A high-temperature oxidation-resistant and high-temperature softening-resistant high-strength Cu alloy and its preparation method

Abstract

A high-strength Cu alloy that is resistant to high-temperature oxidation and softening and a preparation method thereof belong to the field of high-temperature resistant copper alloys. By analyzing the enthalpy interactions between the basic components of the strengthening phase L12-type (Cu,Ni)3Al phase in the Cu-Ni-Al alloy and considering the synergistic addition of Cr and Zr elements, the atomic cluster formula is determined to be: m (Cu 98.99 / 100 Cr 0.89 / 100 Zr 0.12 / 100 )+{[Al‑Ni8Cu4]Al3}( m =0.5~2), and the alloy composition is regulated by adjusting the m value. The atomic percentage of the copper alloy is Cu: 49.00~72.00 at.%, Ni: 8.33~33.33 at.%, Al: 4.17~16.67 at.%, Cr: 0.30~0.65 at.%, and Zr: 0.04~0.08 at. Through the synergistic effect of Cr and Zr, the thermal stability of the L12-type (Cu,Ni)3Al phase is improved while avoiding conductivity loss, refining grains, pinning grain boundaries, and blocking oxygen diffusion channels, thereby improving the overall performance of the alloy. The series alloy has an electrical conductivity of 4.88-12.5%IACS, a hardness of 195-280HV, an ultimate tensile strength of 620-870MPa, and an oxidation rate of 0.1-0.4mg / cm at 850°C. 2 (Within 200 hours), the softening temperature is higher than 1000℃.

Description

Technical Field

[0001] The invention relates to a high-temperature oxidation-resistant and high-temperature softening-resistant high-strength Cu-based conductive alloy and a preparation method thereof, belonging to the technical field of high-temperature resistant copper alloys. Background Art

[0002] Copper alloys, with their excellent comprehensive mechanical properties and electrical and thermal conductivity, are widely used in research fields such as power generation, chemical engineering, metallurgy, and aerospace. With the advancement of advanced technologies, Cu alloys are increasingly required to operate under demanding conditions such as high temperatures and heavy loads. Examples include slot wedge alloys for large, high-speed turbine generator rotors, lining materials for rocket engine combustion and thrust chambers, and inert anodes for aluminum electrolysis. These practical operating conditions place higher demands on Cu alloys' strength, electrical conductivity, and resistance to high-temperature softening and oxidation.

[0003] So far, high-strength thermally stable copper alloys are mainly aluminum bronze, but their high temperature resistance and service temperature are limited. 69.77 Al 20.54 Fe 4.96 Ni 4.72 (at.%) alloy (C63000), its softening resistance temperature does not exceed 650℃ and can only ensure stable service below 400℃. In ZL201710513961.6, the softening resistance temperature of Cu-Ni-Al alloy is increased to 1000℃ by the cubic checkerboard L12-type (Cu,Ni)3Al phase. However, in this system, the chaotic occupancy of Cu and Ni leads to a large amount of Cu dissolved in the L12-type (Cu,Ni)3Al phase, which reduces its stability to a certain extent and is easy to dissolve back at high temperatures. In addition, Cu is a metal resistant to medium and low temperature oxidation, but under high temperature conditions, Cu will undergo severe oxidation, which is very unfavorable for high temperature service. It is obviously impossible to solve the above problems in the ternary alloy system. It is necessary to develop new high-temperature resistant Cu alloys by rationally adding alloying elements to meet industrial needs. Summary of the Invention

[0004] In order to solve the deficiencies in the prior art, the present invention proposes a high-temperature oxidation-resistant and high-temperature softening-resistant high-strength Cu alloy designed based on a cluster method and a preparation method thereof. In order to improve the oxidation resistance of the Cu-Ni-Al alloy on the basis of ensuring its softening resistance, strength and electrical conductivity, Cr and Zr are selected for synergistic addition. The thermal stability of the L12 type (Cu, Ni) 3Al phase is improved by the solid solution of alloying elements, and the high melting point single Cr phase is introduced. At the same time, the grain boundary segregation of the Zr element and the precipitation of the single Cr phase at the grain boundary are used to improve the grain boundary cohesion, pin the grain boundary and hinder the diffusion channel of the grain boundary oxygen. The addition amount of Cr and Zr elements is based on the cluster formula m(Cu 98.99 / 100 Cr 0.89 / 100 Zr0.12 / 100 )+{[Al-Ni8Cu4]Al3}(m=0.5~2) determined.

