On the extraction of yield stresses from micro-compression experiments

It is widely stated that yield stress extraction from micro-compression testing can be unreliable due to factors such as 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 τCRSS 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 a precise measurement of deformation statistics can only be facilitated if the pillar deformation morphology is closely monitored.This project has received funding from the Euratom research and training programme 2014-2018 under grant agreement No. 740415. T.E.J.E. received funding from EMPAPOSTDOCS-II of the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement number 75436