RAPID SOLIDIFICATION OF MG-AL-ZN-SI ALLOYS

The increasing demands for improved performance, especially in the aerospace industry, have led to the development of new materials with improved mechanical properties combinations. In particular, where weight considerations are in demand, both in terms of cost and performance, the use of low density materials (magnesium, aluminium, titanium), are the prime candidates for structural applications. The present contribution is concerned with the investigation of Mg-Al-Zn-Si alloys. The level of retained microhardness (1 h at 100-degrees-C, 200-degrees-C, 300-degrees-C, 400-degrees-C and 500-degrees-C) of twin-piston rapidly solidified splats was used as an initial indication of the thermal stability of such alloys. X-ray and TEM techniques were employed for microstructural characterization. Promising results were obtained in a Mg-12Al-2.5Zn-3Si (in wt.%) alloy as compared with alloys of the type AZ91-HP and Allied-EA65, under the same conditions of solidification and heat treatment.