Study On Recrystallization In Graphene Reinforced Aluminum Matrix Composites

In this paper,the graphene reinforced aluminum matrix composites were subjected to isothermal hot compression,the rheological behavior was analyzed and the obtained stress-strain curves were corrected for temperature.The constitutive equation and thermal processing map were established,and the microstructure evolution under different parameters was studied.The composites were cold-rolled and annealed,EBSD and SEM characterization methods were used to observe the micromorphology changes at different deformations,discuss the recrystallization temperature range and grain growth method and analyze the microstructure evolution under different annealing condition.The conclusions are as follows:(1)The elastic deformation occurred in the initial stage of the hot compression process of the composites,decreased slightly after reaching to the peak stress and tent to steady state,and then the flow stress increased again.The effect of deformation heating occurred at large strain rate,the greater the strain rate,the more obvious the effect of deformation heating.(2)The thermal processing maps with strains of 0.4,0.8,1.2 and 1.6 under different deformation conditions were constructed,comparing the microstructure of the unstable area and the safety area,it was found that the microstructure of the safety area was more uniform,the thermal processing maps were overlaid to obtain the most suitable processing area with the deformation temperature range of 400-470?and the strain rate range of 0.01-0.08s^-1.With the deformation temperature increasing and the strain rate decreasing,both the grain size and the recrystallization ratio increased,GOS value and KAM value decreased.The agglomerated graphene particles acted as particle induced nucleation,the grains differing from<100>texture appeared,and the<100>texture was weakened.The larger the amount of deformation,the greater the degree of recrystallization,the greater the degree of<100>texture weakening.(3)After the composites were cold rolled,graphene was in a strip shape parallel to the rolling direction,The larger the rolling deformation,the more slender the graphene,the hardness increased from 36.4HV to 58HV.Annealing the cold-rolled specimens with a deformation of 70%,it was found the recrystallization temperature range was250-275?combining hardness and microstructure.The abnormal growth of nucleus appeared in the process of recrystallization because of the pinning effect of graphene on the grain boundary.(4)With annealing temperature and time increasing,the proportion of low angle grain boundaries decreased,the average misorientation increased and the degree of recrystallization increased.Because the role of graphene in retarding grain boundary migration is greater than the effect of the surface energy on promoting grain growth after full recrystallization,the grains no longer grow with the annealing time continues increasing.