High temperature deformation and associated 3D characterisation of damage in magnesium alloys

International audienceA way to overcome the low deformability of magnesium alloys at room temperature is to increase the temperature of forming operations. The stress exponent n, which is known to be a key parameter in the control of plastic stability, generally decreases when temperature increases. Nevertheless, low n-values are not enough to ensure large capacity of deformation since fracture can also result from strain induced cavitation. In the present investigation, both the mechanisms of high temperature deformation and damage were studied in selected Mg alloys. Since damage data can also give information on the deformation mechanisms, the strain induce cavitation behaviour was mainly studied thanks to X-ray micro tomography which provides 3D information like the cavity shapes or the variation with strain of the number of cavities. Moreover, additionally to conventional post mortem analyses, it was attempted to perform the 3D damage characterisation in in situ conditions, namely directly during high temperature deformation tests