Effect of heat treatment on the microstructure and elevated temperature tensile property of Fe-doped NiAl-Cr(Mo)-(Hf,Dy) eutectic alloy

The microstructure and elevated temperature tensile property of Fe-doped NiAl-Cr(Mo)-(Hf,Dy) eutectic alloy before and after heat treatment were investigated by SEM, TEM and elevated temperature tensile test. The result shows that the as-cast alloy has higher elevated temperature strength. The heat treatment leads to the coarsening and local dissolution of lamellar structure, and thus results in the weak decrease of elevated temperature strength and the increase of the ductility. Moreover, the observation of side surface reveals that the micropores in the heat-treated alloys, hindering the facture of tensile specimen, are less than those in the as-cast alloy. Meanwhile, more dimples and lamellar neckings are observed in the fracture surface of heat-treated alloys, even the dislocation substructure occurs in Cr(Mo) phase. This demonstrates that the heat treatment results in the decrease of elevated temperature strength and the increase of ductility.