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

In this work, a desirable combination of mechanical properties is achieved at 550 degrees C by tailoring the boundary microstructure between the primary alpha phase (alpha(p)) and the transformed beta structure (beta(trans)) in a dual-phase Ti-6242s titanium alloy. The alpha(p)/beta(trans) boundary is displaced by a transition region that consists of beta nano-plates or nanoprecipitates gradually penetrating into the alpha(p) in a particular semi-equiaxed microstructure (S-ES). The results show that the alpha(p)/beta(trans) boundary, where strain concentration easily occurs during deformation in the equiaxed microstructure (ES), induces recrystallization softening in the alpha phase. However, the transition region in the S-ES alleviates the strain localization and thus effectively inhibits the recrystallization softening that occurred in the alpha phase with concentrated strain. These beta plates/precipitates in this region in turn enable an appropriate accumulation of dislocations. Significant improvement in the high-temperature strength, similar to 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.