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Metastable 304 austenitic stainless steel was subjected to rolling at cryogenic and room temperatures, followed by annealing at different temperatures from 500 to 950°C. Phase transition during annealing was studied using X-ray diffractometry. Transmission electron microscopy and electron backscattered diffraction were used to characterize the martensite transformation and the distribution of austenite grain size after annealing. The recrystallization mechanism during cryogenic rolling was a reversal of martensite into austenite and austenite growth. Cryogenic rolling followed by annealing refined grains to 4.7 μm compared with 8.7 μm achieved under room-temperature rolling, as shown by the electron backscattered diffraction images. Tensile tests showed significantly improved mechanical properties after cryogenic rolling as the yield strength was enhanced by 47% compared with room-temperature rolling. [ABSTRACT FROM AUTHOR]

A strongly basal textured AZ31 magnesium alloy were cryorolled at liquid-nitrogen temperature at various strains. The microstructure and texture of the rolled sheets have been investigated using electron backscatter diffraction (EBSD) and X-ray diffraction. The microstructural and textural evolutions of the AZ31 magnesium alloy during cryorolling have been discussed. A lot of twins were observed in the rolled sheets. The influence of strain on the twin types and variant selection during cryorolling for the magnesium alloy has been discussed quantitatively based on the orientation data collected using EBSD. The influence of the twins on the microstructural and textural evolutions for the AZ31 magnesium alloy during cryorolling has also been discussed. The mechanical properties of the cryorolled sheets were tested by uniaxial tensile tests at the ambient temperature with a strain rate 10s in the tensile direction respectively along the rolling and transverse directions of the rolled sheets. The relationships between the mechanical properties and microstructure of the cryorolled sheets have been discussed in the present work. The active twinning during rolling at that cryogenic temperature has been found to play an important role in influencing the microstructure, texture, as well as the mechanical properties of the AZ31 magnesium alloy. [ABSTRACT FROM AUTHOR]

Mechanical properties in conjunction with microstructural evolution during annealing of 5052 Al alloy deformed at cryogenic temperature were investigated and compared with those yielded by the ARB process. ARB was conducted up to 7 cycles under conditions where the reduction in thickness per cycle was 50% and the rolling temperature was 300°C. To investigate the effect of annealing temperature, cryo-rolled sheets with 85% reduction were annealed in a temperature range of 150≈300°C for one hour. Strengths of 5052 Al alloy ARB processed at 300°C increased with increasing number of cycles and decreased rapidly after 6 or 7 cycles. This indicated that, during the ARB process, work hardening proceeded at low strains and subdivision of grains and dynamic recovery occurred at high strains. Tensile strength and yield strength of cryo-rolled 5052 Al alloy decreased as the annealing temperature increased. The volume fraction of recrystallized and coarsened grains appeared to have the most significant influence on strength and ductility in sheets annealed at 250°C. [ABSTRACT FROM AUTHOR]