Dynamic co-precipitation of α-Mn / Mg12Ce in creep resistant Mg-Sr-Mn-Ce alloys

Quaternary Mg-Sr-Mn-Ce alloys with trace Ce additions exhibit four times lower creep strain than the ternary Mg-Sr-Mn alloys at 200 °C and 50 MPa. Upon thermal exposure, the main phase transformation is the precipitation of both α-Mn and Mg12Ce / α-Mn in intradendritic regions from supersaturated Mg matrix. It was seen that 2D plates of Mg12Ce phases formed with their habit plane perpendicular to g = 21¯1¯0 and affected the size, morphology and orientation of the α-Mn precipitates. 2D plates form obstacles to dislocations impeding basal and prismatic slip. Dynamic co-precipitates of Mg12Ce / α-Mn act a key role in creep strengthening via dislocation pinning.