New approach to analysis of grain refinement

Abstract

Grain refinement of aluminium and magnesium alloys has been a challenging topic for decades and this is partly due to the complex nature of the mechanisms occurring during solidification and the lack of a common experimental method allowing comparison of data from different research groups. A new analytical approach that plots grain size versus the inverse of the growth restriction factor Q enables additional valuable information to be revealed about the efficiency and potency of grain refiner particles and master alloys. The present paper describes the new analytical approach and then gives examples where insights into the grain refinement mechanisms have been achieved. For aluminium alloys, the new analytical approach compares the effectiveness of different master alloys and examines the mechanism of poisoning of grain refinement by Zr. For magnesium alloys, the new analytical approach is applied to explain phenomena such as superheating and native grain refinement. With this new analytical approach and the knowledge it generates, the potential for the discovery of new or improved refiners is significantly enhanced