Review of Size Effects during Micropillar Compression Test: Experiments and Atomistic Simulations

Shahbeyk, Sharif; Voyiadjis, George Z.; Habibi, Vahid; Astaneh, Sarah Hashemi; Yaghoobi, Mohammadreza

doi:10.3390/cryst9110591

Cited by 15 publications

(6 citation statements)

References 67 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The exceptionally higher nano-indentation stresses and especially the significantly higher strain hardening coefficients obtained both for the current (111) and (100) α-iron crystal surfaces-as well as for the earlier-described AP strength properties described for {210} crystal surfaces-relative to microand macro-indentation properties or test measurements on conventional bulk materials, relate generally to the particular higher stress environments involved with the much smaller dislocation line lengths that are operative at nano-scale dimensions [26,27]. A main contribution to the higher strength values has been more often associated therefore with the Taylor theory of flow stress dependence on the dislocation density.…”

Section: Discussionmentioning

confidence: 60%

Dislocation Reaction Mechanism for Enhanced Strain Hardening in Crystal Nano-Indentations

Armstrong

Elban

2019

Crystals

View full text Add to dashboard Cite

Stress–strain calculations are presented for nano-indentations made in: (1) an ammonium perchlorate (AP), NH4ClO4, {210} crystal surface; (2) an α-iron (111) crystal surface; (3) a simulated test on an α-iron (100) crystal surface. In each case, the calculation of an exceptionally-enhanced plastic strain hardening, beyond that coming from the significant effect of small dislocation separations in the indentation deformation zone, is attributed to the formation of dislocation reaction obstacles hindering further dislocation movement. For the AP crystal, the exceptionally-high dislocation reaction-based strain hardening, relative to the elastic shear modulus, leads to (001) cleavage cracking in nano-, micro- and macro-indentations. For α-iron, the reaction of (a/2) <111> dislocations to form a [010] Burgers vector dislocation obstacles at designated {110} slip system intersections accounts for a higher strain hardening in both experimental and simulated nano-indentation test results. The α-iron stress–strain calculations are compared, both for the elastic deformation and plastic strain hardening of nano-indented (100) versus (111) crystal surfaces and include important observations derived from internally-tracked (a/2) <010> Burgers vector dislocation structures obtained in simulation studies. Additional comparisons are made between the α-iron calculations and other related strength properties reported either for bulk, micro-pillar, or additional simulated nano-crystal or heavily-drawn polycrystalline wire materials.

show abstract

Section: Discussionmentioning

confidence: 60%

Dislocation Reaction Mechanism for Enhanced Strain Hardening in Crystal Nano-Indentations

Armstrong

Elban

2019

Crystals

View full text Add to dashboard Cite

show abstract

“…For BCC crystals with the ©100ª orientation, log(¸c/G) vs. log(D/b) plots are more variable than those of FCC crystals. The distribution of the data points of the critical shear stress for all the BCC crystals collected by Shahbeyk et al 23) expands over a wide band region with a negative slope. The width of the distribution is not much different from that of FCC metals, but what is different is that the distribution of the data points of BCC metals is more or less uniform in the band, in contrast to the rapidly decreasing point density away from the theoretical curve in FCC metals.…”

Section: Bcc Micropillar Crystals With ©100ª Orientationmentioning

confidence: 95%

“…According to the comprehensive review by Greer and De Hosson, 22) the slope of the line best fitted to log(¸c/G) vs. log(D/b) plots for a number of FCC metals data is about ¹0.65. The fitting for the more collected data for FCC crystals in the latest review by Shahbeyk et al 23) indicated m µ ¹0.64. Thus, it is safe to say that the exponent for FCC metal crystals is in-between ¹0.6 and ¹0.7.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Evidence for the Single-Ended-Source Controlled Yield Strengths of Micropillar FCC and BCC Metal Single Crystals

2022

View full text Add to dashboard Cite

It has been established experimentally from the beginning of 21st century that the yield strengths at room temperature of submicron sized face-centered-cubic and body-centered-cubic metallic single crystals fabricated with the focused ion beam milling process increase dramatically with decreasing specimen diameter. In this paper, the mechanisms of the strengthening have been discussed theoretically on the basis of the single-ended source activation controlled deformation in submicron sized crystals. The experimental results of the power-law dependent yield strength with the decrease of specimen size have been reproduced quantitatively for both types of metallic crystals, where in some bodycentered-cubic metals we take into account the effect of the Peierls potential for the screw dislocation motion on the source activation stress.

show abstract

“…The same dependence has been found for integrated circuit-connected measurements on gold micro-wires [21] as well as for thin copper wires [22] and other nickel nano-pillar [23] materials, also with consideration taken into account of the nano-polycrystal grain structures. The status of nano-polycrystal micro-pillar strength properties have been reviewed by Shahbeyk et al [24]. Kiener et al [25] have provided an analysis of the strength properties on the basis of the small volumes of the materials that were tested.…”

Section: Crystal (Grain) Size-dependent Strengthsmentioning

confidence: 99%

Crystal Strengths at Micro- and Nano-Scale Dimensions

Armstrong

Elban

2020

Crystals

View full text Add to dashboard Cite

Higher strength levels, achieved for dimensionally-smaller micro- and nano-scale materials or material components, such as MEMS devices, are an important enabler of a broad range of present-day engineering devices and structures. Beyond such applications, there is an important effort to understand the dislocation mechanics basis for obtaining such improved strength properties. Four particular examples related to these issues are described in the present report: (1) a compilation of nano-indentation hardness measurements made on silicon crystals spanning nano- to micro-scale testing; (2) stress–strain measurements made on iron and steel materials at micro- to nano-crystal (grain size) dimensions; (3) assessment of small dislocation pile-ups relating to Griffith-type fracture stress vs. crack-size calculations for cleavage fracturing of α-iron; and (4) description of thermally-dependent strain rate sensitivities for grain size strengthening and weakening for macro- to micro- to nano-polycrystalline copper and nickel materials.

show abstract

Review of Size Effects during Micropillar Compression Test: Experiments and Atomistic Simulations

Cited by 15 publications

References 67 publications

Dislocation Reaction Mechanism for Enhanced Strain Hardening in Crystal Nano-Indentations

Dislocation Reaction Mechanism for Enhanced Strain Hardening in Crystal Nano-Indentations

Theoretical Evidence for the Single-Ended-Source Controlled Yield Strengths of Micropillar FCC and BCC Metal Single Crystals

Crystal Strengths at Micro- and Nano-Scale Dimensions

Contact Info

Product

Resources

About