Improvement of compressive strength and ductility in NiAl–Cr(Nb)/Dy alloy by rapid solidification and HIP treatment

The NiAl–Cr(Nb)/Dy alloy was fabricated by conventionally casting and rapid solidification and treated by hot isostatic pressing treatment (HIP). The results reveal that Cr2Nb phase contains much of Ni and Al elements and retains the C14 crystal structure at room temperature. The rapid solidification refines the NiAl phase, Cr2Nb phase and needle-like Cr2Nb precipitates in NiAl matrix. Moreover the rapid solidification increases α-Cr phase and results in the formation of Cr7Ni3 phase with stacking faults and microtwins inside. The HIP treatment transforms the needle-like Cr2Nb precipitate in the NiAl phase into sphere shape and blunts the tip of the Cr2Nb phases along the NiAl phase boundary. In addition, the HIP treatment leads to some moveable dislocations in the alloy, which is beneficial to the compressive ductility. The mechanical test shows the rapidly solidified alloy with HIP treatment has the best mechanical properties, whose compressive ductility is more than ten times that of the as cast alloy.