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A simple model for grain refinement during solidification
xliv
ABSTRACTS
Enschede,
OF ARTICLES
The Netherlands
Received May 17,
17.
1974
The texture development of silver single crystals and polycrystalline high purity silver and a series of Ni-Co alloys was examined, immediately after rolling and after various annealing treatments. X-ray diffraction and electron-microscopical observations showed that the development of the (841}<447> + (310}<001> + (852}<245> recrystallisation texture can be explained by the inverse Rowland transformation as the primary nucleation mechanism followed by recrystallisation twinning and growth selection of secondary twins. 16.
TO APPEAR IN ACTA MET
RAPID DIFFUSION OF NITROGEN AND CARBON ALONG INTERPHASE INTERFACES IN IRON-BASE DIFFUSION COUPLES A. G. Dirks*& J. L. Meijering Laboratorium voor Metaalkunde, Technische Hogeschool, Delft Rotterdamseweg 137, Delft (The Netherlands) *Now at: Natuurkundig Laboratorium, Philips Gloeilampenfabrieken B.V. Eindhoven (The Netherlands)
The interfacial diffusion of nitrogen and carbon along boundaries between two f.c.c, phases in ironpalladium diffusion couples was examined. The interfacial diffusion of nitrogen was quite marked, but that of carbon could not be detected. Nitrogen moves the miscibility gap in the ironpalladium system towards higher palladium contents. As in the case of iron-nickel, phase boundaries between ferrite and austenite in iron-palladium were readily penetrated by both nitrogen and carbon. The results of carburization and decarburization experiments at right angles to the diffusion gradient in binary iron-carbon couples were also consistent with a high interfacial permeability of phase boundaries for interstitial elements.
8, No.
8
THE DEFORMATION MECHANISMS OF A UNIDIRECTIONALLY SOLIDIFIED Ni-W EUTECTIC ALLOY A. Lasalmonie* & J. W. Martin** *Office National d'Etudes et de Recherches Aerospatiales (ONERA) 92320 Chatillon (France) **Dept. of Metallurgy, University of Oxford, Parks Rd. Oxford, England Received April
23, 1974
The eutectic Ni-47.5 wt% W was unidirectionally solidified to form a regularly aligned composite containing a volume fraction of 0.06 of W fibres with diameter approx, l~m in an ~ NiaW(8) matrix. Material of matrix composition (Ni-38 wt% W) was also produced, and the structure and orientation of the B-precipitates studied by transmission electron microscopy. Tensile tests were carried out on the composite material, and the deformation microstructures studied. Superlattice stacking-faults and microtwins were observed in the B-phase. The W fibres are found to lower the yield stress of the alloy, but greatly to increase the matrix ductility, by multiplying the number of slip systems in the ~-B phases. 18.
Received May 28, 1974
Vol.
A SIMPLE MODEL FOR GRAIN REFINEMENT DURING SOLIDIFICATION I. M a x w e l l & A. Hellawell Dept. of Metallurgy & Science of Materials, University of Oxford, Parks Rd. Oxford, England
Received May 20, 1974 Assuming (i) a spatially isothermal melt (ii) a heterogeneous nucleation rate according to the classical theory (iii) spherical diffusion controlled growth, the number of heterogeneous nucleation events that occurs during the initial stage of a liquid ÷ solid reaction has been computed as a function of nucleant particle density using AI-Ti as the model system. The influence of cooling rate, substrate activity, and alloy constitution has been investigated, the last by comparison with the refinement obtainable in the systems AI-Zr and AI-Cr. The predictions of the model are in acceptable accord with observed behaviour considering the necessary assumptions of the model.
ABSTRACTS
Enschede,
OF ARTICLES
The Netherlands
Received May 17,
17.
1974
The texture development of silver single crystals and polycrystalline high purity silver and a series of Ni-Co alloys was examined, immediately after rolling and after various annealing treatments. X-ray diffraction and electron-microscopical observations showed that the development of the (841}<447> + (310}<001> + (852}<245> recrystallisation texture can be explained by the inverse Rowland transformation as the primary nucleation mechanism followed by recrystallisation twinning and growth selection of secondary twins. 16.
TO APPEAR IN ACTA MET
RAPID DIFFUSION OF NITROGEN AND CARBON ALONG INTERPHASE INTERFACES IN IRON-BASE DIFFUSION COUPLES A. G. Dirks*& J. L. Meijering Laboratorium voor Metaalkunde, Technische Hogeschool, Delft Rotterdamseweg 137, Delft (The Netherlands) *Now at: Natuurkundig Laboratorium, Philips Gloeilampenfabrieken B.V. Eindhoven (The Netherlands)
The interfacial diffusion of nitrogen and carbon along boundaries between two f.c.c, phases in ironpalladium diffusion couples was examined. The interfacial diffusion of nitrogen was quite marked, but that of carbon could not be detected. Nitrogen moves the miscibility gap in the ironpalladium system towards higher palladium contents. As in the case of iron-nickel, phase boundaries between ferrite and austenite in iron-palladium were readily penetrated by both nitrogen and carbon. The results of carburization and decarburization experiments at right angles to the diffusion gradient in binary iron-carbon couples were also consistent with a high interfacial permeability of phase boundaries for interstitial elements.
8, No.
8
THE DEFORMATION MECHANISMS OF A UNIDIRECTIONALLY SOLIDIFIED Ni-W EUTECTIC ALLOY A. Lasalmonie* & J. W. Martin** *Office National d'Etudes et de Recherches Aerospatiales (ONERA) 92320 Chatillon (France) **Dept. of Metallurgy, University of Oxford, Parks Rd. Oxford, England Received April
23, 1974
The eutectic Ni-47.5 wt% W was unidirectionally solidified to form a regularly aligned composite containing a volume fraction of 0.06 of W fibres with diameter approx, l~m in an ~ NiaW(8) matrix. Material of matrix composition (Ni-38 wt% W) was also produced, and the structure and orientation of the B-precipitates studied by transmission electron microscopy. Tensile tests were carried out on the composite material, and the deformation microstructures studied. Superlattice stacking-faults and microtwins were observed in the B-phase. The W fibres are found to lower the yield stress of the alloy, but greatly to increase the matrix ductility, by multiplying the number of slip systems in the ~-B phases. 18.
Received May 28, 1974
Vol.
A SIMPLE MODEL FOR GRAIN REFINEMENT DURING SOLIDIFICATION I. M a x w e l l & A. Hellawell Dept. of Metallurgy & Science of Materials, University of Oxford, Parks Rd. Oxford, England
Received May 20, 1974 Assuming (i) a spatially isothermal melt (ii) a heterogeneous nucleation rate according to the classical theory (iii) spherical diffusion controlled growth, the number of heterogeneous nucleation events that occurs during the initial stage of a liquid ÷ solid reaction has been computed as a function of nucleant particle density using AI-Ti as the model system. The influence of cooling rate, substrate activity, and alloy constitution has been investigated, the last by comparison with the refinement obtainable in the systems AI-Zr and AI-Cr. The predictions of the model are in acceptable accord with observed behaviour considering the necessary assumptions of the model.