A heat treatment method for achieving ultra-high strength of aluminum bronze alloy

Abstract

The present invention belongs to the technical field of thermal processing of copper alloy materials, and specifically relates to a heat treatment method for achieving ultra-high strength of QAl11-6-6 aluminum bronze alloy, characterized by comprising the following main steps: 1) cutting extruded or centrifugally cast QAl11-6-6 aluminum bronze alloy tubes and bars into fixed lengths or machining them into parts, holding them at a temperature of 0.5 to 2.0 hours for a first high-temperature heat treatment, and immediately quenching and cooling them in room temperature water after being removed from the furnace; 2) holding them at a temperature of 2 to 4 hours for a second high-temperature heat treatment, and air-cooling them after being removed from the furnace; 3) holding them at a temperature of 2 to 4 hours for a low-temperature heat treatment, and air-cooling them after being removed from the furnace; and 4) performing another electric pulse treatment at 500°C for 1 to 8 minutes, followed by air cooling. The QAl11-6-6 aluminum bronze tube, bar or machined parts prepared by the special heat treatment method of the present invention have a tensile strength of 1116 MPa, a yield strength of 1021 MPa, and an elongation of 5.9%. They can replace imports and are used to manufacture key structural parts under special working conditions such as heavy load, heavy pressure, severe wear, and severe corrosion.

Description

Technical Field

[0001] The invention belongs to the technical field of thermal processing of copper alloy materials, and in particular relates to a special heat treatment method for achieving ultra-high strength of aluminum bronze alloy. Background Art

[0002] Highly alloyed QAl11-6-6 aluminum bronze has the strength, hardness and wear resistance of high-strength steel, while its corrosion resistance, oleophilic lubrication, and heat dissipation properties are all better than those of high-strength steel. Ultra-high-strength QAl11-6-6 aluminum bronze, with a yield strength and tensile strength of over 1000 MPa, is usually used to replace imports and is used to manufacture key structural parts under special working conditions such as heavy loads, heavy pressure, strong wear, and strong corrosion, solving the problem of key materials. QAl11-6-6 aluminum bronze is a heat-treatable copper alloy, and a "solid solution + aging" heat treatment method is generally used to achieve an increase in its strength and hardness. However, in order to make the alloy parts achieve ultra-high strength of over 1000 MPa in yield strength and tensile strength, while having good plastic toughness (elongation after fracture is not less than 3.5%), it is impossible to achieve this using the conventional "solid solution + aging" heat treatment method. Further increasing the content of alloying elements like Al, Fe, and Ni can improve the alloy's strength and hardness, but this significantly reduces its plasticity and toughness, making it extremely difficult to form and machine. Therefore, my country currently relies primarily on imports for the ultra-high-strength aluminum bronze required for certain specialized applications. Developing a specialized heat treatment based on the existing QAl11-6-6 aluminum bronze composition to achieve the ultra-high strength required for these applications has become an urgent challenge for the industry. Summary of the Invention

[0003] The purpose of the present invention is to provide a heat treatment method for achieving ultra-high strength of QAl11-6-6 aluminum bronze alloy, so as to solve the key material problems under special working conditions in important fields in my country.

[0004] The present invention provides a heat treatment method for achieving ultra-high strength of QAl11-6-6 aluminum bronze alloy, which includes four steps: two high-temperature heat treatments, one low-temperature heat treatment, and one electric pulse treatment. The operation method is as follows:

[0005] Step 1: Cut the extruded or centrifugally cast QAl11-6-6 aluminum bronze alloy tube and rod into fixed lengths or machine them into parts, place them in a resistance furnace heated to 850-950°C and keep them warm for 0.5-2.0 hours for the first high-temperature heat treatment, and immediately quench and cool them in room temperature water after taking them out of the furnace.

