PLASTIC COCRNI-BASED MEDIUM-ENTROPY ALLOY WITH 2.0 GPA-LEVEL ULTRA-HIGH YIELD STRENGTH AND PREPARATION METHOD THEREOF

Abstract

The present disclosure belongs to the field of preparation of high-performance alloy materials, and specifically relates to a plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength and a preparation method thereof. The alloy is prepared by melting and casting, homogenization treatment, solution heat treatment, cold deformation and aging heat treatment. After cold deformation and aging heat treatment, the prepared alloy has a dual heterogeneous microstructure due to the discontinuous precipitation of the strengthening phase and the incomplete recrystallization composition. The CoCrNi-based medium-entropy alloy of the present disclosure has ultra-high yield strength (2.0 GPa) and sufficient safety in use (uniform elongation of more than 8%), which can be processed into various forms of products, and has a wide range of applications in the production of fasteners used in the fields of aerospace, navigation, oil and gas, food processing, springs, non-magnetic components, and instrument parts.

Claims

1. A plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength, wherein comprising the following components in atomic percentage: Cr: 14-25%, Ni: 25-35%, Al: 4-7%, Ti: 4-7%, Mo: 0-5%, and the balance is Co.

2. The plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength according to claim 1, wherein comprising the following components in atomic percentage: Cr: 17-22%, Ni: 28-30%, Al: 5-6%, Ti: 5-6%, Mo: 0-2%, and the balance is Co.

3. The plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength of claim 1 with a composition selected from (Co.sub.40Ni.sub.30Cr.sub.20Al.sub.5Ti.sub.5).sub.0.995Mo.sub.0.5 (at. %), (Co.sub.43Ni.sub.30Cr.sub.15Al.sub.6Ti.sub.6 (at. %), (Co.sub.40Ni.sub.30Cr.sub.20Al.sub.5Ti.sub.5).sub.0.985Mo.sub.1.5 (at. %), (Co.sub.43Ni.sub.30Cr.sub.15Al.sub.6Ti.sub.6).sub.0.995Mo.sub.0.5 (at. %), (Co.sub.43Ni.sub.30Cr.sub.15Al.sub.6Ti.sub.6).sub.0.99Mo.sub.1 (at. %), (Co.sub.43Ni.sub.30Cr.sub.15Al.sub.6Ti.sub.6).sub.0.985Mo.sub.1.5 (at. %), (Co.sub.40Ni.sub.30Cr.sub.20Al.sub.5Ti.sub.5).sub.0.99Mo.sub.1 (at. %), (Co.sub.40Ni.sub.30Cr.sub.20Al.sub.5Ti.sub.5).sub.0.98Mo.sub.2 (at. %) and (Co.sub.40Ni.sub.30Cr.sub.20Al.sub.5Ti.sub.5).sub.0.98Mo.sub.2 (at. %).

4. The plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength of claim 1 having a uniform elongation of more than 8%.

5. The plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength of claim 1 formed into a fastener.

6. A method for preparing the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength according to claim 1, comprising the following steps: (1) Preparing an alloy according to the atomic percentage of claim 1 and melting into an ingot; (2) Homogenizing the ingot to form a homogenized casting; (3) Performing solution heat treatment on the homogenized casting to obtain an alloy casting with FCC single phase; (4) Performing cold deformation with a deformation of 70-90% on the casting after solution heat treatment; (5) Performing aging heat treatment on the cold deformed material to obtain the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength.

7. The method for preparing the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength according to claim 6, wherein in step (2), the homogenization treatment is performing heat preservation at 1000-1200° C. for 12-24 h, after the completion of the heat preservation, quenching to room temperature.

8. The method for preparing the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength according to claim 6, wherein in step (3), the solution heat treatment is performing heat preservation at 1150-1200° C. for 2-8 h, after the completion of the heat preservation, quenching to room temperature.

9. The method for preparing the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength according to claim 6, wherein in step (4), the cold deformation is cold rolling, or rotary swaging and/or drawing at room temperature.

10. The method for preparing the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength according to claim 6, wherein the temperature of the aging heat treatment is 600-800° C., and the time is 4-28 h.

11. A method for preparing the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength, comprising the following steps: (1) Preparing an alloy according to the atomic percentage of claim 1 and melting into an ingot; (2) Homogenizing the ingot to form a homogenized casting; (3) Performing solution heat treatment on the homogenized casting to obtain an alloy casting with FCC single phase; (4) Performing cold deformation with a deformation of 70-90% on the casting after solution heat treatment; (5) Performing aging heat treatment on the cold deformed material to obtain the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength.

12. The method for preparing the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength according to claim 11, wherein in step (2), the homogenization treatment is performing heat preservation at 1000-1200° C. for 12-24 h, after the completion of the heat preservation, quenching to room temperature.

