Advanced Materials Letters

Interconnected open-cell Al foams, with various fractions of recycled Al alloy scrap, have been produced using a sintering and dissolution process (SDP). The foams are suitable for various functional applications, such as heat exchangers, bone-replacement implants, interconnects, catalyst supports, and sound insulators. Firstly, the NaCl paste was pelletised, by hand, to make spherical balls of approximately 5 mm diameter. The Al alloy scrap was obtained from turning operation in lathe machine.  Porous structure was obtained after dissolution of the NaCl balls. The microstructure of Al foams was examined using SEM and EDX.  The results show that pores were uniformly distributed along Al matrix and interconnected with surrounding pores. The compressive strength of the foams with small scrap content of 20 wt.% is increased. However, when scrap content is higher, the strength is decreased, as a result of incomplete thermal bonding between Al powder and scrap particle, and excessive oxide content in foam microstructure.

Titanium foams are advanced materials with macroporous structure that have a great potential in a variety of areas such as biomedical and functional applications. They are characterized by their reduced density and stiffness, with high permeability and excellent biocompatibility. One production technique for Ti foams with promising results is Metal Injection Moulding (MIM). So far most of the porous titanium produced by this technique has a very basic design with low percentage of porosity, thus limiting its potential in the biomedical industry, among others. In this study, the use of MIM in combination with a space holder to produce single and multi-layered porous Ti with high volume percentage of porosity will be explored. The results show that it is possible to produce Ti foam with a total volume percentage of porosity of 61 % through MIM technology. In addition, it is also feasible to combine different porous layers resulting in multi-layered porous titanium parts with gradient porosity that could have a huge potential in a wide range of applications, especially for biomedical implants, where these pores can promote bone ingrowth as well as reduce stiffness to match that of the natural bone, thus alleviating the stress shielding problem.