Identifying the high entropy characteristic in La-based metallic glasses

Abstract

High temperature deformation was probed in a La-based high entropy metallic glass with an evident slow β relaxation. The correlation between high configurational entropy and high temperature deformation mechanism was analyzed.On the one hand, by increasing the strain rate, the degree of deviation from Newtonian behavior in high entropy metallic glasses is lower than that of conventional metallic glasses, which is ascribed to the high configurational entropy. On the other hand, high configurational entropy leads to a decrease of activation volume in high temperature deformation of metallic glasses. Identifying the influence of high configurational entropy on the deformation mechanism paves the way for further understanding of the mechanical behavior of metallic glasses.

Identifying stress-induced heterogeneity in Cu20Zr20Ni20Ti20Pd20 high-entropy metallic glass from machine learning atomic dynamics

“…The activation volume of the HEMG is 27 nm 3 smaller than that of Cu 50 Zr 50 MG (31 nm 3 fitted from the curves in Ref. [34] ), consistent with the experimental results [22] . Note that the smaller activation volume of the HEMG may be due to its smaller molar volume, if we assume that the HEMG sample has the same atomic packing density as the Cu 50 Zr 50 .…”

“…During the stress holds, local irreversible atomic rearrangements are continually activated and lead to the macroscopic viscoplastic flow. According to Zhang et al, the activation volume can be fitted from the relation of the applied stress σ and steady-state strain rate , as expressed by Ω = k B T∂ln /∂σ, where k B is Boltzmann constant [22] . The activation volume of the HEMG is 27 nm 3 smaller than that of Cu 50 Zr 50 MG (31 nm 3 fitted from the curves in Ref.…”

“…Compared with conventional single/double element-based MGs, HEMGs show ultrahigh strength [19,20] and enhanced intrinsic ductility [4] . A series of research on creep reported that HEMGs have a smaller serration during plastic flow [21] , a smaller apparent activation volume [19,22,23] , and a slower annihilation of free volume [22] , than conventional MGs. Such a mechanical behavior of HEMGs is interpreted by a more homogeneous atomic arrangement [24,25] with less loose packing "defects" [24] , from the structural perspective, and it is also caused by the sluggish atomic diffusion [20,26] and the inactive response of atomic motion to stress [19,26] , in the view of dynamics.…”

Metal-carbide eutectics with multiprincipal elements make superrefractory alloys

“…On the basis of the compositions depicted in table S1, the configurational entropy values for the BCC and carbide phases are calculated to be 1.56 R and 1.08 R —both are distinctively larger than those for conventional alloys, which usually only have a value of less than 0.69 R (where R is the gas constant) ( 4 ). It has been suggested that high configuration entropy may lead to sluggish diffusion in MPEAs ( 40 – 42 ). For example, a comparison of the tracer diffusion of Ni in pure Ni, ternary CrFeNi, quaternary CoCrFeNi, and quinary CoCrFeMnNi alloys as a function of homologous high temperature revealed that the diffusion rate of Ni decreases with an increase in the number of elements because of the increased variability of local energy barriers for a diffusion atom ( 40 ).…”