Fe-Ni-Co-Al superelastic alloy with relatively low thermal expansion coefficient and ultrahigh strength and preparation method of Fe-Ni-Co-Al superelastic alloy

Abstract

The invention provides a Fe-Ni-Co-Al superelastic alloy and a preparation method thereof, the expression of the superelastic alloy is FeaNibCocAld, a, b, c and d respectively represent the atomic percent (at.%) of corresponding elements, a = 40-50, b = 25-35, c = 10-20, d = 5-15, and a + b + c + d = 100. The preparation method of the superelastic alloy comprises the steps of smelting, rolling and heat treatment. The aluminum alloy has a lower thermal expansion coefficient, and the activity of crystal defects is controlled by adjusting the element ratio, rolling and heat treatment processes, so that the mechanical property of the aluminum alloy is influenced. The Fe43Ni30Co16Al11 hyperelastic alloy disclosed by the invention is subjected to rolling and heat treatment processes, so that the strength of the Fe43Ni30Co16Al11 hyperelastic alloy is increased by more than four times compared with that of The thermal expansion coefficient of the hyperelastic alloy is less than 2.7 * 10 <-6 >, the tensile strength of the hyperelastic alloy is up to 1940MPa, and the maximum recoverable strain capacity of the hyperelastic alloy is 3.3%. The method is simple in process, can be used for preparing superelastic alloys in various different shapes due to the excellent plasticity of the superelastic alloy, and is suitable for large-scale industrial application.

Description

Technical Field

[0001] The invention relates to a Fe-Ni-Co-Al alloy with superelasticity and a preparation method thereof, belonging to the technical field of iron-based superelastic alloy materials. Background Art

[0002] Objects have the phenomenon of expansion and contraction due to temperature changes. Its ability to change is the change in length value caused by a unit temperature change under constant pressure, which is expressed by the coefficient of thermal expansion. As the temperature rises, the thermal motion of atoms increases and the bonding force between atoms weakens. The displacement of atoms from the equilibrium position gradually increases, reflecting the increase in the coefficient of thermal expansion (CTE). Materials with high CTE values ​​will cause large thermal stresses, which will cause serious degradation of components and even structural failure. Superelasticity (SE) is defined as the shape recovery of deformation in the austenite phase after unloading. The recoverable deformation of general metal materials is often limited to about 0.2%, but for superelastic alloys, even if the deformation is much greater than the elastic stage, it can still recover after unloading.

[0003] So far, alloys with lower thermal expansion coefficients include classic Invar alloy (FeNi36), super Invar alloy (FeNi31C05), etc. Traditionally manufactured Invar alloys have excellent ductility due to the solid single-sided central cubic structure, but relatively low strength. High-performance alloys with both low thermal expansion behavior and good mechanical properties are urgently needed in industrial applications.

[0004] The Fe-Ni-Co-Al alloy is obtained by adjusting the element ratio, and the Fe-Ni-Co-Al alloy is subjected to appropriate rolling and heat treatment processes. 0.64 Ni 0.36 The alloy has superelasticity, excellent mechanical properties and low thermal expansion coefficient. Summary of the invention

[0005] The invention provides a Fe-Ni-Co-Al superelastic alloy and a preparation method thereof. The superelastic alloy has a lower thermal expansion coefficient and excellent mechanical properties.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0007] A Fe-Ni-Co-Al superelastic alloy, the composition of the superelastic alloy is Fe a Ni b Co c Al d, where a, b, c, d, and e represent the atomic percentage (at.%) of the corresponding element, a=40-50, b=25-35, c=10-20, d=5-15, and a+b+c+d=100.

[0008] The molecular formula of the Fe-Ni-Co-Al superelastic alloy is preferably Fe (40～50) Ni (25～35) Co (10～20) Al (5～15) , more preferably Fe (41～43) Ni (30～33) Co (15～20) Al (9～12) Most preferably, Fe 43 Ni 30 Co 16 Al 11 .

[0009] A method for preparing a Fe-Ni-Co-Al superelastic alloy comprises the following steps:

[0010] (1) Alloy smelting: Iron, nickel, cobalt and aluminum are weighed in proportion and arc-smelted in a non-consumable vacuum arc furnace to obtain metal ingots for use.

[0011] (2) Rolling process: The metal ingot is cut into suitable sizes and then cold rolled with a large deformation of ≥80%.

