Effect of Heat Treatment on the Microstructure of Multiphase NiAl-based Alloy

<正>The alloy Ni-AI26.6-Cr13.4-CoS.1-Ti4.3-W1.3-Mo0.9（at,pct） was fabricated from superalloy K44 and AI element using vacuum induction and casting technique.Investigations to this alloy reveal that a new phase Cr3Ni2 possessing low melting point and poor ductility is formed,which is distributed as a network along NiAI matrix grain boundaries.Subsequent different solution and aging treatments are carried out and lead to microstructural changes to various extents.Rapid cooling after solution at 1250℃for 20 h gives rise to macrocracks in the specimen while slow cooling after the same treatment results in the formation of sphericα-Cr solid solution and needle-like Ni3Al phase,which are embedded in NiAI matrix.It is comfirmed that aging treatments initiate lath-shaped Ni3Al phase and pearl-shapedα-Cr phase to precipitate from the NiAI matrix,which own orientation relationships with these precipitates.