Microstructure and mechanical properties after annealing of equal-channel angular pressed interstitial-free steel

Hazra, Sujoy S.; Pereloma, Elena V.; Gazder, Azdiar A.

doi:10.1016/j.actamat.2011.03.026

Cited by 78 publications

(29 citation statements)

References 50 publications

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“…Similar observations on the general form of the subgrain size distribution were made on annealed ECAP Al alloys [8,10]. Apart from sluggish growth kinetics beyond 30 s for the ECAP material, coarsening via recovery-like processes is further evidenced by the preservation and sharpening of the deformation texture [15,16]. Due to the high fraction of strain-induced HAGBs (~63%) after ECAP, annealing results in a homogeneous softening (or continuous recrystallisation) without a discernible nucleation and growth sequence [17].…”

Section: Resultssupporting

confidence: 54%

“…Coarsening behavior during annealing: When the hardness -based fraction softened [15] is plotted against annealing time (Fig. 2), the 95% CR samples soften more than the ECAP samples irrespective of holding time due to the higher stored energy after additional CR.…”

Section: Resultsmentioning

confidence: 99%

“…When the ideal texture components are overlaid on the boundary map with a 20° tolerance angle ( Fig. 1(a)), preferential clustering of orientation components is absent as their spatial distribution remains inhomogeneous [15]. After 95% CR, the EBSD map in Fig.…”

Section: Resultsmentioning

confidence: 99%

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Effect of Annealing on the Microstructure, Texture and Mechanical Properties of Severely Deformed Interstitial Free Steel

Hazra

Gazder

Pereloma

2012

MSF

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Abstract. Ti-stabilised interstitial free (IF) steel initially subjected to 8 passes, route B C equal channel angular pressing (ECAP) was further cold rolled (CR) at room temperature to 95% thickness reduction. Both samples were isothermally annealed at 710 °C following which their microstructures and micro-textures were compared via electron back-scattering diffraction (EBSD).The mechanical properties first obtained by shear punch testing (SPT) were later corroborated by uniaxial tensile tests. In the case of the ECAP material, continuous recrystallisation is followed by abnormal growth at prolonged annealing times with minor increases in high angle boundary (HAGB) fraction. On the other hand, the additionally CR material shows continuous recrystallisation accompanied by a reduction in the HAGB fraction. After 15 s annealing, the ECAP and CR samples exhibit a good strength-ductility balance; which corresponds to ~52% and ~67% softening, respectively.

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Section: Resultssupporting

confidence: 54%

Section: Resultsmentioning

confidence: 99%

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Effect of Annealing on the Microstructure, Texture and Mechanical Properties of Severely Deformed Interstitial Free Steel

Hazra

Gazder

Pereloma

2012

MSF

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“…5). When the homogeneous IF-steel is deformed to increase strength, its ductility usually drops dramatically, especially when the strength is above 400 MPa (22)(23)(24)(25)(26). In contrast, the ductility of GS sample is 5-10 times higher than that of the homogeneous nanograined structures within the strength range of 450-600 MPa.…”

Section: Discussion and Summarymentioning

confidence: 89%

Extraordinary strain hardening by gradient structure

Jiang

Chen

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

1,013

415

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Gradient structures have evolved over millions of years through natural selection and optimization in many biological systems such as bones and plant stems, where the structures change gradually from the surface to interior. The advantage of gradient structures is their maximization of physical and mechanical performance while minimizing material cost. Here we report that the gradient structure in engineering materials such as metals renders a unique extra strain hardening, which leads to high ductility. The grain-size gradient under uniaxial tension induces a macroscopic strain gradient and converts the applied uniaxial stress to multiaxial stresses due to the evolution of incompatible deformation along the gradient depth. Thereby the accumulation and interaction of dislocations are promoted, resulting in an extra strain hardening and an obvious strain hardening rate up-turn. Such extraordinary strain hardening, which is inherent to gradient structures and does not exist in homogeneous materials, provides a hitherto unknown strategy to develop strong and ductile materials by architecting heterogeneous nanostructures.gradient structured metal | nanocrystalline metal M ankind has much to learn from nature on how to make engineering materials with novel and superior physical and mechanical properties (1, 2). For examples, the clay-polymer multilayers mimicking naturally grown seashells are found to have exceptional mechanical properties (3). Another example is the gradient structure, which exists in many biological systems such as teeth and bamboos. A typical gradient structure exhibits a systematic change in microstructure along the depth on a macroscopic scale. Gradient structures have been evolved and optimized over millions of years to make the biological systems strong and tough to survive nature. They are greatly superior to manmade engineering materials with homogeneous microstructures.Here we report the discovery of a hitherto unknown, to our knowledge, strain hardening mechanism, which is intrinsic to the gradient structure in an engineering material. The gradient structure shows a surprising extra strain hardening along with an up-turn and subsequent good retention of strain hardening rate. Strain hardening is critical for increasing the material ductility (4-6). We also show a superior ductility-strength combination in the gradient structure that is not accessible to conventional homogeneous microstructures. Microstructural Characterization of Gradient StructureWe demonstrate these behaviors in a grain-size gradient-structured (GS) sample, i.e., two GS surface layers sandwiching a coarse-grained (CG) core, produced by the surface mechanical attrition treatment (SMAT) (7) in a 1-mm-thick CG interstitial free (IF)-steel sheet (SI Materials and Methods). The GS layers on both sides have a gradual grain-size increase along the depth (Fig. 1A). In the outermost layer of ∼25-μm thickness are nearly equiaxial nanograins with a mean size of 96 nm (Fig. 1B). The grain size increases gradually to 0.5 and 1 μm at ...

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“…Nevertheless, most of the literature discusses the recrystallization behavior of face-centered cubic (FCC) materials, particularly Al, Cu, and Ni. Only a few works report on the microstructural evolution of body-centered cubic (BCC) during annealing so far [18][19][20][21][22] . In the case of BCC single crystals processed by ECAP, in especial niobium single crystal 23 , the number of reported studies is certainly even smaller.…”

Section: Introductionmentioning

confidence: 99%

Microstructural Stability of a Niobium Single Crystal Deformed by Equal Channel Angular Pressing

et al. 2017

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A [211]-oriented niobium single crystal was deformed by equal channel angular pressing (ECAP) at room temperature using the route B c to a total strain of 9.2. A sharp cube texture develops after ECAP processing. The deformed samples were annealed in vacuum from 400ºC (673 K) to 900ºC (1173 K) for 1 h to evaluate their microstructural stability. Scanning electron microscopy (SEM) was used to image the microstructures of as-deformed and annealed specimens. Electron backscatter diffraction (EBSD) was employed to determine the respective microtextures before and after annealing. Coarsening of the microstructure occurs at a maximum rate at 550ºC (823 K) due to discontinuous recrystallization. Normal grain growth replaces discontinuous recrystallization as the main coarsening mechanism above 700ºC (973 K).

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Microstructure and mechanical properties after annealing of equal-channel angular pressed interstitial-free steel

Abstract: . (2011). Microstructure and mechanical properties after annealing of equal-channel angular pressed interstitial-free steel. Acta Materialia, 59 (10), 4015-4029.

Cited by 78 publications

References 50 publications

Effect of Annealing on the Microstructure, Texture and Mechanical Properties of Severely Deformed Interstitial Free Steel

Effect of Annealing on the Microstructure, Texture and Mechanical Properties of Severely Deformed Interstitial Free Steel

Extraordinary strain hardening by gradient structure

Microstructural Stability of a Niobium Single Crystal Deformed by Equal Channel Angular Pressing

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