Grain Refinement of Al–Si–Cu Alloys by AlB₂ and (Al,Ti)B₂

The history of grain refinement with AlB₂ in Al–Si and Al–Si–Cu casting alloys is reconsidered in light of findings published recently by Zheng and co-workers. When using boron as a grain refiner, some problems may be encountered. These are considered briefly. Fundamental aspects of grain refinement are also discussed and useful future experiments proposed.