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Diffusion in the MoNi, MoFe and MoCo systems
Vol.
8, No. 6
ABSTRACTS OF ARTICLES TO APPEAR IN ACTA MET
current theories shows that the experimental results can qualitatively be explained in terms of the electron drag model. 13.
EFFECT OF STACKING FAULT ENERGY ON THE MUTUAL CROSS SLIP OF UNLIKE DISLOCATIONS I: COALESENCE MODE M. J. Marcinkowski, K. Sadananda & R. J. Taunt Engineering Materials Group Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742 Received January 17, 1974 Revised April 22, 1974
A detailed numerical analysis has been made of the cross slip behavior associated with extended screw type dislocations of opposite sign in face centered cubic metals and alloys which pass one another on parallel slip planes. It is shown that below some critical interplanar spacing, the mutual interaction between the extended dislocations is sufficient to bring about coalesence, followed by spontaneous cross slip and subsequent mutual annihiliation. Just above this critical interplanar spacing, the extended dislocations may pass one another with a maximum interaction and thus a maximum stress. This maximum stress, i.e., strengthening, decreases with increasing stacking fault energy and provides an alternate hypothesis to the pile-up model for Stage III work hardening behavior in face-centered-cubic metals and alloys. 14.
EFFECT OF STACKING FAULT ENERGY ON THE MUTUAL CROSS SLIP OF UNLIKE DISLOCATIONS If: STAIR ROD MODE
xxxiii
A detailed numerical analysis has been made with respect to the critical conditions for cross slip of a pair of extended screw type dislocations of opposite sign in which each of the partial dislocations cross slips separately with the resultant production of a stairrod dislocation. It is shown that contrary to the findings in Part I where dislocation coalesence was the mode of cross slip, the stair rod mode limits the maximum strengthening in such a manner that it increases with stacking fault energy. Furthermore, it is shown that while cross slip via the stair rod mode is more favorable at low stacking fault energies, the coalesence mode becomes the more favorable mechanism at high stacking fault energies. 15.
THE SOLUBILITY OF HYDROGEN NICKEL AND COBALT
IN
S. W. Stafford & Rex B. McLellan William Marsh Rice University Materials Science Department Houston, Texas 77001 Received April 22, 1974 The solubility of hydrogen in nickel and cobalt at atmospheric pressure has been measured over large temperature ranges. Large departures from Arrhenius behavior have been found for polycrystalline nickel and cobalt, but equilibrations using a nickel single crystal did not show curvature in the Arrhenius plot. The measured solubility data have been interpreted using a solid solution model involving sites of differing energy at which solute atoms can be located. 16.
DIFFUSION IN THE Mo-Ni, Mo-Fe AND Mo-Co SYSTEMS
M. J. Marcinkowski, R. J. Taunt & K. Sadananda Engineering Materials Group Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742
C. P. Heijwegen*& G. D. Rieck Laboratory of Physical Chemistry, Eindhoven University of Technology, Eindhoven, Netherlands *Now at: Hoogovens IJmuiden, B.V. IJmuiden, Netherlands
Received January 17, 1974 Revised April 22, 1974
Received November 28, 1973 Revised March 25, 1974
xxxiv
ABSTRACTS OF ARTICLES TO APPEAR IN ACTA MET
Interdiffusion phenomena at temperatures between 800 and 1300°C have been investigated in the Mo -Ni, Mo-Fe and Mo-Co systems using the diffusion couple technique combined with the techniques of microscopy, microprobe analysis, X-ray diffraction and micro-identation hardness testing. The layer growth of the s-solid solutions obeys the parabolic law only above 1000°C. The layer growth of the intermetallic phases ~o(MoNi) and ~-(Fe~Mo~) is parabolic, that in the ~-(Co7Mo6~ phase only in incremental coupl~s. It is shown that the diffusion coefficients of the s-solid solutions of the three binary systems are independent of concentration. Arrhenius' relation applies in all cases, and a number of Q values have been calculcated. Marker experiments show that only in the s-solid solutions with Ni and Fe, the Mo atoms diffuse fastest.
