Effect of Copper Additions on Microstructure, Casting and Mechanical Properties of Az91 Magnesium Alloy
In this study, the effect of Cu element addition varied between 0.5 - 1.0 and 2.0 wt.% on the microstructure,
casting and mechanical properties of AZ91 magnesium alloy were investigated. The microstructural results showed that as
increasing Cu additions into the AZ91 alloy, caused coarsening of the phases occurring at grain boundaries. Addition of 2%
Cu forms darker phases and shows a more homogeneous distribution in the structure of the grains. When examining the
effect on casting properties; as the increasing of Cu additions the fluidity of AZ91 alloy increased was observed. In the hot
tear tests two different mold systems were used. Hot tearing were observed in the longest section in the tests using " the mold
same diameter, different lengths" and when the "the mold different diameter, same lengths" were used, Hot tears disappeared
in all of the samples with a diameter of 12 and 16 mm while all the samples with a diameter of 8 mm had a hot tear with Cu
additions. Little bit decrease in hardness observed with the addition of 0.5 wt.% Cu while 1.0 wt.% and 2.0 wt.% Cu
additions showed a slight increase in hardness. Tensile strength of the alloy increased with the addition of Cu to the AZ91
alloy, but the AZ91 alloy also showed a slight decrease in elongation.
Keywords: AZ91, Fluidity, Hot Tearing, Magnesium.