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Metallurgical and Materials Transactions B

, Volume 3, Issue 11, pp 2835–2842 | Cite as

Laves phase precipitation in Fe-Ta alloys

  • Russell H. Jones
  • V. F. Zackay
  • E. R. Parker
Alloy Phases and Structure

Abstract

Development of an iron-base alloy hardened by particles of an intermetallic compound rather than a carbide is a desirable goal because of the greater thermal stability of such a dispersion. As a first step in the development of iron-base alloys hardened with the Laves phase, structural studies of binary Fe-Ta alloys have been undertaken. The structures of two phase Fe-Ta alloys have been studied by means of optical and transmission electron microscopy, X-ray diffraction, electron beam microprobe analysis, and scanning electron microscopy. The hardness change as a function of time at 600°, 700°, and 800°C has been determined for binary alloys with 1 at. pct Ta and 2 at. pct Ta in iron. Also, the uniaxial tensile strengths of solution treated, quenched, and aged samples have been determined. These studies suggest that the compound, Fe2Ta, is isomorphous with the structure type, MgZn2, (C14) and has a range of compositional homogeneity. The latter results correspond with the predictions of the Engel-Brewer correlation. Also, it has been found that precipitation occurs at grain boundaries, dislocations, and randomly throughout the matrix. Particles which form at dislocations have a (100)α habit plane; whereas a (110)α habit plane has been reported by others1,3 for the hexagonal Laves phase in α iron. Hypereutectoid composition alloys quenched from the ö phase field have a completely retained § structure. Isothermal decomposition at 600°, 700°, and 800°C of alloys with the retained § structure results in a sizable hardness increase in 2 at. pct Ta alloys but only a modest increase in 1 at. pct Ta alloys. Brittle fracture of aged tensile specimens tested at room temperature reveals that the ductile-brittle transition temperature in tension is above room temperature.

Keywords

Habit Plane Lave Phase Isothermal Decomposition Uniaxial Tensile Strength Boundary Allotriomorphs 
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

© The Metallurgical of Society of AIME 1972

Authors and Affiliations

  • Russell H. Jones
    • 1
  • V. F. Zackay
    • 2
  • E. R. Parker
    • 2
  1. 1.Westinghouse Research LaboratoriesPittsburgh
  2. 2.Department of Materials Science and EngineeringUniversity of CaliforniaBerkeley

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