Influence of Ni additions on the microstructure and tensile property of W-Cu composites produced by direct energy deposition

Abstract

In this paper, the direct energy deposition technology was applied to produce the W-Cu composites. The Ni powder ranging from 1 to 10 wt% was added into the W-Cu mixed powder to improve the wettability between W and Cu. The influence of Ni additions on the microstructural characterization, phase composition, relative density, and tensile property of thin wall samples was investigated. The morphology and temperature history of the melt pool were detected to analyze the microstructure evolution. The research results show that there were plenty of aggregations of W particles and residual pores in the joint area of the 60W40Cu thin wall sample. Due to the effect of Ni additions on reducing the surface tension between W and liquid Cu, the W particles tended to be uniformly distributed in the matrix with the increase of Ni content. Meanwhile, Ni additions decreased the cooling rate of the melt pool, which promoted the transformation from columnar grains to dendrites in the matrix. Furthermore, the Ni additions could significantly increase the relative density and tensile strength of W-Cu composites. When Ni content was increased from 0 wt% to 10 wt%, the relative density rose from 83.1% to 98.4%, the tensile strength of longitudinal and transverse specimens was nearly 3 and 5 times respectively as high as that of the specimens without Ni content.