Study on the microstructure and mechanical properties of ZK60 magnesium alloy with submicron twins and precipitates obtained by room temperature multi-directional forging

The current study suggested that nano-scale twins in magnesium alloys can significantly affect the elastic limit, ultimate strength and corrosion performance. However, the complicated process of nano-scale twins preparation limits its industrial application. In this paper, the microstructure with submicron twins and precipitates of ZK60 magnesium alloy was designed by room temperature multi-directional forging (MDF) process, aiming to improve the enhancement effect of submicron twins by compensating the denseness of coherent interfaces with diffusely distributed precipitates. The results show that the MDFed ZK60 alloy can obtain high strength (yield stress (YS): 248.5 MPa, ultimate tensile strengths (UTS): 371.4 MPa). Good comprehensive mechanical properties can be finally achieved after heat treatment at 150 °C (YS: 226.5 MPa, UTS: 352.6 MPa, elongation: 17.1%). Submicron lamellar {10–12} twins were formed within the alloy due to the small strains in multi-passes of forging. During heat treatment at 150 °C, a large amount of β₁' phase was diffusely precipitated within the matrix and twins. The presence of precipitates effectively increases the denseness of dislocation motion barriers in submicron twins, which enables twin-boundary enhancement of ZK60 magnesium alloy. This work provides a new idea for the design of low-cost magnesium alloy forgings in industry.