Creep resistance in magnesium alloys

Mg creep resistant alloys have seen increased interest in the 1980s and 90s due to the weight reduction objectives of automotive companies. Development of Mg-Al based alloys with rare earth (RE) and alkaline earth element additions has led to the automotive application of Mg-6Al-2Sr (AJ62) alloy in the BMW engine block and the Mg-4Al-4RE (AE44) alloy in the engine cradle of the Corvette in 2002-2004. Most creep resistant Mg alloy development activities during this period emphasised the creation of stable grain boundary intermetallic phases in the cast microstructure. This elevated the creep performance of automotive Mg alloys to higher temperature and stress combinations (175 degrees C, 70 MPa). Further improvement in creep performance can only arise from an in depth understanding of the creep mechanisms and the related microstructural interactions in Mg alloy systems. This paper gives an in depth review of creep mechanisms in Mg alloys and provides insight into alloy design principles for further development of creep performance in Mg.