| The effects of microstructure, including the volume fraction, size and shape of primary solid phases, on the tensile and corrosion behaviors of thixoformed 357(Al-7%Si-0.6%Mg) alloy were examined. It was found that the tensile elongation of 357-T5 alloy increased exponentially from 3.1 to 8.6% with increasing the solid volume fraction from 55 to 68%. The yield and tensile strength, however, showed no notable dependency on the solid volume fraction. The resistance to pitting corrosion with high solid volume fraction was substantially lower than that with low solid volume fraction in thixoformed 357-T5 alloy, which is believed to be due to the area effect as related to the galvanic corrosion between Si particle and eutectic Al phase. The tensile and corrosion behaviors of thixoformed 357-T5 semisolid alloy were discussed on the basis of the detailed micrographic and fractographic observations. |
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