The effects of Mn additions on the microstructure and mechanical properties of Al–Si–Cu casting alloys

The effects of Mn on the microstructure and mechanical properties of Type 319 aluminum casting alloys have been examined. It is shown that, as the Mn content is increased up to 0.65 wt.pct (corresponding to an Fe/Mn ratio of ∼1.2) in the baseline alloy (Al–7 wt.%Si–3.8 wt.%Cu–0.5 wt.%Fe), the plate-like β intermetallic phase is completely converted to the Chinese script α phase resulting in improved tensile properties. Excess amounts of Mn, however, deteriorate the mechanical properties by increasing the total amount of iron-containing intermetallic phases. The porosity and volume percent of intermetallic phases are correlated with the tensile properties in order to determine the role of Mn on Type 319 casting alloys.