Effect of Extrusion Temperature on Mechanical Properties of AZ91 Alloy in Terms of Microstructure and Texture Development

Abstract

This study investigates the effect of extrusion temperature on room temperature tensile properties of as-extruded AZ91 plates regarding microstructure and texture development. Forward extrusion was performed at 300, 350 and 400 °C with an extrusion ratio of 25:1. Yield strength rather increases from 212 to 224 MPa as extrusion temperature rises, despite grain growth from 11.9 to 41.2 µm. To understand the underlying mechanisms of this unusual hardening, the effects of microstructural features are discussed with emphasis on grain size, precipitates, stored strain energy and texture. Microscopic analyses and simulation results reveal that grain refinement, continuous precipitates and stored strain have no decisive effect on yield strength. Development of stronger basal texture leads to an increase in yield strength. Texture strengthening makes basal slip more difficult to be activated when loading along the extrusion direction. Based on this, stronger basal texture plays a more dominant role in increasing yield strength.