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Processing and Properties of Superplastic Alloys

  • T. H. Alden
Part of the Battelle Institute Materials Science Colloquia book series (volume 31)

Abstract

The special utility of superplastic alloys depends basically on the remarkable variation with temperature and grain size of the mechanical properties of ultrafine-grained materials. At the first level, the property may be the flow stress, which is extremely small at high temperature but increases rapidly as the temperature falls. This permits a variety of hot-working processes at small forces, yet provides the unique service toughness which is conferred by small grain size. In addition, superplastic alloys processed by free stretching at high temperature show unique ductility which allows single-die sheet forming into complex shapes. The engineering work on these processes is now in a fairly advanced state, especially for the Zn-Al eutectoid alloy and some titanium alloys.

Ultrafine grain size is achieved and maintained most easily (though not uniquely) in concentrated two-phase alloys. This restriction is a fairly severe one, especially since many such alloys contain intermediate phases which, while ductile at high temperature, are brittle at service temperatures. An additional requirement, if a homogeneous microstructure is to be achieved, is that the alloy be hot worked in an initially single-phase condition or at least that the phases be intimately mixed. The latter criterion is usually satisfied in as-cast eutectics, which are the most common type of superplastic alloy.

Keywords

Flow Stress Creep Rate Superplastic Behavior Superplastic Material Superplastic Alloy 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Plenum Press, New York 1977

Authors and Affiliations

  • T. H. Alden
    • 1
  1. 1.Metallurgy DepartmentU.B.C.VancouverCanada

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