Abstract
The thermal deformation behaviour of Mg-9Gd-4Y-2Zn-0.5Zr alloy at temperatures of 360–480 °C, strain rates of 0.001–1 s−1 and a maximum deformation degree of 60% was investigated in uniaxial hot compression experiments on a Gleeble 3800 thermomechanical simulator. A constitutive equation suitable for plastic deformation was constructed from the Arrhenius equation. The experimental results indicate that due to work hardening, the flow stress of the alloy rapidly reached peak stress with increased strain in the initial deformation stage and then began to decrease and stabilize, indicating that the deformation behaviour of the alloy conformed to steady-state rheological characteristics. The average deformation activation energy of this alloy was Q = 223.334 kJ·mol−1. Moreover, a processing map based on material dynamic modelling was established, and the law describing the influence of the machining parameters on deformation was obtained. The experimental results indicate that the effects of deformation temperature, strain rate and strain magnitude on the peak dissipation efficiency factor and instability range were highly significant. With the increase in the strain variable, the flow instability range increased gradually, but the coefficient of the peak power dissipation rate decreased gradually. The optimum deformation temperature and strain rate of this alloy during hot working were 400–480 °C and 0.001–0.01 s−1, respectively.
Highlights
Magnesium (Mg) alloys have become a popular lightweight structural material and are widely used in automobiles, high-speed railways and aircraft [1–5]
An increasing number of studies have found that adding rare earth (RE) elements into Mg alloys can improve the properties of the alloys at both room and high temperature [9–13]
The results show that this alloy was suitable for hot working at high strain rates and that the main deformation mechanism involved dislocation climbing at high temperatures
Summary
Magnesium (Mg) alloys have become a popular lightweight structural material and are widely used in automobiles, high-speed railways and aircraft [1–5]. It is well-known that Mg alloys have poor plasticity and formability at room temperature because of their dense hexagonal close-packed structure [6,7]. An increasing number of studies have found that adding rare earth (RE) elements into Mg alloys can improve the properties of the alloys at both room and high temperature [9–13]. After deformation, this process can form fine crystalline materials
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