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An in-situ analysis of local strain accommodation on transformation induced plasticity (TRIP) aided multi-phase steel was performed with a correlative application of characterization techniques such as digital image correlation (DIC), electron backscatter diffraction (EBSD), and micro-mechanical testing. The local strain on the complex microstructure of the multi-phase steel was measured during a tensile test using an innovative DIC method (which does not employ artificial patterns), in conjunction with a scanning electron microscope. The constituent phases of the examined surface were identified by postprocessing implemented on the EBSD maps. This was further verified by nano-indentation, consequently enabling systematic and quantitative analyses of the strain partitioning between the phases. Soft acicular ferrite accommodated the largest strain with sites of intense strain localization around the hard, neighboring martensite. The retained austenite transformed gradually into martensite because of the applied strain and caused strain localization in the neighboring acicular ferrite. This verified that DIC method proposed in this study enables precise and effective data collection at the interfaces between different phases that could have certainly been blocked by the DIC patterns in the conventional method.

The cornerstone of materials design is solving materials-related optimization problems to obtain microstructural or processing variables that lead to the most desirable material properties. Because the objective of materials design is to maximize their performance, the related optimization problems often require a global solution. This type of unconstrained optimization overlooks the feasibility of the solution, which is a key engineering issue. For any practical application, feasibility should be reflected in the constraints included in the optimization problems. Nevertheless, the constraints related to feasibility are considerably complex due to the high dimensionality of the design space and non-physical aspects of the constraints, such as machine specifications, material dimensions, and available initial microstructure. In this work, we propose the use of a simple support vector machine (SVM) trained with information in an existing database to model complex feasibility constraints for material optimization. We present a problem involving optimization of the initial texture of a body-centered cubic (BCC) polycrystalline material to obtain specific target textures after cold-rolling. Both unconstrained and constrained optimizations are conducted for comparison, and the results demonstrate that constrained optimizations yield viable solutions while unconstrained optimizations do not.

At 700 °C and 200 MPa, the creep rupture time of W-containing alumina-forming austenitic heat-resistant (WAFA) steel increases from 1044 to 3119 h by pre-strain. Pre-strain introduces a lot of dislocation into the matrix and most of the dislocations remain stable to the end of creep without recovery and recrystallization. In addition, the dislocations have enabled secondary NbC and Laves phase to be uniformly distributed and refined. However, the dislocations lower grain boundary strength due to the coarsening of precipitates along grain boundaries Therefore, the increase in the creep rupture time in spite of deterioration of grain boundary strength is attributed to the dislocation strengthening and enhanced precipitation hardening within grains.

The hot workability of two cold-work tool steels were evaluated and compared. A D2 and an advanced alloy based on 8% Cr steels (TDx) were deformed at high temperatures between 900 and 1100 °C with strain rates 0.001–10 s− 1 via hot compression test. From the flow curves, processing maps were constructed based on the dynamic material model. The deformed microstructures were observed and compared in various scales with respect to the deformation conditions. Although the two alloys exhibited a large similarity in the flow instability consideration of the processing map, their behavior in microstructure evolution was different. While both alloys exhibited a tendency of strain localization in the conditions of instability, the efficiency of power dissipation in the processing maps showed an intricate correlation with the progress of dynamic recrystallization and carbide precipitation. TDx showed a distinctive behavior of carbide precipitation and a larger resistance to dynamic recrystallization, which implied a requirement on more delicate control of hot working conditions.

