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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。
The microstructure and mechanical properties of Ti-45Al-7Nb (at%) alloy under directional solidification with liquid metal cooling were investigated. The results show that both the solidification path and the orientation of the sheet in the steady zone are affected by the drawing rate during directional solidification. When the drawing rate is 0.36mm / min, the primary phase of the alloy is α phase, and the growth of the layer perpendicular to the growth direction is dominant. When the drawing rate is between 1 ~ 10mm / min, the primary phase changes to β phase , The solidification process will experience β single phase zone, the orientation of the layers is mostly 0 ° and 45 ° with the growth direction; when the pull rate increases to 20mm / min, the alloy primary phase is still β phase, followed by L + β → α peritectic reaction, the growth of the lamellar layer with the angle between 45 ° ~ 75 ° with the direction of drawing is dominant.