A novel (CoFeNi)₈₂Ti₅Al₅V₈ medium entropy alloy showing an ultra yield strength and a good ductility by L1₂ nanoparticles strengthening and dislocation strengthening

This paper designed a novel (CoFeNi)(82)Ti5Al5V8 medium entropy alloy (MEA) with "fcc + L1(2)" typical structure using JMatPro. The microstructure of the alloy, like recrystallization/non-recrystallization and L1(2) nanoparticle size, can be well controlled by thermal-mechanical processing. The result shows that the (CoFeNi)(82)Ti5Al5V8 MEA exhibits a good combination of ultra high yield strength of 1500 MPa and ultimate tensile strength of 1747 MPa with total ductility of 10.8 % when the volume fraction of non-recrystallized region with highdensity L1(2) nanoparticles (46 nm) is up to 91 %. Here, the high volume fraction non-recrystallization region is along with the high-density dislocations (6.29 x 10(14) m(-2)). Thus, the high strength of present MEA is mainly attributed to L1(2) nanoparticle precipitation strengthening and dislocation strengthening, which contributes 686 MPa and 305 MPa to the total yield strength (accounting for 66 %), respectively. Therefore, the idea of combining precipitation strengthening with dislocation strengthening offers a paradigm to develop advanced structural materials for modern industrial applications.