EFFECT OF TEMPERING ON THE MECHANICAL PROPERTIES OF LOCALLY PRODUCED ALUMINIUM BRONZE
Publication Date : 01/02/2007
An investigation into the effects of tempering on the mechanical properties of as-cast locally produced aluminium bronze was carried out. The alloy was produced and sand cast into cylindrical bars at the foundry shop of the National Metallurgical Development Center, Jos. The as-cast bars were cut and machined into tensile, impact and hardness test samples. The machined specimens were heat-treated at 850OC, soaked for three (3) hours and then rapidly quenched in water before tempering at temperatures of 450OC, 550OC and 650OC respectively. The tensile strengths, hardness values and impact energy (toughness) of the both the heat-treated and as cast samples were determined. It was observed that tempering significantly increased the tensile and impact strength (toughness) of the alloy with an appreciable increase in hardness. However, it is worth noting that the resultant mechanical properties of the heat-treated alloy depend on the phases present in the microstructure after hardening and tempering, as the presence of substantial reprecipitates of the beta martensite in the already formed alpha and gamma phases during tempering greatly enhances these mechanical properties.
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