompatibility, irregular zirconia (IZrO₂) was used as sandblast particle in the present study to compare the different characteristic between IZrO₂SLA and IAl₂O₃SLA surfaces. SEM, optical profilometry and XRF analysis were performed for comparison of surface characteristic. Combined with acid-etching, IZrO₂ could generate suitable primary and secondary roughness with, respectively, 10–30 µm pits and 1–3 µm micro pits. Three-dimensional roughness parameters (S_a, S_z, S_dr and S_ds) revealed that because of the lower Vickers hardness and higher Specific gravity of IZrO₂, IZrO₂SLA surface was less rough than IAl₂O₃SLA surface. Meanwhile, resulted from its different physical properties, IZrO₂ (0.13 ± 0.07%) was detected significantly less on IZrO₂SLA surface than IAl₂O₃ (6.74 ± 0.74%) on IAl₂O₃SLA surface. Therefore, IZrO₂SLA could easily prepare titanium surface with suitable multi-level morphology and moderate roughness for osseointegration. Furthermore, fewer sandblast particles residual on IZrO₂SLA surface, worries from harmful residue could be greatly reduced due to the biocompatibility of IZrO₂.

As an extension of our previous work to develop a high corrosion resistant alloy for coating applications, a fundamental study of high temperature corrosion behavior of spark plasma sintered CoNiCrAlY alloys with varying Si content as 0, 10, 20 and 30% by mass has been performed. The high temperature corrosion tests were carried out in the liquid phase (melted salt) of Na₂SO₄–NaCl at elevated temperatures of 923 and 1073 K for up to 720 ks and at 1273 K for 72 ks. Our results demonstrate that the CoNiCrAlY alloy suffers from internal corrosion attack at these temperatures. On the other hand, the addition of 30 mass% Si leads to beneficial effects not only in the suppression of the formation of internal corrosion products, but also in reducing the growth of external oxide layer. In this paper, the high temperature corrosion behavior of CoNiCrAlY–Si alloys and the influences of Si addition on the corrosion resistance are intensely discussed.

The wettability of Sn–9mass%Zn and Sn–3mass%Ag–0.5mass%Cu eutectic alloys and the new lead-free alloys Sn–17mass%Bi–0.5mass%Cu and Sn–30mass%Bi–0.5mass%Cu on a Cu substrate has been investigated by the sessile drop method in Ar atmosphere as a function of time and temperature. The wetting time for Sn–Bi–Cu alloys is much longer than that for Sn–3mass%Ag–0.5mass%Cu eutectic alloy at their liquidus or eutectic temperature. However, the Sn–9mass%Zn alloy has poor wettability on a Cu substrate since Zn may be oxidized to ZnO, resulting in ZnO covering the surface of the droplet. The contact angles of the ternary alloys on a Cu substrate do not decrease monotonically with increasing temperature but do change with time. The wettability on a Cu substrate increases in the order Sn–9mass%Zn, Sn–3mass%Ag–0.5mass%Cu, Sn–17mass%Bi–0.5mass%Cu, Sn–30mass%Bi–0.5mass%Cu, as indicated by their contact angles of 115.8, 49.6, 37.6 and 27.1°, respectively, at 523 K. The addition of Bi clearly greatly improves the wettability of the alloys.

Al-doped Mg_0.5(1+x)Al_xTi_2−x(PO₄)₃ has been prepared by a sol–gel method and the conductivity has been evaluated by an ac impedance method to determine the optimum lattice volume for Mg-ion conduction. Instead of using Ti in the samples, 10–15 mol%Al was used, resulting in lattice contraction in the c-axis direction. The samples, sintered at 500–800°C for 12 h by a reaction sintering method, had a relative density of 70–80% and their grain size was 2–3 µm. The ionic conductivity calculated from the grain and grain boundary resistance at 600°C was 7.1 × 10⁻⁵ and 1.3 × 10⁻⁵ S/cm, respectively. The activation energy of the grain conductivity was 128 kJ/mol in the temperature range of 300 to 600°C. By comparing ionic conductivity of various-doped titanium phosphates, optimum lattice volume was estimated to be 1.304 nm³.

