钕对NiAl基共晶合金高温流变行为的影响

Effect of Doping Nd on Flow Behavior of NiAl-Based Eutectic Alloys at High Temperature

研究了钕对NiAl-28Cr-5.5 Mo-0.5 Hf共晶合金显微组织及高温流变行为的影响。结果表明:NiAl-28Cr-5.5 Mo-0.5 Hf基体合金是由黑色的Ni Al相和灰白色的Cr(Mo)相组成的共晶组织,在相界处聚集有白色的Ni2Al Hf(Heusler)相,加入稀土钕可细化组织;Ni Al-28Cr-5.5 Mo-0.5 Hf(wNd=0.05%)合金在较高的应变速率(ε.=1.94×10-2s-1和.ε=1.94×10-3s-1)下,含稀土合金的流变应力大于不含稀土合金的流变应力,而在低应变速率(.ε=1.94×10-4s-1)下,这种强化现象消失。幂指数规律和温度补偿的幂指数规律可以很好地描述各种合金的高温压缩流变行为。加入稀土可降低合金的应力指数和变形激活能,这是因为稀土偏聚在相界上,致使相界上的空位浓度发生变化。

The microstructure and high temperature flow behavior of the as-cast NiAl-28Cr-5.5Mo-0.5Hf alloys with or without Nd were investigated. The microstructure of NiAl-28Cr-5.5Mo-0.5Hf alloy consists of NiAl matrix phase and Cr（Mo） phase, as well as the white Ni2 AlHf （Heusler） phase precipitated at the interfaces. Doping of （WNd=0. 05%） Nd caused refinement of eutectic cells and eutectic spacing. At higher strain rate （ε= 1.94×10^-2 s^-1 and ε=1. 94×10^-5 s^-1）, the flow stress level is higher than that of alloy without Nd. At lower strain rate, the strengthening effect disappeared. The high temperature flow behavior can be depicted by power law equation and temperature-compensated power law equation. The decrease of the stress exponent and active energy can be attributed to the change of the content of voids due to the segregation of Nd at grain boundaries for the alloy with the addition of Nd.