CN113278895A

CN113278895A - A high-strength FeCrAl-based alloy

Info

Publication number: CN113278895A
Application number: CN202110491841.7A
Authority: CN
Inventors: 张广杰; 王先平; 杨俊峰; 李刚; 何琨; 刘瑞; 谢卓明; 张临超; 方前峰
Original assignee: Hefei Institutes of Physical Science of CAS; Nuclear Power Institute of China; Luan Institute of Anhui Institute of Industrial Technology Innovation
Current assignee: Hefei Institutes of Physical Science of CAS; Nuclear Power Institute of China; Luan Institute of Anhui Institute of Industrial Technology Innovation
Priority date: 2021-05-06
Filing date: 2021-05-06
Publication date: 2021-08-20

Abstract

The invention discloses a high-strength FeCrAl-based alloy, which relates to the technical field of nuclear fuel cladding materials. FeCrAl alloy powder and nano-ZrC and ZrH ₂ powder are first subjected to mechanical alloying ball milling treatment, and then spark plasma sintering is performed to obtain an ingot. Finally, the ingot is obtained by equal channel angular extrusion. According to the action principle of dispersion strengthening and grain boundary purification on the performance improvement of metal materials, in order to improve the comprehensive properties of FeCrAl, especially the elongation and strength, the nano-sized high-hard phase ZrC is dispersed and distributed at the grain boundaries and crystallites of FeCrAl. In the grain, the strength of FeCrAl is improved through the regulation of phase and grain boundaries; at the same time, in order to improve the plastic deformation ability of FeCrAl-ZrC, the purification effect of the grain boundary during the formation of metallic Zr and zirconium by ZrH ₂ is used to improve the elongation. In addition, the equal-channel angular extrusion process was introduced after spark plasma sintering, and high-density dislocations were introduced through large plastic deformation to further improve the comprehensive mechanical properties of FeCrAl‑ZrC‑ZrH ₂ .

Description

High-strength FeCrAl-based alloy

Technical Field

The invention relates to the technical field of nuclear fuel cladding materials, in particular to a high-strength FeCrAl-based alloy.

Background

The urgent need for clean energy makes the development of nuclear energy increasingly necessary, and nuclear energy safety is the central importance of the continued development of nuclear energy. To further increase the safety threshold of nuclear energy, accident-resistant fuel concepts have been proposed, and the most critical of these is the development of accident-resistant fuel cladding to replace the zirconium alloy cladding currently in use. As a material for the accident-resistant cladding, in addition to properties similar to those of zirconium alloy, such as high strength, low neutron absorption, radiation resistance, high thermal conductivity, etc., a high resistance to water vapor oxidation is required. The FeCrAl alloy has good comprehensive performance and extremely excellent steam oxidation resistance, so that the FeCrAl alloy is separated from other candidate accident-resistant cladding materials. At present, the preparation processes of FeCrAl-based alloy are mostly reported to be a vacuum melting-forging-hot rolling-normalizing-tempering process and a ball-milling powder mixing-SPS sintering (-forging) process, and although the preparation processes are mature, the mechanical properties of the prepared alloy need to be further improved. For example, the invention patent CN111809119A discloses a dispersion strengthening FeCrAl alloy material, which utilizes the ball-milling powder mixing-SPS sintering-forging process to prepare FeCrAl alloy with good processing property and stable structure, but the mechanical property of the FeCrAl alloy is required to be further improved.

Disclosure of Invention

Based on the technical problems in the background art, the invention provides a high-strength FeCrAl-based alloy which is prepared by adopting a process of mechanical alloying ball-milling powder mixing, discharge plasma sintering, equal channel angular extrusion, and has the advantages of simple preparation process, low cost and excellent comprehensive mechanical property.

A high-strength FeCrAl-base alloy is prepared from FeCrAl alloy powder, nano-ZrC and nano-ZrH₂The powder is firstly subjected to mechanical alloying ball milling treatment, then is subjected to discharge plasma sintering forming to obtain an ingot, and finally is subjected to equal channel angular pressing treatment to obtain the product.

Preferably, the annealing treatment is carried out after 1 pass of equal channel angular pressing is carried out on the cast ingot.

In the invention, the sample after extrusion is annealed to reduce the internal stress caused by large extrusion deformation.

Preferably, the process parameters of the annealing treatment are as follows: annealing at 600-750 deg.C for 40-80 min.

