Hf对Ni-Ti-Al合金高温变形行为影响

Effect of Hf Addition on the High-Temperature Deformation Behavior of Ni-Ti-Al Alloys

采用热模拟实验研究了Ni50Ti46-xAl4Hfx(x=0～6,at%)合金的微观组织特点和高温变形行为。合金由基体相NiTi和第二相Ti2Ni组成。Hf全部溶解在基体相和第二相中,并且促进了第二相的析出,显著提高了合金的高温强度。Ni-Ti-Al-Hf合金在700～800℃下变形行为的研究表明:合金具有良好的高温压缩性能,流变应力随着应变速率的减小或变形温度的增加而降低,其高温变形行为符合温度补偿幂规律描述。Hf的添加使合金的应力指数(n)和变形激活能(Q)上升,这主要是由于Hf的固溶强化、促进Ti2Ni相析出强化和高温稳定性造成的。

The microstructure and high temperature deformation behavior of Ni50Ti46-xAl4 Hf x（x=0～6,at%） alloys were investigated by compressive tests at elevated temperatures.Results show that the Ni-Ti-Al-Hf alloys consist of NiTi and Ti2 Ni phases.Hf exists as the solid solution element in both of NiTi and Ti2 Ni,and promote the precipitation of Ti2Ni,thus greatly improving the yield stress of the alloys at high temperatures.The alloys possess good compressive property.The flow stress generally decreases with the increasing deformation temperature or the decreasing initial strain rate.The deformation feature of the Ni-Ti-Al-Hf alloys could be adequately described by standard power law.The addition of Hf increases the stress exponent（n） and activity energy（Q）,resulting from its strong solid solution strengthening effect and high-temperature stability and the promotion of precipitation strengthening effect of Ti2 Ni phase.