Evaluation of Structure and Mechanical Properties of Multi Layered Al/Ti Composite Produced by Accumulative Roll Bonding (ARB) Process Ashrafif@cc.iut.ac.ir Techniques of severe plastic deformation have been of continual interest in the production of novel metallic microstructures. Among these techniques, accumulative roll bonding has been extensively used to produce multi-layered composites. ARB process can be used as an innovative and appropriate way of multi-layer composite production for the sake of its simplicity and cheaper primary commodity. Multi-layered Al/Ti composites were produced by accumulative roll bonding (ARB) process using Al 1100 and commercial Ti sheets. Sheets were cut into 5cm×10 cm in size and degreased with acetone and wire brushed. Al sheets 500?m thick and Ti sheets 600?m thich were used in this study. After degreasing with acetone and scratch brushing by circular steel brush, the brushed sheets were stacked in the manner of two aluminum layers clad alternatively to one titanium layer. Roll bonding was conducted under the condition that the reduction in thickness per cycle was 50%. This 1.8 mm multilayer sample was rolled down to 0.8 mm thick. The roll-bonded sheet was cut into two sheets of initial dimensions. The sample was scratch brushed, stacked and then rolled again. This procedure was repeated for up to eight cycles. In this process, it was observed that Ti layers necked and fractured as accumulative roll bonding passes increased. multilayered Al/Ti composite with homogeneously distributed fragmented Ti layers in aluminum matrix was produced After eight ARB passes. Structure and mechanical properties of these multi-layer composites were evaluated at different passes of ARB process. During ARB, it was observed that the strength and micro-hardness of produced composites increased as the strain increased with the number of ARB passes. The maximum tensile strength reached 360 MPa at the eighth cycle. Microhardness of Al and Ti layers experienced a sharp rise after eight cycles of ARB from 28 VHN and 187 VHN to 71 VHN and 315 VHN. Fracture surface of the samples after the tensile test were examined using scanning electron microscopy (SEM). Observation revealed evidence of a mixture of mechanisms: cleavage and ductile failure. The crystallite size of Al and Ti were calculated using MAUD software that based on Riet-Veld method. transmission electron microscopy micrograph showed that the Al grain size reached to 300 nanometer after 8 cycles of ARB. It was observed that the layer thickness of diffused atoms between Al and Ti were increased by increasing the number of ARB cycles. X-ray diffraction patterns of the rolled samples show that there is no new crystalline phase. Heat
