Extraction of plasticity parameters of GaN with high temperature, in situ micro-compression

Wheeler, Jeffrey M.; Niederberger, Christoph; Tessarek, Christian; Christiansen, Silke; Michler, Johann

doi:10.1016/j.ijplas.2012.08.001

Cited by 76 publications

(45 citation statements)

References 64 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…14); GaN, ∼8 GPa (ref. 31); CrAlN/Si 3 N 4 , ∼16 GPa (ref. 32) and Zn-based metallic glasses15, ∼2 GPa—and are in the same strength level of the defect-free Mo-alloy columns produced from etching NiAl–Mo eutectic compounds33 and about half of that of pure W whiskers34, still our HEA pillars exhibit much better ductility.…”

Section: Resultsmentioning

confidence: 99%

Ultrastrong ductile and stable high-entropy alloys at small scales

2015

View full text Add to dashboard Cite

Refractory high-entropy alloys (HEAs) are a class of emerging multi-component alloys, showing superior mechanical properties at elevated temperatures and being technologically interesting. However, they are generally brittle at room temperature, fail by cracking at low compressive strains and suffer from limited formability. Here we report a strategy for the fabrication of refractory HEA thin films and small-sized pillars that consist of strongly textured, columnar and nanometre-sized grains. Such HEA pillars exhibit extraordinarily high yield strengths of ∼10 GPa—among the highest reported strengths in micro-/nano-pillar compression and one order of magnitude higher than that of its bulk form—and their ductility is considerably improved (compressive plastic strains over 30%). Additionally, we demonstrate that such HEA films show substantially enhanced stability for high-temperature, long-duration conditions (at 1,100 °C for 3 days). Small-scale HEAs combining these properties represent a new class of materials in small-dimension devices potentially for high-stress and high-temperature applications.

show abstract

Section: Resultsmentioning

confidence: 99%

Ultrastrong ductile and stable high-entropy alloys at small scales

2015

View full text Add to dashboard Cite

show abstract

“…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2 , [87] Mo 2 BC, [85] WC, [21] Fe 3 Al, [88] Co 3 (Al,W), [89] CMSX-4, [36] Si, [31] GaAs, [2] InSb, [90] Al 2 O 3 (unpublished), MgO, [25] (Fe,Ni) 2 Nb, [30] (Mg, Al) 2 Ca (courtesy of C. Zehnder), Nb 2 Co, [34] AlN, [91] GaN, [92] doped ZrO 2, [93] LiF, [94] Al 7 Cu 2 Fe, [95] FeZn 13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

2017

MRS Communications

View full text Add to dashboard Cite

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...

show abstract

“…The plastic behavior of GaN films has been studied primarily through indentation tests [15][16][17], However, indentation tests are difficult to interpret because they produce a complex stress field below the indenter and induce slip on multiple slip sys tems [18]. Recently, Wheeler et al [19] performed compression tests on [0001] -oriented GaN micropil lars in situ in a scanning electron microscope at temperatures up to 479.3 °C. Those tests were oriented for single slip on the [1120] (1100) prismatic slip system.…”

Section: Introductionmentioning

confidence: 99%

“…That model relates the plastic deformation in the crystal to the movement and multiplication of dislocations and assumes a power law relating the resolved shear stress and the dislocation velocity. Wheeler et al [19] use a hyperbolic sine model to relate the shear flow stress and dislocation velocity for pyramidal slip in GaN, which is based on the model for steady-state creep first proposed by Garofalo [23]. Wheeler et al [19] use a hyperbolic sine model to relate the shear flow stress and dislocation velocity for pyramidal slip in GaN, which is based on the model for steady-state creep first proposed by Garofalo [23].…”

Section: Introductionmentioning

confidence: 99%

Constitutive Relations for Modeling Single Crystal GaN at Elevated Temperatures

Maniatty

Karvani

2014

Journal of Engineering Materials and Technology

View full text Add to dashboard Cite

P ro fe sso r F e llo w A S M E D epartm ent o f M e c h a n ic a l, A erospace, and N ucle a r E n g in e erin g, R ensselaer P o ly te c h n ic In stitute, T ro y, N Y 1 2 1 8 0 -3 5 9 0 e -m a il: m a nia a @ rp i.e d u P aym an KarvaniM e m . A S M E D epartm ent o f M e c h a n ic a l, A erospace, and N ucle a r E n g in e erin g, R ensselaer P o ly te c h n ic In stitute, T ro y, N Y 1 2 1 8 0 -3 5 9 0 e -m a il: p ay m a a n @ g m a il.c o m Constitutive Relations for Modeling Single Crystal GaN at Elevated TemperaturesThermal-mechanical constitutive relations for bulk, single-crystal, wurtzite gallium nitride (GaN) at elevated temperatures, suitable for modeling crystal growth processes, are pre sented. A crystal plasticity model that considers slip and the evolution o f mobile and immo bile dislocation densities on the prismatic and basal slip systems is developed. The experimental stress-strain data from Yonenaga and Motoki (2001, "Yield Strength and Dislocation Mobility in Plastically Deformed Bulk Single-Crystal GaN," J. Appl. Phys., 90(12), pp. 6539-6541) for GaN is analyzed in detail and used to define model parameters for prismatic slip. The sensitivity to the model parameters is discussed and ranges for pa rameters are given. Estimates for basal slip are also provided.

show abstract

Extraction of plasticity parameters of GaN with high temperature, in situ micro-compression

Cited by 76 publications

References 64 publications

Ultrastrong ductile and stable high-entropy alloys at small scales

Ultrastrong ductile and stable high-entropy alloys at small scales

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

Constitutive Relations for Modeling Single Crystal GaN at Elevated Temperatures

Contact Info

Product

Resources

About