Harold Margolin

The mechanism of void formation, void growth, and tensile fracture in an alloy consisting of two ductile phases

An investigation has shown that it is possible to relate void formation, void growth, and tensile ductility to microstructural features in an α-β titanium alloy, Ti-5.25A1-5.5V-0.9Fe-0.5Cu, heat treated to a constant yield strength. Equations relating tensile void growth rates to microstructure for both equiaxed,E, and Widmanstätten plus grain boundaryα, W + ITG. B.,in aged β morphologies have been derived. A mechanism for void formation at α-β interfaces is presented which accounts for the observed fact that voids do not form at Widmanstätten α platelets. Tensile fracture is shown to be intergranular in nature and occurs when a critical crack length-stress relationship is satisfied. The amount of ductility achievable in a specimen depends upon the rate of void growth. If the rate is large, the void reaches a critical size for fracture at a lower applied stress and strain and hence the ductility is less.

A rationalization of stress-strain behavior of two-ductile phase alloys

An extensive literature review indicated that the law of mixture rule can at times account for stress-strain behavior of two-ductile phase alloys in terms of the stress-strain behavior of component phases. In the present investigation, various factors which can contribute to the stress-strain behavior of two-ductile phase alloys are considered, using Ti-Mn alloys as the model system. Particular attention is focused on the effect of elastic, elasto-plastic, and plastic interactions between the phases on the stress-strain behavior. It is shown that the law of mixture cannot adequately explain the stress-strain behavior. The following equation is proposed to describe the stress-strain behavior of two-ductile phase alloys: Pα-β = fαPαc+ fβPβc+ Iα-βp, where Pα-β is a given stress-strain property, fα and f/gb are respective volume fractions of α and β-phases, Pαc and Pβc are corrected properties of α and β-phases, and Iα-βp is the interaction term. It is found that for α- β Ti-Mn alloys, for 0.2 pct yield strength, Iα-βp is positive, negative, or zero depending on the microstructure; but Iα-βp is always positive for the ultimate tensile strength and strain hardening rates and its magnitude depended on the microstructure. The reasons for the nature or sign of the interaction parameter for a given property are discussed in detail.

Finite Element Method (FEM) Calculations of Stress-Strain behavior of alpha-beta Ti-Mn alloys: Part II. Stress and strain distributions

By use of a NASTRAN18 Computer Program, the Finite Element Method (FEM) has been employed to calculate the effect of particle size, matrix, and volume fraction on the stress-strain relations of α-β titanium alloys. It was found that for a given volume fraction, the calculated stress-strain curve was higher for a finer particle size than for a coarse particle size within the range of the strains considered, and this behavior was seen for all the different volume fraction alloys considered. For a 50:50 vol pct α-β alloy, the stress-strain curve withβ, the stronger phase, as the matrix was higher than that with α, the softer phase, as the matrix. The calculated stress-strain curves for four different vol pct α alloys were compared with their corresponding experimental curves, and in general, good agreement was found. Whenever there were discrepancies, they were discussed by comparing the morphology of the mesh used in the calculations with the morphology of the actual materials.

β brass bicrystal stress-strain relations

AbstractThe stress-strain relations of three isoaxial and one nonisoaxial bicrystal whose grain boundaries are parallel to the stress axis have been studied. From one set of isoaxial bicrystals it has been possible, for a given strain, to determine the average stress % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfKttLearuqr1ngBPrgarmqr1ngBPrgitL% xBI9gBamXvP5wqSXMqHnxAJn0BKvguHDwzZbqegm0B1jxALjhiov2D% aeHbuLwBLnhiov2DGi1BTfMBaebbfv3ySLgzGueE0jxyaibaieYlf9% irVeeu0dXdh9vqqj-hEeeu0xXdbba9frFj0-OqFfea0dXdd9vqaq-J% frVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr0-vqpWqaaeaabi% GaciaacaqabeaadaabauaaaOqaamaanaaabaGaeq4WdmhaamaaBaaa% leaaiqGacaWFNbGaa8Nyaaqabaaaaa!42CF!

The interrelationship of fracture toughness and microstructure in a Ti-5.25Al-5.5V-0.9Fe-0.5Cu alloy

\overline \sigma _{gb}

An apparatus for pressure casting of fibre-reinforced high-temperature metal-matrix composites

in the grain boundary deformation zone from the relationship % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfKttLearuqr1ngBPrgarmqr1ngBPrgitL% xBI9gBamXvP5wqSXMqHnxAJn0BKvguHDwzZbqegm0B1jxALjhiov2D% aeHbuLwBLnhiov2DGi1BTfMBaebbfv3ySLgzGueE0jxyaibaieYlf9% irVeeu0dXdh9vqqj-hEeeu0xXdbba9frFj0-OqFfea0dXdd9vqaq-J% frVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr0-vqpWqaaeaabi% GaciaacaqabeaadaabauaaaOqaaGGaaiab-n8aZnaaBaaaleaacqWG% ubavaeqaaOGaeyypa0Jae83Wdm3aaSbaaSqaaGabciaa+jgaaeqaaO% Gaey4kaSIaemOvay1aaSbaaSqaaiaa+DgacaGFIbaabeaakiabcIca% OmaanaaabaGae83WdmhaamaaBaaaleaacGaAu73zaiacOrTFIbaabe% aakiabgkHiTiab-n8aZnaaBaaaleaacaGFIbaabeaakiabcMcaPaaa% !55F0!

Pressure casting of a zirconia-toughened alumina fiber-reinforced NiAl composite

\sigma _T = \sigma _b + V_{gb} (\overline \sigma _{gb} - \sigma _b )