Improved parallelism of graded W–Cu–SiC materials by adjusting the coefficient of thermal expansion

Abstract

Differences between the coefficients of thermal expansion (CTE) in graded layers cause large deformations and poor parallelism in functionally graded materials (FGM). To address this, SiC has been added to avoid CTE mismatches and obtain high-parallelism tungsten copper silicon-carbide (W–Cu–SiC) FGM. In this work, homogeneous W–Cu–SiC composites and seven-layered W–Cu–SiC FGM formed from thin graded layers were fabricated by tape casting followed by hot-press sintering. The microscopic structures and properties of the W–Cu–SiC composites were investigated using field emission scanning electron microscopy, X-ray diffraction, and bending strength and CTE tests. The effects of W content on the relative density, bending strength and CTE of W–Cu–SiC composites were studied. The bending strength of the 40W–40Cu–20SiC (vol%) reached an optimal value of 753.0 MPa. Varying the components ratios of the W–Cu–SiC composites produced little variation in the CTE, effectively reducing the interfacial thermal and residual stresses of the W–Cu–SiC FGM. The interfaces of the W–Cu–SiC FGM were bonded well, with no cracks or delamination, and thus a high parallelism was achieved in W–Cu–SiC FGM.