Effect of Cu concentration on the semi-solid deformation behavior and microstructure of Ti–Cu alloy

Abstract

The semi-solid compressive deformation behavior of Ti-Cu alloys was investigated by Gleeble-3500 hot simulator at the deformation temperatures ranging from 1273 to 1473 K with strain rates ranging from 5 3 10 23 to 5 3 10 21 s 21. The relationship between Cu concentration and flow stress was analyzed, and the deformation apparent activation energy was also calculated. The results show that Cu concentration has significant influence on the flows' behavior of Ti-Cu alloys, especially at high semi-solid deformation temperatures. The Ti-14Cu exhibits the highest flow stress at 1273 and 1373 K, Ti-2.5Cu alloy exhibits the highest flow stress at 1473 K, and Ti-7Cu alloy shows the lowest flow stress at all tested temperatures, which corresponds to liquid fraction caused by varied Cu concentration and the deformation temperature. The difference in microstructure suggests that the shape and distribution of Ti 2 Cu precipitates are significantly affected by Cu concentration. The increase in Cu concentration leads to the growth and precipitation of acicular Ti 2 Cu along grain boundaries at high semi-solid deformation temperatures. The deformation apparent activation energy of Ti-14Cu alloy significantly decreases from solid deformation to semi-solid deformation owing to the change in main deformation mechanism from plastic deformation of solid particles to solid particles' slippage and rotation of grain boundaries.