Abstract
The relationship between porosity formation and shrinkage morphology has been investigated in an AC4CH alloy modified with strontium. It has been shown that strontium changes solidification morphology and porosity distribution from a concentrated to a dispersed type. Namely in a nonmodified conical casting, microshrinkages are observed beneath interior shrinkage, while microporosities are dispersed by strontium modification throughout the casting without forming the microshrinkage. Gas content and porosity volume increase with strontium additions from 50ppm to 300ppm, becoming constant with strontium over 300ppm. The volumes of interior and exterior shrinkages decrease with increases in gas content and porosity volume.
