Microstructural changes during annealing of cast Ni–Cr–Hf alloys

Abstract

In order to gain knowledge of the nickel–rich corner of the Ni–Cr–Hf phase diagram, microstructures of cast alloys and their evolution towards equilibrium conditions have been followed by optical and scanning electron microscopy, microprobe analysis, and quantitative metallography. The evolution of as–cast microstructures involves the development of a Ni₅Hf plate–like precipitate in two–phase alloys, and various morphological changes in three–phase alloys. As–cast structures are compared with those obtained by arc melting. Direct processing of the scanning electron microscope image has proved to be a valuable tool for microstructural characterization of the transforming phases.

MST/349