Microstructure And Properties Of Tungsten Coated Diamond/Aluminum Composites

In this paper, in order to improve the interface bonding strength of diamond particles and aluminum matrix, the diamond particles are plated a metal layer of tungsten interface nanolayer by magnetron sputtering. The coating thickness is controlled by controlling the magnetron sputtering time. The theoretical thermal conductivity can calculated by the Acoustic Mismatch Model. Moreover, we can obtain the rule of thermal conductivity and interfacial thermal resitance with the variation of the coating thickness and design the reasonable coating thickness. The uncoated diamond/aluminum composites and the coating diamond/aluminum composites with a tungsten interface nanolayer were made by squeeze casting process and vacuum pressure infiltration process. Scanning Electron Microscope(SEM), Atomic Force Microscope(AFM) and Transmission Electron Microscope(TEM) are used to observe the microstructure of the diamond/aluminum composites. Laser Thermal conductivity Tester(LFA) and Thermal Expasion Istrument(DIL) are used to measure the mechanical properties and thermal properties of diamond/aluminum composites.For the uncoated diamond/aluminum composites, the aluminum matrix bonds to square {001} surfaces of the diamond, but does not stick to the {111} surfaces when the diamond surface is not specifically prepared. And there are some voids and cracks at the interface. For diamond/aluminum composites with nickel plating, the aluminum matrix almost coated with all of the surfaces of the diamond particles. There is no selective adhesion and voids, cracks at the interface. And the interfacial bonding between diamond and aluminum matrix is better. Therefore, the interfacial bonding and the interfacial bonding strength between diamond and aluminum matrix is improved by adding nickel plating.The interfacial bonding between the diamond particles and the aluminum matrix, and the properties of composites are improved by increasing tungsten interface nanolayer. When the thickness of tungsten interface nanolayer is 100 nm, the W-diamond/aluminum composites have the highest thermal properties: 622 W/( m·K), 11.87% higher than that of the composites without the W interface nanolayer, and the best mechanical properties: 304 Mpa, 24.08% higher than the uncoating diamond/aluminum composites. With the increase of coating thickness, the interfacial thermal conductance increase, then the thermal conductivity of diamond/aluminum reduce. When the W coating thickness are 150 nm and 200 nm, the thermal conductivity of W-diamond/aluminum composites are 595 W/( m·K) and 588 W/( m·K).Study the stability performance of diamond/aluminum composites by putting composites in hot and humid environment and high-low temperature cycle environment.When the uncoated diamond/aluminum composite are putted in hot and humid environment 30 days, its’ thermal property decreased 23.02%, its’ mechanical property decreased 33.06%. However, the properties of diamond/aluminum composites with tungsten interface nanolayer are very stable. When the uncoated diamond/aluminum composite undergo 200 high-low temperature cycles, its’ thermal property decreased 17.27%, its’ mechanical property decreased 26.53%. And the properties of diamond/aluminum composites with tungsten interface nanolayer are still steady.