Simultaneous enhancement of strength and ductility of body-centered cubic TiZrNb multi-principal element alloys via boron-doping

Body-centered cubic(BCC)multi-principal element alloys(MPEAs)have intrinsic high strength but poor ductility,which greatly limits their potential applications.Here we present the boron-doping strategy to enhance the strength and ductility of TiZrNb MPEAs simultaneously.The yield strength and ductility of the TiZrNb MPEA with boron addition of 500 ppm are increased by 19.0%and 48.7%compared to the boron-free TiZrNb MPEA,respectively.Boron-doping induced high efficiency in grain refinement from~96.0μm to~16.2μm is the main factor for strengthening.Dislocation dominated deformation mechanism involving cross slip and dislocation pining in the TiZrNb containing 500 ppm boron serves to enhance the strain-hardening capacity,resultant the enhancement of ductility from 7.8%to 11.6%.While the planar slip of dislocations is the dominated deformation mechanism for the boron-free TiZrNb.