Effect of Thickness on the Thermal Conductivity and Microstructure of Die-Cast AZ91D Magnesium Alloy

  • PDF / 2,395,067 Bytes
  • 8 Pages / 593.972 x 792 pts Page_size
  • 64 Downloads / 186 Views

DOWNLOAD

REPORT


INTRODUCTION

BEING among the lightest commercial structural materials, magnesium alloys have an excellent combination of high specific strength, high specific stiffness, desirable damping ability, good thermal conductivity, and superior recyclability. Thus, they possess wide industrial application prospects in various fields from aerospace to 3C products.[1–3] It has been reported that the thermal conductivity of pure magnesium is 158 W (m K)1 at ambient temperature, which is the third one following that of the pure Cu and pure Al.[4] Therefore, magnesium and its alloys have significant application prospects in devices that have special requirements for heat dissipation, mechanical properties and weight reduction, such as laptops, mobile phones and highpower LED radiators.[5] High requirements are desired for magnesium alloy products in these devices. The thermal conductivity of magnesium alloys is influenced by many factors, such as elements, heat treatments and YUE MING, XUANXI XU, and HENGYU WEN are with the College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China. GUOQIANG YOU and JIANHUA ZHAO are with the College of Materials Science and Engineering, Chongqing University and also with the National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400044, China. Contact e-mail: [email protected] Manuscript submitted April 15, 2019.

METALLURGICAL AND MATERIALS TRANSACTIONS A

forming processes. Ying et al.[6] investigated the thermal conductivity of the as-cast and the as-extruded binary Mg-Zn alloys with Zn concentration ranging from 0.5 to 5.0 wt pct. It was found that, with the increasing concentration of Zn, the thermal conductivity decreased gradually in both the as-cast and the as-extruded binary Mg-Zn alloys. Solution and intermetallic compounds in alloys with higher Zn concentrations were considered as the scattering sources of electrons and phonons, which resulted in a reduction in thermal conductivity. Su et al.[7] studied the effect of heat treatments on the thermal conductivity of Mg-Nd alloys, and found that the thermal conductivity of the as-cast Mg-Nd alloys was higher than that of T4 counterparts, but lower than that of corresponding T6 alloys. These were ascribed to the scattering of electrons and phonons by solution atoms. Peng et al.[8] discussed the influence of the extrusion temperature on thermal conductivity of Mg-2.0Zn-1.0Mn-0.2Ce alloy. The thermal conductivity first increased to the maximum value of 131 W/(m K) when the extrusion temperature increased from 340 C to 400 C, and then reduced to 125 W/(m K) when the extrusion temperature continuously increased to 430 C, while the solid solution was deemed the main factor affecting the thermal conductivity. Magnesium alloys are mainly formed by the die-cast process. However, little attention has been paid to the thermal conductivity of die-cast magnesium alloys. Thickness is the main factor affecting the microstructure and properties of die-cast magnesium components, but

the effect