Showing papers on "Superplasticity published in 1969"
TL;DR: In this article, a fine grid scribed on the Mg-Al alloy of several grain sizes over a wide range of strain rates was used to measure the contribution of grain strain and the strain associated with grain boundary deformation.
137 citations
TL;DR: In this article, microstructural changes that occur during superplastic deformation of the Al-Cu eutectic alloy are considered, and it is shown that considerable modification occurs to the shapes and distribution of the inter-metallic CuAl2 particles during deformation.
Abstract: The microstructural changes that occur during superplastic deformation of the Al–Cu eutectic alloy are considered. It is shown that considerable modification occurs to the shapes and distribution of the inter-metallic CuAl2 particles during deformation. This effect may be understood in terms of sliding and diffusion-controlled shape changes associated with grain boundaries within the intermetallic. The roles of interface sliding and of diffusion creep in superplasticity are discussed.
59 citations
Patent•
18 Mar 1969
TL;DR: In this paper, a method of forming superplastic metal alloys by heating the alloy to a temperature at which it is super-plastic and then forming the alloy is presented.
Abstract: A method of forming superplastic metal alloys by heating the alloy to a temperature at which it is superplastic and then forming the alloy, in which the formed alloy is heated to a temperature above the superplastic temperature range in order to render it resistant to deformation before it is removed from the forming tool.
44 citations
22 citations
TL;DR: In this article, a more detailed examination of the creep behavior predicted by the theories showed that while recovery theories are good for normal creep, they are unsatisfactory for superplastic creep.
20 citations
Patent•
20 Aug 1969TL;DR: The microstructure and the impurity distribution in a solid which has been directionally solidified from a melt or solution can be strongly influenced by rubbing the solid-liquid interface during solidification.
Abstract: The microstructure and the impurity distribution in a solid which has been directionally solidified from a melt or solution can be strongly influenced by rubbing the solid-liquid interface during solidification. If the solid has two or more phases, a major effect will be the production of a fine-grain microstructure. The grains in addition to being small will be roughly equiaxial and not possess the usual columnar, dendritic and substructures. If the solid is single phase, the rubbing should break up the diffusion layer in the liquid, which is, typically, enriched in one or more of the constituents, and the equilibrium segregation coefficient between the solid and the liquid should be realized in normal freezing. Fine-grained microstructures have recently become of interest in the field of superplasticity and an important application of normal freezing of a single-phase material is in the desalination of water.
13 citations
TL;DR: In this paper, the Pb-Sn eutectic alloy in the superplastic state yielded velocity fields nearly identical with those obtained using lead, and the authors attributed the small differences observed in the velocity fields to differences in boundary friction.
Abstract: Flow studies in extrusion tests revealed that the Pb-Sn eutectic alloy in the superplastic state yielded velocity fields nearly identical with those obtained using lead. Slight differences observed in the velocity fields were attributed to differences in boundary friction. The test results appear to support the contention that the flow field within a plastically moving metal or alloy essentially is unique for identical boundary conditions. It is suggested that moderate variations in the properties of the material and in the flow condition will contribute only minor changes in the velocity distribution. Uniqueness is supported by the present results but not proved unequivocally.
10 citations
10 citations
TL;DR: In this paper, a theory for ductile fracture in a material with a strain-rate-sensitive yield stress is proposed, based on the hypothesis that fracture is the result of internal necking between adjacent microscopic cavities.
Abstract: A theory for ductile fracture in a material with a strain-rate-sensitive yield stress is proposed, based on the hypothesis that fracture is the result of internal necking between adjacent microscopic cavities. The theory is developed for a plane-strain element containing uniformly distributed cavities and this model is used to examine the effects of strain-rate-sensitivity on the strain to fracture in ductile materials. The results suggest possible explanations for both “blue-brittleness” behaviour and the “superplasticity” effect.
8 citations
6 citations
TL;DR: In this article, a design was developed which permitted the application of very low stresses stimulating quasistatic creep rates over a 20 to 1 strain range, as well as higher stress configurations required to produce significantly elevated creep rates.
Abstract: In conducting constant stress creep tests of ductile metals means must be provided to alter the applied load in response to changes in specimen geometry. Over the years a variety of automatic devices has been developed which compensates for the limited range of geometrical change usually encountered. Interest in superplastic metals exhibiting homogeneous plastic deformations of several hundred percent and total extensions of up to 2000% at almost zero applied stress levels creates the need to extend the techniques of creep testing. In this investigation it was desired to keep the test apparatus as simple as possible to permit its use in a variety of test programs, including elevated temperature and combined creep‐fatigue experiments. As a result, a design was developed which permitted the application of very low stresses stimulating quasistatic creep rates over a 20 to 1 strain range, as well as higher stress configurations required to produce significantly elevated creep rates. Test results with a low st...
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