Sliding at twin boundaries during high-temperature creep

Wirmark, G.; Nilsson, Jan-Olof; Dunlop, G. L.

doi:10.1080/01418618108239395

Cited by 14 publications

(4 citation statements)

References 13 publications

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“…Interfacial sliding can occur on growth defect (or annealing) twins (Wirmark et al 1981), which is consistent with present observations. The periodic arrangement of dislocations in the boundary observed in Figure 13d may be due to boundary movement (Pond et al 1978), to ledges caused by a deviation from an exact lattice coincidence or twin relationship across the boundary (Brandon 1966), or to boundary migration (Gleiter et al 1980;Ray & Smith 1980).…”

Section: Mechanical Behavioursupporting

confidence: 90%

Experimental deformation of flint in axial compression

Mainprice

Paterson²

2005

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The experimental deformation of flint, a water-rich (1-2 wt%) fine-grained (1 Ixm) microcrystalline quartz, has been studied using a gas-confining medium apparatus at 300 MPa confining pressure in the temperature range 500-1000 ~ In constant strainrate axial compression tests a mechanically unstable behaviour with peaked and undulating stress-strain curves, especially at the faster strain rates, is manifest. The rheology of these tests can be approximately described by the traditional power-law equation with a stress exponent (n) of between 3 and 5, and an apparent activation energy (Q) of 108 kJ mo1-1. However, the strain-independent ('steady-state') equation is only a partial description of the data. The mechanical properties were studied at lower stresses using stress relaxation testing, this method has the advantage of recording specimen response over a very small strain interval (c. 1%), i.e. nearly constant structure. These tests revealed that in a high stress regime above 100 MPa the rheology was only weakly dependent on strain and very similar to the constant strain-rate behaviour. Below 100 MPa the rheology can be described by a power law with Q = 64 kJ mol-l and n = 1. The low-stress behaviour is extremely sensitive to specimen strain, the strain rate decreasing with increasing strain for a given stress.The optical microstructure reveals that the mechanical instabilities are related to localized displacement zones, sometimes en echelon, consisting of relatively large grains (10 ~m). The important reduction of the integral infrared absorption of deformed specimens, a 98% reduction of the initial water content, suggests that a pore fluid was developed by specimen dehydration in the sealed (undrained) assembly. The presence of pores or bubbles decorating grain boundaries and microfractures normal to the piston-specimen interface both testify to the presence of the pore fluid during deformation. The pore fluid pressure may have approached the confining pressure resulting in a near-zero effective pressure. Transmission electron microscopy revealed the presence of many Brazil micro-twins parallel to grain boundaries. The twins are thought to be growth defects indicating rapid grain growth during deformation. Dislocations in the basal plane were observed with a 1/3 (a)-type Burgers vector. Dislocations were also observed in the grain boundaries, possibly caused by grain-boundary sliding in the low stress regime.The complete lattice preferred orientation (LPO) of homogeneously deformed specimens has been determined by X-ray texture goniometry. The inverse pole figures have a strong concentration of compression axes parallel, and a weaker concentration normal, to the c-axis. The local c-axis pole figures in heterogeneously deformed specimens were characterized by the photometric technique. The c-axis pole figures in the bulk are identical to that determined by X-rays in homogeneously deformed specimens. In the displacement zones the fabrics are asymmetric with respect to the zone boundaries. The asymmetry is not...

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Section: Mechanical Behavioursupporting

confidence: 90%

Experimental deformation of flint in axial compression

Mainprice

Paterson²

2005

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“…Combined with MD simulations, TBS induced by full dislocations (extended dislocations) sliding on TB has been first revealed at atomic scale, contributed largely to the total strain in the early stage of deformation. Furthermore, direct evidence shows dislocations emitted from the twin boundary‐free surface junctions and from free surface further assist the plastic deformation and finally achieved a superplasticity of ≈166% in single crystalline copper nanowire comparing with the reported maximum strains less than 49% . Besides, a severe necking which is over 93% has also occurred.…”

mentioning

confidence: 72%

“…In most twin‐structured polycrystalline materials, the effect induced by TBS may be annihilated at grain boundaries. Furthermore, TBS, which has been only detected during high‐temperature creep may contribute a tiny friction to the total strain . Comparing with the elasticity which is critical to the strength of materials, less attention has been paid to the plasticity of nanoscale twin‐structured single crystalline materials.…”

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confidence: 99%

In Situ Observation of Twin Boundary Sliding in Single Crystalline Cu Nanowires

Yue

Zhang

et al. 2017

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Using a homemade, novel, in situ transmission electron microscopy (TEM) double tilt tensile device, plastic behavior of single crystalline Cu nanowires of around 150 nm are studied. Deformation twins occur during the tests as predesigned before the experiments. In situ observation of twin boundary sliding (TBS) caused by full dislocation (extended dislocation) is first revealed at the atomic scale which is confirmed by molecular dynamics (MD) simulation results. Combined with twin boundary migration and multiple dislocations nucleated from surface, TBS causes a superlarge fracture strain which is over 166% and a severe necking which is over 93%, far beyond the typical values for most nanomaterials without twins.

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“…18 Our data are consistent with these observations on Sn-Ag-Cu, as well as with observations on other metals that grain boundary sliding is inhibited by the presence of boundaries with coincident site lattice orientations. 19 On the other hand, intermetallic compounds (IMC), if they play a significant role in the pinning of dislocations in Sn-Ag-Cu, could be the basis of a dislocation model to also explain our creep deformation data, either for the case of Ag that is uniformly distributed in small precipitates within the solder joint, or for the case where it is preferentially located at grain boundaries. In both cases, in the absence of significant grain boundary sliding, the dependence of creep resistance, 60 deg twins, and grain size on Ag reported here would be largely coincidental.…”

Section: Dynamic Chip Warpage Measurementsmentioning

confidence: 99%

Large-Scale Correlations in the Orientation of Grains in Lead-Free Solder Joints

Sylvestre¹,

Blander²

2008

Journal of Elec Materi

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A large number of lead-free Sn-Ag-Cu controlled collapse chip connection (C4) solder joints ($100 lm in diameter) in flip-chip microelectronic packages were studied by electron backscatter diffraction (EBSD) in order to describe the statistical distribution of grain size and coincident site lattice boundaries associated with 60 deg twins in the Sn phase, as a function of silver content. It is shown that lower silver content results in smaller grains, and a lower propensity for grains to exhibit twinning symmetries. Indirect measurements of the creep properties of these joints were also obtained as a function of silver content, showing that, in the strain rate and temperature conditions that are the most relevant to the microelectronic industry, solder joints with low silver content are more susceptible to creep deformation.

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Sliding at twin boundaries during high-temperature creep

Cited by 14 publications

References 13 publications

Experimental deformation of flint in axial compression

Experimental deformation of flint in axial compression

In Situ Observation of Twin Boundary Sliding in Single Crystalline Cu Nanowires

Large-Scale Correlations in the Orientation of Grains in Lead-Free Solder Joints

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