[0005] The technical solution adopted by the present invention is: a high-temperature oxidation-resistant and high-temperature softening-resistant high-strength Cu-based conductive alloy designed based on a cluster method, wherein the atomic percentage of the Cu-based conductive alloy composition is Cu: 49.00-72.00 at.%, Ni: 8.33-33.33 at.%, Al: 4.17-16.67 at.%, Cr: 0.30-0.65 at.%, and Zr: 0.04-0.08 at.%;

[0006] The atomic cluster formula of the conductive alloy is: m(Cu 98.99 / 100 Cr 0.89 / 100 Zr 0.12 / 100 )+{[Al-Ni8Cu4]Al3}, where m=0.5~2, and the alloy composition is controlled by adjusting the m value.

[0007] The phase composition of the alloy changes with the increase of Cu content. When the Cu content is 49.00at.%≤Cu at.%≤62.00at.%, where the atomic cluster formula is 0.5≤m≤1, the alloy structure consists of a Cu-based solid solution with an FCC structure, an L12-type (Cu, Ni)3(Al, Cr) phase precipitated within the grain, and an L12-type (Cu, Ni)3(Al, Cr) phase precipitated at the grain boundaries. When the Cu content is 62.00at.%<Cu at.%≤72.00at.%, where the atomic cluster formula is 1<m≤2, the phase composition is a Cu-based solid solution with an FCC structure, a nanoscale elemental Cr phase precipitated within the grain, a coherent L12-type (Cu, Ni)3(Al, Cr) phase precipitated within the grain, and a micrometer-scale elemental Cr phase precipitated at the grain boundaries.

[0008] The performance indicators of the alloy are: electrical conductivity 4.88-12.5% ​​IACS, hardness 195-280HV, ultimate tensile strength 620-870MPa, oxidation rate at 850℃ within 200 hours 0.1-0.4mg / cm 2 , the softening temperature is higher than 1000℃.

[0009] A method for preparing a high-strength Cu-based conductive alloy that is resistant to high-temperature oxidation and softening: preparing Cu, Ni, Al, Cr, and Zr raw materials according to the weight percentage conversion of the Cu-based conductive alloy;

[0010] Using non-consumable vacuum arc melting and high-purity argon protection, the prepared Cu, Ni, Al, Cr and Zr raw materials with a purity of more than 4N are repeatedly melted to obtain alloy ingots with uniform composition;

[0011] The melting point of the molten alloy was obtained using a thermogravimetric analyzer, and the alloy was dissolved at a temperature 100°C lower than the melting point, kept warm for 6 hours, and then air-cooled. Subsequently, the alloy was aged at 900°C for 4 hours and then cooled with the furnace. Finally, the alloy was aged at 450°C for 4 hours.

[0012] By analyzing the enthalpy interaction between the basic components of the L12 type (Cu,Ni)3Al phase in the Cu-Ni-Al alloy, it is determined that Al is the central atom, Ni and Cu are shell atoms, and Cu is the connecting atom. The cluster formula is determined to be [Al-Ni8Cu4]Al3. The solid solubility of Cr and Zr elements in Cu is relatively small, and their addition amount is determined according to their maximum solid solubility in Cu. Therefore, the cluster formula of Cu-Ni-Al-Cr-Zr alloy is expressed as m(Cu 98.99 / 100 Cr 0.89 / 100 Zr 0.12 / 100 )+{[Al-Ni8Cu4]Al3}(m=0.5-2), by adjusting the m value, a high-temperature oxidation-resistant and high-temperature softening-resistant high-strength Cu alloy composition designed based on a cluster-based approach is determined. The Cu alloy includes components in atomic percentages of Cu: 49.00-72.00 at.%, Ni: 8.33-33.33 at.%, Al: 4.17-16.67 at.%, Cr: 0.30-0.65 at.%, and Zr: 0.04-0.08 at.%.

