Effects of silicon on the metallurgy and sintering response of Al-Ni-Mg PM Alloys

In this investigation the effects of minor amounts of silicon on the sintering response, microstructure, and mechanical properties of experimental Al-Ni-Mg PM alloys were assessed. Associated experimental techniques included thermal dilatometry, pilot-level sintering trials, EPMA, XRD, apparent hardness measurements, and tensile testing. A sequential approach of study advancing through binary (Al-Mg), ternary (Al-Mg-Si and Al-Ni-Mg) and quaternary (Al-Ni-Mg-Si) systems was adopted. It was found that silicon additions promoted the formation of a persistent liquid phase and ultimately diffused into the α-aluminum grains. Only trace levels were detected in the Al3Ni intermetallic. Despite this limited chemical interaction, silicon significantly altered the morphology of Al3Ni in alloys of low nickel content. Silicon also imparted a natural age hardening effect in several alloys and positive gains in yield strength and UTS for all.