Nano-grained 70/30 brass strip produced by accumulative roll-bonding (ARB) process

Accumulative roll-bonding process is the only severe plastic deformation (SPD) process using rolling deformation itself, and has been used for 70/30 brass up to 6 cycles at ambient temperature under unlubricated conditions. Microstructural characterizations were done by transmission electron microscopy (TEM). After 6 cycles it was found that continuous recrystallization occurred and the microstructure covered with small recrystallized grains with an average diameter below 100 nm. The tensile tests and Vickers macro- and microhardness were conducted on the ARBed 70/30 brass. A scanning electron microscopy (SEM) study was performed in order to observe the shear bands and also to clarify the failure mechanism. The tensile strength and hardness became two and three times greater than the initial value respectively. However, the elongation dropped abruptly at the first cycle, then increased slightly. Strengthening in ARBed 70/30 brass explained by strain hardening in the first step and grain refinement at high strains. Observations revealed that the failure mode in ARBed 70/30 brass was a shearing ductile rupture with elongated shallow shear dimples.