Preferably, the equal channel angular pressing treatment is pressing by adopting a C path; the extrusion was carried out using extrusion dies having an intersection angle of 90 °.

The C path refers to that the sample rotates 180 degrees around the extrusion direction after each extrusion and then carries out the next extrusion.

Preferably, the chemical composition of the FeCrAl alloy powder comprises the following components in percentage by weight: 12.5-13% of Cr, 3.6-4.0% of Al, 1.5-1.7% of Mo, less than or equal to 0.015% of P, less than or equal to 0.015% of S, less than or equal to 0.02% of O, less than or equal to 0.015% of N, and the balance of iron and impurities.

Preferably, the addition amount m of the nano ZrC powder_ZrCAnd weight m of FeCrAl alloy powder_FeCrAlThe relationship between them is: m is_ZrC/m_FeCrAl＝0.5～1.0wt.％。

Preferably, the nano ZrH₂Amount of powder added m_ZrH2And weight m of FeCrAl alloy powder_FeCrAlThe relationship between them is: m is_ZrH2/m_FeCrAl≤1.0wt.％。

Preferably, the ball milling treatment is dry milling in an inert atmosphere; the ball milling time is 18-22 h, and the ball-to-material ratio is 11-13: 1, the ball milling speed is 250-350 r/min.

Preferably, the spark plasma sintering is sintering in an argon atmosphere containing a small amount of hydrogen, and the volume percentage of hydrogen to argon is 3: 97.

has the advantages that: according to the principle of the effect of dispersion strengthening and grain boundary purification on the improvement of the performance of a metal material, in order to improve the comprehensive performance, particularly the elongation and the strength of FeCrAl, a nano-sized high-hardness phase ZrC is dispersed and distributed at the grain boundary and in the grain of FeCrAl, and the strength of FeCrAl is improved through the regulation and control of the phase boundary and the grain boundary; meanwhile, in order to improve the plastic deformation capability of FeCrAl-ZrC, ZrH is utilized₂The grain boundary purification effect during the formation of metal Zr and zirconium compounds is used for improving the elongation. In addition, an Equal Channel Angular Pressing (ECAP) process is introduced after spark plasma sintering, and FeCrAl-ZrC-ZrH is further improved through large plastic deformation₂The comprehensive mechanical property of (2); and annealing the extruded sample to reduce the internal stress caused by large extrusion deformation.

Drawings

FIG. 1 is a SEM of raw material powder and the corresponding size fraction in the example of the present inventionLaying out a layout; wherein, (a) FeCrAl, (b) ZrC and (c) ZrH₂；

FIG. 2 is a representation of FeCrAl +1 wt.% ZrC +0.2 wt.% ZrH prepared in an example of the present invention₂A comparison graph of mechanical properties of the alloy before and after equal channel angular extrusion treatment; wherein (a) ultimate tensile strength at room temperature, and (b) elongation.

Detailed Description

The chemical components of the FeCrAl alloy powder used in the following examples were Cr 12.71%, Al 3.7%, Mo 1.63%, P0.01%, S0.003%, O0.019%, N0.005%, and the balance iron and impurities; the average size of the particles was about 16.5um, and the morphology of the particles was as shown in FIG. 1 (a).

The average particle size of the nano ZrC powder used in the following examples is about 20.1nm, and the morphology of the particles is shown in FIG. 1 (b); nanometer ZrH₂The particle size of the powder is bimodal, the large particle size is mainly 4-6 μm, the small particle size is mainly 0.5-1 μm, and the particle morphology is shown in FIG. 1 (c).

The technical solution of the present invention will be described in detail below with reference to specific examples.

Examples

Preparation of FeCrAl +1 wt.% ZrC +0.2 wt.% ZrH₂Alloy (I)

S1, weighing 79.04g of FeCrAl alloy powder, 0.8g of nano ZrC powder and 0.16g of ZrH₂Adding the mixture into a ball milling tank, carrying out 3 times of gas washing on the ball milling tank by using Ar gas, finally filling the ball milling tank with the Ar gas and keeping micro-positive pressure, and then carrying out dry milling in a horizontal planetary ball mill, wherein the ball milling parameters are set as ball-material ratio of 12: 1, the rotating speed is 300r/min, the ball milling is stopped for 20min after 60min, the ball milling time is 20h, and the nano ZrH is obtained₂Fully and uniformly mechanically alloying ZrC and FeCrAl alloy powder, and taking out mixed powder in a ball milling tank after ball milling; the spherical FeCrAl is seriously deformed, ZrC and ZrH after the mechanized ball milling₂The particles are embedded in the FeCrAl or attached to the surface of the FeCrAl.

