On the extraction of yield stresses from micro-compression experiments

Abstract

It is widely stated that yield stress extraction from micro-compression testing can be unreliable due to factors such as the pillar taper, pillar-punch misalignment and lateral displacement for example through discrete slip events. This study reports on how these factors can be eradicated when using digital image correlation based strain mapping. This approach is demonstrated through a conventional micropillar compression experiment using the hexagonal MAX phase system Cr2AlC. The use of this approach enables the uncertainty of the extracted yield stress values to be significantly reduced and effectively increases the precision of critical resolved shear stress extraction for basal plane slip from ±52% to ±4% of the mean value. The findings suggest that the statistical variations commonly observed in micro-compression tests may frequently be linked to systematic errors in the stress measurements taken, and that precise evaluation of deformation statistics can only be facilitated if the pillar deformation morphology is closely monitored.