Strengthening mechanism of lamellar-structured Ti-Ta alloys prepared by powder metallurgy

Titanium-tantalum alloys with lamellar microstructure were fabricated by cold isostatic pressing under 400 MPa and pressure-free sintering at 1600 °C. By such a low-cost powder metallurgy method, the Ti-Ta alloy exhibited the tensile yield strength of 1124 MPa at room temperature, which was twice that of the cast Ti-Ta alloys. The microstructure and mechanical properties were characterized in detail to elucidate the deformation behavior and the strengthening mechanism of the Ti-Ta alloys prepared by powder metallurgy. With the increasing Ta content, the width of the α laths decreased, and that of the β laths increased, leading to the precipitation of the acicular α in the β laths. Correspondingly, the yield and ultimate strength increased, while the strain to failure decreased. Lamellar structure strengthening was determined to be the dominating mechanism for the high strength of the Ti-Ta alloys prepared by powder metallurgy. After quantitatively evaluating the contributions of laths, solute atoms, prior β grain boundaries, and dislocations, a model was established to illustrate the yield strength of the Ti-Ta alloys. The calculated values agreed well with the measured strength values of the Ti-Ta alloys, indicating that this model is effective in forecasting the strength of the dual-phase Ti alloys with lamellar structure.