Dynamic Transformation Behaviours And Mechnisim Of Industrial Pure Titanium During High Temperature Deformation

Titanium alloy thermal processing is an important part in the processing and production of titanium alloys.The study found that the α→β dynamic transformation will occur during the thermal deformation of the titanium alloy near the transformation point,which may have a positive effect on the superplastic behavior and micro structure of the titanium alloy.To this end,this article selects two typical TA2 and TA3 titanium alloys to study the dynamic phase transformation behavior.Through the analysis of the microstructure and texture evolution law during the hot deformation process,the dynamic phase transformation and its inverse phase transformation mechanism are revealedThe research indicated that:α→β dynamic phase transformation process includes three stages:(1)Part of the a phase at the grain boundary changes to β phase,which makes the grain boundary widenly;(2)Lamellar β phases grows from the a phase grain boundary into the grain,(3)The lamellar β phase extends and widens gradually,more and more lamellar appear,and finally transforms into big β grains.The reverse phase transformation process mainly includes two stages:(1)Metastablc β phase produced by dynamic transformation will change back to a phase gradually,and the enriched iron element will diffuse slightly.The no-transformed grains will recover,eliminating intra-grain distortion;(2)No-transformed grains begin to grow,and "swallow" alpha laths gradually.In addition,the β phase grains generated by dynamic phase transformation have the following orientation relationship with the original a phase grains:(1010)α//(110)β,[0001]α//[110]β,and in the reverse phase transformation,follow the Burgers relation:(0001)α//(110)β,[1120]α//[111]β.Dynamic transformation phenomenon is appeared in the grain whitch occured prismatic slip,and plays a softening role during the thermal processing of the titanium alloy.Therefore,the dynamic transformation phenomenon can be controlled by adjusting the grain orientation,and then its softening effect during the thermal deformation process can be controlled.In addition,dynamic phase transformation and reverse phase transformation have a significant impact on the micro structure and room temperature mechanical properties of titanium alloys,which provides new ideas for the organization and performance optimization of titanium alloys.