Ultra-high thermal conductivity Mg-based materials with upgrading reinforced efficiency via three-dimensional GF/CF network structure

Abstract

The proposal for second-generation magnesium (Mg) matrix thermal management materials creates opportunities to further enhance the thermal conductivity of Mg alloys (surpassing that of pure Mg). Yet, the formidable challenge is the unsatisfactory reinforced efficiency of reinforcements. Herein, the three-dimensional GF (graphite flake)/CF (carbon fiber) continuous network structure in the Mg-2.10Nd-0.36Zn-0.06Zr alloy matrix was constructed by the differential stir casting and subsequent direct extrusion process. The microstructure of the GF/CF Mg-based materials with diverse GF diameters was characterized at multiple scales. The three-dimensional GF/CF continuous network structure was established when the GF diameters reached 150 μm. The in-situ formation of Nd₂O₃ effectively filled the interface, which ameliorated the interfacial bonding and ensured the continuous transmission of heat flow. The Mg-based materials with the three-dimensional GF/CF continuous network structure demonstrated an ultra-high thermal conductivity of 171 W/(m·K) with an outstanding reinforced efficiency of 64.4% and a low density of 1.85 g/cm³. This performance represents the pinnacle of comprehensive heat conduction among Mg-based materials reported to date. The heat-conduction behaviors were demonstrated thoroughly through diverse thermal conductivity models and actual microstructural finite element (FE) simulations. This research proposes a promising methodology towards the ultra-high thermal conductivity Mg-based materials with remarkable reinforced efficiency and lightweight properties, which contributes to the development of advanced second-generation Mg-based thermal management materials.