Effect of Cooling Rates on Microstructures Evolution and Nanohardness of Rapidly Solidified Ti-48Al-4Cr Alloy

the effect of cooling rates on microstructure of Ti-48AL-4Cr (at%) alloy rapidly solidified at different wheel speeds were experimentally investigated by the single roller melt-spinning technique. The results indicate that after rapid solidification at the wheel speed of 10 and 20 m/s, the microstructures mainly consist of equiaxed gamma phase, a few volume fraction of alpha(2), B2 phase particles and lamellar structures in the gamma phase matrix. At the wheel speed of 30 m/s, the matrix changes to alpha(2) phase and the lamellar structures disappear. The nanohardness increases with the cooling rate increasing. It enhances from 4.98 +/- 0.10 GPa under normal pressure to 7.48 +/- 0.16 GPa under 4 GPa. The nanohardness increases from 5.04 +/- 0.09 GPa of conventional cast Ti-48ALalloy to 10.48 +/- 0.13 GPa of rapidly solidified Ti-48AL-4Cr alloy with the wheel speed of 30 m/s. This research has provided the basis of further study on the microstructures, reducing the segregation and enhancing the mechanical properties of TiAl alloy.