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The microstructure and the mechanical properties of a multilayer composite laminate based on aluminum 7075 and 2024 alloys produced by hot roll bonding were examined. The composite laminate has been tested at room temperature under Charpy-impact tests, three-point bend tests, and shear tests on the interfaces. The toughness of the post-rolling tempered and T6-treated composite laminate, measured by impact-absorbed energy in the crack-arrester orientation, was more than 20 times higher than that of the monolithic Al 7075 alloy and 7 times higher than that of Al 2024 alloy. The outstanding toughness increase of the composite laminate in the post-rolling tempered and T6-treated condition is mainly due to the mechanism of ''interface predelamination.'' By this fracture mechanism, the interfaces are debonded before the main crack reaches them, warranting delamination in all interfaces. Therefore, delamination and crack renucleation in every layer are responsible for the improvement in toughness.

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a b s t r a c tA hypoeutectic Al-7 wt% Si alloy was subjected to high-pressure torsion (HPT) at room temperature using an imposed pressure of 6 GPa and torsional straining through five revolutions. Different thermal treatments, prior to the HPT processing, resulted in reducing supersaturated Si concentration in comparison to the as-cast material. Microstructural parameters and microhardness were evaluated in the present work. Processing by HPT produced significant grain refinement with grain sizes of about 200-400 nm. Furthermore, fine deformation-induced Si precipitates from the supersaturated solid solution were observed, which are very useful in retaining the fine microstructure during HPT processing. The microhardness increase was outstanding, with values for processed samples twice higher (84 HV) than that for the ascast Al-7 wt% Si alloy (44 HV). The results demonstrate that the refining and strengthening of the Al matrix by HPT processing depend on the available supersaturated solid solution during the processing.