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US-12624425-B2 - Alloy material, alloy product formed of alloy material, and mechanical device including alloy product

US12624425B2US 12624425 B2US12624425 B2US 12624425B2US-12624425-B2

Abstract

Provided is an alloy material in which coarse growth or aggregation and precipitation of an undesired intermetallic compound phase can be suppressed, an alloy product formed of the alloy material, and a mechanical device including the alloy product. The alloy material according to the present invention includes: 5 at % or more and 40 at % or less of each of Co, Cr, Fe, and Ni; more than 0 at % and 8 at % or less of Mo; 1 at % or more and less than 8 at % of Ti; more than 0 at % and 4 at % or less of at least one kind of Ta or Nb; and a remainder consisting of unavoidable impurities, in which a total content of Ti and the at least one kind of Ta or Nb is 3 at % or more and 8 at % or less. In the alloy product formed of the alloy material, a total occupancy of η phase and Laves phase precipitates having a size of 1 μm or more is suppressed to be 5 area % or less.

Inventors

  • Tatsuya Kimura
  • Hiroshi SHIRATORI
  • Kazuya Shinagawa
  • Kosuke Kuwabara
  • Yuzo Daigo

Assignees

  • PROTERIAL, LTD.

Dates

Publication Date
20260512
Application Date
20210929
Priority Date
20200929

Claims (7)

  1. 1 . An alloy material consisting of: 25 at % or more and 38 at % or less of Co; 16 at % or more and 23 at % or less of Cr; 12 at % or more and 20 at % or less of Fe; 17 at % or more and 28 at % or less of Ni; 1 at % or more and 7 at % or less of Mo; 1 at % or more and 4.5 at % or less of Ti; 0.5 at % or more and 4 at % or less of Ta; 0 at % or more and 4 at % or less of Nb; and a remainder being unavoidable impurities, wherein a total content of Ti, Ta, and Nb is 3 at % or more and 8 at % or less.
  2. 2 . The alloy material according to claim 1 , wherein the content of Ti is 2 at % or more and 4.5 at % or less.
  3. 3 . An alloy product that is formed of the alloy material according to claim 1 , wherein when a secondary electron image of a cross-section of the alloy product is observed with a scanning electron microscope, a total occupancy of n phase and Laves phase precipitates having a size of 1 μm or more is 5 area % or less.
  4. 4 . The alloy product according to claim 3 , wherein ultrafine particles having an average particle size of 130 nm or less are dispersed and precipitated in matrix crystal grains of the alloy product.
  5. 5 . A mechanical device comprising the alloy product according to claim 3 .
  6. 6 . The alloy material according to claim 1 , wherein the content of Mo is 2 at % or more and 7 at % or less.
  7. 7 . The alloy material according to claim 1 , wherein the content of Cr is 16 at % or more and 21 at % or less.

Description

TECHNICAL FIELD The present invention relates to a technique of an alloy having excellent corrosion resistance and mechanical characteristics and particularly relates to an alloy material called high-entropy alloy, an alloy product formed of the alloy material, and a mechanical device including the alloy product. BACKGROUND ART Recently, as alloys of a new technical idea that is clearly different from technical ideas of alloys in the related art (for example, alloys to which small amounts of multiple kinds of sub-component elements are added to one to three kinds of major component elements), high-entropy alloys (HEA)/multi-principal metal alloys (MPEA) have been proposed. HEA/MPEA are said to be alloys including at least four kinds of principal metal elements (each of which does not account for a majority and accounts for, for example, 5 to 35 at %), and are known to exhibit the following characteristics. Examples of the characteristics include: (a) stabilization of a mixed state caused by a negative increase in the mixing entropy term of the Gibbs free energy equation; (b) diffusion delay by a complex microstructure; (c) improvement of mechanical characteristics by high lattice strain caused by a difference in size between constituent atoms; and (d) improvement of corrosion resistance caused by a combined effect (also referred to as “cocktail effect”) of coexistence of multiple kinds of elements. For example, PTL 1 (WO2017/138191A) discloses an alloy member formed of a high-entropy alloy, the alloy member including: 5 at % or more and 35 at % or less of each of Co (cobalt), Ni (nickel), Cr (chromium), Fe (iron), and Ti (titanium); more than 0 at % and 8 at % or less of Mo (molybdenum); and a remainder consisting of unavoidable impurities, in which ultrafine particles having an average particle size of 40 nm or less are dispersed and precipitated in matrix crystal. According to PTL 1, an alloy member having excellent homogeneity in alloy composition and microstructure and excellent shape controllability that is formed of a high-entropy alloy having high mechanical strength and high corrosion resistance can be provided. In addition, PTL 2 (WO2019/088157A) discloses an alloy material including: 5 at % or more and 35 at % or less of each of Co, Cr, Fe, Ni, and Ti; more than 0 at % and less than 8 at % of Mo; more than 0 at % and 4 at % or less of an element having an atomic radius more than those of Co, Cr, Fe, and Ni; and a remainder consisting of unavoidable impurities. PTL 2 describes that an alloy material having higher mechanical characteristics and higher corrosion resistance can be provided by adding one or more kinds as elements having a larger atomic radius among Ta, Nb, Hf, Zr, and Y to the chemical composition of PTL 1 as a base. CITATION LIST Patent Literature PTL 1: WO2017/138191APTL 2: WO2019/088157A SUMMARY OF INVENTION Technical Problem In the alloy material described in PTL 1 or PTL 2, ultrafine particles are dispersed and precipitated in matrix crystal grains, and excellent mechanical characteristics and corrosion resistance higher than or equal to those of other Ni-based alloys or stainless steel are exhibited. However, in the alloy material, when an undesired intermetallic compound phase (for example, η phase (Ni3Ti phase) or Laves phase (Fe2Ti phase)) grows coarsely or aggregates and precipitates, mechanical characteristics (for example, tensile strength or ductility) deteriorate significantly. The present inventors investigated various applications assuming that the alloy material described in PTL 1 or PTL 2 is a base, and found that it becomes difficult to control precipitates as the volume of an alloy product to be manufactured increases. The present inventors conducted various investigations on the reason and considered that this phenomenon is affected by a difficult control of the cooling rate in a pseudo-solution heat treatment step caused by an increase in the heat capacity of the alloy product. From the viewpoint of the reliability or manufacturing yield of the alloy product, it is preferable that the alloy product exhibits expected characteristics with high reproducibility without an effect on the volume or heat capacity (hereinafter, referred to as volume/heat capacity). To that end, it is desired that coarse growth or aggregation and precipitation of the undesired intermetallic compound phase can be controlled and suppressed. Accordingly, an object of the present invention is to provide an alloy material in which coarse growth or aggregation and precipitation of an undesired intermetallic compound phase (for example, η phase (Ni3Ti-based phase) or Laves phase (Fe2Ti-based phase) can be suppressed, an alloy product formed of the alloy material, and a mechanical device including the alloy product. Solution to Problem (I) According to one aspect of the present invention, there is provided an alloy material including: 5 at % or more and 40 at % or less of each of Co, Cr, Fe, and Ni