A variable temperature, tensile testing cryostat

Wielke, B.

doi:10.1016/0011-2275(76)90097-7

Cited by 5 publications

(1 citation statement)

References 3 publications

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“…The gas spray cryostat used was operated with liquid nitrogen for temperatures above 85 K. The temperature region 6 t o 90 K was covered by sparying helium. Further more experimental details are described in [41]. Moreover the relation between work hardening and shear strain rate was measured on Zn a t various temperatures.…”

Section: Methodsmentioning

confidence: 99%

Easy-glide hardening of Zn and Cd between 4.2 and 400 K

Wielke

1976

Phys. Stat. Sol. (a)

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The work hardening coefficient in the easy glide range is measured on Zn and Cd single crystals in the temperature range from 4.2 to 400 K. For low temperatures T/Tm ⪅ 0.15 work hardening was found to decrease rapidly with rising temperature, passes a minimum and at T/Tm = 0.3 there is a well developed maximum of work hardening. The location of this maximum depends on the shear strain rate. If the temperature becomes T/Tm ⪆ 0.3 the well known decrease of work hardening due to recovery processes can be observed. The measured temperature dependence of work hardening is contradictory to the established theories of work hardening of hexagonal metals, which affirm a constant ∂A in the low temperature range.

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Section: Methodsmentioning

confidence: 99%

Easy-glide hardening of Zn and Cd between 4.2 and 400 K

Wielke

1976

Phys. Stat. Sol. (a)

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Cottrell-stokes law in Cadmium and Zinc

Wielke

Tikvic

Schoeck

1977

Phys. Stat. Sol. (a)

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Tensile test experiments with change of temperature and strain rate are performed on Cd and Zn single crystals in a temperature range between 4.2 and 300 K. I n the range 30 < T < 200 K the Cottrell-Stokes law, A t / A In at and A t / A Tt, is found to be valid from the very beginning of plastic deformation u p to the maximum work hardening in stage B. The activation volume a t the critical resolved shear stress of Cd and Zn is of the order v = (2 to 4) x 104b3 and decreases to a value of (1.5 to 3) x 102b3 for Cd a t fracture. The free activation enthalpy AG increases proportionally to T a t constant strain rate up to a temperature of about 180 K. This indicates that the preexponential factor has a constant value which is of the order of a, = lO(5*1) s-l. The obstacle density, estimated from these values increases from lo7 at the critical shear stress up t o 10" cme2 at fracture. Contrary to the general opinion in the literature, it is rather unlikely that grown-in forest dislocations alone act as thermally activated obstacles, since their density is smaller by several orders of magnitude. An Einkristallen aus Cd und Zn werden im Temperaturbereich zwischen 4,2 und 300 K Dehnungsexperimcnte mit Temperatur-und Geschwindigkeitswechseln durchgefiihrt. I m Interval1 30 < T < 200 K gilt das Cottrell-Stokes'sche Gesetz At/A In ut und AT/ATt sofort vom Beginn der Verformung bis weit in den Bereich B der Verfestigungskurve. Das Aktivierungsvolumen betriigt fur Cd und Zn an der kritischen Schubspannung w = (2 bis 4) x 104b3 und fallt auf (1,5 bis 3) x 102b3 fur Cd beim Bruch. Die freie Aktivierungsenthalpie steigt bei konstanter Abgleitgeschwindigkeit proportional zur Temperatur bis etwa T = 180 K. Das bedeutet, daB der prgexponentielle Faktor annahernd konstant bleibt, er hat die GroBenordnung u, = l O ( 5 i 1) s-1.Die aus dem Aktivierungsvolumen abgeschatzte Hindernisdichte steigt von lo7 an der kritischen Schubspannung auf loll cm-2 beim Bruch. Eingewachsene Waldversetzungen, die in der Literatur allgemein als thermisch aktivierbare Hindernisse in Cd und Zn angesehen werden, scheiden daher als alleinige Hindernisse Bus, da ihre Dichte um mehrere GroDenordnungen kleiner ist.

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Work-hardening of Cd single crystals between 293 and 500 K

Uçar

Düzgün

1993

Phys. Stat. Sol. (a)

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A variable temperature, tensile testing cryostat

Cited by 5 publications

References 3 publications

Easy-glide hardening of Zn and Cd between 4.2 and 400 K

Easy-glide hardening of Zn and Cd between 4.2 and 400 K

Cottrell-stokes law in Cadmium and Zinc

Work-hardening of Cd single crystals between 293 and 500 K

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