中文摘要：

采用感应加热定向凝固炉对Ti-47.5Al-6Nb-2Cr-0.5Si（at%）合金在抽拉速率6、15、25、100μm/s下进行定向凝固实验。结果表明：抽拉速率为6μm/s时,固/液界面是胞枝状,片层取向与生长方向夹角为45°,初生相为β相;抽拉速率为15～100μm/s时,固/液界面以树枝状向前推进,且随着抽拉速率的增加,一次枝晶间距减小,片层取向与生长方向的夹角由45°向90°转变,初生相由β相转变为α相;抽拉速率大于6μm/s时,组织中出现硅化物析出相,且随着抽拉速率的增大,析出相越来越多,分布变密,沿生长方向逐渐成线条状。

英文摘要：

Directional solidification experiments of Ti-47.5A1-6Nb-2Cr-0.5Si （at%）alloy were conducted by using induction heating furnace at the drawing rates of 6, 15, 25 and 100 μm/s. The results show that： when the drawing rate is 6 μm/s, the solid/liquid interface is cellular dendrite, the angel between the lamellar orientation and growth direction is 45°, and the primary phase is β phase. When the drawing rate is 15--100 μm/s, the solid/liquid interface pushes ahead in dendritic interface, and the primary dendritic spacing decreases with increasing the drawing rate. Correspondingly, the angel between the lamellar orientation and growth direction varies from 45° to 90°, and the primary phase varies from β phase to ct phase. When the drawing rate is greater than 6 izm/s, silieide precipitated phase appears in microstructure. As the drawing rate increases, the precipitated phase becomes more and more. The distribution is denser and denser, and the precipitated phase connects into lines along the growth direction gradually.