Fabrication of diamond/W-Cu functionally graded material by microwave sintering

A four-layered W/Cu functionally graded material (FGM) (W90% þ Cu10%/W80% þ Cu20%/W70% þ Cu30%/W60% þ Cu40%, wt.% fraction) and a four-layered diamond/W-Cu FGM (W90% þ Cu10%/W80% þ Cu20%/W70% þ Cu30%/W55% þ Cu40% þ diamond5%, wt.% fraction) were fabricated by microwave sintering. The thermal conductivity and thermal shock resistance of diamond/W-Cu FGM and W-Cu FGM were investigated. The morphologies of the diamond particles and different FGMs were analyzed using AFM, SEM, EDS, and TEM. The results show that a 200 nm rough tungsten coating was formed on the surface of the diamond. The density of the tungsten-coated diamond/W-Cu FGM, obtained by microwave sintering at 1200 ℃ for 30 min, was 94.66%. The thermal conductivity of the four-layered diamond/W-Cu FGM was 220 W·m^-1·K^-1, which is higher than that of the four-layered W/Cu FGM (209 W m^-1 K^-1). This indicates that adding an appropriate amount of tungsten-coated diamond to the high Cu layer W/Cu FGM improves the thermal conductivity of the composite. The diamond/W-Cu FGM sintered at 1200 ℃ for 10 min exhibited better thermal shock resistance than diamond/W-Cu FGM sintered at 1100 ℃ for 10 min