Obtaining ultrafine-grained structure in copper/steel/copper multi-laminated composite by different accumulative roll bonding methods

Abstract

The relative rollers rotation during roll-bonding affects the effective strain applied to composite layers. In this paper, the differential speed accumulative roll bonding (DSARB) and conventional accumulative roll bonding (CARB) methods were incorporated to fabricate Cu/St/Cu multi-laminated composites. Based on the observation of microstructures, the evolution of microstructure of composites contained necking and rupturing of St layers. In the composite fabricated by DSARB, the St layers showed more irregularities and better distribution in Cu matrix compared to CARB. Based on the observation of grain structures, both methods resulted in ultra-fine-grained structure in layers. However, the DSARB method led to a more pronounced decrement in grain size. The lowest grain size of St and Cu were 2.9 μm and 1.4 μm, respectively, in the DSARB method. Similarly, this method could result in a higher hardness of 401 HV for St and 232 HV for Cu. Also, compared to composite processed by CARB, higher yield and ultimate strength values of 488 MPa and 798 MPa were seen in composite fabricated by DSARB, after seven passes. Furthermore, the fracture surface showed shallower and more sheared dimples in the composite fabricated by DSARB.