Rapid Solidification of Ti-Al Alloys under Electromagnetic Levitation Condition

摘要

Ti-Al alloys are usually difficult to undercool because of their high reactivity in the liquid state. In this paper, the maximum undercoolings of 328 (0. 17TL) and 383K (0. 22TL) were achieved respectively for liquid Ti-20at%Al and Ti-51at%Al alloys under electromagnetic levitation condition. On the basis of high undercooling, we investigated the containerless rapid solidification of Ti-Al alloys. For Ti-20at%Al alloy, the XRD analysis indicated that the solidification microstructure consists of the two phases α-Ti and α2-Ti3Al. The solidification microstructure for Ti51at%Al alloy involves two phases γ-TiAl and α2-Ti3Al. Meanwhile,the microstructure formation mechanisms of Ti-20at%Al and Ti-51at%Al alloys studied. With the increase of undercooling,the solidified microstructure of Ti-20at%Al alloy significantly changes from dispersive distribution to lamellar structure,and that of Ti-51at%Al alloy changes from coarse grain and lamellar structure to lamellar structure. Furthermore,the microhardness of Ti-20at%Al and Ti-51at%Al alloys reaches the maximum value up to 557 and 712HV respectively at the undercooling of 260 and 246K.