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

The effect of thermal treatments at 750, 900 and 1000 degrees C on the micr ostructure and mechanical properties of a rapidly solidified Ni3Al-Cr ahoy is reported. The microstructure of the ribbons in the as-rapidly solidified (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 al pha-Cr particles precipitated after annealing at 750 degrees C. No signific ant changes in the microstructure were observed for longer times. The alpha -Cr precipitates tended to dissolve in the Ni3Al matrix after annealing at 900 and 1000 degrees C. This dissolution seems to be controlled by the latt ice Cr-diffusion in Ni3Al since the volume fraction of alpha-Cr particles d ecreased with increasing time and/or temperature of thermal treatments. The mechanical properties of the ribbons were influenced by the microstructura l changes such as grain size, volume fraction and size of the alpha-Cr prec ipitates, that occurred during the annealing treatments. Thus, ribbons in t he RS condition and after annealing at 750 degrees C were brittle however, they exhibited ductile behaviour after thermal treatments at 900 and 1000 d egrees C. (C) 2000 Elsevier Science S.A. All rights reserved.