Al-Si系鋳造用合金におよぼすCaの影響について

抄録

Al-Si alloys such as silumin and lautal are used for casting widely because of good castability. Metalic silicon which contains Ca as an impurity is used on alloying. Thus, some amount of Ca is believed to be present in Al-Si alloys. However, roles of Ca in Al-Si alloys have not been completely clarified yet. In this study, effects of Ca on mechanical properties (Figs. 3 and 4), castability (Figs. 58) and microstructures (Photo. 1) of silumin and lautal were investigated. The composition of the samples is shown in Table 1. The results obtained are summarized as follows:
(1) Ca showed a modification effect. Because of this effect, the presence of Ca, less than 0.05%, resulted in increase of tensile strength and elongation. However, when the amount of Ca was over 0.05%, tensile strength and elongation decreased due to formation of CaSi₂. Ca hardly affected hardness.
(2) The small amount of Ca in alloys decreased fluidity and feeding ability of melts significantly.