A novel method to fabricate high strength and ductility Ti-3Al-5Mo-4.5 V alloy based on TiH2 and pre-hydrogenated master alloy powders

Abstract

Fabrication of high-performance titanium (Ti) alloys containing high-melting-point elements is challenging via blended elemental powder metallurgy (BEPM), because of the inevitable high porosity induced during pressing and sintering processes. Herein, we propose a novel master-alloy pre-hydrogenation (MAPH) method to fabricate sintered TC16 (Ti-3Al-5Mo-4.5 V) alloy, which possess a nearly full-density (99.2%) and good mechanical properties, i.e., an UTS of ∼ 1004.6 MPa, a YS of ∼934.2 MPa and an EL of ∼15.8%. The pre-hydrogenated 7.5Ti-3Al-5Mo-4.5V-Hx (7.5TiMA-Hx) powder particles show a morphology of sharp corners. Therefore, the 7.5TiMA-Hx and TiH2 particles can get interlocked compactly during compaction and shrink simultaneously during the dehydrogenation process, which minimizes the difference in volume mismatch and ensures the overall uniformity after sintering. Besides, the interlocking compact structure makes the element diffusion easier between the 7.5TiMA-Hx and TiH2 matrix particles, which promotes the healing of porosity. The low porosity can reduce the tendency for propagation of cracks along the grain boundaries of the α layer, leading to a good balance between the strength and ductility of the sintered TC16-7.5TiMA-Hx alloy.