Temperature-dependent stacking fault energy, deformation behavior, and tensile properties of a new high-entropy alloy

Abstract

The stacking fault energy (SFE), deformation behavior, and tensile properties of a new high-entropy alloy (HEA), Fe35Mn35Co10Cr10Ni10 (in at. %), were investigated at room temperature (RT) and −100 °C. Deformation substructure evolution during tensile loading was studied using electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM). A transition in the slip configuration occurred from fully wavy to completely planar with the decrease in temperature from room temperature (RT) to −100 °C. The studied alloy revealed the onset of deformation twinning only during deformation at −100 °C and the same was absent during RT deformation. SFE of the studied alloy at −100 °C was ∼34.2 (±4) mJ/m2. SFE determination required the value of the distance between Shockley partial dislocations and the same was determined employing the transmission electron microscopy (TEM) based weak-beam dark field (WBDF) technique. SFE of the studied alloy could not be estimated at RT due to the presence of closely spaced partial dislocations (perhaps due to very high SFE) and therefore partial separation by the presently employed WBDF technique couldn’t be achieved. The role of friction stress was limited and SFE was revealed as the main factor in defining the active slip mode in HEAs containing no apparent short-range ordering and similar shear moduli. Activation of planar slip-induced dislocation features such as Taylor lattices, microbands, and twinning at −100 °C provided greater work hardening resulting in improved tensile properties compared to RT.