Abstract
Some mechanical properties at room and elevated temperatures of extrusions of the magnesium-1 wt% aluminium alloy powder, the magnesium-0.6 wt% zirconium alloy powder and a 50/50 mixture of these two powders have been investigated in comparison with a magnesium-1 wt% aluminium cast-billet extrusion. The powder extrusions are higher in hardness, ultimate tensile strength and yield strength, but lower in elongation than those of the cast-billet extrusion. The former extrusions also exhibit a higher creep strength at 350°∼450°C which seems to be very much concerned with the amount of the dispersed oxide. However, this results in a poor rupture ductility. The metallograhic observation of cavities in creep-ruptured specimens shows that the cavities originate preferentially in the longitudinal grain boundaries where the oxide layer exists, rather than at the transverse grain boundaries. The cavities grow toward the transverse direction, the continuation of which results in the fracture of specimens.
