The Effect Of Initial Grain Size And Gallium Element On The Recrystallization Behavior Of Pure Aluminum Under Small Deformation Conditions

Single crystals are essential in studies in materials science and surface science,since only in single crystals it is possible to study the directional dependence of various properties.For pure metals with multiple allotropes or for alloys with remarkable micro-segregation,the method of recrystallization in small strain is feasible to prepare single crystals.For the suppose to support the preparation of single crystals by the recrystallization method,the recrystallization behavior in small strain was investigated in this study,as well as the effects of alloying elements and initial grain size on the final grain size.Coarse-grained pure aluminum with 0-10%deformation is annealed for 30 min.The result shows that the grain size increases and then decreases after annealing for 30 min and the deformation of the coarsest grain corresponds to the critical strain.Below the critical strain,recrystallization cannot occur and only recovery can.And it is deduced that the recovery may slightly retard the following grain coarsening process,thus leading to a decrease in the grain size below critical strain as compression increase.Just above the critical strain,recrystallization can occur with the formation of few nuclei,thus leading to large-grain-sized microstructure.Far above the critical strain.recrystallization easily occurs with numerous nuclei or high nucleation rate,thus leading to grain refinement.Besides,the result of annealing at different temperature shows that the critical strain decreases with annealing temperature.When annealed at 400?,the critical strain of fine-grained pure aluminum is 1%,which is lower than coarse-grained pure aluminum.It was known that fine-grained microstructures can gain higher stored energy of deformation than coarse-grained microstructures at the same deformation.The critical strain of Al-1.8at.%Ga alloys is 1%,which is also lower than coarse-grained pure aluminum.It should be attributed to the high grain boundary migration rate of Al-Ga alloys.As known,the nucleation in small strain is SIBM,and it is related to the grain boundary migration.Obviously,the high boundary migration rate can accelerate the nucleation.In addition,annealing of samples with different grain size shows that coarse-grained pure aluminum presents more remarkable grain-coarsening effect.In other words,coarse-grained initial microstructure is more suitable to prepare large grains by recrystallization method.