Microstructure and microhardness of Ti-48Al alloy prepared by rapid solidification

To improve the microstructure and microhardness, Ti-48Al (at.%) alloy was rapidly solidified by melt spinning under different cooling rates. The microstructure and microhardness of rapidly solidified Ti-48Al alloy were systematically investigated. Results show that the average lamellar colony size of the alloy reduces from 60.6 µm to 11 µm as the cooling rate increases from 2.3×10 5 to 5.1×10 5 K·s −1 , caused by the increase of nucleation rate at a higher cooling rate. At the high cooling rate of (4.3–5.1)×10 5 K·s −1 , the ± phase is the primary phase, and a few metastable α phases are reserved, which then transform into α 2 phase and subsequently lead to the formation of α 2 equiaxed grain. The lamellar spacing also decreases with the increase of cooling rate. The relationship between lamellar spacing ( d ) and cooling rate ( v ) is d =33.6 v −1.34 . The microhardness increases with the increase of cooling rate because the refined lamellar spacing and grain size can improve the microhardness.