[0006] Step 2: Place the QAl11-6-6 aluminum bronze alloy tubes and bars or machined parts that have undergone the first high-temperature heat treatment in a resistance furnace heated to (750-850)°C for 2-4 hours for a second high-temperature heat treatment, and then air-cool after being taken out of the furnace;

[0007] Step 3: Place the QAl11-6-6 aluminum bronze alloy tubes and bars or machined parts that have undergone the second high-temperature heat treatment in a resistance furnace heated to (450-550)°C for 2-4 hours for low-temperature heat treatment, and then air-cool after being taken out of the furnace;

[0008] Step 4: The QAl11-6-6 aluminum bronze alloy tube, bar or machined parts that have undergone low-temperature heat treatment are subjected to an electric pulse treatment at 500°C for 1 to 8 minutes, followed by air cooling.

[0009] Preferably, the first high-temperature heat treatment parameters in step 1 are: keeping warm in a resistance furnace at 880-920° C. for 0.5-1.0 hour, and immediately quenching and cooling in room temperature water after being taken out of the furnace.

[0010] Preferably, the second high-temperature heat treatment parameters in step 2 are: keeping warm in a resistance furnace at 780-820° C. for 2.5-3.3 hours, and air cooling after being taken out of the furnace.

[0011] Preferably, the low-temperature heat treatment parameters in step 3 are: keeping warm in a resistance furnace at 480-520° C. for 2-3 hours, and air cooling after being taken out of the furnace.

[0012] Preferably, the electric pulse treatment parameters in step 4 are: the QAl11-6-6 aluminum bronze alloy tubes and bars or machined parts that have undergone low-temperature heat treatment are subjected to another electric pulse treatment at 500°C for (3-5) min, followed by air cooling. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0014] Figure 1 This is the metallographic structure of the sample of Example 1 of the present invention;

[0015] Figure 2 This is the metallographic structure of the sample of Example 2 of the present invention;

[0016] Figure 3 This is the metallographic structure of the sample of Comparative Example 1 of the present invention;

[0017] Figure 4 This is the metallographic structure of the sample of Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0018] The technical principle of the present invention is briefly described as follows: QAl11-6-6 aluminum bronze alloy tubes and bars, extruded or centrifugally cast, are cut into lengths or machined into parts. A first high-temperature, short-term heat treatment is performed at 850-950°C for 0.5-1.0 hours to promote the decomposition of the second phase in the alloy and allow the solute atoms in the alloy to dissolve in the copper matrix. A second high-temperature, long-term heat treatment is then performed at 750-850°C for 2-4 hours to promote the full dissolution of alloying elements such as Al, Fe, and Ni in the copper matrix. After solutionization, the alloy is immediately removed from the furnace and quenched in room-temperature water to strongly inhibit the high-temperature precipitation of the second phase in the alloy, thereby obtaining a supersaturated solid solution. The alloy is then subjected to a subsequent low-temperature heat treatment at 450-550°C for 2-4 hours, which not only eliminates quenching stresses in the alloy but also allows the strengthening phases to be uniformly dispersed and fully precipitated, thereby improving the alloy's strength. After the first three steps of treatment, the yield strength of the alloy can reach 950-1000MPa, while the elongation after fracture is less than 3%, failing to achieve the expected ultra-high strength and good plasticity and toughness. Therefore, the alloy needs to be subjected to a special electric pulse treatment. The alloy is treated with an electric pulse at 500℃×(1-8)min to induce a phase transformation in the alloy, and more iron-rich κ phase precipitates from the α phase and is arranged along the direction of current, thereby increasing the tensile strength of the alloy and effectively improving the plasticity of the alloy. The tensile strength and yield strength of the alloy both reach more than 1000MPa, and the elongation after fracture reaches more than 5.0%.

