Strength-ductility balance optimization of Fe2NiCr0.5Cu0.2Al0.3Ti0.1 multicomponent alloy via doping trace amounts of boron

Precipitation strengthening/hardening technique is known to significantly improve the strength of multicomponent/high-entropy (MCA/HEA) alloys at the expense of their serious embrittlement. Therefore, a proper adjustment of precipitated particles' type, size, and volume fraction is critical to achieve a good strength-plasticity balance. This study proposes a new MCA design approach involving doping trace amounts of boron to strengthen the ductile face-centered cubic (FCC) matrix phase instead of conventional thermomechanical processes to achieve excellent performance. A 90 ppm boron doping in the Fe2NiCr0.5-Cu0.2Al0.3Ti0.1 MCAs significantly improved their mechanical properties, increasing their yield strength by 33.2% and ultimate tensile strength by 25.1% at relatively high ductility (21.3-25.2%). The addition of trace amounts of boron inhibited the formation and segregation of coarse BCC-based Heusler particles at the grain boundaries while promoting the formation of fine L1(2)-type nanoscale precipitates, possessing a coherent relationship with the matrix. These findings are considered instrumental in designing the optimal strategy for enhancing balanced strength/ductility properties of FCC-based MCAs/HEAs with high economic feasibility and a wide range of industrial applications.