The microstructure and electrochemical behavior of the Pd_42.5Cu₃₀Ni_7.5P₂₀ as-quenched bulk metallic glass and its crystallized alloys after heat-treatment at 623 and 723 K were investigated. The results revealed that the Pd_42.5Cu₃₀Ni_7.5P₂₀ bulk metallic glass and its crystallized alloys were spontaneously passivated in 0.144 M NaCl and Hanks’ solution with a low passive current density and a wide passive region. The transpassive potential of the fully crystallized alloy heat-treated at a higher temperature was lower than those of the as-quenched bulk metallic glass and partially crystallized alloy. The difference in the microstructure of the as-quenched bulk metallic glass, the partially crystallized alloy and the fully crystallized alloy was responsible for their different transpassive potentials. The wider passive region of the alloys in Hanks’ solution is attributed to the presence of HCO₃⁻, HPO₄²⁻, SO₄²⁻ and H₂PO₄⁻ ions in the solution, which act as corrosive inhibitors.

Electrical conductivity (σ) enhancement, control, aging stability, and linear relation between σ and reciprocal temperature (1/T) in PTFE (Teflon) had been examined by homogeneous low potential electron beam irradiation (HLEBI). Irradiations up to 0.432 MGy were found to raise the σ of PTFE more than two orders of magnitude. In addition, control of electron movement or Fermi level by HLEBI on polymers seems possible since at low HLEBI levels up to 0.216 MGy, a strong dependence on σ was observed. Aging stability investigation showed the saturated conductivities at 10⁶ s (σ_s) (2.5 × 10⁻¹⁶ and 3.6 × 10⁻¹⁵ S m⁻¹) obtained at EB doses of 0.0432 and 0.432 MGy, respectively were approximately 4.9 and 70.6 times higher than σ of untreated PTFE (5.1 × 10⁻¹⁷ S m⁻¹). Although the aging initially reduced the σ of irradiated samples, σ_s were remarkably higher than the untreated. For example, the lower dose 0.0432 MGy samples decayed significantly, but its σ_s value (2.5 × 10⁻¹⁶ S m⁻¹) was still about 490% above untreated condition at 5.1 × 10⁻¹⁷ S m⁻¹. ESR (electron spin resonance) measurements showed aging for 10⁶ s only slightly reduced the peak intensity of irradiated PTFE. This indicated the charge carriers generated did not easily decay. Results agree with the literature where PTFE was irradiated with VUV and radicals such as CF₃⁺ did not substantially decay with aging. Since the slopes of linear relationships between logarithmic electrical conductivity (ln σ) and reciprocal temperature (1/T) of all PTFE samples irradiated were approximately equal to that before treatment from 303 to 375 K, HLEBI didn’t convert the σ system. The small irradiation dose of 0.0432 MGy raised the electrical conductivity at room temperature. At higher temperatures above ∼375 K, the 0.0432 and 0.432 MGy-HLEBI generated drops in conductivity σ. When unstable dangling bonds with isolated radicals at terminated sites are assumed to be formed in irradiated PTFE, the σ recovery by heating to 424 K as well as high σ of irradiated PTFE could be explained. HLEBI probably generated dangling bonds in the form of radicals acting as acceptors to carry charge. Since a chemical dopant was not needed to act as a charge carrier, HLEBI could probably be an attractive method to attain homogeneous doping of organic films.

In order to obtain a high reflecting coating for the LED lead frame, Sn displacement deposition was done and the reflection characteristics of displacement deposited Sn was investigated. The Sn coating on the lead frame is expected to result in fine solderability and reduction of the cost relative to Ag coating. Before Sn displacement deposition, Cu electro deposition was carried out to offer a fresh and bright Cu layer (Electroplated Cu, ED Cu) to Sn displacement deposition. With immersion time from 2–4 min, Sn layer was deposited on ED Cu in the bath of Sn displacement deposition. As a result, optical density of Sn layer was more than 0.8 and the reflectance of that was around 90% at the immersion time 2–3.5 min, indicating the Sn layer had excellent reflection characteristics compared with Ag. It is also confirmed that lower roughness, smaller grain size and fewer whiskers resulted in higher reflectance of Sn layer, indicating good reflection characteristics for LED lead frame.

