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The laminated metal composites (LMCs) of dissimilar metals (aluminium alloys: AA1100/AA7075) were fabricated using the accumulative roll bonding technique in conjunction with cold rolling. The LMCs of ultrafine grained AA1100 and nanostructured precipitates of AA7075 achieved metallurgical bonding. The microstructure of the bonding interfaces and constituent metals was investigated using scanning electron microscopy and transmission electron microscopy for the LMCs with different layers. The deformation incompatibility and shear actions were analyzed using the microanalysis of dissimilar bonding interfaces. The mechanism of grain refinement of LMCs was investigated and described based on the microstructure characterization. The mechanical properties, strengthening mechanism, and fracture mechanism of LMCs were also investigated. The research results showed that the strengthening mechanism of LMCs is the recombination action of grain refinement, dislocation, and laminated interfacial strengthening. The coordinated deformation of dissimilar metals and the layer thickness are important in improving the mechanical properties of LMCs consisting of dissimilar metals.

The ultrafine grain structure is very difficult to fabricate by severe plastic deformation (SPD) for metals with poor formability. In this paper, a fabrication technology of ultrafine structured dissimilar laminated metal composite sheets (LMCS) was developed for poor plastic metals which have low elongation by hot accumulative roll bonding (ARB) in conjunction with cold rolling. The hot ARBed 1100/7075 LMCS was cold rolled at room temperature after recrystallization annealing treatment. An ultrafine structured dissimilar LMCS was obtained without undergoing severe cold rolled deformation. The mechanical properties were enhanced and optimized by using heat treatment technology. The accelerated refining mechanism of grain was revealed by microstructure characterization of the composite sheet. The enhanced strength was mainly derived from the fine layers, refined grains, increased dislocation accumulation, and abundant dispersoids. The results of the research are helpful in improving the mechanical properties of dissimilar LMCS and optimizing the preparation technology.

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