Design of zero thermal expansion and high thermal conductivity in machinable xLFCS/Cu metal matrix composites

Abstract

Materials having good comprehensive performances, such as zero thermal expansion (ZTE), high thermal conductivity, and machinability are in great demand for electronics, precision instruments, and aerospace applications. However, the challenge is that very few materials meet such requirements. In this study, a multicomponent reinforcement with negative thermal expansion (NTE) is designed for metal matrix composites (MMCs) to achieve wide-temperature-range ZTE, high thermal conductivity, and certain machinability. Taking advantage of the giant NTE in La(Fe,Co,Si)13 system, its originally narrow NTE temperature range can be broadened in the multicomponent material (xLFCS). When xLFCS is used as a reinforcement in MMCs and combined with copper, the thermal expansion coefficient of the xLFCS/39.7 vol%Cu composite can be adjusted to nearly zero (−0.2 × 10−6 K−1) over a wide temperature range of 200–320 K. The thermal conductivity of this composite is 44.1 W m−1 K−1, which is about seven times that of LFCS itself. In addition, compared with other ZTE metal-based materials, the present composite has good machinability. This work reports a metal matrix composite with high thermophysical properties and proposes an easy-to-operate method for broadening the temperature range of NTE or ZTE.