Creep properties at 125°C of an AM50 Mg alloy modified by Si additions

The creep behaviour of an AM50 alloy modified by the addition of different proportions of Si was investigated at 125 degrees C. Increases from 0.3 to 1.5 wt.% Si led to a significant reduction in secondary creep rate. The time to rupture under 100 MPa increased with Si content and peaked with Si = 0.5-0.8 wt.%; further increases in Si content did not induce significant variations in creep strength, since the reduction in creep rate was offset by a parallel reduction in ductility. Microstructural investigations led to the identification of the major strengthening phases: beta-Mg17Al12 and Mg2Si. Results are discussed and analysed in the light of the more recent data on the creep response of other Mg-Al alloys.