HE-Arc engineering students had to face real issues encountered by a company.
Some metallic materials, especially aluminium casting alloys, are relatively fragile. At microscopic level, they are composed of tiny, brittle particles embedded in a metal matrix, a bit like nuts in a bar of chocolate. These particles offer clear advantages: they increase a material’s mechanical strength and resistance to wear. For aluminium alloys especially, these particles also increase their fluidity. However, their major disadvantage is that they make materials more fragile.
The purpose of my dissertation was to propose new methods of studying fractures in particles, and eventually, to make alloys stronger. To achieve this, we had to go back to the source of the problem, that is, to understand the fracturing process in these small, brittle particles. With the research team, we developed several micromechanical techniques for testing strength and fracturing for this type of particle, for different materials. By using these techniques, we finally understood why silicon particles were breaking so easily. And with that knowledge, we could consider new methods for improving these alloys.
These aluminium casting alloys are used in many car components: pistons, engine blocks, aluminium wheel rims, and gearboxes. They are also used in other industries such as aerospace, shipbuilding, rail and power transmission. Basically, 25% of aluminium produced worldwide is a casting alloy.
The micromechanical testing methods developed in this project are totally new. Many materials can now be analysed at the level of their fracturing process. This new approach brings together numerous existing technologies that have made enormous progress these past few years and which have become more accessible, such as electron microscopy, ion beam micromachining, micromechanical testing, and finite element modelling.
Martin Müller is 33 years old, he is married with one kid. Born and raised in Argentina, he moved to Switzerland in 2012. Since the end of his thesis, he works for Nespresso. In his spare time, Martin, a music lover, is an enthusiastic guitar and piano player.