Vol.
8, No. 6
8, No. 6
ABSTRACTS OF ARTICLES TO APPEAR IN ACTA MET
current theories shows that the experimental results can qualitatively be explained in terms of the electron drag model. 13.
EFFECT OF STACKING FAULT ENERGY ON THE MUTUAL CROSS SLIP OF UNLIKE DISLOCATIONS I: COALESENCE MODE M. J. Marcinkowski, K. Sadananda & R. J. Taunt Engineering Materials Group Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742 Received January 17, 1974 Revised April 22, 1974
A detailed numerical analysis has been made of the cross slip behavior associated with extended screw type dislocations of opposite sign in face centered cubic metals and alloys which pass one another on parallel slip planes. It is shown that below some critical interplanar spacing, the mutual interaction between the extended dislocations is sufficient to bring about coalesence, followed by spontaneous cross slip and subsequent mutual annihiliation. Just above this critical interplanar spacing, the extended dislocations may pass one another with a maximum interaction and thus a maximum stress. This maximum stress, i.e., strengthening, decreases with increasing stacking fault energy and provides an alternate hypothesis to the pile-up model for Stage III work hardening behavior in face-centered-cubic metals and alloys. 14.
EFFECT OF STACKING FAULT ENERGY ON THE MUTUAL CROSS SLIP OF UNLIKE DISLOCATIONS If: STAIR ROD MODE
xxxiii
A detailed numerical analysis has been made with respect to the critical conditions for cross slip of a pair of extended screw type dislocations of opposite sign in which each of the partial dislocations cross slips separately with the resultant production of a stairrod dislocation. It is shown that contrary to the findings in Part I where dislocation coalesence was the mode of cross slip, the stair rod mode limits the maximum strengthening in such a manner that it increases with stacking fault energy. Furthermore, it is shown that while cross slip via the stair rod mode is more favorable at low stacking fault energies, the coalesence mode becomes the more favorable mechanism at high stacking fault energies. 15.
THE SOLUBILITY OF HYDROGEN NICKEL AND COBALT
IN
S. W. Stafford & Rex B. McLellan William Marsh Rice University Materials Science Department Houston, Texas 77001 Received April 22, 1974 The solubility of hydrogen in nickel and cobalt at atmospheric pressure has been measured over large temperature ranges. Large departures from Arrhenius behavior have been found for polycrystalline nickel and cobalt, but equilibrations using a nickel single crystal did not show curvature in the Arrhenius plot. The measured solubility data have been interpreted using a solid solution model involving sites of differing energy at which solute atoms can be located. 16.
DIFFUSION IN THE Mo-Ni, Mo-Fe AND Mo-Co SYSTEMS
M. J. Marcinkowski, R. J. Taunt & K. Sadananda Engineering Materials Group Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742
C. P. Heijwegen*& G. D. Rieck Laboratory of Physical Chemistry, Eindhoven University of Technology, Eindhoven, Netherlands *Now at: Hoogovens IJmuiden, B.V. IJmuiden, Netherlands
Received January 17, 1974 Revised April 22, 1974
Received November 28, 1973 Revised March 25, 1974
xxxiv
ABSTRACTS OF ARTICLES TO APPEAR IN ACTA MET
Interdiffusion phenomena at temperatures between 800 and 1300°C have been investigated in the Mo -Ni, Mo-Fe and Mo-Co systems using the diffusion couple technique combined with the techniques of microscopy, microprobe analysis, X-ray diffraction and micro-identation hardness testing. The layer growth of the s-solid solutions obeys the parabolic law only above 1000°C. The layer growth of the intermetallic phases ~o(MoNi) and ~-(Fe~Mo~) is parabolic, that in the ~-(Co7Mo6~ phase only in incremental coupl~s. It is shown that the diffusion coefficients of the s-solid solutions of the three binary systems are independent of concentration. Arrhenius' relation applies in all cases, and a number of Q values have been calculcated. Marker experiments show that only in the s-solid solutions with Ni and Fe, the Mo atoms diffuse fastest.
Vol.
8, No. 6