Two Parameter Weibull Analysis of the Effect of Chemical Modification of Al–7si–0.3 Mg Alloy on Ultimate Tensile Strength

Double oxide films are one of the primary reasons that cause casting defects particularly in dross forming alloys. It is not clear whether the beneficial effect of modification melt treatment in Al–Si alloys is entirely due to the transformation of acicular eutectic Si to fibrous morphology. In the present work, the effect of chemical modification of Al–7Si–0.3 Mg alloy on casting reliability was assessed from the Weibull analysis of tensile strengths. The findings show that the modification melt treatment of Al–Si alloy has a beneficial effect as indicated by consistently higher Weibull modulus. Apart from transformation in the silicon morphology, modifiers decrease the scatter present as a result of various defects, particularly the bi-film, resulting in higher reliability for the modified castings.