Lap joining of crystalline pure aluminum and metallic glass (Zr₄₈Cu₃₆Al₈Ag₈ and Cu₅₀Zr_42.5Al_7.5) was carried out by using magnetic pulse welding. Transmission electron microscopy was performed for the welding interface in order to investigate microstructure of the intermediate layer produced at the welding interface. The welding interface exhibited characteristic wavy morphology as well as similar- and dissimilar-metal joints. The intermediate layer was produced along the wavy interface. TEM observation and electron diffraction pattern analysis revealed that the intermediate layer was not monolithic but had a multi-phase structure. A part of the layer consisted of the extremely fine grains and amorphous phase particles. The other part of the layer was composed of the stacked extremely thin amorphous layers. STEM-EDS analysis found that the chemical composition of the amorphous phase in the intermediate layer was not constant and was different from that of the metallic glass matrix.

Coronary stent has been popular method for the treat of coronary artery stenosis while stent fracture has been observed sometimes after implantation. Tensile fatigue behavior of stent plays an important role and the effective analysis method of stent properties is needed. In addition, from the data of patients we know that the stent always appears to have an elliptical shape in the vessels and it may affect the performance of stent. In this study, the tensile fatigue performance of one stent was analyzed by the finite element simulation method. An effective simulation process was performed to analyze the tensile fatigue behavior under different maximum strain and the effect of diameter of stent was considered. An equivalent stress (SEQA) was applied in evaluation and the results showed different results by comparing with Mises stress. A Goodman fatigue analysis was performed using the equivalent stress and fracture was predicted. Also, the effect of elliptical shape was analyzed and it showed no significant difference of SEQA between the circle and elliptical model on tensile fatigue performance.

A single-structured torque sensor using a magnetostrictive ring attached to the steering shaft of the steering-by-wire system of an automobile was developed. An (Fe_0.80Ga_0.15Al_0.05)₉₉Zr_0.5C_0.5 alloy, which exhibited the large magnetostriction of 134 ppm and the strong tensile stress of over 800 MPa, was used for the magnetostrictive torque ring. However, the sensitivity of the torque ring sensor was 0.12 × 10⁻⁴ T N⁻¹ m⁻¹, which is smaller than the 0.8 × 10⁻⁴ T N⁻¹ m⁻¹ needed for a steering-by-wire system. The ring was therefore heat-treated at 743 K under a compressed stress of 100 MPa via the spark plasma sintering method to increase the sensitivity of torque. As a result, the sensitivity of the torque ring sensor increased to 0.72 × 10⁻⁴ T N⁻¹ m⁻¹ although depending on the residual magnetic flux density.

In this study, glass substrate was re-used from old TFT-LCD, and characteristics of the re-used glass substrate were investigated. For the characterization, ITO layer was separated from the glass substrate by decomposing the color filter layer which is located between ITO layer and glass substrate using color filter stripping solutions. Surface roughness and optical transmittance of the glass substrate after removal of ITO and color filter layer were measured, and they were compared with those of newly produced one. As a result, surface roughness of re-used glass substrate between the two samples was rarely different. As well, difference in optical transmittance between the two samples was rarely different attributed to the surface roughness. Therefore, glass substrate was clearly re-used from old TFT-LCD panel. For more investigation, new ITO layers were coated onto the two glass substrates using ITO ink, respectively. After coating, electrical resistance and optical transmittance was investigated to observe effect of the roughness on the characteristics.

To clarify the high temperature electrochemical properties of Y-doped CaZrO₃, the electrical conductivity of the poly-crystalline specimen was measured for various kinds of hydrogen and oxygen-containing atmospheres by employing the two-terminal AC method. The H/D isotope effect of the electrical conductivity was examined in detail in order to specify the conditions in which the proton conduction was dominant. In the temperature range from 973 to 1273 K, it was found that protons are the dominant charge carrier both in hydrogen-rich and oxygen-rich atmospheres. At higher temperatures of 1373 to 1673 K, the dominant charge carrier is estimated to be the positive hole in oxygen-rich atmospheres, whereas to be the oxide ion vacancy in hydrogen-rich atmospheres by the analysis of the atmospheric dependence of the electrical conductivity. These results were almost the same as those of Al-doped CaZrO₃ which were reported previously by the present authors.

