INFLUENCE OF HEAT TREATMENT ON THE STRUCTURE AND MECHANICAL PROPERTIES OF Ni3Al-BASED ALLOYS

This study investigates two Ni3Al - based intermetallic alloys containing differing amounts of zirconium, boron and chromium. Gradual homogenisation was accomplished through long-lasting annealing, up to 100 hours, at 1000 degrees C or 1200 degrees C in air or argon atmospheres. A higher level of homogeneity of the cast without chromium alloy was obtained in comparable heat treatment conditions. Annealing temperature has an essential influence on the homogenisation process of the investigated alloys. This influence is much more essential than annealing time and environmental conditions. These treatment conditions are critical for microstructure, as well as the properties of the investigated alloys. For matched conditions of plastic working an optimum level of strain hardening was obtained. This did not cause a loss of cohesion in the investigated alloys, but it was sufficient to start a recrystallisation process. The fine-grained structure of the investigated alloys is responsible for the improvement in their mechanical properties.