Influence of the Billet Volume Distribution on Macro Deformation and Microstructure Response in Transitional Region of Ti-Alloy Multi-rib Component Under Isothermal Local Loading

The folding, die underfilling, rib shifting and average grain size of primary equiaxed α were investigated using five different unequal thickness billets in transitional region of Ti-alloy multi-rib component under isothermal local loading and compared with integral loading. In terms of the macro deformation, the results show that the material transfers from the second-loading zone into the first-loading zone and the die underfilling decreases with the initial volume of the first-loading zone increasing, which reduces the risk of folding and rib shifting. However, that folding and rib shifting did not appear during the integral loading. Nevertheless, when the initial volume of the first-loading zone reaches a certain value, the die underfilling is aggravated both in local and integral loading. With respect to the microstructure, as the initial volume of the first-loading zone increases, the average grain size is decreased after the first-loading step, but increased after the second-loading step with consideration of one single loading step, which lead to the grain size being barely influenced by different billet volume distribution under both loading steps.