Thermomechanical processing of metallic materials
OwnerGino Palumboinventor
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Abstract
In the fabrication of components from a face centred cubic alloy, wherein the alloy is cold worked and annealed, the cold working is carried out in a number of separate steps, each step being followed by an annealing step. The resultant product has a grain size not exceeding 30 microns, a "special" grain boundary fraction not less than 60%, and major crystallographic texture intensities all being less than twice that of random values. The product has a greatly enhanced resistance to intergranular degradation and stress corrosion cracking, and possesses highly isotropic bulk properties.
Claims10
In the fabrication of articles from an austenitic stainless, iron-based or nickel-based face-centered cubic alloy wherein the alloy is subjected to cold working and annealing steps which are effective to produce recrystallization, the improvement which comprises selecting the number of said cold working and annealing steps so that said alloy is subjected to at least three cold working and annealing cycles to produce a special grain boundary fraction of at least 60%;
- each said cycle consisting of
- i) a cold working step in which the alloy is subjected to a forming reduction of up to 30%, and
- ii) an annealing step in which the alloy obtained from the cold working step is annealed at a temperature in the range of 900.degree.-1050.degree. C. for a time of 2-10 minutes.
In the fabrication of articles from a face-centered Fe- or Ni- based alloy wherein the alloy is subjected to cold working and annealing steps, said cold working and annealing steps being effective to produce recrystallization;
- the improvement which comprises randomizing grain texture and enhancing resistance of the alloy to intergranular degradation and increasing the special grain boundary fraction to at least 60% by performing said cold working and annealing steps so that said metal is subjected to:
- i) a cold working step in which the alloy is subjected to a forming reduction of up to 30%;
- ii) an annealing step in which the reduced alloy is annealed at a temperature in the range of 900.degree.-1050.degree. C. for a time of 2-10 minutes, and
- iii) repeating steps i) and ii) at least 3 times.
Dependencies are inferred from the claim text.