Liquid Copper Infiltration and Characterization of Additively Manufactured W Lattice Structures

Abstract

Tungsten-copper composites (W-Cu) have a wide range of engineering applications ranging from arc-resistant electrodes, high voltage electrical contacts to heat sinks for integrated circuits and plasma-facing components of fusion reactors. They combine high corrosion and erosion resistance, very good thermal and electrical conductivity, low thermal expansion, with good mechanical properties.  However, the fabrication of such materials is limited in terms of shape complexity and internal distribution of individual phases. Furthermore, the dissimilar thermo-mechanical properties (melting temperature, thermal conductivity, coefficient of thermal expansion) of the constituent phases impose severe constraints on the fabrication and use of W-Cu composites. To overcome the challenges of component design and enable greater freedom in terms of composition, W-Cu composites were produced by a combination of additive manufacturing and liquid melt infiltration (LMI). Porous W lattice structures were manufactured by laser powder bed fusion (LPBF) followed by infiltration with molten Cu. A series of composites was produced with variation in Cu content from 5-60 vol. % and evaluated in terms of thermal, electrical, and mechanical properties. The LPBF-LMI W-Cu composites exhibited comparable thermo-mechanical properties as W-Cu materials manufactured using powder metallurgical processing, but with an expanded composition range and shape complexity. Lower thermal expansion coefficients (4.5-5.8 ×10-6 K-1) and improved thermal stability of Young’s modulus, only exhibiting a 27-33 GPa decline within the 27 to 827 °C temperature range, were observed over the entire composition range, which was ascribed to the W phase connectivity in all W-Cu composites, independent on the Cu volume fraction.

Keywords: Metal matrix composites, laser powder bed fusion, liquid metal infiltration, thermomechanical properties