Role of plastic deformation in tailoring ultrafine microstructure in nanotwinned diamond for enhanced hardness

Hu, Wentao; Wen, Bin; Huang, Quan; Xiao, Jianwei; Wang, Yanbin; Zhao, Zhisheng; He, Julong; Liu, Zhongyuan; Xu, Bin; Tian, Yongjun

doi:10.1007/s40843-016-5161-2

Cited by 24 publications

(17 citation statements)

References 50 publications

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“…Previous works suggested that {111} deformation twins can be produced by shearing the diamond structure in the

(\bar{1} 10)

plane along the

[11 \bar{2}]

direction. [ 40–42 ] In the process of HPHT sintering, β‐SiC with a diamond‐like structure may bear a certain degree of shear stress (as mentioned earlier for the elliptical cross section of the bulk), leading to the formation of deformation twins and stacking faults.…”

Section: Resultsmentioning

confidence: 99%

Nanocrystalline Cubic Silicon Carbide: A Route to Superhardness

Sun

Wei

et al. 2022

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Superhard materials other than diamond and cubic boron nitride have been actively pursued in the past two decades. Cubic silicon carbide, i.e., β‐SiC, is a well‐known hard material with typical hardness <30 GPa. Although nanostructuring has been proven to be effective in enhancing materials’ hardness by virtue of the Hall–Petch effect, it remains a significant challenge to improve hardness of β‐SiC beyond the superhard threshold of 40 GPa. Here, the fabrication of nanocrystalline β‐SiC bulks is reported by sintering nanoparticles under high pressure and high temperature. These β‐SiC bulks are densely sintered with average grain sizes down to 10 nm depending on the sintering conditions, and the Vickers hardness increases with decreasing grain size following the Hall–Petch relation. Particularly, the bulk sintered under 25 GPa and 1400 °C shows an average grain size of 10 nm and an asymptotic Vickers hardness of 41.5 GPa. Boosting the hardness of β‐SiC over the superhard threshold signifies an important progress in superhard materials research. A broader family of superhard materials is in sight through successful implementation of nanostructuring in other hard materials such as BP.

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“…Previous works suggested that {111} deformation twins can be produced by shearing the diamond structure in the

(\bar{1} 10)

plane along the

[11 \bar{2}]

Section: Resultsmentioning

confidence: 99%

Nanocrystalline Cubic Silicon Carbide: A Route to Superhardness

Sun

Wei

et al. 2022

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“…The difficulty in assessing the hardness, especially with a variable temperature, partially lies in the fact that hardness is an engineering quantity determined using a specific measurement method and cannot be evaluated directly using quantum mechanics [16]. During the hardness measurement, plastic deformation must occur in the sample (e.g., a permanent impression or dent), which is correlated with the dislocation behaviors in the sample [1,17,18]. While this dislocation-governed plastic deformation has been widely investigated for metals [19][20][21][22], understanding the plastic deformation and therefore the hardness of covalent materials is still an active research area [23].…”

Section: Introductionmentioning

confidence: 99%

Temperature-dependent hardness of zinc-blende structured covalent materials

et al. 2021

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Understanding the temperature-dependent hardness of covalent materials is of fundamental scientific interest and crucial technical importance. Here we propose a temperature-dependent hardness formula for zinc-blende structured covalent materials based on the dislocation theory. Our results indicate that at low temperatures, the Vickers hardness is primarily modulated by Poisson's ratio and the shear modulus, with the latter playing a dominant role. With an increase in temperature, the governing mechanism for the plastic deformation switches from shuffle-set dislocation control to glide-set dislocation control, and the hardness decreases precipitously at elevated temperatures. Moreover, the intrinsic parameter a 3 G is revealed for zinc-blende structured covalent materials, which represents the resistance of a material to softening at high temperatures. This temperaturedependent hardness model agrees remarkably well with the experimental data of zinc-blende structured covalent materials. This work not only sheds light on the physical origin of hardness, but also provides a practical guide for the design of superhard materials.

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“…The {111} planes are the most common twin planes in diamond, with the highest lattice site density and the shortest lattice translations ( ). There are four equivalent {111} twin planes, whose relations are described by the Thompson tetrahedron and deformation twinning is facilitated by dislocations with Burgers vector of types gliding on {111}. , To estimate the stress in NPD samples beyond lattice saturation, we examine the initiation of dislocations when an effective differential stress Δ σ g is applied to a grain, parallel to the normal of the (111) planes, to facilitate {111} deformation twinning . Compressing along the normal of one given {111} plane, e.g.…”

Section: Resultsmentioning

confidence: 99%

Plastic Deformation and Strengthening Mechanisms of Nanopolycrystalline Diamond

et al. 2021

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Bulk nanopolycrystalline diamond (NPD) samples were deformed plastically within the diamond stability field up to 14 GPa and above 1473 K. Macroscopic differential stress Δσ was determined on the basis of the distortion of the 111 Debye ring using synchrotron X-ray diffraction. Up to ∼5(2)% strain, Debye ring distortion can be satisfactorily described by lattice strain theories as an ellipse. Beyond ∼5(2)% strain, lattice spacing d 111 along the Δσ direction becomes saturated and remains constant with further deformation. Transmission electron microscopy on as-synthesized NPD shows well-bonded grain boundaries with no free dislocations within the grains. Deformed samples also contain very few free dislocations, while density of {111} twins increases with plastic strain. Individual grains display complex contrast, exhibiting increasing misorientation with deformation according electron diffraction. Thus, NPD does not deform by dislocation slip, which is the dominated mechanism in conventional polycrystalline diamond composites (PCDCs, grain size >1 μm). The nonelliptical Debye ring distortion is modeled by nucleating dislocations or their dissociated partials gliding in the {111} planes to produce deformation twinning. With increasing strain up to ∼5(2)%, strength increases rapidly to ∼20(1) GPa, where d 111 reaches saturation. Strength beyond the saturation shows a weak dependence on strain, reaching ∼22(1) GPa at >10% strain. Overall, the strength is ∼2–3 times that of conventional PCDCs. Combined with molecular dynamics simulations and lattice rotation theory, we conclude that the rapid rise of strength with strain is due to defect-source strengthening, whereas further deformation is dominated by nanotwinning and lattice rotation.

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Role of plastic deformation in tailoring ultrafine microstructure in nanotwinned diamond for enhanced hardness

Cited by 24 publications

References 50 publications

Nanocrystalline Cubic Silicon Carbide: A Route to Superhardness

Nanocrystalline Cubic Silicon Carbide: A Route to Superhardness

Temperature-dependent hardness of zinc-blende structured covalent materials

Plastic Deformation and Strengthening Mechanisms of Nanopolycrystalline Diamond

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