Effect of Aluminium Addition and Grain Refinement on the Microstructure, Mechanical and Physical Properties of Leaded Brass Alloys

Because Cu-Zn alloys have excellent combination of both physical and mechanical properties such as high thermal and electrical conductivities, good tribological behaviour, relative stability in corrosive environments and high mechanical strength, their study is very important for industrial and academic purposes. Review of previous experiments of leaded brasses focused on the effect of small addition of Al on microstructure and mechanical properties and did not evaluate physical behaviour of the alloy. In the current work, the influence of heavy aluminium addition and grain refinement for leaded brasses was investigated and the analysis is extended to physical properties evaluation. The results obtained show that mechanical properties are directly dependent on the microstructure which is in agreement with previous experiments. Initial addition of Al to the alloys does not result to heavy increase in hardness, but further increase in Al and addition of inoculants lead to significant change in hardness. The same pattern of modification was observed in both compressive strength and ultimate tensile strength. For the physical properties, there is little discrepancy to the sequence of their modification, most especially after grain refinement. There is a steady decrease in electrical conductivity even after grain refinement. This is not the case for thermal properties. The thermal conductivity reduced and then increased tremendously after Ti addition. The microstructure was modified with the addition of Al and Ti grain refiners. The presence of Al promoted formation of β-phase seen in the dark regions of the microstructure while Ti aided equiaxed grain formation.