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Date of Publication:2012-01-01

Journal:稀有金属材料与工程

Volume:41

Issue:3

Page Number:472-476

ISSN No.:1002-185X

Abstract:The microstructure evolution, crystallographic texture and dislocation configuration during recrystallization of the cold-drawn Ti6Al4V alloy were investigated by optical microscope (OM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Recrystallization treatment in the 60% cold worked samples was carried out at various temperatures between 700 degrees C and 880 degrees C and holding time from 1 min to 240 min. The results demonstrate that recrystallization of the 60% cold-drawn alloy and subsequent grain growth have led a phase to fine equiaxed grains, while beta phase distribute along grain boundaries of the alpha-phase in strip shape or small grains. The value of recrystallization activation energy of the alloy after 60% cold deformation is 107 kJ/mol, which is about 50% higher than that of the deformed pure titanium experienced the equal deformation. The microstructure evolution at different grain stages can be classified as recoveration, nucleation and grain growth stages. It is shown that the recovery involves rearrangement of dislocation cells into subgrains, formation of nuclei through growth or coalescence of subgrains, and growth of nuclei by high angle boundary migration during the annealing of the Ti6Al4V alloy. The as-cold drawn wires present strong <10<(1)over bar>0> fiber texture. The recovery subgrains with particular crystal orientations provide preferential sites for the nucleation during subsequent recrystallization annealing and grow to be new grains. The texture at the end of primary recrystallization is consistent with the deformed state depending on the crystallographic orientation; while in the grain growth stage, misoriented grains resulting from the recrystallization mechanisms would subsequently grow by consuming neighboring small grains, so the original texture is weakened.

Note:新增回溯数据