Extrusion limit diagram of AZ91–0.9Ca–0.6Y–0.5MM alloy and effects of extrusion parameters on its microstructure and mechanical properties

Abstract

An AZ91–0.9Ca–0.6Y–0.5MM (AZXWMM91100) alloy, which has higher corrosion resistance, ignition resistance, and extrudability than a commercial AZ91 alloy, has been developed recently. In this study, the AZXWMM91100 alloy is extruded at various temperatures (300–400 °C) and ram speeds (1–14.5 mm/s), and the cracking behaviors, microstructure, and tensile properties of the extruded materials are systematically analyzed. On the basis of the pressure limit and surface and internal cracking limit, the extrusion limit diagram providing a safe extrusion processing zone is established. All of the materials extruded at temperatures and speeds within the safe extrusion processing zone have high surface quality and moderate tensile ductility with an elongation higher than 10%. Moreover, they have a fully recrystallized grain structure and contain undissolved particle stringers arranged parallel to the extrusion direction. The grain size of the extruded material does not show any relationship with the Zener–Hollomon parameter (Z). However, the yield strength (YS) of the extruded material is inversely proportional to the logarithm of the Z value, and their relationship is expressed as YS = −31.2•log(Z) + 536. These findings may broaden the understanding of the AZXWMM91100 alloy with excellent chemical and physical properties and provide valuable information for the development of high-performance extruded Mg products using this alloy.

Keywords

• Magnesium
• Extrudability
• Extrusion limit diagram
• Microstructure
• Tensile properties