[0013] The alloy's phase composition changes with increasing Cu content, transforming from an FCC-structured Cu-based solid solution, intragranular L12-type (Cu, Ni)3(Al, Cr) phases, and grain boundary L12-type (Cu, Ni)3(Al, Cr) phases to an FCC-structured Cu-based solid solution, intragranular nanoscale elemental Cr phases, intragranular coherent L12-type (Cu, Ni)3(Al, Cr) phases, and grain boundary micron-sized elemental Cr phases. The Cu-Ni-Al-Cr-Zr alloy has an electrical conductivity of 5.5-17.8% IACS, a hardness of 195-280 HV, an ultimate tensile strength of 620-870 MPa, and an oxidation rate of 0.1-0.4 mg / cm at 850°C. 2 (within 200 hours), the softening resistance temperature is higher than 1000℃.

[0014] The method for preparing a high-strength Cu alloy that is resistant to high-temperature oxidation and softening at high temperature based on a cluster method design:

[0015] (1) Using non-consumable vacuum arc melting and high-purity argon protection, the prepared Cu, Ni and Al raw materials with a purity of more than 4N are repeatedly melted to obtain an alloy ingot with uniform composition;

[0016] (2) The melting point of the molten alloy was obtained using a thermogravimetric analyzer; the alloy was solutionized at a temperature 100°C lower than the melting point, kept at that temperature for 6 hours, and then air-cooled; subsequently, the alloy was aged at 900°C for 4 hours and then cooled with the furnace; finally, the alloy was aged at 450°C for 4 hours.

[0017] The beneficial effects of the present invention are:

[0018] 1. By analyzing the enthalpy interactions of the Cu-Ni-Al-Cr-Zr alloy and the basic components of the strengthening L12-type (Cu,Ni)3Al phase in the Cu-Ni-Al alloy, Al was identified as the central atom, Ni and Cu as shell atoms, and Cu as the connecting atom. The cluster formula was determined to be [Al-Ni8Cu4]Al3. This alloy cluster formula was obtained to rationally configure the content of each component, which is simple and convenient, avoiding multiple attempts to control the alloy composition.

[0019] 2. Cr is an antioxidant element with a very low solid solubility in Cu. It improves the thermal stability of the L12 (Cu,Ni)3Al phase and the alloy's oxidation resistance while avoiding a loss in electrical conductivity. Zr can refine grains and segregate at grain boundaries, improving the grain refinement and strengthening effect while blocking oxygen diffusion channels.

[0020] When the Cu content is 49.00 at.% ≤ Cu at.% ≤ 62.00 at.%, and the atomic cluster formula is 0.5 ≤ m ≤ 1, the alloy structure consists of an FCC structured Cu-based solid solution, an L12-type (Cu, Ni) 3 (Al, Cr) phase precipitated within the grain, and an L12-type (Cu, Ni) 3 (Al, Cr) phase precipitated at the grain boundary.

[0021] When the Cu content is 62.00at.%<Cu at.%≤72.00at.%, and the atomic cluster formula is 1<m≤2, the phase composition of the alloy is FCC structure Cu-based solid solution, nanoscale elemental Cr phase precipitated within the crystal, coherent L12 type (Cu,Ni)3(Al,Cr) phase precipitated within the crystal, and micron-scale elemental Cr phase precipitated at the grain boundary.

[0022] The synergistic effect of Cr and Zr ensures the mechanical properties, electrical properties, high temperature softening resistance and high temperature oxidation resistance of the alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Cu after aging treatment 49.66 Ni 33.33 Al 16.67 Cr 0.30 Zr 0.04 (at.%) SEM secondary electron image of the alloy.

[0024] Figure 2Cu after aging treatment 62.00 Ni 25.00 Al 12.50 Cr 0.44 Zr 0.06 (at.%) SEM secondary electron image of the alloy.

[0025] Figure 3 Cu after aging treatment 72.00 Ni 18.18 Al 9.09 Cr 0.65 Zr 0.08 (at.%) SEM secondary electron image of the alloy. DETAILED DESCRIPTION

[0026] The specific embodiments of the present invention are described in detail below in conjunction with the technical solutions.

