High Strength-Thermal Conductivity Mg–Ga–Ca–Ce Sheet by Hot-Extrusion and Rolling

Abstract

The thermal conductivity of magnesium alloys is increasingly required for fast heat dissipation in the automotive and electronic fields. However, the methods for mechanical property improvement such as grain refinement and alloying tend to deteriorate their thermal conductivity. In this work, a novel low-alloy Mg–2Ga–0.6Ca–0.6Ce alloy exhibits a surprisingly good combination of high strength and high thermal conductivity compared with the other samples. The wrought alloys are of small grain sizes (< 2 μm), have high yield strength (> 272 MPa) and exhibit excellent thermal conductivity (> 143 W·m⁻¹·K⁻¹). The as-extruded alloy exhibits excellent yield strength (272 MPa) and high thermal conductivity (144.6 W·m⁻¹·K⁻¹) at room temperature. After 30% rolling, the yield strength is further increased to 283 MPa, and the thermal conductivity is slightly reduced to 143.2 W·m⁻¹·K⁻¹. The effects of Ca and Ce addition on mechanical properties and thermal conductivity are analyzed from dislocation density, dynamic recrystallization fraction (f_DRX), average grain size (d_DRX) and texture characteristics. The higher yield strength can be attributed to the combination of grain boundary strengthening, dislocation strengthening and second phase strengthening. Moreover, the addition of Ca and Ce can obviously reduce solute Ga atoms in α-Mg, which is the key to high thermal conductivity. Therefore, adding two alloying elements, Ca and Ce, significantly improves both tensile properties and thermal conductivity.

Graphical Abstract