The aging behavior and orientation relationships in Fe–31.4Mn–11.4Al–0.89C low-density steel were investigated with respect to constituent phases and precipitates, including γ-austenite matrix, β-Mn, and α-precipitate. After aging treatment at 550 °C for various periods of time, the microstructural changes and corresponding mechanical response were characterized by Vickers hardness measurement combined with EBSD and TEM observations. The precipitation sequence during the aging treatment showed that nano-sized κ-carbides firstly precipitated within the γ-austenite matrix at the incipient stage of aging, and induced the primary age hardening. After aging for 300 min, the lath-type β-Mn phase was formed, leading to the dramatic secondary hardening response. The α-precipitates with partial D0 3 order were subsequently produced at the β-Mn interior, grain/phase boundary region, and the γ-austenite interior after further aging over 10,000 min. The misorientation-angle distribution, Rodrigues–Frank vector space, and orientation relationship stereogram (OR stereogram) from EBSD measurements were employed for analyzing γ-matrix/β-Mn and β-Mn/α-precipitate interphase boundaries, respectively. The OR stereograms showed that the preferred orientation relationships were represented as ( 111 ) γ / / ( 221 ) β − M n , ( 01 1 ¯ ) γ / / ( 01 2 ¯ ) β − M n , ( 2 ¯ 11 ) γ / / ( 5 ¯ 42 ) β − M n for γ-matrix/β-Mn interface, and ( 012 ) β − M n / / ( 001 ) α , ( 02 1 ¯ ) β − M n / / ( 010 ) α , ( 100 ) β − M n / / ( 100 ) α for β-Mn/α-precipitate interface, respectively. The orientation relationships obtained from the OR stereograms were clarified by checking the deviation angle distributions of interface segments from the ideal orientation relationships, as well as the TEM diffraction patterns at the interface boundaries. In addition, the misorientation distribution between γ-matrix and α-precipitate was examined and compared to conventional fcc/bcc orientation relationships.

We investigated the effect of W addition on the creep and precipitation behavior of alumina-forming austenitic (AFA) heat-resistant steels at 700 °C and 160 MPa. Our results showed that the creep rupture time of the W containing AFA (WAFA) increased more than that of the AFA due to enhanced precipitation hardening of Laves phase and suppression of sigma phase formation. W increased the volume fraction of Laves phase and enhanced precipitation hardening by higher driving force for the precipitation and affinity of the Laves phase. Therefore most W were consumed for the precipitation of the Laves phase, however Mo content contributed to the precipitation of M 23 C 6 as well as precipitation of Laves phase due to the lower affinity of Laves phase. The M 23 C 6 in AFA contained enough Mo to form the sigma phase, which served as an initiation site for cavitation and crack propagation. The sigma phase grew and coarsened at the expense of M 23 C 6 and Mo-rich Laves phase to match the stoichiometric composition of the sigma phase, and finally creep strength of AFA was greatly reduced.

In this work, high-cycle fatigue property of high nitrogen steels which have different deformation modes was explored. The samples, Fe-18Cr-10Mn-0.4N (0.4N) and Fe-18Cr-10Mn-0.6N (0.6N), were fabricated under different nitrogen partial pressures in order to obtain the different deformation modes by controlling stacking fault energy: Deformation-Induced Martensite Transformation (DIMT) in 0.4N and deformation twins in 0.6N. Owing to solid solution strengthening of nitrogen, the fatigue limit of 0.6N is higher than that of 0.4N. However, a ratio of the fatigue limit to the yield strength of 0.6N is lower than that of 0.4N. This result is ascribed to the different influence of the deformation modes on fatigue damages. The DIMT formed in 0.4N could restrict the path of moving dislocations, and thus the fatigue property was relatively improved with the decrease of the fatigue damages by the DIMT. The deformation twins, on the other hand, were not clearly activated during fatigue of 0.6N, and therefore did not affect the fatigue damages.

Mechanically induced martensitic transformation (MIMT) and consequent plastic flow behavior with respect to austenitic texture were investigated in a lean duplex stainless steel. Different grain sizes and textures with fixed phase fractions were obtained via varying the thermomechanical processes. Nearly random distribution of austenitic orientation exhibited a distinguished flow curve from the others with a major D {4 4 11}〈11 11 8〉 component due to more gradual enhancement of hardening by less martensitic transformation. In order to compare the susceptibility to the transformation with respect to individual austenitic orientations and the experimental textures, interaction energy between the imposed stress and transformation strain was calculated by a classical transformation and a crystal plasticity model. The results indicated that a larger stress imposed on the D component led to higher interaction energy and a steeper progress of MIMT observed in the textured materials.

