Preparation and Thermal Properties of BN and LPSO Hybrid Reinforced Magnesium Matrix Composite

Hexagonal boron nitride (h-BN) is a ceramic material with high thermal conductivity (TC) and low coefficient of thermal expansion (CTE), which can improve multiple thermal properties of metal-matrix composites as a reinforcing particle, but its wettability with metal melt is very poor. In order to enhance the wettability between the h-BN and magnesium alloy melt, the electroless plating was used to coat a thin layer of pure nickel on h-BN particles, which was proved to be effective and efficient in this study. The results showed that by adding Y element to magnesium alloy melt to consume Ni element melted from the nickel-plating layer, the long period stacking ordered (LPSO) structure composed of Mg-Ni-Y was successfully formed, and the magnesium matrix composite reinforced by hybrid h-BN and LPSO structure was obtained. After ultrasonic treatment (UT), the TC of the magnesium composite containing 3 vol% h-BN and 14.16 vol% LPSO is 99.92 W/(m·K), which is a 8.3% enhancement compare to the composite without UT. The average CTE (293-373 K) of the composite is 18.36×10-6 K-1, which is reduced by 29.4% compared with pure magnesium.