Comparative studies on the structure and properties of rapidly solidified and conventionally cast AM60 magnesium alloys

The flow stress and work-hardening of rapidly solidified, (RS), and conventionally cast, (IM), AM60 magnesium alloy has been investigated under conditions of uniaxial tension and compression at 4 K, 78 K and 298 K. Rapid solidification combined with plastic consolidation through hot extrusion permit to obtain the alloy with reduced grain size and refined intermetallic particles, which otherwise precipitate in the form of large aggregates in commercial alloys. RS alloy exhibit higher strength and better ductility than IM material. Enhancement of mechanical properties of RS alloy is discussed in terms of the features of material's microstructure. The analysis of work-hardening reveals that independently of deformation temperature and deformation mode, RS alloy shows a lower capacity of defects storage in the substructure. This behaviour is attributed to reduced non-basal slip and forest hardening and enhanced recovery of basal dislocations at grain boundaries in fine-grained RS alloy. Grain boundary sliding does not play an important role in the deformation process. Fracture of the alloys is particle-stimulated and occurs by nucleation and growth of voids around second phase particles. Refining particles by rapid solidification lead to the better ductility of RS alloy irrespective of deformation temperature.