Impression creep of LiF single crystals

Yu, Edward; Li, J. C. M.

doi:10.1080/14786437708239760

Cited by 91 publications

(31 citation statements)

References 11 publications

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“…Surprisingly, there is no equivalent transition in the data for LiF despite the very large number of individual datum points extending over a range of nine orders of magnitude in the normalized strain rate. In fact, the experimental results for LiF are in remarkably good agreement although results are plotted from six independent investigations [67][68][69][70][71][72]. Furthermore, the results for LiF extend to an exceptionally low normalized strain rate of _ ekT=DGb% 3 · 10 -15 .…”

Section: Experimental Evidence On Metals In the Regime Anticipated Fosupporting

confidence: 58%

“…2 Normalized creep rate versus normalized stress for polycrystalline [55] and single crystal [66] CaO Fig. 3 Normalized creep rate versus normalized stress for polycrystalline [67] and single crystal [68][69][70][71][72] LiF estimating an appropriate value for D based on the measured activation energy in creep testing. The plot in Fig.…”

Section: Experimental Evidence On Metals In the Regime Anticipated Fomentioning

confidence: 99%

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Fifty years of Harper–Dorn creep: a viable creep mechanism or a Californian artifact?

2007

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Fifty years ago, in a series of classic creep experiments conducted at the University of California in Berkeley, Harper and Dorn obtained unique experimental data revealing the possibility of a new and heretofore unrecognized flow process occurring in pure aluminum when tested at low stresses and at temperatures very close to the melting temperature. This flow mechanism, subsequently designated Harper-Dorn creep, has been the center of much argument and speculation in the ensuing years. The present paper looks back over the last half-century and charts the various developments in attempts to obtain a more detailed understanding of whether Harper-Dorn creep is (or is not) a viable creep process. Examples are presented for both metals and non-metals. It is concluded that, although it appears Harper-Dorn creep may occur only under restricted conditions associated with high purity materials and low initial dislocation densities, nevertheless there is good evidence supporting the validity of this creep mechanism as a viable and unique flow process.

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Section: Experimental Evidence On Metals In the Regime Anticipated Fosupporting

confidence: 58%

Section: Experimental Evidence On Metals In the Regime Anticipated Fomentioning

confidence: 99%

Fifty years of Harper–Dorn creep: a viable creep mechanism or a Californian artifact?

2007

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“…Indentation with sharp punches has been widely used for material characterisation, but also applications of flat-ended cylindrical indenters can be found in literature [10][11][12][13][14]. They concern investigations on mechanical properties of materials and measurements of the elastic modulus of thermal barrier coatings [15].…”

Section: Introductionmentioning

confidence: 99%

Indentation of metals by a flat-ended cylindrical punch

Riccardi

Montanari

2004

Materials Science and Engineering: A

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The paper reviews the fundamentals of indentation theory for punches with cylindrical geometry, presents a deep-indentation finite element (FE) simulation and discusses an experimental technique for flat-ended cylindrical indentation. This technique is based on the use of cylindrical punches with diameters up to 1 mm and allows pressure-penetration curves to be drawn from which yield stress and elasticity modulus can be determined. Several materials have been tested including pure metals, steels and refractory alloys; yield stress has been determined and compared with literature values. By testing at different temperatures it was also possible to determine the ductile-to-brittle transition temperature (DBTT) for some alloys that show such phenomenon.

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“…The punch stress σ p varies linearly with the equivalent uniaxial stress σ as σ p ϭ κσ, where κ is a material-dependent constant with a magnitude of ϳ3-4.5. [24][25][26][27][28][29] Thus, the constant A′ in Eq. 1 is given by A′ ϭ A/(κ) n , A being the conventionally used Dorn constant.…”

Section: Methodsmentioning

confidence: 99%

“…It has also been shown that the function f(φ), which represents the nominal depth of the plastic zone size under the indenter, is proportional to φ during steady-state creep, 19 being expressible as f(φ) ϷCφ, which is a constant ϳ1-1.6. [24][25][26][27][28][29] The temperature-compensated impression creep velocity can therefore be written as (2) Equation 2 provides a basis for obtaining the activation energy Q from a plot of ln(VT/G) versus 1/T at constant σ p /G, and the stress exponent n from a plot of ln(VT/G) versus σ p /G at constant T.…”

Section: Methodsmentioning

confidence: 99%

Impression creep characterization of 90Pb-10Sn microelectronic solder balls at subsolvus and supersolvus temperatures

Pan

Dutta

Jadhav

et al. 2005

Journal of Elec Materi

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The creep behavior of Pb-10wt.%Sn, a common high-lead solder used in microelectronic packaging, was studied by impression creep testing of ball-gridarray (BGA) solder balls attached to an organic substrate, both above and below the solvus temperature (408 K). Below the solvus temperature, the solder microstructure consists of roughly equiaxed grains of the Pb-rich solid solution α, which contains Ͻ5wt.%Sn in solution, with a coarse dispersion of Sn-rich β precipitates. Here, the creep behavior of the solder is controlled by dislocation climb via dislocation core diffusion, yielding n Ϸ4 and Q Ϸ60 kJ/mole. Above the solvus temperature, where the entire 10wt.%Sn is in solution, the creep mechanism becomes controlled by viscous glide of dislocations, limited by solute drag, with n Ϸ3 and Q Ϸ92 kJ/mole. Based on experimental data, creep equations for the as-reflowed solder in the two temperature regimes are given. Comparison of the present data with those available in the literature showed good agreement with the proposed laws.

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Impression creep of LiF single crystals

Cited by 91 publications

References 11 publications

Fifty years of Harper–Dorn creep: a viable creep mechanism or a Californian artifact?

Fifty years of Harper–Dorn creep: a viable creep mechanism or a Californian artifact?

Indentation of metals by a flat-ended cylindrical punch

Impression creep characterization of 90Pb-10Sn microelectronic solder balls at subsolvus and supersolvus temperatures

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