The deformation behavior of alumina-forming austenitic heat-resistant steels at high temperatures was studied to elucidate their hot workability using two types of alloys, i.e. AFA and MAFA. Uniaxial compression tests were performed between the temperature range of 800–1100 °C with strain rates of 0.005–5.0 s− 1. From the constitutive relationship between flow stress, temperature and strain rate, the activation energies for hot deformation were estimated. Both of the investigated alloys exhibited higher activation energies (AFA: 618.8 and MAFA: 711.1 kJ/mol) than other conventional alloys under similar conditions. Processing maps based on dynamic material model and microstructures after the tests indicated that the hot working of both alloys became more efficient and stable with increasing temperature and decreasing strain rate, which was attributed to more active operation of restoration processes such as dynamic recovery and recrystallization. In both alloys, secondary NbCs were precipitated during the test. Due to their pinning effect on dislocations, grain and sub-grain boundaries, the progress of restoration processes was hindered, which contributed to their high activation energy. In spite of the common types of restoration processes, MAFA with increased Nb and C content exhibited degraded hot workability due to more extensive precipitation of NbC.

The precipitation behavior and creep properties of lower phosphorus (P) alumina-forming austenitic (AFA LP ) heat-resistant steel were investigated and compared to those of AFA. The creep rupture time and hardness of the investigated steels were improved with the decrease of the P content. The TEM and EELS analyses confirmed an enhanced P concentration in the M 23 C 6 precipitates along the grain boundaries. The P promoted the precipitation of M 23 C 6 and also suppressed the precipitation of secondary NbC in the earlier stage of aging. The creep rupture time of AFA became shorter compared to AFA LP due to the reduction in the fraction of secondary NbC which acts as a dominant strengthening phase during creep. The suppression of secondary NbC precipitation by P increased the Nb content in the austenite matrix and accelerated the precipitation of the Laves phase in the intermediate stage. However, the difference in Vickers hardness caused by Laves phase was not large in both alloys because the volume fraction of Laves phase strongly depended on the nominal content of Mo rather than Nb. The Vickers hardness at the earlier stage is determined by the precipitation of secondary NbC and the difference of the hardness maintained at the final stage. Thus, it is found that P degrades the creep rupture time and P is a detrimental element in terms of creep and precipitation hardening in AFA steels.

The β-Mn formation behavior of high-Mn low-density steels was investigated in terms of the morphological characteristics and alloying element distribution after aging treatments. A dramatic difference in the formation kinetics and morphology of β-Mn was observed depending on the addition of Al, which may increase the driving force for β-Mn formation. In addition, the effects of the aging process on the fracture behavior were examined in uniaxial tensile tests combined with microstructural observations. A severe loss of ductility resulted from the β-Mn formation and ordering of ferrite into the D03 phase, which was transformed before the β-Mn formation process.

The feasibility controlling the morphology of retained austenite in TRIP steel was investigated utilizing double bainitic transformation which is two-step isothermal heat treatment. The change in morphology of the retained austenite from a blocky to film type improved the tensile properties owing to higher mechanical stability of film-like retained austenite.

A trace addition of Zr to a multicomponent Al-14Si-3Cu-4.5Ni casting alloy has often been found to form a coarse plate-like Zr-rich intermetallic compound with a size of a few tens of μm at the beginning of solidification. Evaluation of the phase composition has confirmed that the Zr-rich intermetallic phase consists of multicomponent constituent elements, mainly Al, Si, Ni and Fe, and is present in a form of (Al,Si)3(Zr,Ni,Fe). The existence of such a complex (Al,Si)3(Zr,Ni,Fe) phase has not yet been predicted by phase equilibria calculation of the multicomponent Al-14Si-CuNiMg systems. In this paper, transmission electron microscopy studies combined with electron backscattered diffraction pattern analysis reveals the crystallography information of the (Al,Si)3(Zr,Ni,Fe) phase for the first time and identifies it as a modified Al3Zr-D023 crystal (tetragonal, I4/mmm(139)) with slightly changed lattice parameters of a = b = 3.275 A and c = 15.475 A. The primary (Al,Si)3(Zr,Ni,Fe) phase is found to nucleate directly onto AlP particles. The mechanical properties of the Zr-rich intermetallics were also investigated using nanoindentation at both room and elevated temperatures and were compared to those of the Si phase.

