定向凝固Ti-45Al-7Nb合金的组织特征

研究了液态金属冷却定向凝固条件下Ti-45Al-7Nb(at%)合金的组织特征。结果表明:定向凝固过程中合金的凝固路径及稳态区片层取向均受到抽拉速率的影响。当抽拉速率为0.36mm/min时,合金的初生相为α相,与生长方向垂直的片层组织生长占优;抽拉速率介于1～10mm/min时,合金初生相变为β相,凝固过程中会经历β单相区,片层取向多为与生长方向成0°和45°;当抽拉速率增加至20mm/min时,合金初生相仍为β相,随后发生L+β→α包晶反应,与抽拉方向之间的夹角介于45°～75°之间的片层组织生长占优。

Microstructure of the Directional Solidified Ti-45Al-7Nb Alloy

By the liquid metal cooling method,the microstructure character of directional solidification of Ti-45Al-7Nb(at%) alloy was examined.The results show that both the solidification behavior and lamellar orientations are affected by withdrawing rate.The primary phase is α phase,and lamellar orientation is perpendicular to the growth direction at the withdrawing rate of 0.36 mm/min.The primary phase converts into β phase at the withdrawing rate of 1～10 mm/min,alloy solidify completely into the β phase field,and lamellar orientation tends to parallel or incline with the angle of 45° to the growth direction.When the withdrawing rate increases to 20 mm/min,the primary is also β-phase,followed by the peritectic reaction of L + β → α,and lamellar orientation is inclined with the angle of 45°～75° to the withdrawing direction.