Study On Microstructure Evolution And Solute Redistribution In Binary Al Alloy Processed By High-pressure Torsion

It is of great significance to study the microstructure evolution and solute redistribution of ultrafine-grained materials processed by severe plastic deformation.Five binary Al alloys(Al-0.1 at%Si,Al-0.5 at%Si,Al-1.0 at%Si,Al-1.0 at%Mg,Al-1.0at%Cu)were investigated.They were subjected to high-pressure torsion deformation(1R,5R and 10R),and were investigated combining hardness testing,electron backscatter scanning diffraction,transmission electron backscatter scanning diffraction,transmission electron microscopy,and atom probe tomography.The microstructure and solute redistribution of binary Al-Si alloys with different Si contents and binary Al alloys with different solute elements after high-pressure torsion were systematically studied.The results indicate that with the increase of strain,the hardness of Al-0.1 at%Si alloy increases firstly and then tends to saturation,while the hardness of Al-0.5 at%Si and Al-1.0at%Si alloys increases rapidly and then decreases gradually.After high-pressure torsion,the grain size of the alloy is about 200-400 nm,and gradually increases with the number of highpressure Torsion turns.Si distributes nonuniformly in the matrix,which enrichs on dislocation,and precipitates in the crystal and on the grain boundary.There is almost no interfacial segregation at grain boundaries except the Si particles.Therefore,migration of grain boundary occurred easily in Al-Si samples,leading to the softening of the material at relatively higher strains.The redistribution of three solute elements is significantly different.Cu,Mg,and Si show segregation,partial segregation,and non-segregation phenomenon at the grain boundaries,respectively.With the increase of deformation,the concentration of Cu in the matrix decreases gradually,the concentration of Mg remains unchanged,and Si atom distributes inhomogeneity The lowest concentration of Cu and Si in the poor zone are similar to their solubility in Al,and the lowest concentration of Mg is low to 0 at%.It is speculated that the redistribution of solute is related to the solute diffusion rate,the deformation mechanism,and the mechanism of the solute element diffusion with vacancies.