Effect of cooling rates on microstructures evolution and nanohardnessof rapidly solidified Ti-48Al-4Cr alloy

Abstract:

In this work the effect of cooling rates on microstructure of Ti-48Al-4Cr(at.%) alloy rapidly solidified at different wheel speeds were experimentally investigated by using the single roller melt-spinning technique. The results indicate that after rapid solidification at the wheel speed of 10m/s and 20m/s, the microstructures mainly consist of equiaxed γ phase, few volume fraction of α₂, B2 phase particles and lamellar structures exists in the γ phase matrix. At the wheel speed of 30m/s, the matrix changes to α₂ phase and the lamellar structures disappear. The nanohardness increases with the cooling rate increasing. It enhances from 4.98±0.10GPa under normal pressure to 7.48±0.16GPa under 4GPa. The nanohardness increases from 5.04±0.09GPa of conventional cast Ti-48Al alloy to 10.48±0.13GPa of rapidly solidified Ti-48Al-4Cr alloy with the wheel speed of 30m/s. This research has provided the basis of further studying on the microstructures, reducing the segregation and enhancing the mechanical properites of TiAl alloy.