Deformation behaviour of ultrafine-grained magnesium with 3 vol.% graphite

Magnesium micropowder was mixed and ball-milled with 3 vol.% graphite powder. The Mg + Graphite composite was deformed in compression at temperatures between room temperature and 300 °C at a constant crosshead speed, giving an initial strain rate between 1.4 · 10 and 1.4 · 10 s . The yield stress of the composite is higher than that of unreinforced magnesium prepared with the same technology. The yield stress and the maximum stress decrease rapidly with increasing temperature. At temperatures higher than room temperature, the true stress– true strain curves exhibit a work-hardening rate close to zero, which indicates a dynamic equilibrium between hardening and softening. Double cross-slip of screw components of + dislocations is considered as the main recovery mechanism.