The microstructure and the intrinsic mechanical behavior of an austenite-based lightweight steel containing 11.4 wt.% Al under aging heat treatment were investigated with respect to β-Mn precipitation. The solution-treated lightweight steel samples were aged at 550 °C for various periods of time. The β-Mn phase nucleated at both ferrite/austenite phase boundaries and austenite/austenite grain boundaries after aging for 300 min, and grew extensively into the austenite matrix with lath-type morphology by further aging treatment. Lattice expansion of austenite and κ-carbide after β-Mn precipitation was observed by X-ray diffractometry (XRD) peak shift. This result suggested that the β-Mn phase expelled carbon to the austenite matrix during formation of β-Mn, which increased the lattice parameter of the austenite and κ-carbide. The Vickers hardness increased dramatically after an aging time of 1000 min. The singular aging behavior also proceeded from precipitation of the β-Mn phase. The intrinsic mechanical property of austenite phase, which was obtained by nanoindentation, was correlated with the increase and inhomogeneous distribution of carbon in the austenite matrix.

Hot ductility of medium carbon steel containing 0.52 wt% of carbon and 0.11 wt% of vanadium was investigated using a hot tensile test performed up to fracture. The hot ductility was evaluated by measuring the reduction of area of the fractured specimens, which were strained at a variety of test temperatures in a range of 600–1100 °C at a strain rate of 2×10 −3 /s. The hot ductility was excellent in a temperature range of 950–1100 °C, followed by a decrease of the hot ductility below 950 °C. The hot ductility continued to drop as the temperature was lowered to 600 °C. The loss of hot ductility in a temperature range of 800–950 °C, which is above the Ae 3 temperature, was due to V(C,N) precipitation at austenite grain boundaries. The further decline of hot ductility between 700 °C and 750 °C resulted from the transformation of ferrite films decorating austenite grain boundaries. The hot ductility continued to decrease at 650 °C or less, owing to ferrite films and the pearlite matrix, which is harder than ferrite. The pearlite was transformed from austenite due to relatively high carbon content.

High-temperature tensile and creep properties of W-added Alumina-Forming austenitic (AFA W ) heat-resistant steel were investigated as compared with AFA steel without W. High-temperature tensile properties of two steels were similar to each other, but creep lifetime of AFA W steel was increased. Microstructural examination using SEM and TEM revealed that creep rate rapidly decreased when Laves phase initially precipitated. This indicated that the precipitation of Laves phase played an important role in hardening of AFA steel. It is also found that AFA W steel exhibited finer and denser Laves phase compared with AFA steel, which is due to partial substitution of W for Mo. The finer and denser distribution of Laves phase contributed to improved creep properties of AFA W steel by enhancement in precipitation hardening.

The precipitation sequence during ageing of Fe–14Cr–20Ni–0.9Nb–2.5Al based alumina-forming austenitic (AFA) steel was explored through a transmission electron microscopy analysis and a small angle neutron scattering experiment. The samples were aged at 700 °C for up to 504 h. Particles of NbC, M 23 C 6 and Ni 3 Al-type L1 2 were observed in the early stage of ageing. Metastable L1 2 particles were formed both in grain interior and along grain boundary. M 23 C 6 carbides precipitated along grain boundary accompanied with precipitation of L1 2 particles. After ageing for longer than 48 h, particles of B2-NiAl and Laves-Fe 2 Nb were newly formed. We suggest the possibility of phase transition from L1 2 to B2 with increase in ageing time. Finally, this study examined the change of mechanical properties during ageing through a Gleeble hot tension test and a Vickers hardness test, and then the relationship between precipitation behavior and mechanical properties was carefully investigated and discussed in terms of precipitation behavior.

