The crystallography and deformation modes of hexagonal close-packed metals

Partridge, P. G.

doi:10.1179/imr.1967.12.1.169

Cited by 763 publications

(99 citation statements)

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“…As we have shown, the material stress-strain responses and associated texture evolution arise either from slip or from a combination of slip and twinning. Slip alone, both the amount and type of slip mode activated, is known to be highly sensitive to strain rate and temperature [32,45,48,79]. Thus, it is possible that the observed rate sensitivity in the macroscopic responses is a consequence of the rate sensitivities of the slip modes activated.…”

Section: Is Twinning Rate Sensitive?mentioning

confidence: 91%

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Strain rate and temperature effects on the selection of primary and secondary slip and twinning systems in HCP Zr

et al. 2015

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We investigate the temperature and rate dependence of slip, twinning, and secondary twinning in high-purity hexagonal close packed a-Zr over a wide range of temperatures and strain rates (from 76 K to 673 K and 0.001 s À1 to 4500 s À1 ). To reliably identify the dominant deformation mechanisms for each condition, we employ electron-backscattered diffraction (EBSD), dislocation theory, multi-scale polycrystal constitutive modeling, and a thermally activated dislocation density evolution based hardening law. We demonstrate with direct comparison with measurement that the constitutive model, with a single set of intrinsic material parameters, can predict the underlying texture evolution, primary and secondary slip and twin activity, and twin volume fraction associated with the different loading orientations and applied temperatures and strain rates. We find that the f1 0 1 2gh1 0 1 1i twin is the preferred tension twin, either as a primary or secondary twin depending on the sample orientation, over the broad temperature and strain rate range tested. In contrast, we show that the preferred contraction twin, whether f1 1 2 2gh1 1 2 3i or f1 0 1 1gh1 0 1 2i, is sensitive to temperature but insensitive to strain rate and whether it is a primary or secondary twin. Based on the concomitant changes in the dominant slip mode predicted by the model and revealed by the texture development, we rationalize that the temperature-induced transition in contraction twinning is due to the increased predominance of basal hai slip at high temperatures (>673 K). Last, our analysis implies that all twin modes studied are rate insensitive and so the strong influence of strain rate and temperature on twinning is due to the rate-sensitivity of slip.

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Section: Is Twinning Rate Sensitive?mentioning

confidence: 91%

“…Of the seven observed twin types in HCP metals [1,2,79], three are tensile (or extension) twins in Zr. Tensile twins are thus named because they accommodate a tensile strain along the c-axis.…”

Section: Influence Of Strain Rate and Temperature On Tensile Twin Selmentioning

confidence: 98%

Strain rate and temperature effects on the selection of primary and secondary slip and twinning systems in HCP Zr

et al. 2015

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“…Below this transition temperature slip is restricted to prismatic slip. Partridge [17] has found that in pure titanium this temperature is about 150°C. However, as the aluminium content increases, the transition temperature for dislocation arrangement increases, too [18].…”

Section: Fatigue Cracks and Dislocation Arrangementmentioning

confidence: 97%

Fatigue of the Near-Alpha Ti-Alloy Ti6242

2009

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Ti6242 is the workhorse of high-temperature Ti-alloys in the high pressure compressor of aero engines. In this study the influence on isothermal fatigue of different load controls, i.e. stress, total strain and plastic strain control at different temperatures and environments was investigated. The alloy had a bimodal microstructure (some 30 vol.% primary alpha), which yields a good balance between fatigue and creep properties. In addition thermomechanical fatigue (TMF) tests were also performed. Modelling lifetime on the basis of a Basquin-Coffin-Manson relationship revealed only marginal scattering in the temperature range between 350°C and 650°C. Increasing the temperature led to a decrease in lifetime. This can be attributed to increased oxidation and creep. The latter one is clearly seen in isothermal tests under stress control. Tests in vacuum resulted in longer lifetimes. In-phase TMF tests exhibited a longer lifetime than out-of-phase tests, with a factor of about 4. Lifetime and stress response of inphase tests are similar to the corresponding lifetime of an isothermal test at the maximum temperature. This similarity can be considered as a starting point for modelling TMF behaviour on the basis of isothermal fatigue.

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“…High plastic anisotropy observed in hexagonal close-packed (h.c.p) metals arises from the activation of both twinning and slip systems [1][2][3][4][5][6]. In zirconium, twinning implies a reorientation of the lattice leading to a mirror image with respect to the twinning plane.…”

Section: Introductionmentioning

confidence: 99%