Process optimization is one pathway to maximizing strength of a given alloy. Thixomolding® is a semi-solid casting process that combines pores reduction with a typical bimodal grain size distribution that can lead to enhanced strength. AZ91D and AZX911 were processed via Thixomolding® using two different processing conditions to change fraction solid of primary particles at the point of injection into the mould. The tensile properties, creep resistance and corrosion behaviour of the alloys were investigated. The creep resistance was measured in the range of 135–150 °C for stresses of 50–85 MPa. The corrosion behaviour was measured via hydrogen evolution for the two alloys and was smaller than that for die-cast AZ91. The AZX911 alloy showed improved creep resistance compared to the AZ91D. The differences in the property profile of the chosen alloys are correlated with their chemical compositions as well as with different microstructures obtained through the different processing conditions.