Microstructure and mechanical properties of a rapidly solidified Ni3Al–Cr alloy after thermal treatments

Abstract

The effect of thermaltreatments at 750, 900 and 1000°C on the microstructure and mechanicalproperties of arapidlysolidified Ni3Al–Cralloy is reported. The microstructure of the ribbons in the as-rapidlysolidified (RS) condition consisted of a partially ordered Ni3Al matrix and a fine Cr-rich second phase located at cell and grain boundaries. New and coarser α-Cr particles precipitated after annealing at 750°C. No significant changes in the microstructure were observed for longer times. The α-Cr precipitates tended to dissolve in the Ni3Al matrix after annealing at 900 and 1000°C. This dissolution seems to be controlled by the lattice Cr-diffusion in Ni3Al since the volume fraction of α-Cr particles decreased with increasing time and/or temperature of thermaltreatments.The mechanicalproperties of the ribbons were influenced by the microstructural changes such as grain size, volume fraction and size of the α-Cr precipitates, that occurred during the annealing treatments. Thus, ribbons in the RS condition and after annealing at 750°C were brittle however, they exhibited ductile behaviour afterthermaltreatments at 900 and 1000°C