A novel approach to fabricate W/Cu functionally gradient materials

A novel approach for fabricating tungsten copper functionally gradient materials (FGMs) with escalated electrical conductivity and sufficiently high density was proposed. It mainly consists of three procedures namely oxidation & volatilization and infiltration. In this way, a 98.5% theoretical density of W/Cu FGM was successfully fabricated. Furthermore, an equation for the increased porosity of tungsten skeleton which has been treated is derived by Shrinking nucleus dynamics model of heterogeneous reaction. Meanwhile, the effect of the different ratio of tungsten powder with different particle size, treatment temperature and time on pore-forming was investigated individually. Scanning electron microscopy and energy dispersed X-ray spectrometer analysis demonstrate that the W/Cu FGMs can be obtained by the oxidation & volatilization and infiltration method. Tungsten skeletons with porosity of continuous gradient distribution was fabricated, the copper content of the W/Cu FGMs decreases gradually from the surface layer to core layer. The fine particle size of W powder is favorable to the formation of porosity, that is, the porosity and amplitude of variation of porosity of the samples with more fine W power are larger. The W/Cu FGMs where tungsten skeletons were treated at higher temperature can acquire higher copper content. The W/Cu FGMs where tungsten skeletons were treated for a longer time can obtain a higher content of copper and a thicker gradient layer. The macro-hardness of W/Cu FGM increases gradually from the near-surface layer to the core layer. The thermal conductivity of the sample is about 198 W/m·K at room temperature and decreases with increasing temperature.