The human jaw is a unique bone that facilitates mastication. The structural properties of the jaw are determined by mechanical stresses transmitted via the teeth. However, it is very difficult to evaluate the impact of these mechanical stresses on bone. In recent years, it has become clear that the orientation of biological apatite (BAp) crystals is closely related to local stress, and is thought to respond more acutely to local stress than bone mineral density (BMD). Few studies have been conducted on BAp crystal alignment in response to mechanical stress in the human jaw, which has a complex masticatory function. The purpose of this study was to quantitatively evaluate BMD and BAp crystal orientation using micro-computed tomography (micro-CT) and microbeam X-ray diffractometry in the anterior cortical bone of human mandible. The intensity and direction of mechanical stresses in both the alveolar area and mandibular base were compared.
The mandibular central incisor region in Japanese bone samples was designated as the region of interest and BMD and BAp crystal orientation in the alveolar area and mandibular base measured. Bone samples were imaged by micro-CT and the data obtained converted into BMD values. BAp crystal orientation was determined by both reflection- and transmission-based microbeam X-ray diffractometry. The diffraction intensity ratio was calculated using X-ray diffraction peaks of (002) and (310).
The results showed no difference in BMD values among regions. BAp crystals were oriented predominantly in the mesiodistal direction in the mandibular base and along the direction of masticatory force in the alveolar area. These findings suggest that the mandibular base exhibits long bone-like characteristics, with the mandibular condyle acting as the head of the bone, while in the alveolar area alignment takes place in the direction of masticatory force resulting from mechanical stress exerted via the teeth. Qualitative evaluation revealed clear differences between the mandibular base and alveolar area, suggesting that BAp crystal orientation offers a more precise indicator of bone quality than BMD.

The Sukpo Zinc Refinery of Young Poong Cooperation (YPC) has recovered zinc and lead from zinc residue by using top submerged lance (TSL) technology since 2007. This recycling operation, named the “TSL Plant”, was designed to operate 2 furnaces each equipped with one top submerged lance. The operation performance shows good metal recoveries. The plant is currently measuring oxygen pressure in its slag bath to respond to the varying slag bath conditions instantly. This paper describes the behaviors of lead and zinc acquired by determining the oxygen pressure in the slag bath and the results of measurements are compared with those of the thermodynamic calculations.

The secondary solidification phase of icosahedral (I-) phase in rolled Mg–Zn–Y alloy is replaced with I + Ca₂Mg₆Zn₃ phases by addition of Ca. Addition of Ca in Mg–Zn–Y alloy significantly accelerates dynamic and static recrystallization resulting in much fine grain size and more random texture. EBSD analysis indicates that the presence of Ca in the α-Mg solid solution matrix may play a role in weakening of basal texture rather than particle stimulation nucleation effect by the second solidification phases.

The workability and ductility of Al–Zn–Mg alloy are lower. In this study, the Zn content (4.44–6.34 mass%) was reduced and the Mg content (1.11–1.28 mass%) was raised to investigate the relationship between microstructures and tensile mechanical properties of Al–xZn–yMg aluminum alloys after friction stir process (FSP). The ZM35 alloy (Zn/Mg ratio is 3.5) and the ZM57 alloy (Zn/Mg ratio is 5.7) had a friction stir process and then three artificial aging treatments were performed to discuss the effects of Zn/Mg ratio on mechanical properties. After FSP and then natural aging for 12 days, the results of the experiment showed that the tensile strengths of ZM35 and ZM57 alloys were lower than the base metal (extruded material with T6, no FSP). Notably, the strength of as-FSP specimens was promoted after aging treatments. Through the mode I (80°C/16 h) treatments and the mode II (80°C/16 h + T6) treatment, the strengths of ZM35 alloy and ZM57 alloy were improved. However, after the mode III (T4 + 80°C/16 h + T6) treatment, the tensile strength and ductility of the ZM57 alloy reduced, and the deterioration rate of ductility reached to 65%; the ZM35 alloy possessed a better ductility, which confirmed the fact that decreasing Zn/Mg ratio improved the workability of friction stir Al–Zn–Mg specimens with an artificial aging treatments.

