The present study was performed on A356 and A413 alloys containing (6–11) %Si. Measured amounts of high-purity La and Ce were added to the molten metal that was allowed thereafter to solidify at a slow rate (~ 0.8 °C/s). The results show that the addition of RE metals (La + Ce) up to 3 wt% leads to an increase in the freezing range through an increase in the melting point of the non-modified alloys by 12 °C, with a decrease in the Al–Si eutectic temperature, by 8 °C, respectively, at 3 wt% addition, regardless of the alloy Si content. Although 0.2% Ce is sufficient to drop the Te2 by about 6 °C, 1.5% Ce is required to raise the Tα2 by about 8–10 °C, regardless of the alloy composition. In the case of A413 alloy, eutectic undercooling was only observed in the non-modified base alloy. In the case of alloys modified with Sr, the presence of Sr neutralizes the effect of RE on the freezing range due to its reaction with RE. Addition of La up to 1.5% has no significant effect on the increase in either Tα2 or Te2 compared to that caused by the addition of the same amount of Ce. The increase in the freezing range with the addition of RE metals leads to the formation of a marked amount of shrinkage porosity, in particular in modified alloys. Due to the high affinity of Sr for oxidation, the porosity observed in Sr-modified alloys is twice as much as that in the non-modified alloys, on account of the porosity resulting from the presence of SrO films, in addition to that from shrinkage porosity resulting from the RE metal addition. The main RE-based intermetallics are: Al–RE–Ti, Al–RE–Si, Al–RE–TR–Si (TR = transition metals). In high Si-containing alloy, i.e., 413 alloy, Al–Re–Si compound was frequently observed.

本研究是在含有 (6-11)%Si 的 A356 和 A413 合金上进行的。将测量量的高纯度 La 和 Ce 添加到熔融金属中，然后使其以缓慢的速度 (~ 0.8 °C/s) 凝固。结果表明，添加高达 3 wt% 的稀土金属 (La + Ce) 通过使未改性合金的熔点增加 12 °C 导致凝固范围增加，同时降低Al-Si 共晶温度分别升高 8 °C，添加 3 wt%，与合金 Si 含量无关。尽管 0.2% Ce 足以使 Te2 降低约 6 °C，但需要 1.5% Ce 才能将 Tα2 升高约 8-10 °C，无论合金成分如何。在 A413 合金的情况下，仅在未改性的基础合金中观察到共晶过冷。对于用 Sr 改性的合金，Sr 的存在抵消了 RE 对冷冻范围的影响，因为它与 RE 反应。与添加相同量的 Ce 相比，添加高达 1.5% 的 La 对 Tα2 或 Te2 的增加没有显着影响。随着稀土金属的添加，凝固范围的增加导致形成显着数量的收缩孔隙，特别是在改性合金中。由于 Sr 对氧化的高亲和力，在 Sr 改性合金中观察到的孔隙率是未改性合金的两倍，这是由于 SrO 薄膜的存在以及收缩引起的孔隙率稀土金属添加导致的孔隙率。主要的稀土金属间化合物是：Al-RE-Ti、Al-RE-Si、Al-RE-TR-Si（TR = 过渡金属）。在高Si合金，即413合金中，