Investigation on the relationship between intermediate temperature embrittlement and intergranular precipitate in Ni(Bi) alloy

Ni and Ni-based superalloys generally exhibit intermediate temperature embrittlement (ITE), which is usually interpreted by the evolution of intergranular precipitates. In this paper, the relationship between ITE and intergranular precipitates was investigated in a binary Ni(Bi) alloy. The tensile ductility of Ni(Bi) alloy shows evident ITE with a maximum between 700 °C and 750 °C. The microstructure of the sample heat treated at 750 °C was observed to be free of precipitates within grains and at grain boundaries. The interpretation of intergranular precipitates for ITE was then discussed and proven to be invalid.

► Tensile ductility of Ni(Bi) alloy reveals maximum embrittlement between 700 °C and 750 °C.
► Microstructure shows no intergranular precipitates after heat treatment at 750 °C for 45 min.
► The interpretation of intergranular precipitates for ITE is proven to be invalid.
► Experimental results provide data point to determine phase diagram of Ni and Bi in very dilute limit.