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A technique for preparing foils of directionally solidified Ni-W eutectic composite for transmission electron microscopy
Interface reactions during preparation of aluminium matrix composites by the sodium process Goddard, D.M.Journal of Materials Science Vol 13 (1978) pp 1841-1848 Aluminium does not wet graphite except at high temperatures where direct infiltration of carbon fibres results in a loss of fibre strength due to formation of aluminium carbide, The 'sodium process' wets carbon fibre with sodium at low temperatures, then forms a sodium tin compound on the fibre surface which is completely miscible with the aluminium or aluminium-alloy matrix. Possibilities for hybrid composites exist as the process is equally effective in fabricating alumina fibre composites. The sodium is confined to the surface and interior of carbon fibres,
The interlaminar shear strength of unidirectional boron aluminium composites Peters, P.W.M. Journal of Composite Materials Vol 12 (January 1978) p 53 The symmetric block shear test is shown to provide a more conservative estimate of shear strength in unidirectional material than the short beam interlaminar shear test configuration. This is particularly so with a highly plastic matrix such as aluminium, and when the shear plane contains many defects. In boron/aluminium the block shear test is effective in maintaining a shear failure mode throughout with no fibre fracture,
A technique for preparing foils of directionally solidified Ni-W eutectic composite for transmission electron microscopy Spurling, R.A. Metallography Vol 11 (1978) p 101 A technique is described for the preparation of thin strain free foils from a model Ni-W composite both parallel and perpendicular to the fibres. Mechanical and electrolytic thinning processes are described and this paper gives the details necessary for uniform polishing of both the W fibres and the matrix, Thermal cyclic loading in a Co-Cr-AI-C eutectic composite Hildebrandt, U.W., and Sahm, P.R. Journal of Materials Science Vol 13 (1978) p 1031 Thermal fatigue measurements have been performed on this aligned eutectic between romm temperature and up to 1000°C for 104 cycles. Irreversible macroscopic effects were observed, which are explained in terms of the different expansion coefficients of the phases. Two microstructural observations were also made, a partial phase transformation and the ripening process of both phases aided by spherordization and solubility effects. These effects were all a function of the temperature cycle,
The termal stabilities of in situ composites in a temperature gradient - 1. The AI-CuAh eutectic Houghton, D.C. and Jones, P.R.H. Acta Metallurgica Vol 16 (1978) pp 695-703 At temperatures above 0.9 of the eutectic temperature, instabilities developed on eutectic plates lying perpendicular to the heat flow The role of twinning in the cyclic direction, and after pinching-off, stress-strain behaviour of migrated through adjacent eutectic directionally solidified ~'/3"-6 plates. Isothermal annealing Bhowal, P.R., Prewo, K.M. and experiments have shown the cause McEvily, A.J. Metallurgical of this behaviour to be thermal TransactionsA Vol 9A (June 1978) diffusion which will become p 747 important at lower homologous In cyclic straining this ~/(Ni)/,y'(Ni3A1)- temperatures over the anticipated (NiaNb) directionally solidified alloy lifetimes of such composites in exhibits a hysteresis loop of special aero-engine applications, form. Under tension 6 twins are created as two out of four possible Volume fraction determination in variants, the other two being cast superalloys and directionally inhibited by the crystallographic solidified eutectic alloys by a new relation between phases. In manual point cot:nt practice compression the plastic strain is Andrews, C.W. Journal of Testing accommodated by untwinning, and and Evaluation Vol 6 No 1 (January gives rise to an inflection in the 1977) p 20 compressive quadrant of the In this work the ASTM hysteresis loop. recommended practice for
48
determining volume fraction by systematic manula point counting is assessed for six conventional and directionally solidified eutectic alloys. The technique involves the use of a nine point grid used directly on the optical microscope or a one hundred point grid placed over micrographs to count features. The results are compared with values obtained using a semi-automatic scanning instrument and agreement shown to be good, although the manually determined volume fractions for the directionally solidified alloys are slightly low.
Unidirectional solidification of cobalt base eutectic alloys Cocks, G.J., Baker, T.J. and Billingham, J. Journal of the AustralasianInstitute of Metals Vol 22 (1977) p 152 The mechanical properties of Co-Cr-A1-Ni, Co-VC and Co-(Ti, V)C directionally solidified alloys have been determined using simple tensile tests and the structure and fracture surfaces examined using optical and scanning electron microscopy. Aligned plates of CoAl are obtained in the first alloy, this structure possessing excellent oxidation resistance at 1000°C although the tensile strength falls dramatically. In the other alloys the oxidation behaviour was dominated by the presence of vanadium, the overall oxidation resistance being poor.
