High-performance Al–Si–Mg cast alloys for electric motor rotors require an optimal balance of electrical conductivity (EC), mechanical strength, and good castability for high-pressure die casting (HPDC). This study investigates the effects of Fe (0.5 wt%), Sr (0.02 wt%), and Mn (0.1 wt%) additions, combined with T5 and T6 heat treatments, in a Ce-containing AlSi3Mg0.5Ce0.5 conductor alloy. The aim is to identify composition–heat treatment strategies that enhance the strength–conductivity trade-off using die-casting-relevant chemistries, with the results based on gravity-cast samples as a screening approach for alloy design. In the as-cast condition, Fe and Sr additions increased yield strength (YS) from 118 to 126 MPa but reduced EC from 45% to 42.4%IACS, primarily due to plate-shaped β-Al₉Fe₂Si₂ intermetallics and refined secondary dendrite arm spacing. Adding 0.1 wt% Mn further lowered EC to 40%IACS via solid-solution electron scattering, with minimal modification of Fe-rich phases. Both T5 and T6 tempers promoted precipitation of MgSi-type and Si nanoparticles, simultaneously improving strength and EC. Peak-aged T5 yielded YS of 195–217 MPa with EC of 44–50%IACS, while T6 peak aging achieved ∼275 MPa YS at reduced EC (41–48%IACS). Over-aging enhanced EC to 45–52%IACS (T5) and 45–51%IACS (T6), with modest strength loss. Although based on gravity-cast samples, this study provides practical alloy-design guidance for die-cast aluminum conductors. T6 treatments offer higher strength with acceptable EC, whereas over-aged T5 conditions maximize EC with moderate strength. Notably, the Fe additions required for improved HPDC compatibility reduce EC less severe than that of Mn additions, and this detrimental effect can be effectively mitigated through optimized heat-treatment strategies to achieve application-relevant property combinations.
Yavari et al. (Wed,) studied this question.