S2, pouring the mixed powder into a graphite mold with the diameter of phi 90mm (the size of the graphite mold can be designed according to the requirement in the specific implementation), and discharging in a discharge plasma sintering devicePlasma sintering to obtain FeCrAl alloy powder and ZrH₂Further alloying the nano ZrC powder to obtain an ingot;

FeCrAl +1 wt.% ZrC +0.2 wt.% ZrH formed by spark plasma sintering in S2 was measured₂The alloy had a hardness of 296.1Hv, an Ultimate Tensile Strength (UTS) of about 850MPa at room temperature, and an Elongation (Elongation) of about 18%.

S3, cutting the cast ingot into round bars with the diameter of 10 x 60mm, then carrying out ECAP extrusion treatment on an equal channel angular extrusion die according to a route C (namely, after each extrusion, the sample rotates 180 degrees around the extrusion direction and then carries out the next extrusion), wherein the intersection angle of the extrusion die is 90 degrees, the extruded sample is annealed at 700 ℃ for 1h in a heating furnace to reduce the internal stress caused by large extrusion deformation, the annealing treatment is carried out after each 1-time equal channel angular extrusion of the cast ingot, the extrusion-annealing operation is repeated, and the equal channel angular extrusion treatment is carried out on the cast ingot for 2 times.

FeCrAl +1 wt.% ZrC +0.2 wt.% ZrH after equal channel angular pressing in S3 was measured₂The hardness of the alloy is about 350Hv, the Ultimate Tensile Strength (UTS) at room temperature is about 1250MPa, and the Elongation (Elongation) is about 12%. The mechanical properties of the alloys obtained in S2 and S3 are compared with those of FIG. 2, and the data show that the tensile strength of the alloy is remarkably increased by introducing an ECAP or other channel angular pressing process after SPS sintering.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.

Claims

1. a high-strength FeCrAl-based alloy is characterized in that, FeCrAl alloy powder and nano _- ZrC, ZrH powder are first subjected to mechanical alloying ball milling processing, and then the ingot is obtained through spark plasma sintering molding, and the ingot is finally carried out etc. Channel corner extrusion processing.

2 . The high-strength FeCrAl-based alloy according to claim 1 , characterized in that annealing treatment is carried out after each pass of equal channel angular extrusion is carried out on the ingot. 3 .

3 . The high-strength FeCrAl-based alloy according to claim 2 , wherein the process parameters of the annealing treatment are: annealing at 600-750° C. for 40-80 minutes. 4 .

4. The high-strength FeCrAl-based alloy according to any one of claims 1-3, characterized in that, the equal-channel corner extrusion treatment adopts C path to extrude; the intersection angle of the extrusion die used for extrusion is 90°.

5 . The high-strength FeCrAl-based alloy according to claim 1 , wherein the chemical composition of the FeCrAl alloy powder, in terms of percentage by weight, comprises: Cr 12.5-13%, Al 3.6-4.0%, Mo 1.5-1.7% 5 . %, P≤0.015%, S≤0.015%, O≤0.02%, N≤0.015%, and the balance is iron and impurities.

6. The high-strength FeCrAl-based alloy according to claim 1, wherein the relationship between the addition amount m _ZrC of the nano ZrC powder and the weight m _FeCrAl of the FeCrAl alloy powder is: m _ZrC /m _FeCrAl =0.5 ~1.0%.

7. The high-strength FeCrAl-based alloy according to claim ₁ , wherein the relationship between the addition amount m ZrH of the nano ZrH powder and the weight m _FeCrAl of the _FeCrAl alloy powder is: m _ZrH /m _FeCrAl≤ 1.0%.

8 . The high-strength FeCrAl-based alloy according to claim 1 , wherein the ball-milling treatment is dry-milling in an inert atmosphere; the ball-milling time is 18-22 hours, the ball-to-material ratio is 11-13:1, and the ball-milling speed is 11-13:1. 9 . It is 250～350r/min.

9 . The high-strength FeCrAl-based alloy according to claim 1 , wherein the spark plasma sintering is sintered in an argon atmosphere containing a small amount of hydrogen, and the volume percentage of hydrogen and argon is 3:97. 10 .