Morphology development of elongated α phases in hot working of large-scale titanium alloy plate

The role of subtransus hot working on microstructure morphology of TA15 titanium alloy plate with elongated α phases was studied by quantitative metallography on different sections. The results show that the microstructure morphology is mainly affected by loading direction. When the sample is compressed along normal direction, microstructure on the section vertical to normal direction has equiaxed primary α phase but microstructure on the section vertical to rolling direction has strip primary α phase with long axis along tangential direction. When the sample is compressed along rolling direction, microstructure on the section vertical to normal direction has strip primary α phase elongated along tangential direction but microstructure on the section vertical to rolling direction consists of strip and irregular broad-band primary α phase. The strip primary α phase aspect ratio is smaller at lower temperature due to the dynamic break-down of α phase. The difference on primary α phase aspect ratio between different sections decreases after compression along distinct directions in two loading passes, suggesting the improvement of equiaxity of primary α phase.