Optimizing the mechanical properties of dual-phase Ti-6242s titanium alloy at 550°C using the boundary architecture

In this work, a desirable combination of mechanical properties is achieved at 550 °C by tailoring the boundary microstructure between the primary α phase (αp) and the transformed β structure (βtrans) in a dual-phase Ti-6242s titanium alloy. The αp/βtrans boundary is displaced by a transition region that consists of β nano-plates or nanoprecipitates gradually penetrating into the αp in a particular semi-equiaxed microstructure (S-ES). The results show that the αp/βtrans boundary, where strain concentration easily occurs during deformation in the equiaxed microstructure (ES), induces recrystallization softening in the α phase. However, the transition region in the S-ES alleviates the strain localization and thus effectively inhibits the recrystallization softening that occurred in the α phase with concentrated strain. These β plates/precipitates in this region in turn enable an appropriate accumulation of dislocations. Significant improvement in the high-temperature strength, ∼240 MPa for the yield strength, is obtained for the S-ES relative to the ES. This work provides a new strategy for achieving outstanding strength at high temperature by designing special boundary architecture in dual-phase titanium alloys.