Development of Advanced Heat Resistant Aluminides Produced by ma Process

采用机械合金化(MA)工艺制备了(Ni3Al+Ni3Nb)、(NiAl+NiNbAl)、(NiAl+Ni3Al)、NiAl和Ni3Al系金属间化合物。以纯镍、纯Nb粉和NiAl预合金粉为原料，在研磨机上进行了MA。用真空热压法制备了镁铝粉末，烧结后的铝化物颗粒细小，平均粒径小于5微米，相对密度大于96%。除了(Ni3Ai+Ni3Nb)和(NiAl+NiNbAl)外，所有铝化物的室温高强度和大于10%的大断裂应变组合被压缩试验所证实。在高温下，这些铝化物表现出稳定的变形，在测试过程中没有断裂。在1173K下观察到了(Ni3Al+Ni3Nb)的应变速率敏感指数m(&gt；0.6)。这种大于0.3的大m值被认为与超塑性的发展有关。

The intermetallics that belong to Ni-Nb-Al system, (Ni_3Al+Ni_3Nb), (NiAl + NiNbAl), (NiAl+Ni_3Al), NiAl and Ni_3Al were produced by mechanical alloying(MA)process with a view to refining microstructures. MA was carried out in the attritor mill using pure nickel, pure niobium powder and NiAl prealloyed powder as starting materials. MA powders were consolidated using the vacuum hot pressing.Sintered aluminides showed fine grain structures with average grain diameter under 5 mu m and relative density above 96%. The combination of high strength and large fracture strain of more than 10% at room temperatures was confirmed by compression test for each aluminide except for both(Ni_3AI+Ni_3Nb) and (NiAl+NiNbAl). At high temperatures, these aluminides exhibited a steady state deformation and no fracture during testing. The strain rate sensitivity exponent of m (>O. 6) was observed for (Ni_3Al+Ni_3Nb) at 1173K. Such large m value more than 0.3 is believed to be associated with the development of superplasticity.