Influence of Cold Rolling on Microstructure, Mechanical Properties and Fracture Behavior of CuZn30 Brass Alloy

In this research work, the CuZn30 brass alloy sheets were cold rolled in various cold rolling amount (25%, 50% and75%) at ambient temperature to study the effect of cold rolling on microstructural, mechanical properties and fracture toughness behavior of this alloy. Microstructure evolution of specimens was examined through optical microscope before and after cold rolling. These analyses indicated that cold rolling triggers the increase of shear bands areas and the orientation of grains along rolling direction. The mechanical properties of the unrolled and rolled CuZn30 brass alloy were investigated by tensile tests and micro-Vickers hardness tests. These analyses revealed the enhance of the cold rolling amount leads to increase in strength and hardness and a decrease in ductility. Fracture behavior of the unrolled and rolled specimens is studied through ASTME 1820 standard fracture tests methods for determining resistance curves (J-Δa) and fracture toughness parameter (j0.2) using center-cracked panels (CCP). The results suggested a significant loss in the fracture toughness parameter of the material (the tenacity at crack initiation J0,2) when the cold rolling amount increases. These finding results are ascribed to the noticeable increase in the number of dislocation and the considerable stretching of equiaxed grains in the rolling direction, due to the hardening created during cold rolling.