Microstructural development in an aluminum alloy-SiC whisker composite

Abstract Microstructural development in a powder metallurgy 2124 aluminum alloy-SiC whisker composite subject to controlled and systematic aging treatments was investigated using analytical transmission electron microscopy, quantitative analysis of precipitate growth, matrix microhardness measurements and studies of changes in electrical conductivity. In order to build a basis for comparison, the precipitation characteristics of the unreinforced matrix material with an identical processing history were also examined. The results indicate that the matrix of the composite material has a much greater density of dislocations than the control alloy. The increased dislocation density facilitates the nucleation of strengthening precipitates whereby the incubation time for precipitate nucleation and the aging time to achieve peak hardness in the matrix are significantly reduced for the composite as compared to the unreinforced matrix material. Theoretical analyses of dislocation generation due to thermal expansion mismatch and of the punching of dislocations at whisker ends are examined in the context of microstructural development in the metal-matrix composite. An attempt is made to address the issues essential to a thorough and systematic microstructural characterization and to develop a framework for a fundamental understanding of microstructural evolution in discontinuous fiber-reinforced metal-matrix composites.

[1]  Minoru Taya,et al.  Dislocations punched-out around a short fiber in a short fiber metal matrix composite subjected to uniform temperature change , 1987 .

[2]  D. J. Hagemaier.  Eddy current standard depth of penetration , 1985 .

[3]  T. Mori,et al.  Note on volume integrals of the elastic field around an ellipsoidal inclusion , 1972 .

[4]  David L. McDanels,et al.  Analysis of stress-strain, fracture, and ductility behavior of aluminum matrix composites containing discontinuous silicon carbide reinforcement , 1985 .

[5]  R. N. Wilson,et al.  The nucleation and growth of S' precipitates in an aluminium - 2.5% copper - 1.2% magnesium alloy , 1965 .

[6]  R. F. Karlak,et al.  Aging characteristics of B4C-reinforced 6061-aluminum , 1984 .

[7]  R. J. Arsenault,et al.  Anin situ HVEM study of dislocation generation at Al/SiC interfaces in metal matrix composites , 1986 .

[8]  D. Thompson.  Metallurgical factors affecting high strength aluminum alloy production , 1975 .

[9]  R. Mehan,et al.  Failure modes in composites. II , 1974 .

[10]  G. Mayer,et al.  Fatigue of metal matrix composite materials , 1986 .

[11]  G. Weatherly,et al.  An electron microscope investigation of the interfacial structure of semi-coherent precipitates , 1968 .

[12]  S. Nutt,et al.  Non-equilibrium phase distribution in an Al-SiC composite , 1985 .

[13]  R. J. Arsenault,et al.  The strengthening of aluminum alloy 6061 by fiber and platelet silicon carbide , 1984 .

[14]  K. Chawla,et al.  Initial dislocation distributions in tungsten fibre-copper composites , 1972 .