Investigation on microstructure and mechanical properties of Al/Al-Zn-Mg-Cu laminated composite fabricated by accumulative roll bonding (ARB) process

In this study, an Al/Al-Zn-Mg-Cu laminated composite was successfully produced for the first time by using Al 1050 and a super high strength 7xxx aluminum alloy sheets through accumulative roll bonding (ARB) process at an elevated temperature. In this process after sandwich preparation, in per cycle applied 50% reduction in total thickness. The microstructural investigations after different ARB cycles showed that ARB process led to a fine distribution of the secondary phases and also a relatively remarkable decrease in their particle size in the Al-Zn-Mg-Cu (AZMC) layer. Furthermore, it was observed that all the layers of the ARBed sheets remained relatively straight without any necking or fracture during the plastic deformation in the first two cycles. Also, the macrostructure showed elongated and ultra-fine grains after the fourth cycle in the AZMC and pure Al (PA) layers, respectively. In addition, computer simulation demonstrated strain and stress gradients in the ARBed sheet. The mechanical examinations displayed a significant improvement of elongation and ultimate tensile strength (UTS) values and also microhardness values of the AZMC layer with increasing the ARB cycles. However, the microhardness variations were so slight (< 4%) in the PA layer during the ARB process. Fractographic observations revealed that the fractured surfaces of the PA layers consist of necking as well as dimples and that of the AZMC ones include dimples and partly shear regions after ARB process.