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A phenomenological theory of interface shear stresses generated by hydrostatic pressure in martensitic materials
Scripts METALLURGICA
Vol. 8, pp. v-x, 1974 Printed in the United States
ABSTRACTS
OF ARTICLES
TO BE PUBLISHED
Pergamon
Press,
Inc.
IN
ACTA METALLURGICA "Acta Met. (to be published)" should be cited in references to material quoted from this section prior to the publica_ion of the relevant article.
i.
SUPERPLASTICITY OF ALUMINIUM
AND STRUCTURE
V. A. Likhachev~ M. M. Myshlyaev~* S. S. Olevskii,** T. N. Chuchman* *A. F. Ioffe Physico-Technical Institute, Academy of Sciences USSR, Leningrad, USSR **Institute of Solid State Physics Academy of Sciences of the USSR, Chernogolovka, USSR Received March 8, 1973; Revised November 26, 1973
In the present work, the plasticity of aluminium of commercial purity has been investigated at different temperatures and strain rates under torsion. Very distinct peaks of plasticity were observed within the temperature range 550 to 750°K. Such a state is referred to as superplasticity. It is shown that for the superplastic state a very strong dependence of deformation before fracture on the rate of deforming is characteristic. A number of electron microscope investigations of the dislocation structure forming under different conditions and at different deformational stages were carried out alongside with the mechanical tests. On the basis of these investigations, a conclusion was made that under the conditions of superplasticity occurring these specimens contain very large grains inside which here and there single dislocations, loops and dipoles, or scarce dislocation networks occur. At the same time, for the specimens deformed at temperatures below the temperature of superplasticity occurring, presence of
very fine practically dislocationfree grains is characteristic, h conclusion is made that a grain size is not always responsible for superplasticity. 2.
A PHENOMENOLOGICAL THEORY OF INTERFACE SHEAR STRESSES GENERATED BY HYDROSTATIC PRESSURE IN MARTENSITIC MATERIALS +
L. E. Pope* and W. E. Warren Sandia Laboratories, Albuquerque, New Mexico 87115 *Now: VR/Wesson, Division of Fansteel, Salt Lake City, Utah 84108 The a p p l i c a t i o n of hydrostatic pressure to martensitic materials generates a shear stress at the martensite-austenite interface due t o t h e different elastic properties of the martensite and austenite phases. A
closed-form solution for the maximum interface shear stress is developed for a single martensite plate in an infinite austenite matrix. The magnitude of this interface shear stress is a function of the applied hydrostatic pressure, the geometry of the martensite place inclusion, and the elastic properties of the phases. Interface shear stresses are calculated and compared to hydrostatic pressure data from 0 to 2.3 kbar. It is found that the interface shear stress is of the correct order of magnitude, when combined with the pressure-volumechange term, to account for the large depression of the austenite start temperature with pressure (-30°C/kbar). The shear modulus and Poisson's ratio are reported for the temperature range of 22 to 350°C for both the austenite and a 95 pct. martensite specimens. +Received May 18, 1973; Revised December 6, 1975
Vol. 8, pp. v-x, 1974 Printed in the United States
ABSTRACTS
OF ARTICLES
TO BE PUBLISHED
Pergamon
Press,
Inc.
IN
ACTA METALLURGICA "Acta Met. (to be published)" should be cited in references to material quoted from this section prior to the publica_ion of the relevant article.
i.
SUPERPLASTICITY OF ALUMINIUM
AND STRUCTURE
V. A. Likhachev~ M. M. Myshlyaev~* S. S. Olevskii,** T. N. Chuchman* *A. F. Ioffe Physico-Technical Institute, Academy of Sciences USSR, Leningrad, USSR **Institute of Solid State Physics Academy of Sciences of the USSR, Chernogolovka, USSR Received March 8, 1973; Revised November 26, 1973
In the present work, the plasticity of aluminium of commercial purity has been investigated at different temperatures and strain rates under torsion. Very distinct peaks of plasticity were observed within the temperature range 550 to 750°K. Such a state is referred to as superplasticity. It is shown that for the superplastic state a very strong dependence of deformation before fracture on the rate of deforming is characteristic. A number of electron microscope investigations of the dislocation structure forming under different conditions and at different deformational stages were carried out alongside with the mechanical tests. On the basis of these investigations, a conclusion was made that under the conditions of superplasticity occurring these specimens contain very large grains inside which here and there single dislocations, loops and dipoles, or scarce dislocation networks occur. At the same time, for the specimens deformed at temperatures below the temperature of superplasticity occurring, presence of
very fine practically dislocationfree grains is characteristic, h conclusion is made that a grain size is not always responsible for superplasticity. 2.
A PHENOMENOLOGICAL THEORY OF INTERFACE SHEAR STRESSES GENERATED BY HYDROSTATIC PRESSURE IN MARTENSITIC MATERIALS +
L. E. Pope* and W. E. Warren Sandia Laboratories, Albuquerque, New Mexico 87115 *Now: VR/Wesson, Division of Fansteel, Salt Lake City, Utah 84108 The a p p l i c a t i o n of hydrostatic pressure to martensitic materials generates a shear stress at the martensite-austenite interface due t o t h e different elastic properties of the martensite and austenite phases. A
closed-form solution for the maximum interface shear stress is developed for a single martensite plate in an infinite austenite matrix. The magnitude of this interface shear stress is a function of the applied hydrostatic pressure, the geometry of the martensite place inclusion, and the elastic properties of the phases. Interface shear stresses are calculated and compared to hydrostatic pressure data from 0 to 2.3 kbar. It is found that the interface shear stress is of the correct order of magnitude, when combined with the pressure-volumechange term, to account for the large depression of the austenite start temperature with pressure (-30°C/kbar). The shear modulus and Poisson's ratio are reported for the temperature range of 22 to 350°C for both the austenite and a 95 pct. martensite specimens. +Received May 18, 1973; Revised December 6, 1975