Microstructure and Mechanical Properties of Multilayered Cu/Ti Composites Fabricated by Accumulative Roll Bonding

Multilayered composites composed of pure copper and titanium (Cu/Ti) have been fabricated by accumulative roll bonding (ARB). The macroscopic lamellar structures, mechanical properties and microstructures of the composites are investigated. The results show that the Cu and Ti layers are bonded well during the ARB processing. With the increasing number of ARB cycles, Ti layers start to neck, fracture and even segregate within the Cu matrix, which is attributed to the activation of shear bands that cut through the multiple metal layers. At larger ARB cycles, the distribution of small fragmentations of Ti inside the Cu matrix is more homogeneous, which is attributed to the fact that the outer surfaces of the previously processed composite are placed in the interior of the subsequent ARB stack. Tensile testing at room temperature shows that the yield strength and the ultimate strength of the composites increased mildly with the increasing ARB cycles, while the uniform elongation of the composites is retained. Microhardness tests reveal that the increase of strength in the composites during ARB mainly results from the reinforcement of the Ti layers. The mechanical behaviors of the composites can be attributed to the effect of the mixed microstructures in the both constituent metals.