[0019] The present invention provides a heat treatment method for achieving ultra-high strength in QAl11-6-6 aluminum-bronze alloy. Compared with existing aluminum-bronze alloy heat treatment processes, its main features and advantages are: a simple and controllable process. The introduction of electric pulse processing technology into the alloy's heat treatment fully utilizes the strengthening phases in the alloy, effectively increasing the alloy's strength and improving the alloy's strength-toughness balance. QAl11-6-6 aluminum-bronze tubes, bars, or machined parts produced using this special heat treatment method achieve a tensile strength of 1116 MPa, a yield strength of 1021 MPa, and an elongation of 5.9%. This method not only achieves ultra-high strength but also exhibits an excellent strength-toughness balance, making it a suitable alternative to imported materials for the manufacture of key structural components subjected to special operating conditions such as heavy loads, heavy pressure, severe wear, and severe corrosion.

[0020] The following is a detailed description of the present invention in combination with the principles and features. The examples given are only used to explain the present invention to make the above and other purposes, features and other advantages of the present invention clearer, and are not used to limit the scope of application of the present invention.

[0021] Example 1

[0022] QAl11-6-6 aluminum bronze alloy, the mass percentages of the elements are: Al: 10.80%, Fe: 6.07%, Ni + Co: 6.22%, unavoidable impurities: <0.5%, balance: Cu. It is melted, cast, and extruded into bars using conventional processes. The extruded bars have a specification of φ16mm. The heat treatment process is as follows:

[0023] (1) The extruded QA11-6-6 aluminum bronze alloy bars were placed in a resistance furnace heated to 860°C for 1.5 hours for high temperature heat treatment, and immediately quenched in room temperature water after being taken out of the furnace.

[0024] (2) Place the QAl11-6-6 aluminum bronze alloy tubes and bars or machined parts that have undergone the first high-temperature heat treatment in a resistance furnace heated to 750°C for 2 hours for a second high-temperature heat treatment, and then air cool them after being taken out of the furnace;

[0025] (3) The QAl11-6-6 aluminum bronze alloy tube and rod that has undergone the second high-temperature heat treatment is placed in a resistance furnace heated to 500°C and kept warm for 2.5 hours for low-temperature heat treatment, and then air-cooled after being taken out of the furnace.

[0026] (4) The QAl11-6-6 aluminum bronze alloy tubes, bars or machined parts that have undergone low-temperature heat treatment are subjected to an electric pulse treatment at 500°C for 3 min and then air-cooled.

[0027] The test shows that the microstructure of the QAl11-6-6 aluminum bronze alloy after the heat treatment process of Example 1 of the present invention is mainly composed of β' phase matrix and KⅡ phase. The electric pulse treatment can change the distribution of KⅡ phase in the aluminum bronze alloy. Part of KⅡ is distributed along the direction of the electric pulse current, such as Figure 1 shown.

[0028] Mechanical property testing results show a tensile strength of 1116 MPa, a yield strength of 1021 MPa, and an elongation of 5.9%, meeting operational requirements. In comparison, the mechanical properties of extruded QAl11-6-6 aluminum bronze alloy are: a tensile strength of 956 MPa and an elongation of 2.3%. This indicates that the heat treatment of the present invention can improve both the strength and plasticity of QAl11-6-6 aluminum bronze materials and parts.

[0029] Example 2

[0030] QAl11-6-6 aluminum bronze alloy, the mass percentages of the elements are: Al: 10.80%, Fe: 6.07%, Ni + Co: 6.22%, unavoidable impurities: <0.5%, balance: Cu. It is melted, cast, and extruded into bars using conventional processes. The extruded bars have a specification of φ16mm. The heat treatment process is as follows:

[0031] (1) The extruded QA11-6-6 aluminum bronze alloy bars were placed in a resistance furnace heated to 860°C for 1.5 hours for high temperature heat treatment, and immediately quenched in room temperature water after being taken out of the furnace.

