POWER-LAW CREEP BEHAVIOUR IN MAGNESIUM AND ITS ALLOYS

POWER-LAW CREEP BEHAVIOUR IN MAGNESIUM AND ITS ALLOYS


Creep is a time-dependent deformation phenomenon of materials under stress at elevated temperatures. The phenomenon of creep allows materials to plastically deform gradually over time, even at well below its yield point or its transformation temperature. The issues of creep are especially significant for magnesium alloys, since they are susceptible to creep from as low as 100 ºC, which inhibits their potential application in areas such as automotive engines.The University of Canterbury has developed a significant level of experience and infrastructure in the area of Electron Backscatter Diffraction (EBSD). EBSD allows microstructures to be characterized by imaging the crystal structure and its orientation at a given point on a specimen surface, whereby the process can be automated to construct a crystallographic “orientation map” of a given surface.In light of this, an opportunity to study creep phenomena by a novel technique was identified. The technique involves performing a tensile creep test on a specimen, but interrupting the process at periodic intervals, at which EBSD was used to acquire crystallographic orientation maps repeatedly on a same surface location at each interruption. This technique allows simultaneous measurement of creep rate and observation of creep microstructure, bringing further insight into the actual mechanisms of creep deformation.