Effect of heat transfer coefficient on measurement of friction factor in hot deformation of Ti-6Al-4V alloy

The ring-compression test of Ti-6Al-4V alloy was carried out at 940°C and the ratio of outer diameter, inner diameter, height of 20:10:7. And the ring compression process was simulated by means of DEFORM-3D software. The results show that the effect of heat-transfer coefficient on measurement of friction factor is significant. The increase of heat-transfer coefficient results in the decrease of interfacial temperature between the workpiece and dies, and in turn leads to the increase of friction. Therefore, for various lubricant media, different heat-transfer coefficients should be chosen to conduct the FE simulation and establish different calibration curves. Combined with the ring-compression test, different heat-transfer coefficients for glass lubricant and dry friction condition are selected to establish the calibration curves, and finally the friction factors of TC4 titanium alloy under high temperature (940°C) deformation for dry friction and glass lubricant condition are determined to be about 0.59 and 0.42, respectively.