The Microstructure Morphology And Texture Evolution Of Alpha-Ti In Ti-6al-4v Alloy During Friction Stir Processing With Low Rotation Speed And Traverse Speed

Friction stir processed Ti-6Al-4V alloys are successfully prepared under low rotation speed (<= 200 rpm) and low traverse speed (<= 50 mm min(-1)). The microstructure of the stir zone is homogeneous in thickness. Effects of process parameters on microstructure and texture evolution of alpha-Ti in the stir zone during friction stir processing are clarified. It is found that traverse speed had a significant impact on microstructure in the stir zone. The equiaxed nano-crystalline alpha-Ti grains without texture formed via friction stir processing below beta transus. The high temperature range and severe deformation range are overlapped when the samples are processed with low traverse speed. Dynamic recrystallization happened repeatedly and fast cooling inhibited grain growth when the stir tool moved away the stir zone. Ti-6Al-4V alloy shows shear texture after friction stir processing below beta transus with higher traverse speed. beta -> alpha transformation occurred and lamellar alpha colonies formed during cooling stage above beta transus when the rotation and traverse speed are increased. The microstructure morphology and texture strength of Ti-6Al-4V plates could be regulated by combining of heating and cooling stages during friction stir processing.