[0012] (3) Heat treatment: The cold-rolled sample is kept at a specific temperature for a specific period of time and then rapidly cooled.

[0013] Preferably, the metallic iron, nickel, cobalt and aluminum are metallic single substances, and the purity of the metallic iron, nickel, cobalt and aluminum is preferably greater than 99.9%.

[0014] Preferably, the vacuum degree during smelting is less than 3×10 -3 Pa, and the smelting process is carried out under argon protection.

[0015] Preferably, the metal ingot during smelting is turned over and smelted repeatedly for more than three times to ensure uniform alloy composition.

[0016] Preferably, the rolling process is: deformation amount ≥ 80%.

[0017] The solution temperature is preferably 500° C., and the solution time is preferably 10 min to 60 min, more preferably 43 min.

[0018] The present invention provides a Fe-Ni-Co-Al superelastic alloy and a preparation method thereof, which has the following advantages over the prior art:

[0019] (1) The alloy prepared by the present invention adjusts the element ratio so that the Fe-Ni-Co-Al superelastic alloy has the excellent mechanical properties of the superelastic alloy and the low thermal expansion coefficient of the Invar alloy. And through rolling with a large deformation of ≥80%, the grains of the alloy are refined, thereby obtaining a strong texture, and finally obtaining ultra-high strength and a large recoverable strain. Compared with the existing Fe-based superelastic alloy, its lower thermal expansion coefficient and excellent mechanical properties, as well as low cost make it have broad application prospects and are very attractive in business, such as precision instruments, pipeline building materials, etc.

[0020] (2) Appropriate heat treatment temperature further improves the strength of the alloy.

[0021] (3) The present invention provides the Fe-Ni-Co-Al superelastic alloy and a preparation method thereof. An ultra-high strength superelastic alloy can be obtained through smelting, cold rolling and heat treatment processes. The preparation process is simple and low-cost and is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The stress-strain curve of the superelastic alloy prepared in Example 1 of the present invention after 80% rolling deformation at room temperature during loading-unloading;

[0023] Figure 2 The stress-strain curve of the superelastic alloy prepared in Example 2 of the present invention after 90% rolling deformation at room temperature during loading-unloading;

[0024] Figure 3 The stress-strain curve of the superelastic alloy prepared in Example 3 of the present invention after 95% rolling deformation at room temperature during loading-unloading;

[0025] Figure 4 The stress-strain curve of the superelastic alloy prepared in Example 4 of the present invention after 95% rolling deformation, solution treatment at 1000°C for 37 minutes and loading-unloading at room temperature;

[0026] Figure 5 The stress-strain curve of the superelastic alloy prepared in Example 5 of the present invention after 95% rolling deformation, solution treatment at 800°C for 37 minutes and loading-unloading at room temperature;

[0027] Figure 6 The stress-strain curve of the superelastic alloy prepared in Example 6 of the present invention after 95% rolling deformation, solution treatment at 600°C for 37 minutes and loading-unloading at room temperature;

[0028] Figure 7The stress-strain curve of the superelastic alloy prepared in Example 7 of the present invention after 95% rolling deformation, solution treatment at 500°C for 37 minutes, and loading-unloading at room temperature;

[0029] Figure 8 The stress-strain curve of the superelastic alloy prepared in Comparative Example 1 of the present invention under loading-unloading at room temperature;

[0030] Fig. 9 The stress-strain curves of the superelastic alloys prepared in Examples 1, 2 and 3 of the present invention and the superelastic alloy prepared in Comparative Example 1 when loaded at room temperature;

[0031] Fig.10 The stress-strain curves of the superelastic alloys prepared in Examples 4, 5, 6 and 7 of the present invention and the superelastic alloy prepared in Comparative Example 1 loaded at room temperature;

[0032] Fig.11 The Fe 43 Ni 30 Co 16 Al 11 Thermal expansion coefficient diagram of superelastic alloy from room temperature to 100°C; DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the present invention are clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are partial embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] Embodiment 1:

[0035] (1) According to the molecular formula Fe 43 Ni 30 Co 16 Al 11 Weigh 26.67444g of 99.9% pure iron, 19.55641g of nickel, 10.47264g of cobalt and 3.296388g of aluminum and place them in a non-consumable vacuum melting furnace for melting. When the furnace vacuum reaches 3.0×10 -3 After Pa, argon gas is filled in for protection and the smelting is repeated for more than 5 times to obtain a metal ingot.

