Investigations On High Magnetic Field On The Recrystallization Of1050Alloy Prepared By ECAP Technology

The aim of present work is to study the influence of annealing time and annealing temperatures with or without the high magnetic field on the recrystallization behavior of specimens prepared by ECAP pressing of2and8passes, using hardness test, optical microscopy and transmission electron microscopy(TEM). The following results are obtained:The macrostructure, dislocation, substructure and texture were examined in detailed after ECAPed sample annealed at150℃-400℃for1h with or without the high magnetic field. The results show that the grain size of2-pass sample is0.86μm. When the temperature is lower than250℃, the deformed structures in2-pass sample become gradually ordering, the deforming band is clearer. The dislocation density decreases at grain interior. The high magnetic field speeds up the ordering process, and dislocation density becomes lower at grain interior. At250℃, fine recrystallized grains can be observed1h sample at all conditions. At300℃, recrystallized grains are observed in2-pass sample. The phenomenon of abnormal growth appears the sample without the high magnetic field, and the grain size is1.47μm.The samples annealed with the high magnetic field have more uniform grain size, the grain boundaries are straighter, and the grain size is1.13μm. The8-pass sample at the same condition has more uniform grain size and smaller equiaxed grains. With increasing temperature, the deformation texture in2-pass sample without the high magnetic field becomes weaker, while changes into recrystallization texture in2-pass sample with the high magnetic field. The deformation texture in8-pass sample changes into recrystallization texture with rising temperature, but the texture strength is relatively weak. By the temperature of200℃～250℃, the softening behavior in8-pass sample occurs, and the hardness of specimen with high magnetic field is lower. The softening in2-pass sample appears between250℃～300℃The macrostructure, dislocation and substructure were examined in detailed after ECAPed sample annealed at280℃for5min-12h with or without the high magnetic field. When annealing time is10min, recrystallization can not be observed in2-pass sample. The samples without the high magnetic field have a high density of dislocation tangles, and the grain size is0.86μm. The samples with the high magnetic field have lower dislocation density, and their subgrain boundaries are clearer, and the grain size is0.94μm. At1h, recrystallization in2-pass sample with and without high magnetic field is observed. The dislocation density in sample at grain interior reduces further, and the number of subgrain in sample with the high magnetic field significantly increases. At4h, the recrystallized grains grow, and the phenomenon of abnormal growth appears in the sample without the high magnetic field. When the8-pass sample annealed at a short time (5min) annealing, the recrystallized grains are observed. Annealed10min, the dislocation density decreases gradually. The grain size of the sample without the high magnetic field is2.50μm. The recrystallized grain boundary is clear and straight in samples with the high magnetic field, and the grain size is2.23μm. As the annealing time increasing, the increment of grain size in8-pass sample is small. It is because8-pass sample has completely refined grains, more uniform and stable organization. Abnormal growth of recrystallized grain is observed in sample annealed without the high magnetic field by TEM observation. The grain size in sample annealed with high magnetic field is more uniform and stable. As the annealing time increases, the hardness of sample reduces. Softening appears at10min in8-pass sample, while is1h for2-pass sample. At the same annealing condition, the hardness of sample with high magnetic field is lower than that of sample without high magnetic field which demonstrates that the high magnetic field accelerates the nucleation of recrystallization.