Basic Research for Development of New TiAl Base Alloys

研究了Ti/Al比、添加Cr、Hf和Nb等第三元素以及使用高纯母材对TiAl合金室温力学性能的影响. Ti/Al比的影响：富Ti合金的强度高于富Al合金。富钛合金的断裂应变（塑性）约为1.8%，大于富铝合金的0.6%。第三元素的影响：（1）Cr：强度随Cr含量的增加而线性增加。添加3at.% Cr含量是二元合金的2倍。添加3at.%的Cr富钛合金的塑性提高到2.7%。富铝合金中添加Cr会降低延展性。(2)Hf的加入对强度的影响与Cr的加入相似。Hf添加量可达4at.%富钛合金的塑性略有下降。Hf添加到富Al合金中使塑性降低到0.8%。(3)Nb ;含3原子%的合金的强度Nb增加到二元合金中的2.5倍。相反的，我不知道。在富铝合金中没有观察到强化效果。在富Ti和富Al合金中，由于添加3at.%的Nb，塑性降低到1/2。3.纯度的影响：使用纯度为99.91%的Ti将延展性提高到2.7%，这是二元合金中的最高值。

The effect of the Ti/Al retio, the addition of third elements (Cr, Hf and Nb) and the use of high purity base metals on mechanical properties of TiAl was studied at room teperature.1. Effect of the Ti/Al ratio : Strength of Ti-rich alloys was higher than than of Al-rich alloys. Fracture strain (ductility) in Ti-rich alloys was about 1.8 % which was larger than that in Al-rich a alloys being 0.6 % .2. Effect of third elements : (1) Cr ; Strength increased linearly with increasing Cr content. The alloy with 3 at.% Cr reached two times of that in a binary alloy. The Cr addition of 3 at.% to Ti-rich alloys improved ductility to 2.7 %. The Cr addition to Al-rich alloys lowered ductility.(2) Hg ; The effect of Hf addition on strength was similar to that in the Cr added alloys. The Hf addition up to 4 at.% to the Ti-rich alloys lowered ductility a little. The Hf eddition to Al-rich alloys decreased ductility to 0.8 %.(3) Nb ; Strength of the alloy with 3 at.% Nb increased to 2.5 times of that in a binary alloy. On the contrary. No strengthening effect was observed in Al-rich alloys. Ductility in Ti- and Al-rich alloys was decreased to 1/2 due to the Nb addition of 3 at.%.3. Effect of purity : The use of Ti with 99.91 % purity increased ductility to 2.7 % which has been the highest value in the binary alloys.