R E S I NMA TRICES Axial fatigue failure sequence and mechanisms in unidirectional fibreglass composites Kim, H.C. and Ebert, L.J.Journalof Composite Materials Vol 12 (April 1978) pp 139-152 The failure sequence of a unidirectionally glass fibrereinforced vinyl ester resin was studied by monitoring changes in the modulus and hysteresis loop energy of the specimens as a function of the number of cycles in axial fatigue. These variations were compared with microstructural changes in the specimens and it was concluded that failure is initiated by fibre surface flow propagation in the first half cycle, leading to interface failure and matrix crack propagation.
COMPOSITES
. JANUARY
1979
The interlaminar shear strength of unidirectional boron aluminium composites Peters, P.W.M. Journal of Composite Materials Vol 12 (January 1978) p 53 The symmetric block shear test is shown to provide a more conservative estimate of shear strength in unidirectional material than the short beam interlaminar shear test configuration. This is particularly so with a highly plastic matrix such as aluminium, and when the shear plane contains many defects. In boron/aluminium the block shear test is effective in maintaining a shear failure mode throughout with no fibre fracture,
A technique for preparing foils of directionally solidified Ni-W eutectic composite for transmission electron microscopy Spurling, R.A. Metallography Vol 11 (1978) p 101 A technique is described for the preparation of thin strain free foils from a model Ni-W composite both parallel and perpendicular to the fibres. Mechanical and electrolytic thinning processes are described and this paper gives the details necessary for uniform polishing of both the W fibres and the matrix, Thermal cyclic loading in a Co-Cr-AI-C eutectic composite Hildebrandt, U.W., and Sahm, P.R. Journal of Materials Science Vol 13 (1978) p 1031 Thermal fatigue measurements have been performed on this aligned eutectic between romm temperature and up to 1000°C for 104 cycles. Irreversible macroscopic effects were observed, which are explained in terms of the different expansion coefficients of the phases. Two microstructural observations were also made, a partial phase transformation and the ripening process of both phases aided by spherordization and solubility effects. These effects were all a function of the temperature cycle,
The termal stabilities of in situ composites in a temperature gradient - 1. The AI-CuAh eutectic Houghton, D.C. and Jones, P.R.H. Acta Metallurgica Vol 16 (1978) pp 695-703 At temperatures above 0.9 of the eutectic temperature, instabilities developed on eutectic plates lying perpendicular to the heat flow The role of twinning in the cyclic direction, and after pinching-off, stress-strain behaviour of migrated through adjacent eutectic directionally solidified ~'/3"-6 plates. Isothermal annealing Bhowal, P.R., Prewo, K.M. and experiments have shown the cause McEvily, A.J. Metallurgical of this behaviour to be thermal TransactionsA Vol 9A (June 1978) diffusion which will become p 747 important at lower homologous In cyclic straining this ~/(Ni)/,y'(Ni3A1)- temperatures over the anticipated (NiaNb) directionally solidified alloy lifetimes of such composites in exhibits a hysteresis loop of special aero-engine applications, form. Under tension 6 twins are created as two out of four possible Volume fraction determination in variants, the other two being cast superalloys and directionally inhibited by the crystallographic solidified eutectic alloys by a new relation between phases. In manual point cot:nt practice compression the plastic strain is Andrews, C.W. Journal of Testing accommodated by untwinning, and and Evaluation Vol 6 No 1 (January gives rise to an inflection in the 1977) p 20 compressive quadrant of the In this work the ASTM hysteresis loop. recommended practice for
48
determining volume fraction by systematic manula point counting is assessed for six conventional and directionally solidified eutectic alloys. The technique involves the use of a nine point grid used directly on the optical microscope or a one hundred point grid placed over micrographs to count features. The results are compared with values obtained using a semi-automatic scanning instrument and agreement shown to be good, although the manually determined volume fractions for the directionally solidified alloys are slightly low.
Unidirectional solidification of cobalt base eutectic alloys Cocks, G.J., Baker, T.J. and Billingham, J. Journal of the AustralasianInstitute of Metals Vol 22 (1977) p 152 The mechanical properties of Co-Cr-A1-Ni, Co-VC and Co-(Ti, V)C directionally solidified alloys have been determined using simple tensile tests and the structure and fracture surfaces examined using optical and scanning electron microscopy. Aligned plates of CoAl are obtained in the first alloy, this structure possessing excellent oxidation resistance at 1000°C although the tensile strength falls dramatically. In the other alloys the oxidation behaviour was dominated by the presence of vanadium, the overall oxidation resistance being poor.
R E S I NMA TRICES Axial fatigue failure sequence and mechanisms in unidirectional fibreglass composites Kim, H.C. and Ebert, L.J.Journalof Composite Materials Vol 12 (April 1978) pp 139-152 The failure sequence of a unidirectionally glass fibrereinforced vinyl ester resin was studied by monitoring changes in the modulus and hysteresis loop energy of the specimens as a function of the number of cycles in axial fatigue. These variations were compared with microstructural changes in the specimens and it was concluded that failure is initiated by fibre surface flow propagation in the first half cycle, leading to interface failure and matrix crack propagation.
COMPOSITES
. JANUARY
1979