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Deformation behavior of age-hardened TiMo alloys
xiv
ABSTRACTS OF ARTICLES TO APPEAR IN ACTA MET
diffusion controlled. Suprisingly, the lengthening rates of coherent plates were found to be much greater than those of the same kinds of plates when semicoherent. In the latter condition, lengthening rates approximate those to be expected on the basis of volume diffusion control. This result is explained by the role of the broad face coherency strain field which accelerates the lengthening. Thus a previous suggestion that such accelerated kinetics are due to diffusional short circuit is shown to be invalid. I0.
CONTROLLED POROSITY BY AN EXTREME KIRKENDALL EFFECT Fritz Aldinger Max-Planck-lnstitut fur Metallforschung, Institut fur Sondermetalle, Stuttgart, Germany Received December I, 1973
Homogenizing of diffusion couples with spherical symmetry results in formation of hollow spheres if the mutual diffusivities of the two components differ by a considerable amount. The particles grow as diffusion from the component of the core into the coating material occurs. An additional expansion takes place due to isotropic expansion of the coating shell resulting in an increasing inner radius of the spherical shell. Theoretical considerations show that isotropic growth [the ratio of shell thickness to shell radius being constant) leads to formation of infinitely large hollow particles if the starting coating thickness approaches zero. Sintering of nickel-or cobalt-coated beryllium powder compacts results in volume growth of several hundred percent and densities of less than 0,S g/cm 3. The deviations of the experimental data from the ideal isotropic model calculations are explained by £he non-uniformity of the applied coatings and by the closing of open porosity between particles in the compacts.
ii.
Vol. 8, No. 3
DEFORMATION BEHAVIOR OF AGEHARDENED Ti-Mo ALLOYS A. Gysler*, G. LUtjering* V. Gerold** *Institut fur Werkstoff-Forschung DFVLR, S0S Porz-Wahn, Germany **Max Planck-lnstitut fur Metallforschung, 7 Stuttgart U~iversity of Stuttgart, Germany (~ Institut fur Metallkunde) Received December i0, 1973
The tensile properties of Ti-Mo alloys hardened by the precipitation of u-particles were correlated to the microscopic deformation behavior. The reduction in macroscopic ductility with increasing precipitation of m-particles could be explained by the fact that the moving dislocations were able to shear the hard m-particles leading to an extreme inhomogeneous slip distribution. Cracks were initiated by slip bands intersecting with each other and with grain boundaries. Depending on the degree of inhomogeneous slip cracks propagated through the matrix, along grain boundaries or along slip bands. The various morphologies of the fracture surfaces were correlated to these micromechanisms. On a microscopic scale all specimens showed a ductile, dimple type of fracture surface even if the specimens failed without any macroscopic ductility. 12.
SPINODAL DECOMPOSITION IN CU9wt PCT Ni-6wt PCT Sn-ll: A CRITICAL EXAMINATION OF MECHANICAL STRENGTH OF SPINODAL ALLOYS L. H. Schwartz, Northwestern University, Evanston, Illinois 60201 J. T. PlewesBell Laboratories, Murray Hill New Jersey 07974 Received December 13, 1975
The origin of mechanical strengthening due to the early stage spinodal decomposition process in a Cu-9wt%Ni-6wt%Sn Alloy has been investigated. The wave-length and relative amplitude A of the composition fluctuation were determined from the position and
ABSTRACTS OF ARTICLES TO APPEAR IN ACTA MET
diffusion controlled. Suprisingly, the lengthening rates of coherent plates were found to be much greater than those of the same kinds of plates when semicoherent. In the latter condition, lengthening rates approximate those to be expected on the basis of volume diffusion control. This result is explained by the role of the broad face coherency strain field which accelerates the lengthening. Thus a previous suggestion that such accelerated kinetics are due to diffusional short circuit is shown to be invalid. I0.
CONTROLLED POROSITY BY AN EXTREME KIRKENDALL EFFECT Fritz Aldinger Max-Planck-lnstitut fur Metallforschung, Institut fur Sondermetalle, Stuttgart, Germany Received December I, 1973
Homogenizing of diffusion couples with spherical symmetry results in formation of hollow spheres if the mutual diffusivities of the two components differ by a considerable amount. The particles grow as diffusion from the component of the core into the coating material occurs. An additional expansion takes place due to isotropic expansion of the coating shell resulting in an increasing inner radius of the spherical shell. Theoretical considerations show that isotropic growth [the ratio of shell thickness to shell radius being constant) leads to formation of infinitely large hollow particles if the starting coating thickness approaches zero. Sintering of nickel-or cobalt-coated beryllium powder compacts results in volume growth of several hundred percent and densities of less than 0,S g/cm 3. The deviations of the experimental data from the ideal isotropic model calculations are explained by £he non-uniformity of the applied coatings and by the closing of open porosity between particles in the compacts.
ii.
Vol. 8, No. 3
DEFORMATION BEHAVIOR OF AGEHARDENED Ti-Mo ALLOYS A. Gysler*, G. LUtjering* V. Gerold** *Institut fur Werkstoff-Forschung DFVLR, S0S Porz-Wahn, Germany **Max Planck-lnstitut fur Metallforschung, 7 Stuttgart U~iversity of Stuttgart, Germany (~ Institut fur Metallkunde) Received December i0, 1973
The tensile properties of Ti-Mo alloys hardened by the precipitation of u-particles were correlated to the microscopic deformation behavior. The reduction in macroscopic ductility with increasing precipitation of m-particles could be explained by the fact that the moving dislocations were able to shear the hard m-particles leading to an extreme inhomogeneous slip distribution. Cracks were initiated by slip bands intersecting with each other and with grain boundaries. Depending on the degree of inhomogeneous slip cracks propagated through the matrix, along grain boundaries or along slip bands. The various morphologies of the fracture surfaces were correlated to these micromechanisms. On a microscopic scale all specimens showed a ductile, dimple type of fracture surface even if the specimens failed without any macroscopic ductility. 12.
SPINODAL DECOMPOSITION IN CU9wt PCT Ni-6wt PCT Sn-ll: A CRITICAL EXAMINATION OF MECHANICAL STRENGTH OF SPINODAL ALLOYS L. H. Schwartz, Northwestern University, Evanston, Illinois 60201 J. T. PlewesBell Laboratories, Murray Hill New Jersey 07974 Received December 13, 1975
The origin of mechanical strengthening due to the early stage spinodal decomposition process in a Cu-9wt%Ni-6wt%Sn Alloy has been investigated. The wave-length and relative amplitude A of the composition fluctuation were determined from the position and