From nano to macro: understanding the microstructural interactions for influencing the mechanical properties of open-cell aluminium alloy foams

The growing need for products with tailored properties and the trend towards constructing lightweight products have made open-cell metal foams increasingly appealing for diverse applications. These materials stand out for their cellular structure, low density, and superior specific strength, making them ideal for impact-absorbing structures, as demonstrated by their extended plastic regime in the compression stress-strain results diagram. Aluminium casting alloys are extensively utilised across various industries, including automotive, defence, aviation and construction, due to their lightweight, excellent castability, cost-effectiveness and favorable mechanical properties. These alloys are promising candidates for metal foams. Factors like material properties, strut microstructure, density, potential anisotropy, and cell topology play crucial roles across different hierarchical levels. Enhancing the properties of metal foams can be achieved by improving the strut properties through careful alloy selection, processing route optimisation and cell topology modification. Building on prior internal research on cast metal foams made from Al-Si alloy, this thesis investigates the contribution of the strut microstructure on the mechanical properties, deformation behavior and failure mechanism both at foam and strut level. Different alloys such as AlSi7Mg0.3 and Al-4.8%Cu in as-cast and heat-treated states were used for the foam specimens to study the impact of phases in binary and ternary alloys.