Low weight steel-magnesium composites achieved by powder compaction

Low weight steel-magnesium composites with various volume fractions of Mg were achieved by a multi-step co-extrusion process. Hollow tubes filed with Mg powders were extruded, annealed, cut and restacked in hollow tubes before subsequent extrusion. This way, fully dense composites with various architectures and length scales were achieved. Microstructure observations revealed that both phases undergo an axisymmetric deformation in the early stage of the process. At higher extrusion ratio, Mg/Fe interfaces become wavy and irregular which is attributed to a strong crystallographic texture. In the as-extruded states, the composites exhibit peculiar elastic to plastic transition with an unusually high strain hardening. Tensile tests performed after annealing prove that this behavior is directly linked to large internal stresses.