Study on mechanical properties of Ti-6Al-4 V titanium alloy with different microstructures under combined tension-bending load

Abstract

Combined tension-bending load is one of the typical service conditions for Ti-6Al-4 V alloy components in engineering applications. In this study, the mechanical properties of Ti-6Al-4 V alloy with equiaxed microstructure (EM), bimodal microstructure (BM), and Widmanstatten microstructure (WM) under combined tension-bending load were investigated experimentally. Combined tension-bending tests were conducted on Ti-6Al-4 V alloy with three microstructures in the range of pre-tension ratios from 0.20 to 0.80. The results showed that the pre-tension load produced a significant strengthening effect on the maximum bending load and bending modulus of the Ti-6Al-4 V alloy. The maximum bending load of the bimodal microstructure increased with the increase of the pre-tension ratio, and that of the equiaxed microstructure and the Widmanstatten microstructure first increased and then decreased. In general, the maximum bending loads of all three microstructures under combined tension-bending were significantly larger than those in the three-point bending mode. The bending modulus of Ti-6Al-4 V alloy with the three microstructures increased significantly with increasing pre-tension ratio. The pre-tension load also significantly enhanced the energy dissipation capacity of the equiaxed microstructure and to a certain extent of the bimodal microstructure, however, it had a detrimental effect on the Widmanstatten microstructure. SEM observations showed that the Ti-6Al-4 V alloy with bimodal microstructure under combined tension-bending load exhibited a mixed fracture mode of equiaxed dimples and parabolic dimples. This study is of significance to guarantee the service safety of Ti-6Al-4 V alloy under combined tension-bending load.