上海科技大学知识管理系统

For SLMed Ti–6Al–4V-xO (x = 0.11, 0.16, 0.21, and 0.25 wt%) alloys, both microstructure and mechanical properties are sensitive to oxygen content. The α′ martensites in as-built state transform to a ‘bimodal’ microstructure containing α lamellae interspersed with β transformed regions after 2 h annealing at 800 °C, 850 °C, 900 °C, and 950 °C followed by air cooling. The α lamellar width decreases and the β phase volume fraction increases with increasing oxygen content, due to reduced diffusivity of Al and V. The solid solution hardening effect of oxygen was quantified as: σ0=472MPa+2159c0.5, where σ0 is the lattice frictional stress and c is oxygen atomic fraction of the alloy. Increased oxygen content causes reduced fracture toughness and higher fatigue crack growth rate in the unstable growth regime, and the appearance of bilinear growth rate of the Paris regime at high annealing temperatures. The absence of the bilinear behaviour in the low oxygen content alloy and for annealing at low temperatures was interpreted in terms of changes in microstructural characteristics caused by oxygen impeding the diffusion of Al and V. © 2024 Elsevier B.V.