A review is given of the studies of aluminium inoculation undertaken within the EU Network “Microstructural Engineering by Solidification Processing” (MEBSP). A wide range of studies of industrial practice of grain refining and of the fundamental mechanisms of nucleation and growth have contributed to improved understanding. Particular advances have been made in understanding the relative performance of different grain refiners.

Metallurgical operations at elevated temperatures, such as those that involve solidification and/or mechanical deformation, can be critically influenced by the thermal stresses and strains that result from expansion and contraction of the material as a function of temperature. With the increasing use of computer-based process models for these operations, there arises a greater need for quantitative data on the thermal expansion coefficient of the relevant alloy at the temperatures involved. After briefly reviewing some existing sources of data for this property, the various techniques for its measurement at elevated temperatures are then described. These include mechanical dilatometry, optical imaging and interference systems, x-ray diffraction methods and electrical pulse heating techniques. Finally the implications, for process modelling, of the available data and measurement techniques are discussed.

The generally reported observations pertinent to any proposed interpretation of the columnar to equiaxed transition (CET) in as solidified alloys are initially considered. The review then proceeds to consider the proposed mechanisms of equiaxed grain formation, the influence of alloy and processing conditions on the CET, criteria for the termination of columnar growth and, finally, deterministic/stochastic models for predicting the CET. In conclusion, the present level of understanding of the CET and current modelling capabilities are summarised and assessed.