Permanent Strength of Metals: A Case Study on FCC Metals Processed by Severe Plastic Deformation

Koizumi, Takayuki; Ogoda, Kazuki; Kuroda, Mitsutoshi

doi:10.1007/s11661-022-06641-1

Cited by 4 publications

(10 citation statements)

References 67 publications

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“…In comparison with the results for 𝜀 = 1 × 10 -6 / s, the difference in 𝜎 0.2 widens after 2 ECAP passes, indicating that the repeated ECAP processes augmented the strain rate sensitivity. For aluminum 7) and copper 8) , in the ultralow-strain-rate tests (𝜀 = ~10 -7 /s), an inversion phenomenon in which 𝜎 of a sample with more ECAP passes was smaller than that of a sample with fewer ECAP passes was observed, but this was not the case for the IF steel used in this study.…”

Section: Effect Of Loading Strain Rate On Flow Stress In Uniaxial Ten...mentioning

confidence: 60%

“…(1) The flow stresses of IF steel observed in tensile tests at ultralow and standard strain rates 𝜎 both monotonically increased with repeated SPD processes, unlike the of aluminum and 𝜎 copper at an ultralow strain rate that decreased with SPD 8) . From 1 to 16 ECAP passes, the fraction of the permanent strength to the total flow stress σ was mostly above 65% (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…In the coarsening approach, of sample "16 passes-O1" increased by 13% relative to that of as-𝜎 i ECAP-processed sample "16 passes", indicating hardening by annealing. Significant hardening by annealing with a fivefold increase in was observed in aluminum 7),8) , while no such hardening 𝜎 i was observed in copper 8) . In SPD-processed metals with fine grains and high dislocation density, hardening by annealing could occur since the heat treatment would reduce the number of mobile dislocations in the grains and the remaining dislocations would form clusters near grain boundaries 26) .…”

Section: Separation Of Permanent and Temporal Strengthsmentioning

confidence: 92%

“…Annealing releases the internal energy and induces recrystallization, which stabilizes the microstructures. The aluminum, positive correlations between m and stress relaxation ratio were observed: i.e., 𝑟 = 0.637 for copper and 𝑟 = 0.786 for aluminum 8) , and the maximum stress relaxation ratios reached 50%…”

Section: Separation Of Permanent and Temporal Strengthsmentioning

confidence: 93%

“…The grain refinement itself does not largely contribute to the increase in 𝜎 gs . Note that, in the cases of copper and aluminum, the Hall-Petch coefficients for 𝜎 gs were negative 8) .…”

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confidence: 95%

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Permanent Strength of Interstitial-free Steel Processed by Severe Plastic Deformation and Subsequent Annealing

2023

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The permanent strengths of interstitial-free (IF) steels with different grain sizes and dislocation densities processed by severe plastic deformation (SPD) and subsequent annealing are systematically investigated. Permanent strength, which is athermal and time-independent, corresponds to the fundamental capability to bear stresses caused by external forces. Sufficiently long-time (24 h) stress relaxation tests were carried out and experimental stress-relaxation time relationships were extrapolated to estimate the permanent strength that remained after an infinite time passed. The flow stresses observed in standard uniaxial tension tests increased with repeated SPD processes, and the fraction of permanent strength to the observed flow stress was mostly above 65%. The permanent strength also increased with repetition of SPD processes, and subsequent low-temperature annealing further augmented the permanent strength. During SPD processes, the dislocation-related strengthening was dominant, while the grain-size-related strengthening was minor, i.e., the Hall-Petch relation does not hold. On the other hand, after low-temperature annealing, the grain-sizerelated strengthening became dominant, quickly replacing the dislocation-related strengthening. In a coarse-grain region, the grain-size-related strength was consistent with the classical Hall-Petch relation. It was confirmed that the original Hall-Petch relation holds only in the coarse-grain region and it indicates "softening with grain coarsening due to annealing", not "strengthening by grain refinement due to SPD".

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Section: Effect Of Loading Strain Rate On Flow Stress In Uniaxial Ten...mentioning

confidence: 60%

Section: Discussionmentioning

confidence: 99%

Section: Separation Of Permanent and Temporal Strengthsmentioning

confidence: 92%

Section: Separation Of Permanent and Temporal Strengthsmentioning

confidence: 93%

mentioning

confidence: 95%

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Permanent Strength of Interstitial-free Steel Processed by Severe Plastic Deformation and Subsequent Annealing

2023

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Microstructure and Mechanical Properties of Low Stacking-Fault Energy Cu-Based Alloy Wires

Semboshi,

Arauchi,

Kaneno

et al. 2024

Metall Mater Trans A

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Innovations in electronic devices and their capabilities have driven the demand for improved conductive materials relevant to device fabrication. To gain insights on developing solid solution-type Cu alloy thin wires with a superior balance of strength and conductivity, this study investigated variations in the microstructures and properties of pure Cu wires and Cu–5 at. pct Zn, Cu–5 at. pct Al, and Cu–5 at. pct In alloy wires during intense drawing and analyzed the effects of stacking-fault energy (SFE) of Cu alloys on their microstructural evolution. During the initial drawing stages, lower SFE Cu–5 at. pct Al and Cu–5 at. pct In alloys yielded more high-density deformation twins than pure Cu and Cu–5 at. pct Zn. Deformation twins promoted grain refinement during drawing. Effective grain refinement and dislocation accumulation during drawing in low-SFE Cu alloys substantially strengthened them without adversely impacting electrical conductivity. During intense drawing in the Cu–5 at. pct In alloy wires, ultrafine fibrous grains (diameter ~ 80 nm) and a high-dislocation density yielded excellent tensile strength and conductivity. These results indicate that adjusting the solute element content in Cu matrix to reduce SFE and optimizing deformation strain via wire drawing significantly improve alloy wire performance.

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Effect of Multiple Reverse Transformation Treatments on Grain Refinement and Mechanical Properties of Biomedical Co–Cr–Mo–N Alloys Fabricated by Electron Beam Melting

Wang,

Miyagi,

Chiba

2023

Materials

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We investigated the improvement of mechanical properties of biograde Co–28Cr–6Mo–0.11N alloy prepared by electron beam melting through grain refinement via multiple reverse transformations. While the effects of single and double reverse transformation treatments on the microstructure have been investigated in previous studies, we investigated the effects of multiple reverse transformation heat treatments. The particle size was refined to 1/4, and the yield strength, tensile silence strength, and elongation were enhanced to 655 MPa, 1234 MPa, and 45%, respectively, satisfying ASTM F75 standards. Moreover, a mixed phase of ε and γ was observed to provide higher yield strength than a single γ structure. The dominant behavior in the γ → ε phase transformation at 1073 K was obvious. Grain growth was suppressed by the grain-boundary pinning effect of the Cr2N phase during reverse transformation to the γ phase. Because no fracture was caused by precipitates such as σ, η, and Cr2N phases, the influence of the precipitates on the tensile properties was small.

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Permanent Strength of Metals: A Case Study on FCC Metals Processed by Severe Plastic Deformation

Cited by 4 publications

References 67 publications

Permanent Strength of Interstitial-free Steel Processed by Severe Plastic Deformation and Subsequent Annealing

Permanent Strength of Interstitial-free Steel Processed by Severe Plastic Deformation and Subsequent Annealing

Microstructure and Mechanical Properties of Low Stacking-Fault Energy Cu-Based Alloy Wires

Effect of Multiple Reverse Transformation Treatments on Grain Refinement and Mechanical Properties of Biomedical Co–Cr–Mo–N Alloys Fabricated by Electron Beam Melting

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