Long-Crack Fatigue Thresholds and Short Crack Simulation at Liquid Helium Temperature

Tobler, R. L.; Berger, J. R.; Bussiba, A.

doi:10.1007/978-1-4757-9050-4_20

Cited by 4 publications

(2 citation statements)

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“…3 clearly shows that the CoCrFeNi HEA has an outstanding combination of strength and ductility. The UTS of this alloy is higher than those of most conventional cryogenic materials, such as aluminum alloys [1], copper alloys [11,35,36], and comparable to the strength of some stainless steels [37] or titanium alloys [3]. Meanwhile, the elongation of the CoCrFeNi alloy at 4.2 K exceeds all of the mentioned cryogenic materials at the strength level above 1 GPa.…”

Section: Mechanical Propertiesmentioning

confidence: 90%

Excellent ductility and serration feature of metastable CoCrFeNi high-entropy alloy at extremely low temperatures

et al. 2018

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Seldom could metals and alloys maintain excellent properties in cryogenic condition, such as the ductility, owing to the restrained dislocation motion. However, a face-centered-cubic (FCC) CoCrFeNi highentropy alloy (HEA) with great ductility is investigated under the cryogenic environment. The tensile strength of this alloy can reach a maximum at 1,251±10 MPa, and the strain to failure can stay at as large as 62% at the liquid helium temperature. We ascribe the high strength and ductility to the low stacking fault energy at extremely low temperatures, which facilitates the activation of deformation twinning. Moreover, the FCC→HCP (hexagonal close-packed) transition and serration lead to the sudden decline of ductility below 77 K. The dynamical modeling and analysis of serrations at 4.2 and 20 K verify the unstable state due to the FCC→HCP transition. The deformation twinning together with phase transformation at liquid helium temperature produces an adequate strain-hardening rate that sustains the stable plastic flow at high stresses, resulting in the serration feature.

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Section: Mechanical Propertiesmentioning

confidence: 90%

Excellent ductility and serration feature of metastable CoCrFeNi high-entropy alloy at extremely low temperatures

et al. 2018

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“…[124] To date, only some conventional alloys are viable for liquid-helium-temperature applications, most of which are fcc structured. [231][232][233][234][235][236] Just as in conventional alloys, some fccstructured HEAs [21,124,237,238] have shown great potential for cryogenic applications. This is seen first hand in Figure 13, where the FeCoNiCrMn and FeCoNiCr HEAs exhibit an enhancement in their mechanical response with decreasing temperatures.…”

Section: Overcoming the "Strength-ductility Trade-off"mentioning

confidence: 99%

Phase Selection, Lattice Distortions, and Mechanical Properties in High‐Entropy Alloys

et al. 2020

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Increasing demand for improved physical, chemical, and mechanical properties led to the development of conventional alloys from single elements. These conventional alloys are made by selecting one or two major elements with desired properties, and other minor components are added to tune the properties to meet performance specifications. The conventional alloy design strategy is mainly based on the "solutesolvent" principle. However, another alloy design strategy based on multiprincipal elements in the near-equimolar ratio has recently been developed. In this multiprincipal element system, it is difficult to distinguish between the solute and the solvent, and various atoms are supposed to be randomly distributed in the crystal lattices (which has not been confirmed yet). This strategy, proposed by Yeh [1] and Cantor, [2] was based on the Boltzmann hypothesis of the relationship between entropy and system complexity. They proposed that the increased configurational entropy of mixing in alloys with multiple alloying elements in near-equiatomic proportions would overcome the enthalpy of compound formation, stabilizing solid solutions (SS) at the expense of intermetallics (IMs) during solidification. These multiprincipal element alloys are named "high entropy alloys" (HEAs), although the exact values of entropy in HEAs have not been experimentally measured yet. Since then, hundreds of HEAs with different combinations have been developed based on transition metals, refractory metals, and compound forming elements. [2-20] Most of these HEAs have been found to possess simple crystal structures such as the face-centered cubic (fcc) Fe-Co-Cr-Mn-Ni HEAs, [2] bodycentered cubic (bcc) Al-Co-Cr-Fe-Ni HEAs, [18] and the hexagonal close-pack (hcp) Ho-Dy-Y-Gd-Tb HEAs [6] when solidified from the melts. Experimental characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), nanoindentation, tensile, wear-and corrosionresistance tests have been used to study the microstructureproperties correlations of HEAs. [3-50] These studies have revealed that HEAs possess superior properties, such as high hardness and strength, [23-29] superior corrosion and wear resistance, [3,30-35] good magnetic properties, [9,36-39,51] structural stability, [7,40,41] attractive mechanical properties at extreme temperature conditions, [21,42-47] and good electronic properties. [48,49] Yeh [50] proposed four core effects of HEAs, namely: 1) high-entropy effect; 2) sluggish diffusion effect; 3) sever lattice distortion effect; and 4) cocktail effect, in which the lattice distortion might be the key factor affecting the properties of HEAs. Although a complete understanding of lattice distortions in HEAs is still not established yet, significant progress in HEAs has been made recently.

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Fatigue Crack Growth Characteristics of the Cryogenic Structural Materials

Suzuki¹,

Hirano²

1994

Advances in Fracture Resistance and Structural Integrity

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Long-Crack Fatigue Thresholds and Short Crack Simulation at Liquid Helium Temperature

Cited by 4 publications

References 5 publications

Excellent ductility and serration feature of metastable CoCrFeNi high-entropy alloy at extremely low temperatures

Excellent ductility and serration feature of metastable CoCrFeNi high-entropy alloy at extremely low temperatures

Phase Selection, Lattice Distortions, and Mechanical Properties in High‐Entropy Alloys

Fatigue Crack Growth Characteristics of the Cryogenic Structural Materials

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