Three types of shot peening treatments were applied to S30432 stainless steel. The effect of shot peening intensity and shot peening method on the residual stress and microstructure has been investigated. The domain size and micro-strain evolutions in near surface layer were characterized systematically via Voigt method. The results reveal that shot peening could induce compressive residual stress in the deformed layer for all shot peening conditions. As the shot peening step and intensity increase, the compressive residual stresses increase in near surface layer, and decease faster in deeper deformed layer. In the deformed layer, the domain size increases, while the micro-strain decreases with the depth increasing. Comparing with the micro-hardness after shot peening, it is concluded that increasing the shot peening step is a considerable way to improve the shot peening effect.

Dynamic phase transformation during subtransus forging was investigated in a powder metallurgy (PM) Ti–1.5Fe–2.25Mo alloy. The results show that compressive deformation restrains the hcp (α)→bcc (β) phase transformation, and induces a local martensitic transformation in the deformed sample during subsequent cooling. Thermodynamic analysis confirms the feasibility of these transformations.

This study evaluated the microstructure and enhancement of the mechanical properties of a cross-roll rolled Ni–10Cr alloy, as compared to a conventionally rolled material. A thickness reduction of 90% was achieved by cold rolling the alloy, which was subsequently annealed at 700°C for 30 min to obtain the fully recrystallized microstructure. In particular, cross roll rolling (CRR) was carried out with a roll mill tilted at a 5° from the transverse direction in the RD–TD plane. After rolling, the electron back-scattering diffraction technique was introduced to investigate the grain boundary characteristic distributions of annealed materials. There was notable grain refinement in the Ni–10Cr alloy as a result of cross roll rolling. Consequently, the average grain size was refined from 135 µm in the initial material to 4.2 µm in the cross-roll rolled material. This refined grain size led to enhanced mechanical properties, such as yield and tensile strengths. Furthermore, the < 111 > // ND texture in the CRR material was better developed than that in the conventionally rolled material, contributing to enhancement of the mechanical properties and formability.

A hybrid welding of high power fiber laser and pulsed metal inert gas (MIG) arc was applied to titanium plate with 6 mm in thickness, and the optimum welding condition to make fully penetrated weld bead as well as the metallurgical and mechanical properties of the welded joint were evaluated. It is found that sound one pass fully penetrated square-groove butt joints without any weld defect can be made by optimizing the welding conditions mainly welding speed, arc current, laser power and laser focus position. The hardness and tensile tests indicate that heat affected zone and weld metal are stronger than base metal. It is considered that the strengthening is attributed to the increment of chemical compositions and substructures.

The present study was carried out to evaluate the microstructural and mechanical properties of a friction stir welded 2.25Cr–1Mo steel. For this work, friction stir welding (FSW) was performed at a tool rotation speed of 300 and 700 rpm and a traveling speed was fixed at 40 mm/min. Phase transformation of the microstructure in the joint was investigated by optical microscopy and scanning electron microscopy. Vickers hardness and tensile test were used to evaluate the mechanical properties of the joints. In the Stir Zone (SZ), fine martensite was observed, indicating that phase transformation and dynamic recrystallization occurred during FSW. The microhardness of the SZ was higher than that of the base metal (BM) due to the phase transformation. After the tensile test, the FSW joint was fractured in the BM region and showed the same yield strength (YS) and ultimate tensile strength (UTS) as that of the BM.

A new class of bulk nanocrystalline nickel dispersed with nano-scale WO₃ particles has been synthesized by conventional electrodeposition. It was found that WO₃ particles of an initial size of 0.1 µm, when suspended in an electrolyte, fragmented into smaller nano-scale particles during deposition accompanied by phase transition from an initial monoclinic to tetragonal structure. The cause and effect relation between the fragmentation and the phase transition of WO₃ particles was discussed. Hopefully, the phenomenon can be applied to establish a novel synthesis for a new class of bulk nanocrystalline metals with dispersed nano-scale particles endowed with higher strength and thermal stability than conventional mono-phase nanocrystalline materials.