Ideal Shear Strengths of fcc Aluminum and Copper

Roundy, David; Krenn, C. R.; Cohen, Marvin L.; Morris, J. W.

doi:10.1103/physrevlett.82.2713

Cited by 453 publications

(257 citation statements)

References 17 publications

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“…37 A 1% level of strain was predefined as the small strain increment for each To simulate the mechanical response under indentation experiments, we applied biaxial shear deformation on the GBs structures, adjusted to mimic the deformation under the indenter by imposing the relations σ zz = σ zx × tan Φ where σ zz is the normal stress, σ zx is the shear stress and Φ is the centerline-to face angle of the indenter (Φ = 68° for Vickers indenter). 38 The other four strain components were relaxed in the biaxial shear deformation.…”

Section: Computational Methodologymentioning

confidence: 99%

Shear-Induced Brittle Failure along Grain Boundaries in Boron Carbide

Yang

Coleman

LaSalvia

et al. 2018

ACS Appl. Mater. Interfaces

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Abstract:The role that grain boundaries (GB) can play on mechanical properties has been studied extensively for metals and alloys. However, for covalent solids such as boron carbide (B 4 C), the role of GB on the inelastic response to applied stresses is not well established. We consider here the unusual ceramic, boron carbide (B 4 C), which is very hard and lightweight but exhibits brittle impact behavior. We used quantum mechanics (QM) simulations to examine the mechanical response in atomistic structures that model GBs in B 4 C under pure shear and also with biaxial shear deformation that mimics indentation stress conditions. We carried out these studies for two simple GB models including also the effect of adding Fe atoms (possible sintering aid and/or impurity) to the GB. We found that the critical shear stresses of these GB models are much lower than for crystalline and twinned B 4 C. The two GB models lead to different interfacial energies. The higher interfacial energy at the GB only slightly decreases the critical shear stress but dramatically increases the critical failure strain. Doping the GB with Fe decreases the critical shear stress of at the boundary by 14% under pure shear deformation. In all GBs studied here, failure arises from deconstructing the icosahedra within the GB region under shear deformation. We find that Fe dopant interacts with icosahedra at the GB to facilitate this deconstruction of icosahedra. These results provide significant insight for designing polycrystalline B 4 C with improved strength and ductility.

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Section: Computational Methodologymentioning

confidence: 99%

Shear-Induced Brittle Failure along Grain Boundaries in Boron Carbide

Yang

Coleman

LaSalvia

et al. 2018

ACS Appl. Mater. Interfaces

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“…This relaxation method has been proven to be an effective tool to calculate the ideal strength, and sheds light on the intrinsic failure mechanism at the atomistic scale. [30][31][32] The tensile stress ij σ was calculated by, 33 …”

Section: Methodsmentioning

confidence: 99%

Structure and Failure Mechanism of the Thermoelectric CoSb₃/TiCoSb Interface

Hao

Aydemir

et al. 2016

ACS Appl. Mater. Interfaces

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Abstract:The brittle behavior and low strength of CoSb 3 /TiCoSb interface are serious issues concerning the engineering applications of CoSb 3 based or CoSb 3 /TiCoSb segmented thermoelectric devices. To illustrate the failure mechanism of the CoSb 3 /TiCoSb interface, we apply density functional theory to investigate the interfacial behavior and examine the response during tensile deformations. We find that both CoSb 3 (100)/TiCoSb(111) and CoSb 3 (100)/TiCoSb(110) are energetically favorable interfacial structures. Failure of the CoSb 3 /TiCoSb interface occurs in CoSb 3 since the structural stiffness of CoSb 3 is much weaker than that of TiCoSb. This failure within CoSb 3 can be explained through the softening of the Sb−Sb bond along with the cleavage of the Co−Sb bond in the interface. The failure mechanism the CoSb 3 /TiCoSb interface is similar to that of bulk CoSb 3 , but the ideal tensile strength and failure strain of the CoSb 3 /TiCoSb interface are much lower than those of bulk CoSb 3 . This can be attributed to the weakened stiffness of the Co−Sb framework due to structural rearrangement near the interfacial region.

