The Reactive Stabilisation of Aluminum-Zinc-X Foams via the Formation of a Transient Liquid Phase Using the Powder Metallurgy Approach

During the past few decades, aluminum foam research has focused on the improvement of properties. These properties include pore structure and process reproducibility. High energy absorption capacity, lightweight and high stiffness to weight ratio are some of the properties that make these foams desirable for a number of diverse applications. The use of a transient liquid phase and melting point depressant was studied in order to improve aluminum foam manufactured through the powder metallurgy process and to create reactive Stabilisation. The transient liquid phase reacts with aluminum and helps encapsulate higher levels of hydrogen, simultaneously reducing the difference between the melting point of the alloy and the gas release temperature of the blowing agent (TiH2). A large difference is known to adversely affect foam properties.;The study of pure aluminum foam formation was undertaken to understand the basic foaming mechanisms related to crack formations under in-situ conditions. Elemental zinc powder at various concentrations (Al-10wt%Zn, Al-33wt%Zn and Al-50wt%Zn) was added to produce a transient liquid phase. Subsequently, an Al-12wt%Si pre-alloyed powder was added to the Al-Zn mixture in order to further reduce the melting point of the alloy and to increase the amount of transient liquid phase available (Al-3.59wtSi-9.6%Zn and Al-2.4wt%Si-9.7wt%Zn). The mechanical properties of each system at optimal foaming conditions were assessed and compared.;It was determined that pure aluminum foam crack formation could be suppressed at higher heating rates, improving the structure through the nucleation of uniform pores. The Al-10wt%Zn foams generated superior pore properties, post maximum expansion stability and mechanical properties at lower temperatures, compared to pure aluminum. The Al-Si-Zn foams revealed remarkable stability and pore structure at very low temperatures (640 to 660°C). Overall, the Al-10wt%Zn and Al-3.59wt%Si-9.6wt%Zn foams offer superior properties compared to pure aluminum.