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Dislocation substructures in the anomalous slip plane of single crystal niobium strained at 50 K
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ABSTRACTS OF ARTICLES TO APPEAR IN ACTA MET
3. THE THERMAL STABILITY OF THE AI-AI 3 Ni EUTECTIC IN A TEMPERATURE GRADIENT D.R.H. Jones and G.J. Ma~+ *Department of Metallurgy and Materials Science, University of Cambridge, England. *+Now with the Central Electricity Generating Board, South Eastern Region, Scientific Services Department, Gravesend, Kent, England
Vol. 8, No. II
result locally from glide in the (0~I) plane. 5. ON THE SINTERING RATE OF CLEAVAGE CRACKS
R. RaJ, W. P a v i n i c h and C.N. Ahlquist Department o f Mechanical E n g i n e e r i n g , U n i v e r s i t y of C o l o r a d o , B o u l d e r , Colorado 80302 R e c e i v e d May 17, 1974 R e v i s e d J u l y 26, 1974
Received July 18, 1974 An investigation has been made of the thermal stability of the aligned, fibrous A1-AI3NI eutectic when subjected to a temperature gradient of approximately 5 K m m -1 perpendicular to the fibre axes. Each specimen was held in a temperature range 868 6 K to 883 + 6 K for times of up to 220 hours. --The results indicated that the eutectic fibres coarsened approximately five times more rapidly in the temperature gradient than they would have done under isothermal conditions at the same temperatures. It is noteworthy that this effect may be an important, limiting factor in the use of eutectic composites as high-temperature materials.
4. DISLOCATION SUBSTRUCTURES IN THE ANOMALOUS SLIP PLANE OF SINGLE CRYSTAL NIOBIUM STRAINED AT 50 K F. Louchet and L.P. Kubin Laboratolre d'Optique Electronique du CNRS 29 rue Jeanne Marvig 31055 Toulouse Cedex - France
Cleavage cracks in partially cleaved single crystals of lithium flouride will ainter as a result of surface tension forces. The rate of slnterlng is found to reach a steady s t a t e ; i t has been measured as a f u n c t i o n o f t e m p e r a t u r e and c r a c k width. The crack tip profile was obtsfmeduslng scanning electron microscopy and was found to have the same general shape irrespective of sintering temperature and crack width. On the basis of the crack tip profile, expressions for the slntering rate were derived for various mass transfer processes. By comparison of theory and experiment it is concluded that at temperatures above 700 °, cracks sinter by volume dlffuson wlth an activation energy of 46 Kcals/mole and at temperature below 700 ° , by surface diffusion with an activation energy of 20 Kcalsl mole. The fracture surface energy was found to be the same for the sintered and the unslntered cracks in spite of a wider crack tlp width for the sintered cracks.
R e c e i v e d J u l y 23, 1974 Anomalous (0~I) slip traces have been detected in Niobium after straining at 50 K. TEM analysis has been peEformed on samples cut parallel to (0II). Dislocatlon substructures, intersections, pinned and serrated dislocations, have been analysed. The intersection of two ~ ¢III) dislocations was found to produce a 4100 ) screw fragments. The planar structure of some of the observed dislocation configurations seems to liv
6. A MDDEL FOR HOT WORKING OCCURRING BY RECRYSTALLIZATION Rolf Sandstram and Rune Lagneborg Materials Center, Royal Institute of Technology, S-100 44 Stockholm 70, Sweden Received April 29, 1974 A t h e o r e t i c a l model i s p r e s e n t e d f o r h o t working when dynamical r e -
ABSTRACTS OF ARTICLES TO APPEAR IN ACTA MET
3. THE THERMAL STABILITY OF THE AI-AI 3 Ni EUTECTIC IN A TEMPERATURE GRADIENT D.R.H. Jones and G.J. Ma~+ *Department of Metallurgy and Materials Science, University of Cambridge, England. *+Now with the Central Electricity Generating Board, South Eastern Region, Scientific Services Department, Gravesend, Kent, England
Vol. 8, No. II
result locally from glide in the (0~I) plane. 5. ON THE SINTERING RATE OF CLEAVAGE CRACKS
R. RaJ, W. P a v i n i c h and C.N. Ahlquist Department o f Mechanical E n g i n e e r i n g , U n i v e r s i t y of C o l o r a d o , B o u l d e r , Colorado 80302 R e c e i v e d May 17, 1974 R e v i s e d J u l y 26, 1974
Received July 18, 1974 An investigation has been made of the thermal stability of the aligned, fibrous A1-AI3NI eutectic when subjected to a temperature gradient of approximately 5 K m m -1 perpendicular to the fibre axes. Each specimen was held in a temperature range 868 6 K to 883 + 6 K for times of up to 220 hours. --The results indicated that the eutectic fibres coarsened approximately five times more rapidly in the temperature gradient than they would have done under isothermal conditions at the same temperatures. It is noteworthy that this effect may be an important, limiting factor in the use of eutectic composites as high-temperature materials.
4. DISLOCATION SUBSTRUCTURES IN THE ANOMALOUS SLIP PLANE OF SINGLE CRYSTAL NIOBIUM STRAINED AT 50 K F. Louchet and L.P. Kubin Laboratolre d'Optique Electronique du CNRS 29 rue Jeanne Marvig 31055 Toulouse Cedex - France
Cleavage cracks in partially cleaved single crystals of lithium flouride will ainter as a result of surface tension forces. The rate of slnterlng is found to reach a steady s t a t e ; i t has been measured as a f u n c t i o n o f t e m p e r a t u r e and c r a c k width. The crack tip profile was obtsfmeduslng scanning electron microscopy and was found to have the same general shape irrespective of sintering temperature and crack width. On the basis of the crack tip profile, expressions for the slntering rate were derived for various mass transfer processes. By comparison of theory and experiment it is concluded that at temperatures above 700 °, cracks sinter by volume dlffuson wlth an activation energy of 46 Kcals/mole and at temperature below 700 ° , by surface diffusion with an activation energy of 20 Kcalsl mole. The fracture surface energy was found to be the same for the sintered and the unslntered cracks in spite of a wider crack tlp width for the sintered cracks.
R e c e i v e d J u l y 23, 1974 Anomalous (0~I) slip traces have been detected in Niobium after straining at 50 K. TEM analysis has been peEformed on samples cut parallel to (0II). Dislocatlon substructures, intersections, pinned and serrated dislocations, have been analysed. The intersection of two ~ ¢III) dislocations was found to produce a 4100 ) screw fragments. The planar structure of some of the observed dislocation configurations seems to liv
6. A MDDEL FOR HOT WORKING OCCURRING BY RECRYSTALLIZATION Rolf Sandstram and Rune Lagneborg Materials Center, Royal Institute of Technology, S-100 44 Stockholm 70, Sweden Received April 29, 1974 A t h e o r e t i c a l model i s p r e s e n t e d f o r h o t working when dynamical r e -