INVESTIGATION ON MICROSTRUCTURE AND SUPERPLASTICITY OF A NiAL-BASED MULTIPHASE ALLOY
NiAl基多相金属间化合物的显微组织,超塑性研究

The microstructure of a NiAl-based multiphase alloy with a composition of Ni-25Al-25Cr has been investigated, which consists of NiAl matrix surrounded by a eutectic of α-Cr, β-Ni(Al,Cr) and γ'-Ni3(Al,Cr), and a large amount of α-Cr precipitates distributed uniformly in NiAl matrix. This alloy exihibits superplasticity elongation as high as up to 480% at 1123-1223 K and strain rates of 2.2×10-4 -3.3×10-2 s-1. The fracture after superplasticity deformation results from cavities generated by grain boundary sliding and cleavage in the grains, the mechanism for superplasticity has also been discussed.