13. The method for preparing the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength according to claim 11, wherein in step (3), the solution heat treatment is performing heat preservation at 1150-1200° C. for 2-8 h, after the completion of the heat preservation, quenching to room temperature.

14. The method for preparing the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength according to claim 11, wherein in step (4), the cold deformation is cold rolling, or rotary swaging and/or drawing at room temperature.

15. The method for preparing the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength according to claim 11, wherein the temperature of the aging heat treatment is 600-800° C., and the time is 4-28 h.

16. The method for preparing the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength according to claim 11, wherein the deformation is 80%.

17. The method for preparing the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength according to claim 11, wherein the alloy has a composition of (Co.sub.40Ni.sub.30Cr.sub.20Al.sub.5Ti.sub.5).sub.0.995Mo.sub.0.5 (at. %) and wherein the ingot was homogenized at 1200° C. for 12 h, the homogenized casting was subjected to solution heat treatment at 1200° C. for 12 h and quenched at room temperature, and the cold-deformed part was subjected to aging heat treatment at 650 C for 24 h.

18. The method for preparing the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength according to claim 11, wherein the alloy has a composition selected from (Co.sub.40Ni.sub.30Cr.sub.20Al.sub.5Ti.sub.5).sub.0.995Mo.sub.0.5 (at. %), (Co.sub.43Ni.sub.30Cr.sub.15Al.sub.6Ti.sub.6 (at. %), (Co.sub.40Ni.sub.30Cr.sub.20Al.sub.5Ti.sub.5).sub.0.985Mo.sub.1.5 (at. %), (Co.sub.43Ni.sub.30Cr.sub.15Al.sub.6Ti.sub.6).sub.0.995Mo.sub.0.5 (at. %), (Co.sub.43Ni.sub.30Cr.sub.15Al.sub.6Ti.sub.6).sub.0.99Mo.sub.1 (at. %), (Co.sub.43Ni.sub.30Cr.sub.15Al.sub.6Ti.sub.6).sub.0.985Mo.sub.1.5 (at. %), (Co.sub.40Ni.sub.30Cr.sub.20Al.sub.5Ti.sub.5).sub.0.99Mo.sub.1 (at. %), (Co.sub.40Ni.sub.30Cr.sub.20Al.sub.5Ti.sub.5).sub.0.98Mo.sub.2 (at. %) and (Co.sub.40Ni.sub.30Cr.sub.20Al.sub.5Ti.sub.5).sub.0.98Mo.sub.2 (at. %).

19. The method for preparing the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength according to claim 11 further comprising forming a fastener from said plastic CoCrNi-based medium-entropy alloy.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present disclosure will be further described in detail below in conjunction with the drawings and embodiments:

[0024] FIG. 1 shows the structure of uneven crystal grains obtained after aging heat treatment of the CoCrNi-based medium-entropy alloy with ultra-high mechanical properties in Example 1 of the present disclosure;

[0025] FIG. 2 shows the mechanical properties of the CoCrNi-based medium-entropy alloy with ultra-high mechanical properties in the tensile process at room temperature in Example 1 of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Example 1

[0026] (1) An alloy with a composition of (Co.sub.40Ni.sub.30Cr.sub.20Al.sub.5Ti.sub.5).sub.0.995Mo.sub.0.5 (at. %) was prepared, where the subscript of each element was the atomic percentage of the element, the alloy was melted into a 5 Kg ingot through a vacuum induction furnace;

[0027] (2) The ingot was homogenized at 1200° C./12 h and quenched to room temperature to obtain a homogenized casting;

[0028] (3) The homogenized casting was subjected to solution heat treatment at 1200° C./2 h and quenched to room temperature to obtain a single-phase alloy casting with face-centered cubic structure (FCC);

[0029] (4) The alloy casting after solution heat treatment was subjected to cold deformation (cold rolling or rotary swaging at room temperature) with a deformation of 80%;

[0030] (5) The cold-deformed part was subjected to aging heat treatment at 650° C./24 h to obtain the plastic CoCrNi-based medium-entropy alloy (sheet or bar) with ultra-high yield strength.

[0031] The microstructure of the obtained CoCrNi-based medium-entropy alloy is shown in FIG. 1. It can be seen that in the microstructure of the alloy, there are both nano-scale recrystallized matrix grain structure and micron-scale unrecrystallized structure, forming a strong heterogeneous structure.

[0032] The obtained alloy sample was stretched at a tensile rate of 10.sup.−3 s.sup.−1. The results are shown in FIG. 2. At room temperature, the tensile ductility of the sample reaches 10%, the yield strength reaches 2000 MPa, and the tensile strength reaches 2018 MPa.

