Influence of Reinforcement Particle Parameters on the Homogeneity of Particle Distribution in Semi-Solid Formed Aluminium Matrix Composites

Abstract

Aluminium matrix composites (AMCs) offer improved mechanical and tribological properties compared to monolithic materials and therefore provide great potential for various applications. This particularly applies to particle-reinforced AMCs revealing comparatively high contents of reinforcement particles. However, these types of composites are difficult to manufacture due to their abrasive characteristics as well as their complex rheological material behaviour. An approach to produce such AMCs is semi-solid powder processing, combining powder pressing and sintering in one step in order to produce fully dense composites with currently only cylindrical shapes. Therefore, the tools as well as the powder mixture are first heated into the semi-solid temperature range of the aluminium powder and subsequently formed using low pressures under 200 MPa. Due to the shear thinning behaviour of the semi-solid aluminium matrix the porous structure of the pressed powder is filled during compaction, resulting in homogenous particle distributions in the component. However, this process results in high process times as well as energy costs, due to the heating inside of the die. In contrast to the semi-solid powder processing in one step, in this paper, a novel process route combining cold uniaxial compaction of particle reinforced aluminium powders having up to 50 vol.% SiC with subsequent semi-solid forming is presented. Here, a particle reinforced and cylindrically shaped green body is utilized as raw material, in order to produce complex components through semi-solid forming. The parts produced in this way are featuring varying wall thicknesses and are used in order to determine the process limits for manufacturing particle reinforced components having up to 50 vol.% SiC. Thereby, the influence of reinforcement particle size as well as particle loading on the homogeneity of the resulting particle distribution of an academic component is investigated. Future main objective of the process route is the manufacturing of complex parts with homogenously distributed particles.