Partition of Nb element on microstructure, tensile and impact properties of a near α Ti–4Nb alloy

Effects of Nb element partition on microstructure, tensile and impact properties of a near α Ti–4Nb alloy are studied by experimental and theoretical methods. Results of the BSE and EDS analysis reveal the partition of Nb element in α and β phase of Ti–4Nb alloy annealed at 750 °C, 800 °C and 830 °C, respectively. Microstructure, tensile and impact properties are distinctly affected by the partition of Nb element. β Phase containing more Nb element plays an important role to strengthen the α matrix. The mismatch between α and β phase caused by partition of Nb element significantly affects the Charpy impact energy and crack propagation behavior of the Ti–4Nb alloy. A simple model depending on the concentration of Nb is proposed to quantify the mismatch between α and β phase based on the empirical electron theory (EET) of solids and molecules.