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.