Cold pressure welding of severely plastically deformed aluminium by divergent extrusion

Abstract

The present investigation is concerned with cold pressure welding (CPW) of severely plastically deformed (SPD) aluminium. As a starting point, commercially purity aluminium is subjected to single pass equal channel angular pressing (ECAP) and subsequently joined by divergent extrusion (DIE). The mechanical integrity of the spliced components is then documented using notch tensile testing, showing that both the strength and the flow properties of the SPD processed base material are fully maintained across the joint after cold welding. This is because the DIE process implies a mixed deformation mode, i.e. homogenous shear deformation in the bulk and plain strain compression at the joint line where bonding occurs. Moreover, finite element (FE) modelling reveals that the combination of contact pressure to yield strength ratio and surface exposure needed to achieve full metallic bonding is comparable with that reported for bond formation in soft annealed aluminium. This means that SPD processing by ECAP does not alter the conditions under which bonding takes place during CPW, which makes the DIE method particularly useful for joining such materials.