The influence of Ce addition on the aging response of AlSi3Mg0.5 cast conductor alloy: Evaluation of electrical conductivity, mechanical properties, and microstructure

Cerium is known as a promising alloying element to modify the microstructure and enhance the properties of Al–Si alloys. In this study, the effect of Ce addition on the aging response of AlSi3Mg0.5 alloy was investigated by analyzing variations in microhardness and electrical conductivity during isothermal aging at 180 ℃, with particular emphasis on the peak-aging condition. The results demonstrated that Ce addition slightly increased peak hardness while delaying peak-aging time. Additionally, Ce-containing alloys exhibited higher electrical conductivity throughout the aging process. Under T5 conditions, 0.5 wt% Ce enhanced yield strength by 15% (188 to 217 MPa) and electrical conductivity by 5% (47.7 to 49.9%IACS (International Annealed Copper Standard)). In contrast, under T6 conditions, the same Ce addition reduced yield strength by 5% (283 to 273 MPa) but improved conductivity by 3% (46.7 to 48.0%IACS). Differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) were used to investigate the precipitation behavior of the alloys. The results indicated that Ce addition increased the activation energy for the formation of β'' and β'/B' phases while decreasing it for Si precipitates. Consequently, the β'' and β'/B' peaks in the DSC heat flow curves shifted to higher temperatures, whereas the Si peak shifted to a lower temperature. TEM further revealed that Ce reduced the number density of β'' and β'/B' precipitates by 48% and 45% under T5 and by 32% and 58% under T6 conditions, respectively. Conversely, the number density of Si precipitates increased by 20% under T5, and for T6, increased from almost zero to 162.24 μm -3 . The combined effects of these precipitates and other microstructural features on strength and electrical conductivity were quantitatively analyzed using strengthening models and Matthiessen’s rule.