Temperature-Dependent Superplasticity and Strengthening in CoNiCrFeMn High Entropy Alloy Nanowires Using Atomistic Simulations

Abstract

High strength and ductility, often mutually exclusive properties of a structural material, are also responsible for damage tolerance. At low temperatures, due to high surface energy, single element metallic nanowires such as Ag usually transform into a more preferred phase via nucleation and propagation of partial dislocation through the nanowire, enabling superplasticity. In high entropy alloy (HEA) CoNiCrFeMn nanowires, the motion of the partial dislocation is hindered by the friction due to difference in the lattice parameter of the constituent atoms which is responsible for the hardening and lowering the ductility. In this study, we have examined the temperature-dependent superplasticity of single component Ag and multicomponent CoNiCrFeMn HEA nanowires using molecular dynamics simulations. The results demonstrate that Ag nanowires exhibit apparent temperature-dependent superplasticity at cryogenic temperature due to (110) to (100) cross-section reorientation behavior. Interestingly, HEA nanowires can perform exceptional strength-ductility trade-offs at cryogenic temperatures. Even at high temperatures, HEA nanowires can still maintain good flow stress and ductility prior to failure. Mechanical properties of HEA nanowires are better than Ag nanowires due to synergistic interactions of deformation twinning, FCC-HCP phase transformation, and the special reorientation of the cross-section. Further examination reveals that simultaneous activation of twining induced plasticity and transformation induced plasticity are responsible for the plasticity at different stages and temperatures. These findings could be very useful for designing nanowires at different temperatures with high stability and superior mechanical properties in the semiconductor industry.

Nanostructured High Entropy Alloys as Structural and Functional Materials

“…Tripathi et al discovered that chemical fluctuations in CoNiCrFeMn HEA NWs facilitate the formation of nucleation sites for FCC-HCP MT. 380 At elevated temperature, the dominance of MT in these HEA nanowires enhances ductility and flow stress. Furthermore, Ruestes and Farkas simulated the tensile deformation of a Fe−Ni−Cr−Co−Cu NW, revealing that dislocations emitted from the free surface govern its mechanical behavior.…”

“…The plastic deformation in these nanowires is accommodated by reversible FCC-HCP martensitic transformations (MT), which offer lower energy barriers compared to deformation twinning pathways (Figure b). Tripathi et al discovered that chemical fluctuations in CoNiCr­FeMn HEA NWs facilitate the formation of nucleation sites for FCC-HCP MT . At elevated temperature, the dominance of MT in these HEA nanowires enhances ductility and flow stress.…”

Effects of Cr Content on Microstructure and Mechanical Properties of Co-Free FeCryNiAl0.8 High-Entropy Alloys

“…High-entropy alloys (HEAs) and multiprincipal element alloys have received considerable interest for community experts and have become a worldwide hot spot since Cantor and Yeh reported their first publication [1,2]. Cr-containing HEAs have exhibited promising potential when applied in high-temperature industrial fields as a result of their remarkable strength [3][4][5][6], favorable ductility [7][8][9], distinguished corrosion resistance [10][11][12], superior wear and oxidation resistance [13][14][15], and acceptable thermal stability [16,17].…”

Atomic investigations on the tension–compression asymmetry of Al x FeNiCrCu (x = 0.5, 1.0, 1.5, 2.0) high-entropy alloy nanowires

“…The shape memory effects are attributed to the reversible transition from FCC to HCP phase. As the temperature rises from 77 K to 1000 K, the plastic deformation mechanism changes from twinning to phase transition, which means that the CoN-iCrFeMn HEA NWs still maintain good plasticity at high temperatures [54]. Ruestes et al [55] found that compared with average atomic materials, the peak stress of FeCoNiCrCu HEA NWs was lower, and the flow stress was higher.…”