Sample size induced brittle-to-ductile transition of single-crystal aluminum nitride

Guo, Junjie; Reddy, Kolan Madhav; Hirata, Akihiko; Fujita, Takeshi; Gazonas, George A.; McCauley, James W.; Chen, Luyang

doi:10.1016/j.actamat.2015.01.043

“…Selection of hard crystals tested by microcompression. ZrB 2 , [87] Mo 2 BC, [85] WC, [21] Fe 3 Al, [88] Co 3 (Al,W), [89] CMSX-4, [36] Si, [31] GaAs, [2] InSb, [90] Al 2 O 3 (unpublished), MgO, [25] (Fe,Ni) 2 Nb, [30] (Mg, Al) 2 Ca (courtesy of C. Zehnder), Nb 2 Co, [34] AlN, [91] GaN, [92] doped ZrO 2, [93] LiF, [94] Al 7 Cu 2 Fe, [95] FeZn 13 , [96] Cu 6 Sn 5 , [24] either conventional or high resolution, is easily performed after compression by the site-specific FIB milling and where necessary further thinning of a transparent membrane from the micropillar (see Figs. 3, 4, 6, and 10, for examples).…”

Section: Prospective Articlementioning

confidence: 99%

Microcompression of brittle and anisotropic crystals: recent advances and current challenges in studying plasticity in hard materials

Korte‐Kerzel

¹

2017

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Recent years have seen an increased application of small-scale uniaxial testing-microcompression-to the study of plasticity in macroscopically brittle materials. By suppressing fast fracture, new insights into deformation mechanisms of more complex crystals have become available, which had previously been out of reach of experiments. Structurally complex intermetallics, metallic compounds, or oxides are commonly brittle, but in some cases extraordinary, though currently mostly unpredictable, mechanical properties are found. This paper aims to give a survey of current advances, outstanding challenges, and practical considerations in testing such hard, brittle, and anisotropic crystals.While the origin of mechanical strength, toughness, and creep resistance is well studied in most metals, much less is known about the properties of more complex crystal structuresdespite their wide use as reinforcement phases and the undiscovered potential in their sheer number and variability. A major challenge in plasticity research of the next years will therefore be to close this gap in knowledge. Small-scale testing techniques have been demonstrated as a key enabling technique for such studies. Most prominent is microcompression, which helps overcome the fundamental challenge of studying plasticity in materials, which suffer from extreme brittleness in conventional testing. [1,2] Their plastic properties may, at first glance, appear to be of only academic interest: aiming to deduce fundamental relationships of crystal plasticity and structure to enable knowledge-guided search and data mining for new structural materials. However, they are in fact essential to performance at the microstructural scale of many advanced and highly alloyed materials and to understanding the effects of alloying strategies aimed at inducing deformability as baseline or reference information. Investigating plasticity in hard crystalsA deep understanding of plasticity and dislocation motion exists in most metallic crystals and strategies to engineer different aspects, for example by adjustment of the stacking fault energy, have been very successful. [3,4] These are being applied-with great effect-to hexagonal metals [3] which in spite of their closely related atomic packing show strongly anisotropic deformation and are therefore much more difficult to deform at low temperatures. In BCC metals, fundamental aspects of dislocation core structure, stress tensor dependence, and resulting non-Schmid behavior, are also still under investigation. [5,6] However, in all of these materials, the availability of large-grained or single crystals with sufficient purity has scarcely been a problem, nor has the ability to deform such samples under carefully controlled conditions. Suitable investigations by conventional, analytical and high-resolution microscopy techniques have also been carried out whenever new methods have allowed researchers to dive deeper into the physics of their plastic deformation.In intermetallics, ceramics, and compounds we face challeng...

