Achieving extraordinary combination of strength and elongation of AZ80-0.5Ca alloy

AZ80-0.5 wt% Ca alloy was fabricated via rheo-cast process, extruded at 450 °C and followed by aging heat treatment. Microstructure and mechanical properties of the alloy were studied before and after extrusion and aging stages. Extrusion modified microstructure of the alloy by refining grain size and re-distribution of β-Mg17Al12 phase. Partial dissolution of the β phase was occurred in both as-cast and extruded alloys by solution treatment. During subsequent aging, more coarse discontinuous precipitates were observed at grain boundaries in the microstructure of as-cast alloy, while some continuous precipitates were also initiated within the grains. In the extruded alloy, more grains were occupied by continues precipitates. In the extruded and direct aged (H-E-D) alloy, hierarchical precipitate structure was observed and most of the grain boundaries areas were preferably occupied by discontinuous precipitates and dynamic precipitates. Changing precipitation behavior in these conditions was mainly attributed to the structure defects introduced by extrusion and amount of the supersaturation of matrix. After extrusion and T6 treatment, the tensile properties and hardness of alloy were increased. An extraordinary combination of strength (253 MPa) and elongation (7.8%) was achieved in AZ80-0.5Ca Alloy in extruded and direct aged state. Also, remarkably improvement in yield strength, ultimate strength and elongation of the H-E-D alloy than the as-cast one was obtained about 101.6%, 180.2% and 730.8%, respectively.