Example 2

[0033] (1) An alloy with a composition of (Co.sub.43Ni.sub.30Cr.sub.15Al.sub.6Ti.sub.6 (at. %) was prepared, and melted into a 5 Kg ingot through a vacuum induction furnace;

[0034] (2) The ingot was homogenized at 1000° C./20 h and quenched to room temperature to obtain a homogenized casting;

[0035] (3) The homogenized casting was subjected to solution heat treatment at 1200° C./3 h and quenched to room temperature to obtain a single-phase alloy casting with face-centered cubic structure (FCC);

[0036] (4) The alloy casting after solution heat treatment was subjected to cold deformation (cold rolling or rotary swaging at room temperature) with a deformation of 75%;

[0037] (5) The cold-deformed part was subjected to aging heat treatment at 650° C./28 h to obtain the plastic CoCrNi-based medium-entropy alloy (sheet or bar) with ultra-high yield strength.

[0038] The obtained alloy sample was stretched at a tensile rate of 10.sup.−3 s.sup.−1. At room temperature, the tensile ductility of the sample reaches 8%, the yield strength reaches 1950 MPa, and the tensile strength reaches 1980 MPa.

Example 3

[0039] (1) An alloy with a composition of (Co.sub.40Ni.sub.30Cr.sub.20Al.sub.5Ti.sub.5).sub.0.985Mo.sub.1.5 (at. %) was prepared, and melted into a 5 Kg ingot through a vacuum induction furnace;

[0040] (2) The ingot was homogenized at 1100° C./24 h and quenched to room temperature to obtain a homogenized casting;

[0041] (3) The homogenized casting was subjected to solution heat treatment at 1200° C./4 h and quenched to room temperature to obtain a single-phase alloy casting with face-centered cubic structure (FCC);

[0042] (4) The alloy casting after solution heat treatment was subjected to cold deformation (cold rolling or rotary swaging at room temperature) with a deformation of 75%;

[0043] (5) The cold-deformed part was subjected to aging heat treatment at 700° C./12 h to obtain the plastic CoCrNi-based medium-entropy alloy (sheet or bar) with ultra-high yield strength.

[0044] The obtained alloy sample was stretched at a tensile rate of 10.sup.−3 s.sup.−1. At room temperature, the tensile ductility of the sample reaches 9%, the yield strength reaches 2001 MPa, and the tensile strength reaches 2012 MPa.

Example 4

[0045] (1) An alloy with a composition of (Co.sub.43Ni.sub.30Cr.sub.15Al.sub.6Ti.sub.6).sub.0.995Mo.sub.0.5 (at. %) was prepared, and melted into a 5 Kg ingot through a vacuum induction furnace;

[0046] (2) The ingot was homogenized at 1200° C./12 h and quenched to room temperature to obtain a homogenized casting;

[0047] (3) The homogenized casting was subjected to solution heat treatment at 1150° C./8 h and quenched to room temperature to obtain a single-phase alloy casting with face-centered cubic structure (FCC);

[0048] (4) The alloy casting after solution heat treatment was subjected to cold deformation (cold rolling or rotary swaging at room temperature) with a deformation of 80%;

[0049] (5) The cold-deformed part was subjected to aging heat treatment at 650° C./18 h to obtain the plastic CoCrNi-based medium-entropy alloy (sheet or bar) with ultra-high yield strength.

[0050] The obtained alloy sample was stretched at a tensile rate of 10.sup.−3 s.sup.−1. At room temperature, the tensile ductility of the sample reaches 10%, the yield strength reaches 1999 MPa, and the tensile strength reaches 2018 MPa.

Example 5

[0051] (1) An alloy with a composition of (Co.sub.43Ni.sub.30Cr.sub.15Al.sub.6Ti.sub.6).sub.0.99Mo.sub.1 (at. %) was prepared, and melted into a 5 Kg ingot through a vacuum induction furnace;

[0052] (2) The ingot was homogenized at 1200° C./12 h and quenched to room temperature to obtain a homogenized casting;

[0053] (3) The homogenized casting was subjected to solution heat treatment at 1200° C./4 h and quenched to room temperature to obtain a single-phase alloy casting with face-centered cubic structure (FCC);

[0054] (4) The alloy casting after solution heat treatment was subjected to cold deformation (cold rolling or rotary swaging at room temperature) with a deformation of 80%;

[0055] (5) The cold-deformed part was subjected to aging heat treatment at 700° C./18 h to obtain the plastic CoCrNi-based medium-entropy alloy (sheet or bar) with ultra-high yield strength.

[0056] The obtained alloy sample was stretched at a tensile rate of 10.sup.−3 s.sup.−1. At room temperature, the tensile ductility of the sample was reached 8%, the yield strength was reached 1990 MPa, and the tensile strength was reached 2018 MPa.

