Effects of Si on the Microstructure and Work Hardening Behavior of Fe-17Mn-1.1C-xSi High Manganese Steels

In order to improve the work hardening capacity under low stresses and the yield strength of conventional Hadfield steels, the effects of Si on the microstructure and work hardening behavior of the Fe-17Mn-1.1C-xSi steels under both quasi-static tensile and low load impact are investigated. It is shown that the increase of the Si contents remarkably improves the yield strength by 36 MPa per 1 wt% Si in the investigated steel system without significant sacrifice of ductility. The decreasing effect of Si on the stacking fault energy is strongly affected by carbon, although the variation of carbon content was small. This led to the unexpected similar stacking fault energy between 1Si and 2Si steel. With the increase of the Si contents for the steels, the critical strain for the onset of mechanical twinning was lowered, which was controlled by the cooperation between the stacking fault energy and solid solution strengthening of Si. This resulted in the earlier initiation of mechanical twins and an increase in the twin volume fraction. Therefore, the work hardening capacities under both quasi-static tensile and low load impact tests were enhanced. It was also found that the impact deformation decreased as more mechanical twins absorbed the impact energy.