Evolution of α phase morphology in hot-rolling TC21 titanium alloy plate

The microstructure evolution and mechanisms of globularization of TC21 titanium alloy with lamellar structure were investigated during hot rolling in the β phase and α+β phase.The results show that the prominent effect of hot working parameters on the break-up and globularization of TC21 titanium alloy with lamellar structure is found.The α lamellar structure along the paralleling rolling orientation and adjacent grain boundaries is broken up and globularized and the intragranular α lamellar is buckled and kinked when TC21 titanium alloy is processed in β phase region(990℃) at strain no less than 0.51 and at 950 ℃ and strain 0.92.When TC21 titanium alloy is deformed at 910 ℃ and 870 ℃,α lamellar is buckled and kinked to become accordion.Then,by TEM analysis,it is found that the mechanism of globularization of TC21 titanium alloy with α lamellar is a comprehensive process that is firstly the formation of α/α interface by dynamic recovery or boundary splitting,secondly the disintegrating of α lamellar due to diffusing,and finally the globularization of α lamellar by termination migration.