[0032] (2) Place the QAl11-6-6 aluminum bronze alloy tubes and bars or machined parts that have undergone the first high-temperature heat treatment in a resistance furnace heated to 750°C for 2 hours for a second high-temperature heat treatment, and then air cool them after being taken out of the furnace;

[0033] (3) The QAl11-6-6 aluminum bronze alloy tube and rod that has undergone the second high-temperature heat treatment is placed in a resistance furnace heated to 500°C and kept warm for 2.5 hours for low-temperature heat treatment, and then air-cooled after being taken out of the furnace.

[0034] (4) The QAl11-6-6 aluminum bronze alloy tubes, bars or machined parts that have undergone low-temperature heat treatment are subjected to an electric pulse treatment at 500°C for 5 min and then air-cooled.

[0035] The test shows that the microstructure of the QAl11-6-6 aluminum bronze alloy after the heat treatment process of Example 2 of the present invention is mainly composed of β' phase matrix and KⅡ phase, and part of KⅡ is distributed along the direction of the electric pulse current. Compared with Example 1, the KⅡ phase in the aluminum bronze alloy is aggregated and gathered into a larger "tadpole-shaped" phase, such as Figure 2 Mechanical properties testing results showed: tensile strength of 1020 MPa, yield strength of 1006 MPa, and elongation at break of 6.63%. In comparison, the mechanical properties of the extruded QAl11-6-6 aluminum bronze alloy were: tensile strength of 956 MPa and elongation of 2.3%. Compared to Example 1, due to the extension of the electric pulse time to 5 minutes, the plasticity was improved, while the strength was slightly reduced, but it still met the requirements.

[0036] Comparative Example 1

[0037] QAl11-6-6 aluminum bronze alloy, the mass percentages of the elements are: Al: 10.80%, Fe: 6.07%, Ni + Co: 6.22%, unavoidable impurities: <0.5%, balance: Cu. It is melted, cast, and extruded into bars using conventional processes. The extruded bars have a specification of φ16mm. The heat treatment process is as follows:

[0038] (1) The extruded QA11-6-6 aluminum bronze alloy bars were placed in a resistance furnace heated to 860°C for 1.5 hours for high temperature heat treatment, and immediately quenched in room temperature water after being taken out of the furnace.

[0039] (2) Place the QAl11-6-6 aluminum bronze alloy tubes and bars or machined parts that have undergone the first high-temperature heat treatment in a resistance furnace heated to 750°C for 2 hours for a second high-temperature heat treatment, and then air cool them after being taken out of the furnace;

[0040] (3) The QAl11-6-6 aluminum bronze alloy tube and rod that has undergone the second high-temperature heat treatment is placed in a resistance furnace heated to 500°C and kept warm for 2.5 hours for low-temperature heat treatment, and then air-cooled after being taken out of the furnace.

[0041] The test shows that after the sample of comparative example 1 was subjected to solution aging heat treatment and no electric pulse treatment, the matrix of the QAl11-6-6 aluminum bronze alloy was composed of α phase and β phase, and a large number of nearly spherical KⅡ phases (C-type phases) were distributed in the matrix. There were intermittent point-shaped or rod-shaped particles distributed on the grain boundaries, such as Figure 3 As shown. Compared to the extruded alloy, the heat-treated structure exhibits more pronounced martensitic characteristics, with a smaller, more evenly distributed α phase. Mechanical property testing results show: tensile strength of 970 MPa, yield strength of 950 MPa, and elongation at break of 2%. Mechanical properties of the extruded QAl11-6-6 aluminum bronze alloy are: tensile strength of 956 MPa, and elongation at break of 2.3%. In comparison, the strengthening effect of the heat treatment in Comparative Example 1 is less pronounced.

[0042] Comparative Example 2

[0043] QAl11-6-6 aluminum bronze alloy, the mass percentages of the elements are: Al: 10.80%, Fe: 6.07%, Ni + Co: 6.22%, unavoidable impurities: <0.5%, balance: Cu. It is melted, cast, and extruded into bars using conventional processes. The extruded bars have a specification of φ16mm. The heat treatment process is as follows:

[0044] (1) The extruded QA11-6-6 aluminum bronze alloy bars were placed in a resistance furnace heated to 860°C for 1.5 hours for high temperature heat treatment, and immediately quenched in room temperature water after being taken out of the furnace.

