Improving mechanical properties of ZM61 magnesium alloy by aging before extrusion

• Aging treatment and subsequent extrusion lead to uniform and fine microstructure.
• An outstanding strength and elongation balance of Mg-6Zn-1Mn alloy.
• Uniform and dispersed spherical precipitates were obtained.

The effect of aging treatment before extrusion on microstructure and mechanical properties of Mg-6Zn-1Mn alloy was investigated. Results showed that the existence of dispersive fine MgZn2 particles before extrusion promoted dynamic recrystallization in subsequent extrusion process and leaded to fine microstructures (grain size 1∼2 μm). The rod-shaped and plate-shaped precipitates in aged alloys transformed to fine and dispersed spherical precipitates after extrusion process. With aging and extrusion treatment, ZM61 alloy showed an outstanding tensile strength and elongation balance (YS 281 MPa, UTS 378 MPa and elongation 19.3%); compressive yield strength increased from 148 MPa to 259 MPa. The tension–compression yield asymmetry was reduced at the same time. The strengthening effect of aging treatment before extrusion in ZM61 alloy proved in this paper provided a new method for the design of relatively inexpensive high-performance magnesium alloys.