[0036] (2) The sample is cold rolled at room temperature using a gate machine with a deformation of 80%.

[0037] (3) Cut the heat treated sample into a size of 1 mm × 3 mm × 10 mm (dog bone shape)

[0038] Embodiment 2:

[0039] (1) According to the molecular formula Fe 43 Ni 30 Co 16 Al 11 Weigh 26.67444g of 99.9% pure iron, 19.55641g of nickel, 10.47264g of cobalt and 3.296388g of aluminum and place them in a non-consumable vacuum melting furnace for melting. When the furnace vacuum reaches 3.0×10 -3 After Pa, argon gas is filled in for protection and the smelting is repeated for more than 5 times to obtain a metal ingot.

[0040] (2) The sample is cold rolled at room temperature using a gate machine with a deformation of 90%.

[0041] (3) Cut the heat treated sample into a size of 1 mm × 3 mm × 10 mm (dog bone shape)

[0042] Embodiment 3:

[0043] (1) According to the molecular formula Fe 43 Ni 30 Co 16 Al 11 Weigh 26.67444g of 99.9% pure iron, 19.55641g of nickel, 10.47264g of cobalt and 3.296388g of aluminum and place them in a non-consumable vacuum melting furnace for melting. When the furnace vacuum reaches 3.0×10 -3 After Pa, argon gas is filled in for protection and the smelting is repeated for more than 5 times to obtain a metal ingot.

[0044] (2) The sample is cold rolled at room temperature using a gate machine with a deformation of 95%.

[0045] (3) Cut the heat treated sample into a size of 1 mm × 3 mm × 10 mm (dog bone shape)

[0046] Embodiment 4:

[0047] (1) According to the molecular formula Fe 43 Ni 30 Co 16 Al 11 Weigh 26.67444g of 99.9% pure iron, 19.55641g of nickel, 10.47264g of cobalt and 3.296388g of aluminum and place them in a non-consumable vacuum melting furnace for melting. When the furnace vacuum reaches 3.0×10 -3 After Pa, argon gas is filled in for protection and the smelting is repeated for more than 5 times to obtain a metal ingot.

[0048] (2) The sample is cold rolled at room temperature using a gate machine with a deformation of 95%.

[0049] (3) The rolled samples were solution treated at 1000°C for 43 min and then water quenched.

[0050] (4) Cut the heat treated sample into a size of 1 mm × 3 mm × 10 mm (dog bone shape)

[0051] Embodiment 5:

[0052] (1) According to the molecular formula Fe 43 Ni 30 Co 16 Al 11 Weigh 26.67444g of 99.9% pure iron, 19.55641g of nickel, 10.47264g of cobalt and 3.296388g of aluminum and place them in a non-consumable vacuum melting furnace for melting. When the furnace vacuum reaches 3.0×10 -3 After Pa, argon gas is filled in for protection and the smelting is repeated for more than 5 times to obtain a metal ingot.

[0053] (2) The sample is cold rolled at room temperature using a gate machine with a deformation of 95%.

[0054] (3) The rolled samples were solution treated at 800 °C for 43 min and then water quenched.

[0055] (4) Cut the heat treated sample into a size of 1 mm × 3 mm × 10 mm (dog bone shape)

[0056] Embodiment 6:

[0057] (1) According to the molecular formula Fe 43 Ni 30 Co 16 Al 11 Weigh 26.67444g of 99.9% pure iron, 19.55641g of nickel, 10.47264g of cobalt and 3.296388g of aluminum and place them in a non-consumable vacuum melting furnace for melting. When the furnace vacuum reaches 3.0×10 -3 After Pa, argon gas is filled in for protection and the smelting is repeated for more than 5 times to obtain a metal ingot.

[0058] (2) The sample is cold rolled at room temperature using a gate machine with a deformation of 95%.

[0059] (3) The rolled samples were solution treated at 600 °C for 43 min and then water quenched.

[0060] (4) Cut the heat treated sample into a size of 1 mm × 3 mm × 10 mm (dog bone shape)

[0061] Embodiment 7:

[0062] (1) According to the molecular formula Fe 43 Ni 30 Co 16 Al 11 Weigh 26.67444g of 99.9% pure iron, 19.55641g of nickel, 10.47264g of cobalt and 3.296388g of aluminum and place them in a non-consumable vacuum melting furnace for melting. When the furnace vacuum reaches 3.0×10 -3 After Pa, argon gas is filled in for protection and the smelting is repeated for more than 5 times to obtain a metal ingot.