[0045] (2) Place the QAl11-6-6 aluminum bronze alloy tubes and bars or machined parts that have undergone the first high-temperature heat treatment in a resistance furnace heated to 750°C for 2 hours for a second high-temperature heat treatment, and then air cool them after being taken out of the furnace;

[0046] (3) The QAl11-6-6 aluminum bronze alloy tube and rod that has undergone the second high-temperature heat treatment is placed in a resistance furnace heated to 500°C and kept warm for 2.5 hours for low-temperature heat treatment, and then air-cooled after being taken out of the furnace.

[0047] (4) The QAl11-6-6 aluminum bronze alloy tubes, bars or machined parts that have undergone low-temperature heat treatment are subjected to an electric pulse treatment at 500°C for 7 minutes and then air-cooled.

[0048] The test shows that after the solution aging heat treatment, the sample in Comparative Example 2 was subjected to a 7-minute electric pulse treatment. Due to the long electric pulse treatment time, the KⅡ phase in the QAl11-6-6 aluminum bronze alloy aggregated and grew, forming large particles, short rods, and tadpole shapes, with the maximum size reaching 15μm, which is not conducive to the strengthening and toughening of the alloy. Figure 4 Mechanical properties testing results show a tensile strength of 1015 MPa, a yield strength of 970 MPa, and an elongation of 2.69%. In comparison, the mechanical properties of the extruded QAl11-6-6 aluminum bronze alloy are: a tensile strength of 956 MPa and an elongation of 2.3%.

[0049] The above embodiments are used to explain the present invention rather than to limit the present invention. Several improvements and modifications may be made without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A heat treatment method for achieving ultra-high strength of aluminum bronze alloy, characterized by: Follow these steps: Step 1: Cut the extruded or centrifugally cast QAl11-6-6 aluminum bronze alloy tubes and bars into fixed lengths or machine them into parts. Place them in a resistance furnace heated to 850-950°C and keep them warm for 0.5-2.0 hours for the first high-temperature heat treatment. After being taken out of the furnace, quench them in room temperature water immediately. Step 2: Place the QAl11-6-6 aluminum bronze alloy tubes and bars or machined parts that have undergone the first high-temperature heat treatment in a resistance furnace heated to (750~850)℃ and keep them warm for 2~4 hours for the second high-temperature heat treatment, and then air-cool them after being taken out of the furnace; Step 3: Place the QAl11-6-6 aluminum bronze alloy tubes and bars or machined parts that have undergone the second high-temperature heat treatment in a resistance furnace heated to (450~550)℃ for 2~4 hours for low-temperature heat treatment, and then air-cool after being taken out of the furnace; Step 4: The QAl11-6-6 aluminum bronze alloy tube, bar or machined parts that have undergone low-temperature heat treatment are subjected to an electric pulse treatment at 500°C × (1~5) min, and then air-cooled.

2. The heat treatment method for achieving ultra-high strength of aluminum bronze alloy according to claim 1, characterized in that: The first high-temperature heat treatment parameters in step 1 are: holding in a resistance furnace at 880-920°C for 0.5-1.0 hour, and immediately quenching in room temperature water after being taken out of the furnace; The second high-temperature heat treatment parameters in step 2 are: holding in a resistance furnace at 780-820°C for 2.5-3.3 hours, and air cooling after leaving the furnace; The low-temperature heat treatment parameters in step 3 are: keeping the temperature in a resistance furnace at 480-520°C for 2-3 hours, and air cooling after leaving the furnace; The parameters of the electric pulse treatment in step 4 are as follows: the QAl11-6-6 aluminum bronze alloy tube, rod or machined part that has undergone low-temperature heat treatment is subjected to another electric pulse treatment at 500°C for (1-5) min, followed by air cooling.

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