Grain Size Tailoring to Control Strain Hardening and Improve the Mechanical Properties of a CoCrFeNiMn High-Entropy Alloy

Shahmir, Hamed; Mehranpour, Mohammad Sajad; Shams, Seyed Amir Arsalan; Lee, Chong Soo; Langdon, Terence G.

doi:10.1007/s44210-022-00003-7

Cited by 11 publications

(6 citation statements)

References 64 publications

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“…The strain-hardening rate (dσ/dε) versus the true strain curve is plotted in Figure 2b to evaluate the strain-hardening response of the HEA after PDA at different temperatures. The strain-hardening rate curves of the annealed samples at 700 and 750 °C show three stages depending on the slope variation, as reported earlier for fcc materials [32][33][34][35]. There is a rapid decrease in the strain-hardening rate below the true strain of ~0.04 in stage I, demonstrating an elastic-to-plastic transition.…”

Section: Mechanical Propertiessupporting

confidence: 78%

“…The results suggest that the area fraction of deformation twins increases during plastic deformation, which confirms the theory of the formation of deformation-induced plasticity in the recrystallized grains. The grain size of these grains is higher than the critical grain size for suppressing DT formation during training (~2 µm) [35].…”

Section: Microstructure Of the Annealed Samples After Plastic Deforma...mentioning

confidence: 92%

“…The strain-hardening ability is higher when the average grain size is higher than 2 µm due to the easier movement and generation of dislocations, together with deformation twinning, which facilitate higher uniform deformation. A lower chance of deformation twinning for very small grain sizes (<2 µm) during straining led to lower strain hardening in the CoCrFeNiMn HEA [35].…”

Section: Strengthening Mechanisms and The Role Of Hetero-deformation ...mentioning

confidence: 99%

“…PDA at intermediate temperatures facilitates the formation of a partially recrystallized microstructure and heterogeneous structure. HEAs exhibit relatively high recrystallization and coarsening temperatures and a slow grain-coarsening behavior during PDA due to their inherent sluggish diffusion and high lattice distortion [35,36,38]. This provides a relatively wide temperature range for partial recrystallization, which facilitates easier tuning of the microstructure during PDA.…”

Section: Significance Of the Heterogeneous Microstructurementioning

confidence: 99%

“…This structure was produced using a simple thermomechanical treatment including medium cold rolling followed by PDA at the intermediate temperature of 650 • C for 60 min. It was previously shown that grain refinement alone is not a promising procedure for achieving strength and ductility synergy [26,35,36]. The heterogeneity due to the controlled recrystallization phenomenon in deformed materials which have an inhomogeneous nature of plastic deformation during cold working is a fundamental aspect of the heterogeneous structure [37].…”

Section: Significance Of the Heterogeneous Microstructurementioning

confidence: 99%

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Hetero-Deformation Induced Hardening in a CoCrFeNiMn High-Entropy Alloy

et al. 2023

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One of the most important issues in materials science is to overcome the strength–ductility trade-off in engineering alloys. The formation of heterogeneous and complex microstructures is a useful approach to achieving this purpose. In this investigation, a CoCrFeNiMn high-entropy alloy was processed via cold rolling followed by post-deformation annealing over a temperature range of 650–750 °C, which led to a wide range of grain sizes. Annealing at 650 °C led to the formation of a heterogeneous structure containing recrystallized areas with ultrafine and fine grains and non-recrystallized areas with an average size of ~75 μm. The processed material showed strength–ductility synergy with very high strengths of over ~1 GPa and uniform elongations of over 12%. Different deformation mechanisms such as dislocation slip, deformation twinning and hetero-deformation-induced hardening were responsible for achieving this mechanical property. Increasing the annealing temperature up to 700 °C facilitated the acquisition of bimodal grain size distributions of ~1.5 and ~6 μm, and the heterogeneous structure was eliminated via annealing at higher temperatures, which led to a significant decrease in strength.

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Section: Mechanical Propertiessupporting

confidence: 78%

Section: Microstructure Of the Annealed Samples After Plastic Deforma...mentioning

confidence: 92%

Section: Strengthening Mechanisms and The Role Of Hetero-deformation ...mentioning

confidence: 99%

Section: Significance Of the Heterogeneous Microstructurementioning

confidence: 99%