On the mechanical properties and deformation mechanisms of manganese sulphide inclusions

Abstract

Manganese sulphide (MnS) inclusions are present in many steels. Some are deliberately introduced to increase machinability (Ånmark et al., 2015 [1]), for example in case-hardened 16MnCrS5. Others are present to the detriment of mechanical behaviour, causing anisotropic properties, a reduction in fatigue resistance as well as the formation of deformation-induced voids during forming. In order to improve the performance of MnS-containing steels, the mechanical properties and deformation mechanisms of these inclusions need to be understood. Due to their small size, micro-mechanical testing using nanoindentation and micropillar compression was performed in order to study the properties of MnS.1101¯10-type slip systems were, in accordance with literature, found as the primary slip system. For specific orientations with low Schmid factors for these systems, however, slip on {100} planes could be activated in micropillar compression, and for both obtained systems, the critical resolved shear stresses for their activation was measured. These findings were subsequently confirmed by electron backscatter-diffraction on cross-sections of deformed micropillars.