[0027] Example 1: Cu 49.66 Ni 33.33 Al 16.67 Cr 0.30 Zr 0.04 (at.%) alloy

[0028] Step 1: Alloy preparation and microstructure characterization

[0029] The composition is Cu 49.66 Ni 33.33 Al 16.67 Cr 0.30 Zr 0.04 The alloy was prepared using 4N pure Cu and Ni and 5N pure Al raw materials, with the concentration of at. % alloy converted to weight percentage. The prepared alloy raw materials were repeatedly melted five times in a non-consumable vacuum arc melting furnace under high-purity Ar gas protection, ultimately producing an alloy ingot with uniform composition. A thermogravimetric analyzer determined the alloy's melting point to be 1250°C, so a solution temperature of 1250°C was selected. The melted alloy was placed in a vacuum tube furnace and heat treated in an Ar atmosphere at a temperature of 1250°C for 6 hours, followed by air cooling at 900°C for 4 hours, furnace cooling at 450°C for 4 hours, and furnace cooling at 450°C.

[0030] Step 2: Characterization of alloy structure and properties

[0031] The X-ray diffraction analysis of the heat-treated sample was carried out using a German Bruker D8 FOCUS X-ray diffractometer. The alloy consists of a FCC structure Cu-based solid solution, L12 type (Cu, Ni) 3 (Al, Cr) phase precipitated within the grain, and L12 type (Cu, Ni) 3 (Al, Cr) phase precipitated at the grain boundary. The microstructure morphology is as follows: Figure 1The alloy has an electrical conductivity of 4.88% IACS, a hardness of 262.3 HV, a tensile strength of 870 MPa, and an oxidation rate of 0.15 mg / cm at 850 °C. 2 (Within 200 hours). According to GB / T33370-2016 "Measurement method of softening temperature of copper and copper alloys", the softening temperature of the alloy is higher than 1000℃.

[0032] Example 2: Cu 62.00 Ni 25.00 Al 12.50 Cr 0.44 Zr 0.06 (at.%) alloy

[0033] Step 1: Alloy preparation and microstructure characterization

[0034] The composition is Cu 62.00 Ni 25.00 Al 12.50 Cr 0.44 Zr 0.06 The alloy was prepared using 4N pure Cu and Ni and 5N pure Al raw materials, with the concentration of at. (at.%) converted to weight percentage. The alloy was then repeatedly smelted five times in a non-consumable vacuum arc melting furnace under high-purity Ar gas protection, ultimately yielding an alloy ingot with uniform composition. A thermogravimetric analyzer determined the alloy's melting point to be 1210°C, so a solution temperature of 1110°C was selected. The melted alloy was then heat treated in an Ar atmosphere in a vacuum tube furnace at 1110°C for 6 hours, followed by air cooling at 900°C for 4 hours, furnace cooling at 450°C for 4 hours, and furnace cooling.

[0035] Step 2: Characterization of alloy structure and properties

[0036] The X-ray diffraction analysis of the heat-treated sample was carried out using a German Bruker D8 FOCUS X-ray diffractometer. The alloy consists of a FCC structure Cu-based solid solution, L12 type (Cu, Ni) 3 (Al, Cr) phase precipitated within the grain, and L12 type (Cu, Ni) 3 (Al, Cr) phase precipitated at the grain boundary. The microstructure morphology is as follows: Figure 2 The alloy has an electrical conductivity of 5.89% IACS, a hardness of 280 HV, a tensile strength of 780 MPa, and an oxidation rate of 0.15 mg / cm at 850 °C. 2 (Within 200 hours). According to GB / T33370-2016 "Measurement method of softening temperature of copper and copper alloys", the softening temperature of the alloy is higher than 1000℃.

[0037] Example 3: Cu 72.00 Ni 18.18 Al 9.09 Cr0.65 Zr 0.08 (at.%) alloy

[0038] Step 1: Alloy preparation and microstructure characterization

[0039] The composition is Cu 72.00 Ni 18.18 Al 9.09 Cr 0.65 Zr 0.08 The alloy was prepared using 4N pure Cu and Ni and 5N pure Al raw materials, with the alloy converted to weight percentage. The prepared alloy raw materials were repeatedly melted five times in a non-consumable vacuum arc melting furnace under high-purity Ar gas protection, ultimately producing an alloy ingot with uniform composition. The melting point of the alloy was determined to be 1180°C using a thermogravimetric analyzer, so a solution temperature of 1080°C was selected. The melted alloy was placed in a vacuum tube furnace and heat treated in an Ar atmosphere at 1080°C for 6 hours, followed by air cooling at 900°C for 4 hours, furnace cooling at 450°C for 4 hours, and furnace cooling at 450°C.

