Unique microstructure and simultaneous enhancements of strength and ductility in gradient-microstructured Cu sheet produced by single-roll angular-rolling

Lee, Hak Hyeon; Yoon, Jae Ik; Park, Hyung Keun; Kim, Hyoung Seop

doi:10.1016/j.actamat.2019.01.021

Cited by 74 publications

(17 citation statements)

References 66 publications

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“…In other words, higher flow stress is needed to overcome this field to sustain further plastic deformation. Several studies have reported that high back stress induces strengthening and hardening in heterogeneous-structured materials [8,[33][34][35][36]. To measure the back stress generated during tensile deformation, LUR tests were performed on the GS (PT90, PT180, PT360) and coarse-grained samples.…”

Section: Back Stress Induced Strengthening and Hardeningmentioning

confidence: 99%

“…where σ r and σ u is the reloading yield stress and unloading yield stress, respectively. The σ r and σ u in each hysteresis loop can be determined by the point at which the effective elastic modulus (E eff ) is reduced by 10%, which was also adopted in some recent studies [8,34]. Figure 8d exhibits the back stress measured using the above method with increasing true strain for the coarse-grained and GS (PT90, PT180, PT360) samples.…”

Section: Back Stress Induced Strengthening and Hardeningmentioning

confidence: 99%

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Outstanding Tensile Properties and Their Origins in Twinning-Induced Plasticity (TWIP) Steels with Gradient Substructures

et al. 2020

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The low yield strength (~300 MPa) of twinning-induced plasticity (TWIP) steels greatly limits their structural applications in the industrial field. Conventional strengthening mechanisms usually cause an enhancement of yield strength but also a severe loss of ductility. In this research, gradient substructures were introduced in the Fe-22Mn-0.6C TWIP steels by different pre-torsional deformation in order to overcome the above limitations. The substructure evolution, mechanical properties, and their origins in gradient-substructured (GS) TWIP steels were measured and compared by electron backscattered diffraction (EBSD), monotonous and loading-unloading-reloading (LUR) tensile tests. It was found that a simple torsional treatment could prepare gradient twins and dislocations in coarse-grained TWIP steel samples depending on torsional strain. The uniaxial tensile tests indicated that a superior combination of high yield strength, high ultimate strength, and considerable ductility was simultaneously obtained in the GS samples. The high yield strength and high ultimate tensile strength were attributed to synergetic strengthening mechanisms, viz., dislocation strengthening, due to the accumulation of high density of dislocations, and very high back stress strengthening due to gradient substructure distribution, which was accommodated through pile-ups of extra geometrically necessary dislocations (GNDs) across the sample-scale. Additionally, high ductility originated from gradient substructure-induced back stress hardening. The present study is also beneficial to the design efforts of high strength and high ductility of other heterogeneous-structured TWIP alloy systems.

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Section: Back Stress Induced Strengthening and Hardeningmentioning

confidence: 99%

Section: Back Stress Induced Strengthening and Hardeningmentioning

confidence: 99%

Outstanding Tensile Properties and Their Origins in Twinning-Induced Plasticity (TWIP) Steels with Gradient Substructures

et al. 2020

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“…The SRAR process guarantees high productivity in that a rotary roll provides a continuous driving force to move a metallic sheet through specially-designed grooves inside a stationary die [14]. Above all, the SRAR process can concentrate shear strain locally on the core region of the metallic sheet [15]. This strain heterogeneity between the core and surface regions leads to heterogeneous microstructural evolution in recrystallization and grain growth during the subsequent heat treatment.…”

Section: Introductionmentioning

confidence: 99%

“…This strain heterogeneity between the core and surface regions leads to heterogeneous microstructural evolution in recrystallization and grain growth during the subsequent heat treatment. As a consequence, the SRAR process can fabricate a new type of heterostructured material called reverse gradient structure, which has a relatively fine-grained core and coarse-grained surfaces [15]. Furthermore, microstructural heterogeneities of reverse gradient structures can be diversified by manipulating the condition of postannealing after SRAR [16].…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, it has been steadily reported that microstructural evolution and mechanical properties of ECAP-processed materials are strongly dependent on the processing route [18][19][20]. Above all, the SRAR process generates heterogeneous shear strain in the thickness direction of the metallic sheet [14,15], so the processing route should be taken into account as a key parameter in tailoring strain distribution and microstructural heterogeneity. Nevertheless, as far as the authors know, there have been no studies on the processing route in the SRAR process.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Processing Route on Microstructure and Mechanical Properties in Single-Roll Angular-Rolling

et al. 2020

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This paper reports the effect of the processing route on the microstructure and mechanical properties in the pure copper sheets processed by single-roll angular-rolling (SRAR). The SRAR process was repeated up to six passes in two processing routes, called routes A and C in equal-channel angular pressing. As the number of passes increased, the heterogeneous evolution of hardness and microstructural heterogeneities between the core and surface regions gradually became intensified in both processing routes. In particular, route A exhibited more prominent partial grain refinement and dislocation localization on the core region than route C. The finite element analysis revealed that the intense microstructural heterogeneities observed in route A were attributed to effective shear strain partitioning between the core and surface regions by the absence of redundant strain. On the other hand, route C induced reverse shearing and cancellation of shear strain over the entire thickness, leading to weak shear strain partitioning and delayed grain refinement. Ultimately, this work suggests that route A is the preferred option to manufacture reverse gradient structures in that the degree of shear strain partitioning and microstructural heterogeneity between the core and surface regions is more efficiently intensified with increasing the number of passes.

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The Cold Angular Rolling Process of Copper Sheets: Unraveling Plastic Deformation Behavior and Unveiling Microstructural Transformations

Lee,

Bhatta,

et al. 2023

Adv Eng Mater

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The cold angular rolling process (CARP) is being developed as a continuous severe plastic deformation (SPD) technique, which can process metal sheets without any length limitations at room temperature. CARP contains cold rolling and equal‐channel angular process components. The sheet thickness is kept consistent before and after CARP, allowing multiple passes of the sheet. The desired microstructure and mechanical properties can be achieved in the processed metallic sheets. The current study is aimed to evaluate the capability of CARP by processing copper sheets with different sheet widths for repetitive passes. The CARP‐treated sheets are examined by lab‐scale X‐ray and high‐energy synchrotron X‐ray diffraction to investigate the evolution in dislocation density, texture, and strain anisotropy, and by tensile testing to identify the bulk mechanical properties. The digital image correlation (DIC) method is applied to tensile testing so that strain localization within the sample gauge was visualized and deformation behavior was evaluated after yielding till post‐necking by estimating the hardening exponent and strain hardening rate of the CARP‐treated sheet. Comparing the reported continuous and multiple‐step processes on Cu and its alloys, the present study confirms CARP is potentially a useful sheet process for strengthening ductile metals.This article is protected by copyright. All rights reserved.

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Unique microstructure and simultaneous enhancements of strength and ductility in gradient-microstructured Cu sheet produced by single-roll angular-rolling

Cited by 74 publications

References 66 publications

Outstanding Tensile Properties and Their Origins in Twinning-Induced Plasticity (TWIP) Steels with Gradient Substructures

Outstanding Tensile Properties and Their Origins in Twinning-Induced Plasticity (TWIP) Steels with Gradient Substructures

Effect of Processing Route on Microstructure and Mechanical Properties in Single-Roll Angular-Rolling

The Cold Angular Rolling Process of Copper Sheets: Unraveling Plastic Deformation Behavior and Unveiling Microstructural Transformations

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