The plasticity of unidirectionally solidified eutectic in the silver-germanium system (in German)

The plasticity of unidirectionally solidified eutectic in the silver-germanium system (in German)

Fabrication of composites by diffusion processing Darroudi, T., Vedula, K. M. and Heckel, R. W. Metallurgical Transactions, Vol 2, No 1, pp 3 2 5 - 3 ...

135KB Sizes 1 Downloads 10 Views

Fabrication of composites by diffusion processing Darroudi, T., Vedula, K. M. and Heckel, R. W. Metallurgical Transactions, Vol 2, No 1, pp 3 2 5 - 3 2 8 (January 1971) Composites of NiA13 fibres in an A1 matrix were successfully produced by first preparing composites of Ni wire in an A1 matrix, by hot pressing, and then annealing these at 600°C in hydrogen. The Ni wires reacted with the A1 matrix to give uniform fibres of NiAI3. This type of reaction is suggested as one means of producing composites by hot pressing and yet avoiding problems of fibre degradation. (71/3/14) Fibre-reinforced materials - potential application in reactor technology Tyson, W. R., Murphy, D. T. and English, P. E. Canadian Metallurgical Quarterly, Vol 9, No 3, pp 445 - 456 (July-September 1970) To test the feasibility of using fibre reinforcement to strengthen reactor tubing, ziracaloy-4 tubes were wound externally with steel wire. The 0"3 mm wire was wound together with A1 foil which was subsequently vacuum melted to bond the wire to the tube. The reinforced tubes were tested to fracture with internal oil pressure. Considerable improvement in strength was observed both at room temperature and at 500°C. (71/3/15) The growth of off-eutectic composites from stirred melts Verhoeven, J. D. and Homer, R. H. Metallurgical Transactions, Vol 1, No 12, pp 3437 - 3441 (December 1970) Theoretical arguments are presented which indicate the feasibility of preparing aligned composites by unidirectional solidification from stirred melts of off-eutectic composition, thus allowing control of volume fraction. Conditions for such a process would probably be improved by solidification from an open system, ie a continuous feed of the alloy to the melt. The implications of the theory are discussed with reference to the AI-A13 Ni system. (71/3/16) Matrix strengthening mechanisms of an iron-fiber/copper-matrix composite as a function of fiber size and spacing Garmong, G. and Shepard, L. A. Metallurgical Transactions, Vol 2, No 1, pp 175 - 180 (January 1971) Composites of Fe f i b r e s - with diameters from 5 x 10 -3 mm to 1 0 m m and volume fractions from 0"03 to 0"97 - in a Cu matrix were prepared by the repeated drawing of Fe-rod/Cutube combinations. The effect of fibre diameter and volume fraction on mechanical properties was studied. The composite elastic moduli agreed



well with the rule of mixtures. Matrix and composite yielding and plastic flow were dependent on fibre diameter and spacing, and exhibited positive deviations of up to about five times the predictions of the rule of mixtures. The results were explained in terms of dislocation motion and differences in Poisson's ratios of the phases. (7113117)

Multiple necking phenomena in metal composites Schoene, C. and Scala, E. Metallurgical Transactions, Vol 1, No 12, pp 3466 3468 (December 1970} Tensile tests were carried out on composites of W wire in matrices of brass. The improvements in tensile properties for volume fractions of W between 5% and 20% were consistently above those predicted by the rule of mixtures. Examination of the composites, after testing, revealed multiple necking along the entire lengths of the W wires. The spacing of necks was close to the critical length for the system. (71[3/18) On the growth of the Ni-W eutectic Kurz, W. and Lux, B. Metallurgical Transactions, Vol 2, No 1, pp 329 331 (January 1971) The solidification of a N i - W eutectic alloy produced a composite structure of 6 vol% W in a matrix of a N i - W solid solution. At slow growth rates and with steep temperature gradients, unidirectional solidification produces a structure of parallel W rods. At increased growth rates W lamellae are formed. A study was made of the rod and lamellae dimensions and separation distances as a function of growth rates. (71/3/19)

The plasticity of unidirectionally solidified enteetic in the silver-germanium system (in German) Krummheuer, W. R. and Alexander, H. A. Zeitschrift fiir Metallkunde, Vol 62, No 2, pp 129 - 135 (February 1971) Unidirectional solidification of the eutectic alloy, Ag-25"9at%Ge, resulted in a microstructure of orientated 'rods' with a star-like cross-section. Dynamic compression tests were carried out on this alloy in the range 2 0 - 6 2 0 ° C and it was found that it behaved as a fibre-reinforced material. (7113/20) Strength diagrams of fibrous composite materials with a unidirectional structure Ivanova, V. S. and Ustinov, L. M. Russian Metallurgy (English translation) No 2, pp 101 - 105 (1970) Theoretical derivations are used to construct four possible three-dimensional diagrams which predict the

strength of 'soft-matrix/rigid-fibre' composites as a function of volume fraction and of fibre-length/criticallength ratio. Sections of these diagrams can be taken to determine the condition of positive reinforcement as a function of the mechanical properties of the matrix. (71/3/21)

The structure and fractography of cemented tungsten carbide Mason, A. and Kenny, P. Metallurgia, Vol 82, No 494, pp 205 - 212 (December 1970) The microstructure and fracture of W C - C o alloys were studied using techniques of electron microscopy and quantitative metallography. In this way it was found possible to relate the mode of fracture to micro-structural parameters such as carbide grain size and distribution, carbide contiguity, volume fraction of Co and mean free path in the Co phase. It was found that the fracture is mainly intergranular but that the proportion of transgranular fracture increases with carbide grain size. The intergranular fracture is partly made up of ductile fracture of the Co layers. The proportion of this ductile fracture increases with the Co content. (7113/22) Structures, faults and the rod-plate transition in eutectics Cline, H. E., Walter, J. L., Lifshin E. and Russell, R. R. Metallurgical Transactions, Vol 2, No 1, pp 189 - 194 (January 1971) Unidirectional solidification was used to prepare eutectic alloys of Ni-W, NiA1-Cr, and NiA1-Cr(Mo). The alloys were selectively etched to reveal the three-dimensional structure when examined in a scanning electron microscope. Both rod and plate structures were observed. Faults in the rod structures were also detected and these were associated with the rod-plate transition. (71/3/23) The tensile properties of a graphitefiber-reinforced aluminium/silicon alloy Pepper, R. T., Upp, J. W., Rossi, R. C. and Kendall, E. G. Metallurgical Transactions Vol 2, No i, pp 117 - 120 (January 1971) By infiltrating surface-treated, graphitefibre yarn with an AI[13wt%-Si alloy, composites were prepared with contained 28vo1% fibres. The uniaxial tensile strength, the mode of fracture and the thermal cycling behaviour of the composites were studied. The tensile strength was higher than that predicted by the rule of mixtures. Thermal cycling did not seem to affect the tensile properties. (71/3/24)