Nature-Inspired Hierarchical Steels

Cao, Shan Cecilia; Liu, Jiabin; Zhu, Linli; Li, Ling; Dao, Ming; J, Lu; Ritchie, Robert O.

doi:10.1038/s41598-018-23358-7

Cited by 47 publications

(30 citation statements)

References 30 publications

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“…Over the past years, a novel approach to microstructure design, known as hierarchical laminate structure, has shown to greatly improve strength and ductility of conventional materials simultaneously, such as Ti alloys and steels, through massive microstructure refinement . Typically, such materials with hierarchical laminate structures consist of a parent phase serving as soft matrix to improve ductility and a hard product phase impeding dislocation motion to strengthen the microstructure.…”

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confidence: 99%

“…Typically, such materials with hierarchical laminate structures consist of a parent phase serving as soft matrix to improve ductility and a hard product phase impeding dislocation motion to strengthen the microstructure. Unfortunately, such heterogeneous materials with high local mechanical disparity among their constituting phases are often prone to internal damage initiation, thus limiting ductility to 3.8–15% for Ti alloys, 20–33% for medium Mn steels, and 23–33% for stainless steels . Therefore, the mechanical properties of such hierarchical laminate materials need to be further improved to minimize the probability of internal damage and failure.…”

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Bidirectional Transformation Enables Hierarchical Nanolaminate Dual‐Phase High‐Entropy Alloys

et al. 2018

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conventional nanostructures, for instance with grain sizes below a critical value of ≈50 nm, can experience softening due to grain boundary sliding. [11,12] Over the past years, a novel approach to microstructure design, known as hierarchical laminate structure, has shown to greatly improve strength and ductility of conventional materials simultaneously, such as Ti alloys and steels, through massive microstructure refinement. [13][14][15][16] Typically, such materials with hierarchical laminate structures consist of a parent phase serving as soft matrix to improve ductility and a hard product phase impeding dislocation motion to strengthen the microstructure. Unfortunately, such heterogeneous materials with high local mechanical disparity among their constituting phases are often prone to internal damage initiation, thus limiting ductility to 3.8-15% for Ti alloys, [13,14] 20-33% for medium Mn steels, [17] and 23-33% for stainless steels. [16] Therefore, the mechanical properties of such hierarchical laminate materials need to be further improved to minimize the probability of internal damage and failure. Also, creating laminate structures in bulk materials often requires imposing complex processing methods, e.g., accumulative roll bonding. [18] Interestingly, a recently developed dual-phase high-entropy alloy (HEA) also exhibits a simultaneous increase of strength and ductility after grain refinement [19][20][21][22][23] as highlighted in Figure 1. The excellent strength-ductility combination of the novel dual-phase HEA has been reported to be related to the transformationinduced plasticity (TRIP) effect, i.e., the displacive phase transformation from the face-centered cubic (FCC γ) matrix into the hexagonal close-packed (HCP ε) phase upon deformation. [19,22] Depending on the magnitude of the stacking fault energy, different compositional variants of recently developed HEAs have shown deformation modes with planar dislocation slip, [24,25] twinning induced plasticity (TWIP), [26] or TRIP effect. [22] Here, we observe another state which is thermodynamically characterized by a similar stability of two co-existing phases (FCC γ and HCP ε). This means that the stacking fault energy of the FCC matrix must assume a near-zero yet positive value so that forward (γ → ε) and backward (ε → γ) transformations can be both triggered in the same material and loading state.We studied the deformation mechanisms in the dual-phase HEA (Fe 50 Mn 30 Co 10 Cr 10 , at%) in more detail via transmission electron microscopy (TEM) analysis and found that this novel TRIP-assisted HEA gradually develops a hierarchical Microstructural length-scale refinement is among the most efficient approaches to strengthen metallic materials. Conventional methods for refining microstructures generally involve grain size reduction via heavy cold working, compromising the material's ductility. Here, a fundamentally new approach that allows load-driven formation and permanent refinement of a hierarchical nanolaminate structure in a novel high-entropy allo...