[0040] Step 2: Characterization of alloy structure and properties

[0041] The X-ray diffraction analysis of the heat-treated sample was carried out using a German Bruker D8 FOCUS X-ray diffractometer. The alloy consists of an FCC structure Cu-based solid solution, nano-scale elemental Cr phase precipitated within the crystal, coherent L12-type (Cu, Ni) 3 (Al, Cr) phase precipitated within the crystal, and micron-scale elemental Cr phase precipitated at the grain boundary. The microstructure morphology is as follows: Figure 3 The alloy has an electrical conductivity of 11.17% IACS, a hardness of 196 HV, a tensile strength of 803 MPa, and an oxidation rate of 0.30 mg / cm at 850 °C. 2 (Within 200 hours). According to GB / T33370-2016 "Measurement method of softening temperature of copper and copper alloys", the softening temperature of the alloy is higher than 1000℃.

Claims

1. A method for preparing a high-strength Cu-based conductive alloy that is resistant to high-temperature oxidation and high-temperature softening, characterized in that: The atomic percentages of the Cu-based conductive alloy components are Cu: 49.00-72.00 at.%, Ni: 8.33-33.33 at.%, Al: 4.17-16.67 at.%, Cr: 0.30-0.65 at.%, and Zr: 0.04~0.08 at.%; The atomic cluster formula of the conductive alloy is: m (Cu 98.99 / 100 Cr 0.89 / 100 Zr 0.12 / 100 )+{[Al-Ni8Cu4]Al3}, where m =0.5~2, the alloy composition is regulated by adjusting the m value; According to the weight percentage of the above-mentioned Cu-based conductive alloy, Cu, Ni, Al, Cr and Zr raw materials are prepared; Using non-consumable vacuum arc melting and high-purity argon protection, the prepared Cu, Ni, Al, Cr and Zr raw materials with a purity of more than 4N are repeatedly melted to obtain alloy ingots with uniform composition; The melting point of the molten alloy was obtained using a thermogravimetric analyzer, and the alloy was dissolved at a temperature 100°C lower than the melting point, kept at this temperature for 6 hours, and then air-cooled. Subsequently, high-temperature aging at 900°C for 4 hours was carried out with furnace cooling; finally, low-temperature aging at 450°C for 4 hours was carried out.

2. A high-strength Cu-based conductive alloy that is resistant to high-temperature oxidation and softening, designed based on a cluster-based approach, characterized by: The preparation method according to claim 1 is used to prepare the product.

3. The high-temperature oxidation-resistant and high-temperature softening-resistant high-strength Cu-based conductive alloy according to claim 2, characterized in that: The alloy phase composition changes with the increase of Cu content. When Cu content is 49.00 at.%≤Cu at.%≤62.00 at.%, the atomic cluster formula is: 0.5≤ m When ≤1, the alloy structure consists of FCC structure Cu-based solid solution, L12 type (Cu, Ni)3(Al, Cr) phase precipitated in the grain, and L12 type (Cu, Ni)3(Al, Cr) phase precipitated at the grain boundary; When Cu content: 62.00 at.%<Cu at.%≤72.00 at.%, atomic cluster formula: 1< m When ≤2, the phase composition is FCC structure Cu-based solid solution, nano-scale elemental Cr phase precipitated in the crystal, coherent L12 type (Cu, Ni)3(Al,Cr) phase precipitated in the crystal, and micron-scale elemental Cr phase precipitated at the grain boundary.

4. A high-temperature oxidation-resistant and high-temperature softening-resistant high-strength Cu-based conductive alloy according to any one of claims 2-3, characterized in that: The performance indicators of the alloy are: electrical conductivity 4.88-12.5%IACS, hardness 195-280HV, ultimate tensile strength 620-870MPa, oxidation rate at 850℃ within 200 hours 0.1-0.4mg / cm 2 , the softening temperature is higher than 1000℃.

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