Strengthening and toughening mechanisms of tailored Al/Al-TiB2 laminated composites fabricated by hot press sintering process

Laminated structure with alternating hard and soft layers can exhibit superior mechanical properties, while the quality of interlayer bonding is difficult to be controlled. This study proposed a hot press sintering process using Al sheet and Al-TiB2 powder mixture as the raw materials to fabricate Al/Al-TiB2 laminated composites with different stacking sequences. The results indicate that both Al/Al-TiB2 and Al/TiB2 interfaces are well bonded, and a mass of stacking faults as well as dislocation loops locate at the interfaces. Al-TiB2 layer always has much smaller grains than Al layer, and its grain size can be further reduced by increasing the TiB2 content. The bending properties of laminated composites are strongly affected by stacking sequence. A high bending strength is achieved if Al-TiB2 act as interlayer, and a superior toughness can be realized if Al act as interlayer. The reinforcing effects of Al-TiB2 layer and extra-strengthening of tailored laminated bimodal structure contribute to enhancing the bending strength. The induced geometric necessary dislocations at Al/Al-TiB2 interface facilitate the release of stress concentration and coordinate the deformation between layers, and the formed tunnel cracks absorb extra fracture energy, resulting in improvement of toughness.