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Bidirectional Transformation Enables Hierarchical Nanolaminate Dual‐Phase High‐Entropy Alloys

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“…Understanding the morphology and structure of biomaterials can contribute towards the design and manufacture of human-made materials [2,68,69]. Similar discrete bimodal grain sizes are observed in manufactured materials for aerospace, such as the ‘dual microstructure’ of some nickel superalloy-based gas turbine disks [70].…”

Section: Discussionmentioning

confidence: 99%

Macro-to-nano scale investigation of wall-plate joints in the acorn barnacle Semibalanus balanoides: correlative imaging, biological form and function, and bioinspiration

Mitchell

Coleman

Davies

et al. 2019

Preprint

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1.AbstractCorrelative imaging combines information from multiple modalities (physical-chemical-mechanical properties) at various length-scales (cm to nm) to understand complex biological materials across dimensions (2D-3D). Here, we have used numerous coupled systems: X-ray microscopy (XRM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), optical light microscopy (LM), and focused-ion beam (FIB-SEM) microscopy to ascertain the microstructural and crystallographic properties of the wall-plate joints in the barnacle Semibalanus balanoides. The exoskeleton is composed of six interlocking wall-plates, and the interlocks between neighbouring plates (alae) allow barnacles to expand and grow whilst remaining sealed and structurally strong. Our results indicate that the ala contain functionally-graded orientations and microstructures in their crystallography, which has implications for naturally functioning microstructures, potential natural strengthening, and preferred oriented biomineralisation. Elongated grains at the outer edge of the ala are oriented perpendicularly to the contact surface, and the c-axis rotates with the radius of the ala. Additionally, we identify for the first time three-dimensional nano-scale ala pore networks revealing that the pores are only visible at the tip of the ala, and that pore thickening occurs on the inside (soft-bodied) edge of the plates. The pore networks appear to have the same orientation as the oriented crystallography, and we deduce that the pore networks are probably organic channels and pockets which are involved with the biomineralisation process. Understanding these multi-scale features contributes towards an understanding of the structural architecture in barnacles, but also their consideration for bioinspiration of human-made materials. The work demonstrates that correlative methods spanning different length-scales, dimensions and modes enable the extension of structure-property relationships in materials to form and function of organisms.

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“…Deformation processes based on the impact of particles have been utilized extensively to harden surfaces, by imparting residual compressive stresses and/or by creating a work-hardened layer for the purpose of improving surface properties, such as resistance to fatigue or wear. 1,2 More recently, these techniques have also been used to make stronger engineering metal alloys, [3][4][5] through the use of techniques such as air blast and ultrasonic shot peening, 6 surface mechanical attrition treatment, 7 particle impact processing, 8 and surface nano-crystallization and hardening, 9 specifically to develop surface hardness and structural gradients. Here we focus on the technique of surface mechanical attrition treatment (or SMAT) which has been widely used in the generation of nanostructures and subsurface gradients to improve the damagetolerance of structural materials.…”

Section: Introductionmentioning

confidence: 99%

“…1 for an AISI 316 L austenitic stainless steel, where we show how the process can induce superior mechanical properties through surface modification. 3,4 Specifically, we compare the microstructure and the mechanical behavior of a SMAT-treated AISI 316 L stainless steel with that of an as-annealed AISI 316 L stainless steel. Following SMAT treatments, the hardness distribution along the crosssection of the SMAT-treated steel is a factor of~3-4 times higher than that of the as-annealed steel (Fig.…”

Section: Introductionmentioning

confidence: 99%

Predicting surface deformation during mechanical attrition of metallic alloys

Cao

Zhang

et al. 2019

npj Comput Mater

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Extensive efforts have been devoted in both the engineering and scientific domains to seek new designs and processing techniques capable of making stronger and tougher materials. One such method for enhancing such damage-tolerance in metallic alloys is a surface nano-crystallization technology that involves the use of hundreds of small hard balls which are vibrated using high-power ultrasound so that they impact onto the surface of a material at high speed (termed Surface Mechanical Attrition Treatment or SMAT). However, few studies have been devoted to the precise underlying mechanical mechanisms associated with this technology and the effect of processing parameters. As SMAT is dynamic plastic deformation process, here we use random impact deformation as a means to investigate the relationship between impact deformation and the parameters involved in the processing, specifically ball size, impact velocity, ball density and kinetic energy. Using analytical and numerical solutions, we examine the size of the indents and the depths of the associated plastic zones induced by random impacts, with results verified by experiment in austenitic stainless steels. In addition, global random impact and local impact frequency models are developed to analyze the statistical characteristics of random impact coverage, together with a description of the effect of random multiple impacts, which are more reflective of SMAT. We believe that these models will serve as a necessary foundation for further, and more energy-efficient, development of such surface nano-crystalline processing technologies for the strengthening of metallic materials.

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Nature-Inspired Hierarchical Steels

Cited by 47 publications

References 30 publications

Bidirectional Transformation Enables Hierarchical Nanolaminate Dual‐Phase High‐Entropy Alloys

Bidirectional Transformation Enables Hierarchical Nanolaminate Dual‐Phase High‐Entropy Alloys

Macro-to-nano scale investigation of wall-plate joints in the acorn barnacle Semibalanus balanoides: correlative imaging, biological form and function, and bioinspiration

Predicting surface deformation during mechanical attrition of metallic alloys

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