Property grading by friction induced and continuous solid-state recycling of aluminium scrap

Abstract. Saving energy and reducing emissions in all sectors is essential if the ambitious climate targets of various European countries are to be met. One way of achieving this is to recycle metallic materials, which require a lot of energy to produce, in a way that minimizes the use of energy and resources. The friction-induced solid-state recycling process enables the energy-efficient recycling of what is in theory an endless aluminium semi-finished product through the continuous rotation of the wheel used. The past investigations proved the energy-efficient recycling of new aluminium scrap (powder, foil, chips) to a full semi-finished product with good properties. The continuous character of the process along with the likewise continuous feeding of the material to be recycled enables both mixing and successive processing of different aluminium alloys. For this purpose, the processed four different aluminium alloys are selectively mixed and processed simultaneously, as well as different alloys are processed one after the other to achieve a gradation of properties along the length of the semi-finished product. The recycled semi-finished product is examined regarding die filling, hardness, tensile strength as well as microstructure. The central result of the investigations is the fact that the friction-induced recycling process has different possibilities for grading the properties and microstructure in a wide range.