SOURCE:

Faculty: Engineering
Department: Metallurgical And Materials Engineering

CONTRIBUTORS:

Nnakwo, K.C;
Nnuka, E.E;

ABSTRACT:

This research investigated the effect of dopants and heat treatment parameters on the structure, physical and mechanical properties of silicon bronze (Cu-3wt%Si). Dopants used were zinc, tin, magnesium, manganese, tungsten, titanium, molybdenum and aluminium in concentrations of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.5, 2, 3 and 5wt% respectively. Permanent die casting method was employed in casting the samples. The heat treatment parameters adopted were solutionizing temperature (900oC), soaking time (30mins) and quenching medium (air). Mechanical and physical properties investigated were percentage elongation, ultimate tensile strength, hardness, impact strength, density, electrical resistivity and conductivity. Optical metallurgical microscope and scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS) were used for the structural analysis. Statistical analysis of variance (ANOVA) was used to analyze the results obtained. Results of the structural analysis revealed that the control specimen consisted of dendrite of primary silicon and coarse intermetallic phase (Cu3Si). The samples doped with the alloying elements consisted of refined and modified dendrite of primary silicon and intermetallic compound respectively. Mechanical tests results indicated that all the alloying elements significantly improved the percentage elongation, ultimate tensile strength, hardness and impact strength of the silicon bronze. The density and electrical resistivity of the developed alloys increased with increase in the concentration of the alloying elements with corresponding decrease in electrical conductivity. Heat treatment further increased the ultimate tensile strength and hardness of the alloys with predominant effect shown in the alloy doped with magnesium. Analysis of the results indicated a correlation between physical and mechanical properties of the studied alloys. The results of the analysis of variance indicated that type and concentration of dopants have statistical significant effect on the tested properties with p-value less than 0.05. Comparative analysis of the developed silicon bronze with those developed by other researchers indicated that the developed silicon bronzes can be used in automobile, building and electrical industries for building components such as electrical conduits, valve stems, tie rods, fasteners, nuts, bolts, screws, rivets and nails.