Forming limit diagram and plane stress fracture toughness of foil AA1050/TiC composites

The forming limit diagram (FLD), mechanical properties and fracture toughness of aluminum foil composites fabricated via accumulative roll bonding (ARB) process have been investigated as its novelty for the first time. To do this, AA1050/TiC composite foils with thickness of 0.2 mm have been fabricated from one up to twelve ARB passes at 320 °C. Also, optical microscopy (OM) was used to investigate the effect of cumulative forming process on the grain structure. The strength of samples improved to 168. 6 MPa after the 12th cumulative rolling pass, registering 248% improvement in comparison with initial AA1050 sample. Also, by cumulating the plastic strain at higher passes, the bonding quality among composite layers enhanced. SEM fracture surface morphology of samples showed the conversion of fracture mode to shear mode for composites fabricated at high number of passes. So, in comparison with the annealed sample, deep dimples are shrinking slowly and their number and depth were reduced. As the criterion of formability and at higher passes, the area under the FLDs, dropped sharply for one pass processed sample and then improved. Results of fracture test revealed that the value of fracture toughness enhanced continually and got to the 30 MPa.m^1/2 at the 12th pass. Grain refinement and ARB process nature are two main mechanisms which are responsible for all ductility changes and mechanical properties.