The Application of Vibration and Inmould Techniques to Grain Refined Magnesium Based Alloy Cast in Investment Casting Process Mould

Abstract

Large grain formed during solidification of a casting is generally a disadvantage. In general, finer grain size leads to higher mechanical properties such as tensile and yield strength, hardness, fatique strength (including thermal fatigue) and toughness (Nelson, 1948; Campbell, 1991). Grain refinement in castings can be achieved by increasing the number of nucleation sites. A large number of crystals is then formed which soon impinge on each other and retard the grain growth. Therefore, enhanced nucleation is the key to grain refinement. This nucleant is heterogeneous, in the sense that it arises from solid nucleant either already present in the melt or added purposely, which act as centres for abundant nucleation.