This study aimed to present the complete history of carbide evolution in a cold-work tool steel along its full processing route for fabrication and application. A sequence of processes from cast to final hardening heat treatment was conducted on an 8% Cr-steel to reproduce a typical commercial processing route in a small scale. The carbides found at each process step were then identified by electron diffraction with energy dispersive spectroscopy in a scanning or transmission electron microscope. After solidification, MC, M 7 C 3 and M 2 C carbides were identified and the last one dissolved during hot compression at 1180 °C. In a subsequent annealing at 870 °C followed by slow cooling, M 6 C and M 23 C 6 were added, while they were dissolved in the following austenitization at 1030 °C. After the final tempering at 520 °C, fine M 23 C 6 precipitated again, thus the final microstructure was the tempered martensite with MC, M 7 C 3 and M 23 C 6 carbide. The transient M 2 C and M 6 C originated from the segregation of Mo and finally disappeared due to attenuated segregation and the consequent thermodynamic instability.

The bulky oxide nodule and its underlying structure were investigated in an alumina-forming austenitic steel exposed to dry air at 1053 K for 336 h. Some bulky oxide nodules were found to be attached on globular phases in the matrix. By combined application of electron backscattering diffraction and energy dispersive X-ray spectroscopy, the bulky nodule was identified as Cr-rich M3O4 underlying which was Nb-rich MO2. Thermodynamic calculation suggested that the MO2 was transformed from the primary NbC near surface.

The relationships between the martensitic phase transformation kinetics, texture evolution, and the microstructure development in the parent austenite phase were studied for a 304L stainless steel that exhibits the transformation-induced plasticity effect under biaxial loading conditions at ambient temperature. The applied loading paths included: pure torsion, simultaneous biaxial torsion/tension, simultaneous biaxial torsion/compression, and stepwise loading of tension followed by torsion (i.e., first loading by uniaxial tension and then by pure torsion in sequence). Synchrotron X-ray and electron backscatter diffraction techniques were used to measure the evolution of the phase fractions, textures, and microstructures as a function of the applied strains. The influence of loading character and path on the changes in martensitic phase transformation kinetics is discussed in the context of (1) texture-transformation relationship and the preferred transformation of grains belonging to certain texture components over the others, (2) effects of axial strains on shear band evolutions, and (3) volume changes associated with martensitic transformation.

The effect of Cu addition on the microstructures and the tempering behavior of cold-work tool steels was investigated. 8% Cr steels with varying amount of Cu added from 0.22 to 2.56 wt% were prepared, then hardened by quenching and tempering. The alloys with different Cu contents showed similar fraction and size of M 7 C 3 carbide. Therefore, it could be known that the addition of Cu did not affect the formation of M 7 C 3 carbide which formed at high temperatures where Cu existed as a solute element. While increased Cu content reduced prior austenite grain size, the as-quenched hardness decreased due to increased volume fraction of retained austenite. During tempering at 520 °C, Cu addition generally led to higher hardness due to delayed softening, while after prolonged duration the softening rate was more diminished at the lowest Cu content. It was observed that Cu suppressed the formation of M 23 C 6 precipitate during tempering. Prior formation and coarsening of Cu precipitate could lead to enhanced tempering resistance in the early stages of tempering, whereas after prolonged duration, the effect was diminished due to the insufficient hardening caused by the suppressed precipitation of M 23 C 6 . By balanced co-precipitation of Cu and M 23 C 6 with refined grain size, the hardness and the impact toughness could be optimized at around 1 wt% of Cu addition.

The effect of a Zr addition on the precipitation behavior and mechanical properties in Nb-containing alumina-forming austenitic (AFA) stainless steels was investigated using tensile tests, scanning electron microscopy (SEM), and scanning transmission electron microscopy (STEM) analysis. The TEM observation showed that a Zr addition led to the formation of a (Nb,Zr)(C,N) complex particle, which coarsened the Nb-rich carbonitride. Tensile tests were performed at an elevated temperature (700 °C), and both the tensile and yield strengths decreased with a Zr addition. This unexpected result of a Zr addition was due to the reduction of the precipitation strengthening by particle coarsening.

