Thermal cycling In (α+β) Ti6Al4V alloy

Abstract

Thermal cycling experiments of Ti6Al4V alloy in forged condition were perform in two phase (α+β) region and single phase β to two phase (α+β) regions. The tensile tests, microstructure observation and hardness were carried out before and after the cycling treatments. Thermal cycling in two phase (α+β) region between 950°C and 100°C resulted large decrease in tensile strength after 50 cycles. However, it increased after 100 cycles. The ductility exhibited large decreased for both the treatments. The cycling between 875°C and 100°C in this region exhibited initial decrease in strength after 50 cycles which further increased after 100 cycles. 150 and 200 cycles treatment did not show much change in strength. There was no much reduction in ductility after 50 and 100 cycles treatment. However, after 150 and 200 cycle treatment, it reduced to large extent. The cycling from single phase β region to two phase (β+β) region between 1150°C and 950°C after 50 cycle did not affect the strength to large extent. However, the treatment exhibited reduction in ductility for both: 5 minute and 3 minute socking at 1150oC. The extent of reduction being large for former compared to that for later. The hardness of all the samples including that for virgin sample exhibited very little variation. The microstructures of the alloy exhibited significant change in (β+β) phase morphologies. Similarly, the change in Young’s modulus, thermal expansion coefficient, dislocation density etc has caused the degradation of the alloy.