Effects of Zn/RE ratio on mechanical performance and thermal conductivity of rolled Mg-6Zn-xGd-1Er-0.5Zr alloys

Mechanical performance and thermal conductivity are the key parameters for Mg alloys used as heat dissipation components in electronic products. This study designed the Mg-6Zn-xGd-1Er-0.5Zr (x = 0, 2, 5 wt.%) alloys including single I phase, I+W phase and single W phase according to various Zn/RE ratios. The rolled ZGE621K alloy exhibited excellent synergy between mechanical performance and thermal conductivity i.e. its tensile strength of 325 MPa, yield strength of 286 MPa, elongation of 10.1 % and thermal conductivity of 138.6 W/(m·k)). The I phase played the roles of work hardening and secondary phase strengthening, increasing yield strength. Conversely, the W phase promoted dynamic recrystallization, weakening basal texture and significantly enhanced elongation. The solute atoms and secondary phases are dominated to affect the thermal conductivity, but the variation in thermal conductivity among the alloys is primarily attributed to the effect of solute RE atoms. Compared to the I phase, the W phase was more effective to purify the α-Mg matrix by incorporating higher solute RE atoms, thereby reducing lattice distortion and enhancing thermal conductivity. It is suggested that the synergistic effect of I phase and W phase is the most effective method for obtaining high mechanical performance as well as thermal conductivity of Mg alloys. The developed Mg alloy sheets combine high strength with high thermal conductivity, addressing the concurrent demands for mechanical performance and efficient heat dissipation in 5 G electronics housings and electric vehicle battery enclosures.

Duke Scholars

Author Zhaohui Wang Pathology