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“…2,6 Calculations of the resolved shear stress at fracture on the highest Schmid factor slip systems result in stresses that are consistent with calculated theoretical shear strengths of pure Cu. [24][25][26] Normalized shear strengths range from µ/50 to µ/11, where µ is the shear modulus of Cu along <110> directions. Fracture strengths for a range of sizes showed significant scatter (Figure 3e), which could be interpreted in the context of a weakest link framework, as often employed in the fracture of ceramics and glasses.…”

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confidence: 99%

Ultrahigh Strength Single Crystalline Nanowhiskers Grown by Physical Vapor Deposition

et al. 2009

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The strength of metal crystals is reduced below the theoretical value by the presence of dislocations or by flaws that allow easy nucleation of dislocations. A straightforward method to minimize the number of defects and flaws and to presumably increase its strength is to increase the crystal quality or to reduce the crystal size. Here, we describe the successful fabrication of high aspect ratio nanowhiskers from a variety of face-centered cubic metals using a high temperature molecular beam epitaxy method. The presence of atomically smooth, faceted surfaces and absence of dislocations is confirmed using transmission electron microscopy investigations. Tensile tests performed in situ in a focusedion beam scanning electron microscope on Cu nanowhiskers reveal strengths close to the theoretical upper limit and confirm that the properties of nanomaterials can be engineered by controlling defect and flaw densities.Single crystalline metal wires, or metal whiskers, with diameters larger than one micrometer have been routinely fabricated 1 and used for experimentally examining mechanical, 2 ferromagnetic, 3 superconductive, 4 and electronic 5 properties. Interest in metal whiskers became intense once it was observed that they could exhibit strengths close to theoretical (ideal) values. 2,6 Whiskers have been grown by the vapor liquid solid method 7 (VLS) or metal halide reduction, 6 the latter of which have demonstrated high strength. 6 This has been attributed to the near-equilibrium nature of the growth process and the resultant absence of defects and flaws in the samples. Extending the fabrication of high quality metal whiskers to submicrometer diameters, as routinely produced for semiconductors, 7-9 is clearly desired but has been largely elusive. However, single crystalline metal nanowires have only occasionally been successfully fabricated. 10 Here we describe the first time to our knowledge the fabrication of metal single crystalline nanowhiskers (NWs) with diameters as small as 20 nm and no defects, as evidenced by their strengths near the theoretical upper limit. Such nanostructures have the potential to serve as model systems for elucidating intrinsic properties in tiny structures, such as quantum effects, and to be used as building blocks in nanotechnological applications where unique functionalities are required.In this study, free-standing, high aspect ratio, single crystalline nanowhiskers of a variety of different materials (copper, gold, silver, aluminum, and silicon) have been successfully grown from partially C-coated, oxidized and nonoxidized Si (100), (110), and (111) substrates under molecular beam epitaxy (MBE) conditions. Both elevated substrate temperatures (on the order of 0.65 T M of the deposited species) and the partial C layer are necessary to achieve nanowhisker growth. In the remainder of this publication we will focus on results from Cu nanowhiskers. Figure 1 shows scanning electron micrographs of two Cu samples with nominal Cu thicknesses of 45 and 200 nm, respectively. In addi...

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Ideal Shear Strengths of fcc Aluminum and Copper

Cited by 453 publications

References 17 publications

Shear-Induced Brittle Failure along Grain Boundaries in Boron Carbide

Shear-Induced Brittle Failure along Grain Boundaries in Boron Carbide

Structure and Failure Mechanism of the Thermoelectric CoSb₃/TiCoSb Interface

Ultrahigh Strength Single Crystalline Nanowhiskers Grown by Physical Vapor Deposition

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Ideal Shear Strengths of fcc Aluminum and Copper

Cited by 453 publications

References 17 publications

Shear-Induced Brittle Failure along Grain Boundaries in Boron Carbide

Shear-Induced Brittle Failure along Grain Boundaries in Boron Carbide

Structure and Failure Mechanism of the Thermoelectric CoSb3/TiCoSb Interface

Ultrahigh Strength Single Crystalline Nanowhiskers Grown by Physical Vapor Deposition

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Product

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Structure and Failure Mechanism of the Thermoelectric CoSb₃/TiCoSb Interface