Specimen Size Effect on Behavior of Mg-3Al-1Zn Magnesium Alloy in Macro to Micro-scale Deformation

Specimen size effect at a room-temperature uniaxial compression of an as-cast AZ31 Mg alloy was studied in detail using experiments and crystal plasticity finite element (CPFE) numerical simulations. The compression samples with a diameter of 1.2 to 15 mm and a height to diameter ratio of 0.8 were compressed at a strain rate of 0.01 s-1. As a result, the samples with lower diameters showed lower flow stress with not only higher standard deviation in terms of strength but also more sensitivity to the strain in terms of the standard deviation of the flow stress. Twin characterization analysis indicated that the specimen size could influence the twin average length and thickness. However, it did not affect the twin volume fraction. The experimental and CPFE simulation results for the flow stress were matched well, especially for the samples with larger diameters. The root sum square of the deviation between experimental and simulation results for flow stress and standard deviation of the flow stress showed a power law type relationship with sample diameter with a clear transition region denoting a micro-scale to macro-scale forming.