Dependence of the specific energy of the β/α interface in the VT6 titanium alloy on the heating temperature in the interval 600–975°C

Abstract

The specific energy of interphase boundaries is an important characteristic of multiphase alloys, because it determines in many respects their microstructural stability and properties during processing and exploitation. We analyze variation of the specific energy of the β/α interface in the VT6 titanium alloy at temperatures from 600 to 975°C. Analysis is based on the model of a ledge interphase boundary and the method for computation of its energy developed by van der Merwe and Shiflet [33, 34]. Calculations use the available results of measurements of the lattice parameters of phases in the indicated temperature interval and their chemical composition. In addition, we take into account the experimental data and the results of simulation of the effect of temperature and phase composition on the elastic moduli of the α and β phases in titanium alloys. It is shown that when the temperature decreases from 975 to 600°C, the specific energy of the β/α interface increases from 0.15 to 0.24 J/m². The main contribution to the interfacial energy (about 85%) comes from edge dislocations accommodating the misfit in direction [0001]_α || [110]_β. The energy associated with the accommodation of the misfit in directions \({\left[ {\bar 2110} \right]_\alpha }\left\| {{{\left[ {1\bar 11} \right]}_\beta }} \right.\) and \({\left[ {0\bar 110} \right]_\alpha }\left\| {{{\left[ {\bar 112} \right]}_\beta }} \right.\) due to the formation of “ledges” and tilt misfit dislocations is low and increases slightly upon cooling.