Microstructure evolution and mechanical properties' improvement of NiAl–Cr(Mo)–Hf eutectic alloy during suction casting and subsequent HIP treatment

A NiAl–Cr(Mo)–Hf eutectic alloy was prepared by suction-casting technique and subsequently hot isostatic pressing treatment. Microstructure and mechanical tests were performed and the results revealed that the suction-cast alloy possessed fine NiAl/Cr(Mo) lamellar, large area fraction of eutectic cell and semi-continuously distributed Ni2AlHf phase at the cell boundaries. After the HIP treatment, the Ni2AlHf particles became fine and distributed evenly in the alloy. Moreover, some of the Ni2AlHf particles along the eutectic cell boundaries were transformed into Hf solid solution phase. Compared with the conventionally cast alloy, the room-temperature compressive ductility and strength of the suction-cast alloy attained significant improvement. In addition, the room-temperature ductility and elevated temperature strength of suction-cast alloy were markedly enhanced by HIP treatment.