Sustaining strength-ductility synergy of SLM Fe50Mn30Co10Cr10 metastable high-entropy alloy by Si addition

Metastable high entropy alloys possesses excellent ductility and toughness, but its low strength hinders its engineering applications. Therefore, many studies have been carried out to improve the strength of metastable high entropy alloys while maintaining high ductility. In this paper, a new high entropy alloy is fabricated by selective laser melting (SLM) with the addition of Si powder into Fe50Mn30Co10Cr10 metastable high entropy alloy powders, with compositions (Fe50Mn30Co10Cr10)(100-x)Si-x (x = 0, 1, 3, 5). The results show that the yield strength and ultimate tensile strength of Si-containing metastable high-entropy alloys gradually increase with the increase of Si elements, and the performance is far better than that of without Si addition. The Si element increases the metastability of the gamma(FCC) phase in the high-entropy alloy, and promotes the phase transformation induced plasticity by adjusting the twinning strain during the deformation process; so that the total elongation of the material prepared by SLM can reach 30% and above. The combined effect of multiple strengthening mechanisms such as dislocation, deformation twinning, and phase transformation has greatly increased the strength of high-entropy alloys. In addition, the excellent strength-ductility combination of the alloy containing Si element indicates that the composition has good printability for laser additive manufacturing, which can provide a reference for expanding the diversification of high-entropy alloys in the additive manufacturing process.