Mechanical and thermal expansion behavior of hipped aluminum–TiB2 composites

Aluminum–TiB2 composites reinforced with 5–20 vol.% ceramic particles were prepared by powder metallurgy (PM) method. Hot isostatic pressing was employed to consolidate the green PM products. The microstructure of metal matrix composites (MMCs) was found to depend greatly on the relative particle size (RPS) ratio between the aluminum and ceramic particles. Microstructural examination revealed that RPS value of 0.56 favors both the densification of MMC compacts and better uniform distribution of ceramic particles. Tensile measurements showed that the Young's modulus and ultimate tensile strength of the Al–TiB2p MMCs tend to increase with increasing TiB2p volume content at the expense of tensile ductility. Thermal expansion property of hipped MMCs was measured in the temperature range from 85 to 600 °C. The results showed that the increase in the volume fraction of TiB2 reinforcement reduces the coefficient of thermal expansion (CTE) of the Al–TiB2 composites. Moreover, the CTE versus temperature plots exhibited an apparent peak minimum at ∼380 °C during the first heating stage for the composites reinforced with TiB2 ≥ 15 vol.%. This peak corresponds to the onset of relaxation for the compressive stress, leading to the Al matrix to deform plastically.