We made a quantitative comparison of three different methods, optical microscopy by tint etchant, EBSD phase mapping and dilatometry for analysis of phase fraction in steel subjected to intercritical annealing and isothermal treatment. While the results from optical microscopy and EBSD technique showed quantitative agreement, the dilatometry gave rather higher martensite fraction compared to the microscopic analyses. Nevertheless, all three methods showed qualitative agreement in the variation of martensitic fraction depending on the processing conditions. The analyses revealed that the martensitic fraction in final microstructure decreased as intercritical annealing temperature increased because it deteriorated the hardenability of austenite. Raising the isothermal treatment temperature increases the martensite fraction due to the increases of austenite fraction, which transformed into martensite afterward.

Ultrafine cellular microstructures around alumina particles in a low-carbon steel were observed, which survived even after cyclic austenitization. This indicates that their formation is closely related to internal stress because of a structural heterogeneity during phase transformation rather than to externally applied forces or deformation. Thermo-elasto-plastic finite element analysis confirmed the evolution of a large hydrostatic pressure around an alumina particle due to thermal mismatch during cooling. Therefore, the fine cellular microstructure might be generated as a result of the hydrostatic pressure, which retards the phase transformation around the particle during cooling. In addition, we observed microstructural similarity with the same steel processed under an ultra-high pressure, which was the evidence for the role of the delay in the transformation caused by the hydrostatic pressure.

In situ and ex situ neutron diffraction were used to investigate the deformation behavior of high-nitrogen, nickel-free duplex stainless steel. During in situ deformation, both ferrite and austenite deformed plastically to the same degree. The stacking fault energy of austenite was evaluated to be 36.2 mJ m–2 from ex situ neutron profiles, which correlated well with the observed deformation microstructure of twin formation. A significant decrease in the effective particle size of austenite was due to the formation of deformation twins.

An interstitial-free steel was austenitized and cooled in a high-pressure high-temperature apparatus. Despite its inherently negligible hardenability, an interstitial-free steel with a full martensitic structure could be obtained even without quenching. Under atmospheric pressure, the microstructure after austenitization and cooling at an even faster rate consisted of massive ferrite. The thermodynamic stabilization of austenite by high pressure (on the gigapascal scale) led to great retardation of ferrite transformation and resulted in a rare microstructure of martensite in interstitial-free steel.

The effect of Al and Mo addition on the development of microstructures and textures of dual phase steels for the usage in car outer panel was studied. The two elements were separately added to a base alloy to compare their effects on the microstructures and textures along the processing route from hot rolling to annealing. They showed common consequence of grain refinement of hot bands, which resulted in the suppression of deformation heterogeneities during cold rolling, subsequently enhanced the desirable γ-fiber and removed some detrimental minor components in the annealing textures. The effect of Mo was stronger than Al, which could be attributed to the fixation of solute C by Mo.

EBSD mapping was used for phase analysis of multi-phase steels. Some products of austenite decomposition could be discriminated using a range of grain-average functions and properties derived from the map data. In DP steels, martensite could be extracted from the ferrite matrix using the average band contrast or a set of geographic information. Bainite in TRIP steel was identified with the local variations of band contrast and orientation inside a grain. As the proposed method reproduced a phase map, a visual confirmation of the result and additional analyses were possible.

The development of deformation texture and microstructure was examined for four different initial textures. IF steel sheets with a majority of α-, ε-, and γ-fiber and near random texture were prepared and cold rolled. The specimens exhibited characteristic behaviors in rolling texture evolution and deformation-induced misorientation development, according to their initial textures, especially at small strain levels. Due to the orientation dependence of intra-granular misorientation accumulation, the different texture evolutions affected the induced misorientation distribution. A larger fraction of γ-fiber orientations was related to more prominent misorientation development, while the initial texture stability simultaneously affected the misorientation development. The unstable, initial ε-fiber texture showed a stronger tendency of misorientation accumulation than the stable α-fiber during the subsequent cold rolling.

