dispersion hardened alloys (rus. сплавы, дисперсионно-твердеющие) — Alloys which strength is determined by dispersed particles released from supersaturated solid solution in the form of a new phase.

Description

Dispersion hardened alloys are a special class of dispersion-strengthened materials containing nanoparticles that inhibit dislocations’ motion. Various alloys build such structures in different ways. To produce such alloys, supersaturated solid solution is first prepared by quenching at the homogenisation temperature. Then it is aged by annealing, which leads to the formation of nanoparticles 100-1000 atoms in size. Plastic deformation of such alloys and the development of dislocations proceed either by cutting a particle if its size is small enough (respective shear stress is determined by the particle's material properties) or by bending it around to form a loop on a particle which is large enough (in this case the critical stress depends on the distance between the particles). As the aging time becomes longer the particle size increases and the transition process switches from the first dislocation development mechanism to the second. Dispersion hardened alloys reach their maximum strength at the aging stage which develops a structure whose deformation follows the first pattern, immediately before the transition to a structure of the second type.

Dispersion hardened aluminium alloys (duralumins) whose main components are copper and magnesium, were, apparently, one of the first examples where a controlled nanostructure of metal alloys was formed to improve their strength. The second historically important example of this type of alloy is the first heat-resistant nickel alloys for gas turbine engines: nimonics (the main alloying elements of nickel matrix were chromium, titanium and aluminium).

Authors

  • Lourie Sergey
  • Mileiko Sergey T.

Source

  1. A. Kelly. High-strength materials (in Russian). — Moscow: Mir, 1976. — 261 p.

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