钇对NiAl-28Cr-5.5Mo-0.5Hf合金显微组织和力学性能的影响

Influence of Yttrium on Microstructure and Mechanical Properties of NiAl-28Cr-5.5Mo-0.5Hf Alloy

采用压缩实验研究了在应变速率为 1 94× 10 - 3s- 1 时随着温度的变化不同Y含量对铸造NiAl 2 8Cr 5 5Mo 0 5Hf合金力学性能的影响 ,同时 ,运用扫描电镜 (SEM)及其能谱和X射线衍射 (XRD)方法分析了合金的显微组织。结果表明 ,加入Y后 ,合金的显微组织随Y含量的增加而逐渐得到细化 ,表现为共晶团的数目增多 ,共晶团内的Cr(Mo)纤维层间距减小 ,胞界处的Cr(Mo)棒减小 ;当Y含量达到 0 1% (质量分数 )时 ,在NiAl和Cr(Mo)的相界处形成稀土化合物Ni1 7Y2 和Al3Y ,削弱了界面结合力 ,导致屈服强度和塑性下降。此外 ,压缩实验测得在不同温度下 ,0 0 5 %Y含量的合金的压缩强度和压缩率优于其它Y含量的合金 ,所以适量Y可以改善NiAl 2 8Cr 5 5Mo 0

The influences of yttrium on the microstructure and mechanical properties of NiAl 28Cr 5 5Mo 0 5Hf alloy were investigated by using SEM, XRD and compressive tests, respectively. The results show that the microstructure of alloys is fined gradually with the yttrium content increasing. This causes the more quantity of grain cells and the finer spacing between Cr(Mo) fibers as well as smaller Cr(Mo) rods. When 0 1% (mass fraction) yttrium and above is added in the matrix, the yttrium compounds of Ni 17 Y 2 and Al 3Y form at the interfaces between NiAl and Cr(Mo) phase, which leads in the decrease of the strength and ductility. In addition, at the strain rate of 1 94×10 -3 s -1 , the compressive strength and ductility of 0 05% Y content alloy is superior to those of other alloys over a range of room temperature to high temperature. Therefore, the proper yttrium can improve the strength and ductility of this alloy.