Influence of Aging Treatment on Precipitation Behavior of η Phase in Ni-Co-Cr Alloy

The influence of aging treatment on precipitation behavior of η phase in a new Ni-Co-Cr fastener superalloy, AEREX350, was investigated by means of optical microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The precipitation behavior of η phase with two kinds of morphologies in this material was found to be sensitive to the temperature and time of aging treatment. Time-temperature-transformation curves of these two η phase were achieved. Furthermore, diffraction patterns revealed the semi-coherent orientation relationship between η phase and γ matrix. This approach may be used to optimize the microstructure of the alloy for excellent mechanical properties.