High strength and ductility in partially recrystallized Fe40Mn20Cr20Ni20 high-entropy alloys at cryogenic temperature

Abstract

The effects of cold rolling and subsequent annealing on the microstructures and mechanical properties of Fe40Mn20Cr20Ni20 high-entropy alloys (HEAs) are investigated. The Cr-rich secondary phases with a tetragonal structure (σ phases) in the Fe40Mn20Cr20Ni20 HEAs are precipitated upon annealing at 600 °C-900 °C for 2 h. The prepared Fe40Mn20Cr20Ni20 HEA annealed at 800 °C for 2 h after cold rolling has a good combination of strength and elongation, with a high yield strength of 438 MPa, a high ultimate tensile strength of 676 MPa, and an excellent elongation to fracture of 32%. The mechanical properties at cryogenic temperature are better than those at room temperature. Typically, for the incompletely recrystallized alloy annealed at 700 °C, the yield strength, tensile strength, and elongation after fracture are increased by 26%, 22%, and 100%, respectively. This trend mainly depends on dislocation and twinning strengthening. The σ phases also improve the cryogenic tensile properties. Furthermore, the recrystallization kinetics of the Fe40Mn20Cr20Ni20 HEAs are explored to correlate with the deformation behavior.

Hot Deformation Behavior of Fe40Mn20Cr20Ni20 Medium-Entropy Alloy

“…Then, the XRD results show that the hot-rolled sample is a single-phase FCC structure and the CR700 sample consists of an FCC phase and a σ phase (Figure 1d). Combining the above results and previous studies [27,28], the particles in the cold-rolled sample are Cr-rich tetragonal σ phase. Partially recrystallized microstructure and dispersed particles combined to form the heterogeneous structure, which gives the CR700 well-balanced tensile mechanical properties at room temperature [28].…”

Novel casting CoCrNiAl eutectic high entropy alloys with high strength and good ductility

“…High entropy alloys (HEAs), which were proposed in 2004, have drawn increasing interest due to their appealing properties relative to conventional alloys consisting of one or two principal elements [1][2][3][4] . Despite alloying various principal elements, HEAs, frequently solidify into simple crystal structures, such as facecentered-cubic (FCC), body-centered-cubic (BCC) and hexagonal-close-packed (HCP) crystal structures or their ordered types (such as L1 2 , B2 and D0 19 ) [5][6][7][8][9][10] . Generally, considering the as-cast mechanical properties of HEAs, FCC-structured HEAs exhibit good ductility but relatively low strength, while BCC or HCPstructured HEAs show high strength but limited ductility [11][12][13] .…”