[0057] Example 6

[0058] (1) An alloy with a composition of (Co.sub.43Ni.sub.30Cr.sub.15Al.sub.6Ti.sub.6).sub.0.985Mo.sub.1.5 (at. %) was prepared, and melted into a 5 Kg ingot through a vacuum induction furnace;

[0059] (2) The ingot was homogenized at 1200° C./24 h and quenched to room temperature to obtain a homogenized casting;

[0060] (3) The homogenized casting was subjected to solution heat treatment at 1200° C./4 h and quenched to room temperature to obtain a single-phase alloy casting with face-centered cubic structure (FCC);

[0061] (4) The alloy casting after solution heat treatment was subjected to cold deformation (cold rolling or rotary swaging at room temperature) with a deformation of 80%;

[0062] (5) The cold-deformed part was subjected to aging heat treatment at 725° C./10 h to obtain the plastic CoCrNi-based medium-entropy alloy (sheet or bar) with ultra-high yield strength.

[0063] The obtained alloy sample was stretched at a tensile rate of 10.sup.−3 s.sup.−1. At room temperature, the tensile ductility of the sample reaches 8%, the yield strength reaches 1990 MPa, and the tensile strength reaches 2018 MPa.

Example 7

[0064] (1) An alloy with a composition of (Co.sub.40Ni.sub.30Cr.sub.20Al.sub.5Ti.sub.5).sub.0.99Mo.sub.1 (at. %) was prepared, and melted into a 5 Kg ingot through a vacuum induction furnace;

[0065] (2) The ingot was homogenized at 1200° C./18 h and quenched to room temperature to obtain a homogenized casting;

[0066] (3) The homogenized casting was subjected to solution heat treatment at 1200° C./4 h and quenched to room temperature to obtain a single-phase alloy casting with face-centered cubic structure (FCC);

[0067] (4) The alloy casting after solution heat treatment was subjected to cold deformation (cold rolling or rotary swaging at room temperature) with a deformation of 80%;

[0068] (5) The cold-deformed part was subjected to aging heat treatment at 700° C./18 h to obtain the plastic CoCrNi-based medium-entropy alloy (sheet or bar) with ultra-high yield strength.

[0069] The obtained alloy sample was stretched at a tensile rate of 10.sup.−3 s.sup.−1. At room temperature, the tensile ductility of the sample reaches 8%, the yield strength reaches 2003 MPa, and the tensile strength reaches 2020 MPa.

Example 8

[0070] (1) An alloy with a composition of (Co.sub.40Ni.sub.30Cr.sub.20Al.sub.5Ti.sub.5).sub.0.98Mo.sub.2 (at. %) was prepared, and melted into a 5 Kg ingot through a vacuum induction furnace;

[0071] (2) The ingot was homogenized at 1200° C./24 h and quenched to room temperature to obtain a homogenized casting;

[0072] (3) The homogenized casting was subjected to solution heat treatment at 1200° C./4 h and quenched to room temperature to obtain a single-phase alloy casting with face-centered cubic structure (FCC);

[0073] (4) The alloy casting after solution heat treatment was subjected to cold deformation (cold rolling or rotary swaging at room temperature) with a deformation of 80%;

[0074] (5) The cold-deformed part was subjected to aging heat treatment at 780° C./6 h to obtain the plastic CoCrNi-based medium-entropy alloy (sheet or bar) with ultra-high yield strength.

[0075] The obtained alloy sample was stretched at a tensile rate of 10.sup.−3 s.sup.−1. At room temperature, the tensile ductility of the sample reaches 8%, the yield strength reaches 1999 MPa, and the tensile strength reaches 2010 MPa.

Example 9

[0076] (1) An alloy with a composition of Co.sub.40Ni.sub.30Cr.sub.20Al.sub.5Ti.sub.5 (at. %) was prepared, and melted into a 5 Kg ingot through a vacuum induction furnace;

[0077] (2) The ingot was homogenized at 1200° C./24 h and quenched to room temperature to obtain a homogenized casting;

[0078] (3) The homogenized casting was subjected to solution heat treatment at 1200° C./4 h and quenched to room temperature to obtain a single-phase alloy casting with face-centered cubic structure (FCC);

[0079] (4) The alloy casting after solution heat treatment was subjected to cold deformation (cold rolling or rotary swaging at room temperature) with a deformation of 80%;

[0080] (5) The cold-deformed part was subjected to aging heat treatment at 600° C./28 h to obtain the plastic CoCrNi-based medium-entropy alloy (sheet or bar) with ultra-high yield strength.

[0081] The obtained alloy sample was stretched at a tensile rate of 10.sup.−3 s.sup.−1. At room temperature, the tensile ductility of the sample reaches 8%, the yield strength reaches 1990 MPa, and the tensile strength reaches 1980 MPa.