The role of applied strain and volume percentage of components on mechanical properties and fracture toughness in multilayered Al/Mg composite fabricated by the accumulative roll bonding process

In this study, for the first time, the effect of applied strains and volume percentage of components of layered composite on the mechanical properties and fracture toughness of Al/Mg were investigated experimentally. The multilayered Al/Mg were produced by the accumulative roll bonding (ARB) process. For the investigation, three Al/Mg composites with different volume percentages (25%, 50%, and 66.6%Al) at different applied strains (0.8–3.2) were produced. The experimental evaluation included microscopic examination by optical microscope imaging, uniaxial tensile test, and plane strain fracture toughness. As the applied strain for all three composites increased, plastic instability in the magnesium reinforcement intensified, but due to the low thickness of the Al layers compared to the Mg layer, uniform structure of Mg distribution in Al for all three composite was not achieved. Also, by adding Al layers to the primary composite, a lower shear strain was applied to the magnesium reinforcement, and instability intensity in the reinforcement layer decreased. For this reason, as Al layers increased, plastic instability diminished. By raising the exerted strain, the values of tensile strength increased, and by adding Al layers, the elongation increased. The maximum amount of tensile strength and elongation for each composite was achieved in the same ARB pass (last pass) and the highest values of UTS and elongation were reached to 384.1 MPa and 1.95% for Al25%Mg, respectively. However, the highest amount of fracture toughness for each composite was obtained in the different exerted strains and the maximum value of 41.4 MPa·m 1/2 was achieved for Al33.3% in the third pass. The present phenomena indicated that many factors such as higher Mg volume with higher energy absorption, plastic instability, thickness ratio, plastic instability, and value of applied strain affected the fracture toughness. In summary, the relationship between fracture toughness with applied strain and also with volume percent of Al was not always straightforward. It depends on other factors, such as how the reinforcement was distributed, the thickness of the layers, the workability, and the addition of aluminum. Also, the applied strain has a more significant effect on increasing fracture toughness in multilayered composite if they cause a uniform distribution of reinforcement particles in the field or continuity in the reinforcement layer.