Influence of heat treatment on microstructure and nanohardness of TiAl alloy solidified under high pressure

The Ti-48at.%Al alloy solidified under different pressures was prepared using a tungsten-carbide six-anvil apparatus and then heat treated at different temperatures.The effect of heat treatment on microstructure and mechanical properties of high pressure solidified Ti-48Al alloy was investigated.The results showed that the phase constitution of the Ti-48Al alloy solidified under high pressure did not change after heat treatment.After 1,100℃/12 h AC(air cooling),the value of c/a showed a slight increase.The Widmanst?tten structure was formed in the samples solidified under 2 GPa and 4 GPa.More defects were found in the high-pressure samples.The volume fraction ofα2 particles increased with an increase in pressure.After 1,150℃/4 h AC,the discontinuous coarsening phenomenon could only be found in the 4 GPa solidified samples.The formation ofα2 phase can lead to the increase of nanohardness.Compared with the samples before heat treatment,the nanohardness increased about 1.0-1.2 GPa.