Influence of α/β interface phase on the tensile properties of laser cladding deposited Ti-6Al-4V titanium alloy

Laser cladding deposited Ti-6Al-4V titanium alloy universally shows more complex microstructures, each of which has significant effect on mechanical properties. Of particular alpha/beta interface phase has been observed in this paper under certain conditions. It demonstrates that the influence of the alpha/beta interface phase on the tensile properties is closely associated with dislocations and twin substructure through comparison experiments. The results show that the alpha/beta interface phase hinders dislocation motion and decreases effective slip length. In addition, the twin substructure has been activated in the alpha/beta interface phase during tensile process and has acted somehow like grain boundaries. Therefore, the strength and the work-hardening rate of the laser cladding deposited Ti-6Al-4V titanium alloy have been significantly improved due to the dynamic Hall-Petch effect. Besides, the alpha/beta interface phase leads to more uniform dislocations distribution, which implies that relative lower local concentrated stress will be produced along the alpha/beta interface phase or colony boundary after the same amount of plastic deformation. Moreover, the twinning-induced plasticity effects in the alpha/beta interface phase further increase the plastic deformation capacity. These results in higher elongation for the laser cladding deposited Ti-6Al-4V titanium alloy. It can be concluded that the current work suggests an effective method to simultaneously improve the strength and plasticity of laser cladding deposited Ti-6Al-4V titanium alloy based on the alpha/beta interface phase. (C) 2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.