Deformation characteristics of cold rolled grains and their contribution to the development of recrystallization texture in IF steel were investigated using EBSD. Quantitative evaluation of the intra-granular orientation spread in the deformed grains was attempted. Both of the GAM and SGS could represent the orientation spread but in different manner. The GAM value was higher in {111}//ND orientations than in other orientation groups implying steep orientation gradient within short ranges in {111}//ND oriented grains. This steep orientation gradient was generally originated from the existence of deformation heterogeneities. Particularly, {111} orientation which was the dominant component in the recrystallization texture showed the maximum values of both GAM and SGS, which was caused by the frequent development of shear bands. SGS values of {001}//ND oriented soft grains were unexpectedly large in spite of their small GAM values. It could be confirmed that their uniform deformation behavior led to the gentle but monotonous orientation gradient in long ranges. The lowest values of both GAM and SGS were obtained in the {112} orientation, probably, because of the highest orientation stability in that orientation during plain strain deformation condition. GAM was more closely related to the development of recrystallization texture and the significance of the steep orientation gradient in the recrystallization behavior should be re-addressed.

Rapid grain growth and artificial aging characteristics during heat treatment is investigated for hot extruded Al-Zn-Mg-Cu-(Sc) alloys. Two Al-0.1wt%Sc alloys with different alloying element content are hot extruded to make T-shape bars at 380°C, and then the bars are solution treated for 2 hours at 480oC followed by artificial aging for 24 hours at 120°C. Microstructural evolution of the hot extruded bar is analyzed with optical microscope and electron back scattered diffraction (EBSD) mapping. Two kind of extruded bar shows different grain growth behavior at surface region and different artificial aging characteristics. The interaction between the precipitates and the grain growth during the heat treatment is thought to be responsible for the different grain growth behavior.

A mathematical model of a hydraulic balancer in steady state condition was derived from a whirling model of a vertical axis washing machine, with the aim of implementing a dynamic analysis of an automatic washing machine during spin drying mode. The centrifugal force acting on the hydraulic balancer depends on the centroidal distance of the fluid in the hydraulic balancer, and the centroidal distance is a function of an eccentricity of the geometric center of the hydraulic balancer from the axis of rotation. A mathematical model of the hydraulic balancer in steady state is validated by the experimental result of the centrifugal force. Experiments were performed on a washing machine during spin drying mode, and results were compared with the simulation result. The parameters affecting the vibration of the washing machine were investigated by the parameter study.

During martensite transformation, parent austenite usually has an orientation relationship with newly transformed martensite and thereby a crystallographic texture of the austenite has a great influence on a texture development in the inherited martensite. For a given orientation relationship, there are several equivalent orientations of the inherited phase, which is called variant. Table 1 shows the 24 variants for Kurdjumov–Sachs (K–S) orientation relationship which is usually observed in carbon steels. In idealized case, all variants can appear in an austenite grain with an equal probability during the transformation. However, it has been reported that some variants preferentially appeared during the transformation. In other words, some variants possibly have greater relative probability to be selected. This phenomenon, which is called variant selection, is known to have a significant effect on the texture development in the inherited phase. The slip system of parent phase, the grain boundary orientation and the existence of stress have been known to affect the variant selection during the transformation and the development of transformation texture. As for the slip activity, the criterion of variant selection was imposed in terms of slip distribution and was applied to diffusion-controlled transformation. Ray et al. reviewed the various kinds of transformation texture that is normally encountered in austenite-to-ferrite transformation in steel. As for the bainitic transformation in steel, the variant selection had been investigated by an experimental observation. Recently, present authors suggested that the probability for a nucleation site to really act during displacive transformation could be derived for each variant as a function of the mechanical interaction energy between externally applied stress and lattice deformation based on the Kurdjumov–Sachs (K–S) relationship. In present study, the variant selection in mechanically induced martensitic transformation of metastable austenite is investigated with respect to the interaction between external stress and lattice deformation of the transformation. The orientations of parent austenite and newly transformed martensite are measured for tensile and compressive deformation using electron back-scattered diffraction (EBSD). For an individual austenite grain, the orientation of 24 K–S variants are evaluated and compared with measured orientation of martensite. The interaction energy between externally applied stress and lattice deformation is calculated for each 24 K–S variant and the probability of variant selection is assessed. The assessed probability is compared with the experimental results.