[0063] (2) The sample is cold rolled at room temperature using a gate machine with a deformation of 95%.

[0064] (3) The rolled samples were solution treated at 500 °C for 43 min and then water quenched.

[0065] (4) Cut the heat treated sample into a size of 1 mm × 3 mm × 10 mm (dog bone shape)

[0066] Comparative Example 1:

[0067] Preparation of Fe 43 Ni 30 Co 16 Al 11 alloy:

[0068] (1) According to the molecular formula Fe 43 Ni 30 Co 16 Al 11 Weigh 26.67444g of 99.9% pure iron, 19.55641g of nickel, 10.47264g of cobalt and 3.296388g of aluminum and place them in a non-consumable vacuum melting furnace for melting. When the furnace vacuum reaches 3.0×10 -3 After Pa, argon gas is filled in for protection and the smelting is repeated for more than 5 times to obtain a metal ingot.

[0069] (2) Cut the heat treated sample into a size of 1 mm × 3 mm × 10 mm (dog bone shape)

[0070] Performance Testing

[0071] 1. Determination of Fe 43 Ni 30 Co 16 Al 11 Coefficient of thermal expansion of superelastic alloys.

[0072] 2. Determine the superelasticity and strength of the alloys prepared in Examples 1 to 7 and Comparative Example 1.

[0073] Determination method: Cut the melted sample into a size of 1mm×3mm×10mm (dog bone shape), and perform a tensile test on the sample in a universal testing machine with a loading rate of 0.00025mm / s and an unloading rate of 0.3mm / min.

[0074] When testing the superelasticity and strength of the alloys prepared in Examples 1 to 7, the following results were obtained:

[0075] A. For the alloy prepared in Example 1, the specimen size for testing its superelasticity and strength was 1 mm × 3 mm × 10 mm (dog bone shape). The test results are as follows: Figure 1 As shown in the figure, it can be seen that when the strength is 946MPa, the recoverable strain reaches 1.7%.

[0076] B. For the alloy prepared in Example 2, the specimen size for testing its superelasticity and strength was 1 mm × 3 mm × 10 mm (dog bone shape). The test results are as follows: Figure 2 As shown in the figure, it can be seen that when the strength is 1003MPa, the recoverable strain reaches 1.72%.

[0077] C. For the alloy prepared in Example 3, the specimen size for testing its superelasticity and strength was 1 mm × 3 mm × 10 mm (dog bone shape). The test results are as follows: Figure 3 As shown in the figure, when the strength is 1172MPa, the recoverable strain reaches 2.01%. Therefore, cold rolling with large deformation can make Fe 43 Ni 30 Co 16 Al 11 It has higher yield strength, tensile strength and higher recoverable strain.

[0078] D. For the alloy prepared in Example 4, the specimen size for testing its superelasticity and strength was 1 mm × 3 mm × 10 mm (dog bone shape). The test results are as follows: Figure 4 As shown in the figure, it can be seen that when the strength is 518MPa, the recoverable strain reaches 1.4%.

[0079] E. For the alloy prepared in Example 5, the specimen size for testing its superelasticity and strength was 1 mm × 3 mm × 10 mm (dog bone shape). The test results are as follows: Figure 5 As shown in the figure, it can be seen that when the strength is 845MPa, the recoverable strain reaches 1.9%.

[0080] F. For the alloy prepared in Example 6, the specimen size for testing its superelasticity and strength was 1 mm × 3 mm × 10 mm (dog bone shape). The test results are as follows: Figure 6 As shown in the figure, it can be seen that when the strength is 1389MPa, the recoverable strain reaches 2.86%.

[0081] G. For the alloy prepared in Example 7, the specimen size for testing its superelasticity and strength was 1 mm × 3 mm × 10 mm (dog bone shape). The test results are as follows: Figure 7 As shown in the figure, when the strength is 1902MPa, the recoverable strain reaches 3.3%. It can be seen that the heat treatment process can make Fe 43 Ni 30 Co 16 Al 11 The strength of the superelastic alloy has been further greatly improved.

[0082] H. For the alloy prepared in Comparative Example 1, the specimen size for testing its superelasticity and strength was 1 mm × 3 mm × 10 mm (dog bone shape). The test results are as follows: Figure 8 As shown in the figure, it can be seen that when the strength is 440MPa, the recoverable strain reaches 1.2%.

