Microstructure and thermophysical properties of Mg-2Zn-xCu alloys
(1. State Key Laboratory of Nonferrous Metals and Processes, GRINM Group Co., Ltd., Beijing 100088, China;
2. GRIMAT Engineering Institute Co., Ltd., Beijing 101407, China;
3. General Research Institute for Nonferrous Metals, Beijing 100088, China)
2. GRIMAT Engineering Institute Co., Ltd., Beijing 101407, China;
3. General Research Institute for Nonferrous Metals, Beijing 100088, China)
Abstract: The microstructure and thermophysical properties of Mg-2Zn-xCu alloys (x=0.5, 1.0 and 1.5, at.%) were investigated through microstructural and thermophysical characterization, heat treatment, and first-principles calculations. It was found that the addition of Cu had influence on the microstructure and thermophysical properties of the alloy. As the Cu content increased, the content of the MgCuZn phase increased in the as-cast alloys along with the electrical and thermal conductivities. After solution treatment, the eutectic structure partially decomposed and Zn atoms dissolved into the matrix, leading to the decrease in both the electrical and thermal conductivities of the alloy. During the early stages of the aging treatment, solute atoms precipitated from the matrix, thus increasing the electrical conductivity of the alloy. After aging for 24 h, the thermal conductivity of Mg-2Zn-1.5Cu alloy reached the maximum of 147.1 W/(m·K). The thermostable MgCuZn phases were responsible for increasing the electrical and thermal conductivities. Smaller amounts of Zn atoms dissolved in the matrix resulted in smaller lattice distortion and higher conductivities. The first-principles calculations findings also proved that the MgCuZn phases had very high conductance.
Key words: Mg-Zn-Cu alloy; heat treatment; electrical conductivity; thermal conductivity; first-principles calculations