Ductility by shear band delocalization in the nano-layer of gradient structure

Yuan, Fuping; Yan, Dingshun; Sun, Jiangda; Zhou, Lingling; Zhu, Yuntian; Wu, Xiaolei

doi:10.1080/21663831.2018.1546238

Cited by 112 publications

(53 citation statements)

References 39 publications

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“…The back stress concept was later used by many groups to explain the strengthening of a metal matrix by secondphase particles in the 1970s [44][45][46]. More recently, back stress has been used to explain the hardening behavior and Bauschinger effect in TRIP steels [47], the transient plastic flow during creep [48], the Bauschinger effect in thin films [38], the hysteresis loop under cyclic loading [49], the extra strain hardening of HS materials [1,2,27,50,51], etc. These reports show that the back stress concept has been widely, if not fully, accepted by the materials community.…”

Section: Brief History Of Back Stressmentioning

confidence: 99%

Perspective on hetero-deformation induced (HDI) hardening and back stress

Zhu

2019

Materials Research Letters

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863

135

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Heterostructured materials have been reported as a new class of materials with superior mechanical properties, which was attributed to the development of back stress. There are numerous reports on back stress theories and measurements with no consensus. Back stress is developed in soft domains to offset the applied stress, making them appear stronger, while forward stress is developed to make hard domains appear weaker. The extra hardening in heterostructured materials is resulted from interactions between back stresses and forward stresses, and should be described as hetero-deformation induced (HDI) hardening and the measured 'back stress' should be renamed HDI stress. IMPACT STATEMENT The 'back stress' hardening in the literature can be described more accurately as hetero-deformation induced (HDI) hardening and the measured 'back stress' should be renamed HDI stress.

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Section: Brief History Of Back Stressmentioning

confidence: 99%

Perspective on hetero-deformation induced (HDI) hardening and back stress

Zhu

2019

Materials Research Letters

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863

135

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“…collecting vast strains for ductility, and to avoid its shortcoming, i.e. fast instability, by stabilizing localized shear band in the gradient structure [63]. This novel strategy overturned our traditional understanding for strain localization.…”

Section: Tensile Behaviors Of Gradient Grained Structuresmentioning

confidence: 99%

“…We exhibited for the first time that localization may induce ductility, instead of catastrophic failure. This enhanced ductility in the gradient structure was fulfilled by the shear band delocalization: shear bands were initiated soon after yielding in the NS surface layer, while were delocalized by propagating along the gage length during the tensile loading, and synergistic work hardening was induced by back stress hardening from the strain gradients in both the axial and depth directions [63]. Using the same SMAT technique, we have produced a gradient structure in an IF steel and large tensile ductility was achieved in the NS surface layer of IF steel without apparent grain growth when confined by the CG substrate [14].…”

Section: Tensile Behaviors Of Gradient Grained Structuresmentioning

confidence: 99%

A Review on Heterogeneous Nanostructures: A Strategy for Superior Mechanical Properties in Metals

Yang

Yuan

et al. 2019

Metals

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Generally, strength and ductility are mutually exclusive in homogeneous metals. Nanostructured metals can have much higher strength when compared to their coarse-grained counterparts, while simple microstructure refinement to nanoscale generally results in poor strain hardening and limited ductility. In recent years, heterogeneous nanostructures in metals have been proven to be a new strategy to achieve unprecedented mechanical properties that are not accessible to their homogeneous counterparts. Here, we review recent advances in overcoming this strength–ductility trade-off by the designs of several heterogeneous nanostructures in metals: heterogeneous grain/lamellar/phase structures, gradient structure, nanotwinned structure and structure with nanoprecipitates. These structural heterogeneities can induce stress/strain partitioning between domains with dramatically different strengths, strain gradients and geometrically necessary dislocations near domain interfaces, and back-stress strengthening/hardening for high strength and large ductility. This review also provides the guideline for optimizing the mechanical properties in heterogeneous nanostructures by highlighting future challenges and opportunities.

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“…While these two properties are mutually exclusive in general, i.e., high yield strength usually results in limited ductility. In the last two decades, several heterogeneous microstructures have been proposed to produce both high yield strength and large tensile ductility in metals and alloys, such as bimodal/multimodal structures [1,9], gradient structures [10][11][12][13], lamella structures [8,14,15], and bimetallic laminates [16][17][18][19][20][21][22][23][24][25][26]. These heterogeneous microstructures generally have various domains with different mechanical properties, and the plastic deformation incompatibility can occur among these domains [8,[27][28][29].…”

Section: Introductionmentioning

confidence: 99%

Superior mechanical properties and deformation mechanisms of heterogeneous laminates under dynamic shear loading

Yuan

Yang

et al. 2019

Materials Science and Engineering: A

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High-strain rate response of low C steel/304 stainless steel (SS) laminates was characterized by hat-shaped specimen using Hopkinson-bar technique at a strain rate of about 7×10 4 s-1. Better dynamic shear properties were observed in the laminates, compared to the plain low C steel plate and the plain 304 SS plate. The laminates were found to postpone the nucleation of adiabatic shear band (ASB) in the hard zone and to delay the propagation of ASB from the hard zone to the soft zone. The conventional maximum stress criterion on ASB nucleation was found not valid any more in the laminates. The hardness difference between the hard zone and the soft zone in the laminates was found to have great influence on the patterns of ASB evolution. Nanotwins were formed in the 304 SS and grain refinement was observed in the martensite low C steel for strain hardening under dynamic shear loading. The mechanical incompatibility across the interfaces was observed to result in strain gradient and geometrically necessary dislocations at the interfaces under dynamic shear loading, contributing to extra strain hardening. The extra hardening was also found to be triggered at the propagation tip of ASB, which helps for achieving better dynamic ductility in the laminates.

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Ductility by shear band delocalization in the nano-layer of gradient structure

Cited by 112 publications

References 39 publications

Perspective on hetero-deformation induced (HDI) hardening and back stress

Perspective on hetero-deformation induced (HDI) hardening and back stress

A Review on Heterogeneous Nanostructures: A Strategy for Superior Mechanical Properties in Metals

Superior mechanical properties and deformation mechanisms of heterogeneous laminates under dynamic shear loading

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