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“…It was found by Heard et al [8] that an intrinsic failure pattern of the AlN known as brittle fracture would be changed to plastic deformation under a high hydrostatic pressure condition. Meanwhile, it was found in an experiment that the decrease of the size of AlN pillar may induce brittle-to-ductile transition, due to the activation of dislocations [9]. Besides, at high pressure, metal oxides with an amorphous structure could undergo severe plastic deformation at moderate temperatures [10,11,12].…”

Section: Introductionmentioning

confidence: 99%

Super Ductility of Nanoglass Aluminium Nitride

Zhao

¹

,

Peng

²

,

Huang

³

et al. 2019

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Ceramics have been widely used in many fields because of their distinctive properties, however, brittle fracture usually limits their application. To solve this problem, nanoglass ceramics were developed. In this article, we numerically investigated the mechanical properties of nanoglass aluminium nitride (ng-AlN) with different glassy grain sizes under tension using molecular dynamics simulations. It was found that ng-AlN exhibits super ductility and tends to deform uniformly without the formation of voids as the glassy grain size decreases to about 1 nm, which was attributed to a large number of uniformly distributed shear transformation zones (STZs). We further investigated the effects of temperature and strain rate on ng-AlNd = 1 nm, which showed that temperature insignificantly influences the elastic modulus, while the dependence of the ultimate strength on temperature follows the T2/3 scaling law. Meanwhile, the ultimate strength of ng-AlNd = 1 nm is positively correlated with the strain rate, following a power function relationship.

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“…4 a as a function of specimen size (the edge length L ). The CRSS values for all slip systems are extremely high exceeding 2.6 GPa regardless of specimen size and exhibit the so-called “smaller is stronger” trends, following an inverse power-law relationship, τ CRSS ∝ L − n ( n : the power-law exponent), as commonly observed in micropillar compression of single crystals of many metallic materials, ceramics, semiconductors and intermetallic compounds 22 – 25 , 30 – 33 , 35 , 36 , 38 , 39 , 42 , 43 . The power-law exponents for the three slip systems of {1 00}[0001], {2 2} < 2 > and {1 01} < 2 > are estimated to be 0.36, 0.30 and 0.11, respectively.…”

Section: Discussionmentioning

confidence: 64%

Room temperature deformation of single crystals of Ti5Si3 with the hexagonal D88 structure investigated by micropillar compression tests

Kishida

¹

,

Fukuyama

²

,

Maruyama

³

et al. 2020

Sci Rep

13

0

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Micropillar compression tests of Ti5Si3 single crystals were conducted at room temperature as a function of loading axis orientation and specimen size in order to investigate their room temperature plastic deformation behavior. Plastic flow by the operation of three deformation modes, {1$${\overline{1}}$$ 1 ¯ 00}[0001], {2$${\overline{1}}$$ 1 ¯ $${\overline{1}}$$ 1 ¯ 2} < 2$${\overline{1}}$$ 1 ¯ $${\overline{1}}$$ 1 ¯ $${\overline{3}}$$ 3 ¯ > and {1$${\overline{1}}$$ 1 ¯ 01} < 2$${\overline{1}}$$ 1 ¯ $${\overline{1}}$$ 1 ¯ $${\overline{3}}$$ 3 ¯ > slip were observed in [2$${\overline{2}}$$ 2 ¯ 05]-, [0001]- and [4$${\overline{3}}$$ 3 ¯ $${\overline{1}}$$ 1 ¯ 0]-oriented micropillar specimens deformed at room temperature, respectively. The CRSS values were evaluated to be very high above 2.7 GPa and were confirmed to increase up to about 6 GPa with the decrease in the specimen size. The fracture toughness values are evaluated to be 0.45 MPa m1/2 (notch plane // (0001)) and 0.73 MPa m1/2 (notch plane //(1$${\overline{1}}$$ 1 ¯ 00)) based on the results of micro-cantilever bend tests of chevron-notched specimens. The fracture toughness values are considerably lower than those for D8l-Mo5SiB2 and D8l-Nb5Si3 evaluated by the same method, indicating the inherent brittleness of binary Ti5Si3 compared to the other transition-metal silicides of the TM5Si3 type (TM: transition-metal).

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Sample size induced brittle-to-ductile transition of single-crystal aluminum nitride

Cited by 40 publications

References 46 publications

Microcompression of brittle and anisotropic crystals: recent advances and current challenges in studying plasticity in hard materials

Microcompression of brittle and anisotropic crystals: recent advances and current challenges in studying plasticity in hard materials

Super Ductility of Nanoglass Aluminium Nitride

Room temperature deformation of single crystals of Ti5Si3 with the hexagonal D88 structure investigated by micropillar compression tests

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