[0083] 3. Testing the tensile properties of the superelastic alloys prepared in Examples 1 to 7 of the present invention and the superelastic alloy prepared in Comparative Example 1 under room temperature loading:

[0084] I. The tensile strength of the superelastic alloys prepared in Examples 1, 2 and 3 and the superelastic alloy prepared in Comparative Example 1 was tested using samples with a size of 1 mm × 3 mm × 10 mm (dog bone shape). The test results are as follows: Fig. 9 As shown in the figure, it can be seen that as the rolling amount increases, Fe 43 Ni 30 Co 16 Al 11 The yield strength and tensile strength of superelastic alloys gradually increase.

[0085] J. For the superelastic alloys prepared in Examples 4, 5, 6 and 7 and the superelastic alloy prepared in Comparative Example 1, the tensile strength of the superelastic alloys was tested at room temperature using a sample size of 1 mm × 3 mm × 10 mm (dog bone shape). The test results are as follows: Fig.10 As shown in the figure, it can be seen that as the heat treatment temperature decreases, Fe 43 Ni 30 Co 16 Al 11 The yield strength and tensile strength of superelastic alloys gradually increase.

[0086] According to Examples 1 to 8 and Comparative Example 1, the present invention significantly improves the yield strength, tensile strength and superelasticity of the superelastic alloy through large deformation cold rolling and reasonable heat treatment process, especially Fe 43 Ni 30 Co 16 Al 11 After the superelastic alloy was cold-rolled with a large deformation of ≥95% and heat-treated at 500℃ for 37min, its tensile strength increased from 440MPa to 1900MPa, and its recoverable strain increased from 1.2% to 3.3%. 43 Ni 30 Co 16 Al 11 The tensile strength and corresponding recoverable strain of superelastic alloys are shown in Table 1. 43 Ni 30 Co 16 Al 11 The thermal expansion coefficients are shown in Table 2.

[0087] Table 1. Preparation process, superelasticity and strength of each group of samples

[0088]

[0089] Table 2. Fe 43 Ni 30 Co 16 Al 11 Thermal Expansion Coefficient of Superelastic Alloys

[0090]

[0091] It can be seen from the above embodiments that the present invention provides a Fe-Ni-Co-Al superelastic alloy, which has a low thermal expansion coefficient of <2.7×10 -6 The tensile strength exceeds 1900MPa, and the recoverable strain is 3.3%. The present invention provides a preparation method of the Fe-Ni-Co-Al alloy, and a superelastic alloy can be obtained by smelting, rolling and heat treatment. The alloy has low production cost, simple preparation process and easy processing and forming, and is suitable for large-scale production.

[0092] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0093] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the techniques of the embodiments of the present invention.

Claims

1. A Fe-Ni-Co-Al superelastic alloy, characterized in that: The composition of the superelastic alloy is Fe a Ni b Co c Al d , where a, b, c, and d represent the atomic percentage (at.%) of the corresponding element, a=40-50, b=25-35, c=10-20, d=5-15, and a+b+c+d=100.

2. The Fe-Ni-Co-Al superelastic alloy according to claim 1, wherein the preparation method comprises the following steps: (1) Melting. Metal iron, nickel, cobalt and aluminum are weighed in proportion and arc-melted in a non-consumable vacuum arc furnace to obtain metal ingots for use. (2) Rolling process. (3) Heat treatment.

3. The method for preparing a Fe-Ni-Co-Al superelastic alloy according to claim 2, characterized in that: The purity of the metal iron, nickel, cobalt and aluminum is equal to or greater than 99.9%.

4. The method for preparing a Fe-Ni-Co-Al superelastic alloy according to claim 2, characterized in that: The vacuum degree of arc melting in step (1) is less than 3×10 -3 Pa, and the smelting process is carried out under argon protection.

5. The method for preparing a Fe-Ni-Co-Al superelastic alloy according to claim 2, characterized in that: The metal ingot subjected to arc melting in step (1) is repeatedly melted more than three times to ensure uniform alloy composition.

6. The method for preparing a Fe-Ni-Co-Al superelastic alloy according to claim 2, characterized in that: The rolling process in step (2) is: a large deformation of ≥80% and a rolling direction that is the force direction of the sample stretching.

7. The method for preparing a Fe-Ni-Co-Al superelastic alloy according to claim 2, characterized in that: The heat treatment process in step (2) is: heat treatment at 300-1200° C. for 1-60 hours.

Images