Influence of Aging Prior to Extrusion on the Microstructure and Mechanical Properties of an Extruded AZ91 Alloy

Herein, aging prior to extrusion is used to regulate the microstructure and mechanical properties of an extruded AZ91 alloys. The results show that pre‐aging can induce numerous precipitates in Mg matrix to refine the recrystallized microstructure during hot extrusion of AZ91 alloys. After extrusion, most precipitates distribute at grain boundaries, suppressing grain growth. Thus, coupling pre‐aging and hot extrusion can effectively enhance the yield strength of the AZ91 alloy and maintain considerable plasticity (>15%) simultaneously. In contrast, the improvement in mechanical properties is not so effective by direct extrusion and subsequent heat treatment. Although the subsequent aging (T6 treatment) can induce dense precipitates inside grains generating strong precipitation hardening, it badly reduce the tensile ductility (to 6.3%) as well. Moreover, the T6 treated sample also exhibits lower yield strength compared with the extruded sample via coupling pre‐aging and hot extrusion. Based on the experimental analyses, the underline mechanisms are discussed.