High-performance zero thermal expansion in Al metal matrix composites

Zero thermal expansion (ZTE) composites reinforced by negative thermal expansion (NTE) compounds exhibiting superior dimensional stability and high thermal conductivities, are urgently needed in the modern industrial field. Unfortunately, conventional strategies for achieving ZTE composites often compromise thermal conductivity by incorporating high-content NTE particles. This study reports an overlooked factor enhancing NTE: the in-situ thermal mismatch stresses within the composites, which provide a significant driving force for lattice distortion. The 50 vol.% Cu₂P₂O₇/Al-Si composite achieves isotropic ZTE, low density, and high thermal conductivity due to pressure-enhanced NTE and a tight interface structure. Synchrotron X-ray diffraction and Density Functional Theory (DFT) calculations have revealed the key mechanism of in-situ residual thermal stress in the composite contributing to the enhancement of NTE in Cu₂P₂O₇. This work proposes a novel design approach for high-performance ZTE materials.