Structural characteristics of Cu/Ti bimetal composite produced by accumulative roll-bonding (ARB)

Highlights: • Processing of Cu/Ti bimetal composite via accumulative roll-bonding resulted in nanostructured Ti reinforcements distributed within an ultrafine-grained Cu matrix. • Roles of mechanical properties and geometry of constituents on fragmentation mechanism of harder layer (Ti) were investigated. • Work-hardening results in formation of shear bands and subsequently localized deformation, necking and fragmentation of Ti layers. • Subsequent rolling decreases the length of Ti segments and less strain is accumulated in fragments with smaller length. Cu/Ti nanostructured bimetal composite was produced by accumulative roll-bonding (ARB) technique and the structural characteristics of this composite were studied both experimentally and by finite element analysis. Macrostructure evolution of the composite layers was investigated by optical and scanning electron microscopes. In addition, transmission electron microscopy (TEM) as well as energy-dispersive X-ray spectroscopy (EDX) techniques were utilized for detailed microstructural investigations. Different finite element simulations were designed based on the experimental results. The results were combined with macrostructural observations to gain a better insight into the fragmentation mechanism of the Ti reinforcements. Necking of the Ti layers was observed after 3 cycles of ARB processing which was found to happen at shear bands, after sufficient work-hardening of the constituents. Further processing resulted in fragmentation and distribution of lens shaped Ti constituents. It was found that such a shape evolution makes it more difficult to deform the Ti segments by further straining and consequently, a more localized strain concentration happens within the Cu matrix near these segments. A significant grain refinement was observed by TEM investigation of the highly strained composite. ARB processing of Cu/Ti bimetal composite resulted in nanostructured Ti reinforcements distributed within an ultrafine-grained Cu matrix.