Cooling rate and structure of commercial aluminium alloys

This chapter explores the structures of aluminium alloy powders produced by different atomization techniques with the structures found in cast ingots, and outlines some implications of the changes for the eventual use of the powder. It illustrates some of the features that are observed in the following alloy systems: aluminium metal matrix composites containing insoluble TiB₂ particles, a superplastic Al–Mg–Zr alloy containing Al₃Zr intermetallics precipitated from the melt, and Ni–Al alloys in which Al₃Ni₂ and Al₃Ni intermetallics are precipitated by peritectic reactions. Various Ni–Al alloys have been atomized at high cooling rates with the aim of producing improved catalysts, as has been shown in work on activated copper produced from atomized Cu–Al alloys at Osaka University. Knowledge of the alloy phase diagrams has helped explain many of the effects observed and has underpinned the experimental programmes.