Si-induced stacking fault energy modulation and its impact on deformation mechanisms in non-equimolar CoCrCuNi alloys

Abstract

X-ray diffraction is utilized to estimate the stacking fault energy (SFE) of the alloy prior to conducting the mechanical test in this research. Subsequently, transmission electron microscopy (TEM) is employed to measure the widths of partial dislocation in specimens subject to tensile testing, enabling the determination of the SFE in the CoCrCuNiSi medium-entropy alloy. The alloys are prepared with small quantities of silicon to investigate its effects on SFE, specifically in three face-centered cubic low SFE alloys. The parameters necessary for SFE calculations are determined by digital image correlation to gain Poisson's ratio and nanoindentation to determine Young's modules. Furthermore, the subsequent mechanical property evaluations are performed to corroborate the precision of both measurements. Observations of the deformed microstructure using electron backscatter diffraction and TEM revealed that the reduction in SFE promotes the mechanisms of twinning-induced plasticity and transformation-induced plasticity effects, thereby contributing to an enhancement in the alloy's strength. The findings substantiate the correlation between SFE and the deformation mechanisms, highlighting the potential for optimizing alloy properties through the addition of minor elements.