Micromechanical properties of low-carbon martensitic stainless steel by microtensile experiments

This paper presents a detailed experimental approach to extract the critical resolved shear stress (CRSS) and the saturation stress of the elementary constituents of the microstructure of quenched S41500 martensitic stainless steel by conducting various microscopy observations and microtensile testing. To the authors' knowledge, the direct extraction of micromechanical properties of a single martensite variant by tensile testing has never been performed. However, the literature does propose studies that measured the mechanical properties of the bulk or small volumes containing a few variants. In this work, a particular attention is dedicated to the preparation of the specimens from the macro to the microscale, where final machining of test specimens was made using a Gallium Focused Ion Beam (Ga-FIB). In the present work, the CRSSs of {110}, {211} and {123} plane-related slip systems were directly measured. The post-experiment analysis showed no significant difference between the slip resistance of those planes. To relate this effort with previous work, a comparison with results from the literature was made using a similar testing procedure in lath martensite, revealing similar values of CRSS. The slip resistance saturation was also measured on different slip systems, and the data suggest a very similar hardening behavior for most of the samples tested. Finally, cross-slip remains, in this alloy, a very potent mechanism to reduce the strain hardening that can arise from clusters of nanoparticles observed by TEM.