A high-plasticity and high-strength Co-V-Ga-Ni high-temperature shape memory alloy and a preparation method thereof

Abstract

The present invention discloses a high-plasticity and high-strength Co-V-Ga-Ni high-temperature shape memory alloy and a preparation method thereof, which relates to the technical field of memory alloys. By introducing nickel into the Co-V-Ga alloy, the prepared Co-V-Ga-Ni alloy material has excellent high-temperature resistance, and at the same time significantly improves the compressive strength and plasticity of the Co-V-Ga-based alloy, reduces its brittleness, and improves its mechanical properties. By introducing nickel, the present invention further reduces the dosage of Ga in the Co-V-Ga-based alloy, thereby reducing the processing cost of the alloy and having high economic value.

Description

Technical Field

[0001] The present invention belongs to the technical field of shape memory alloys, and particularly relates to a high-plasticity, high-strength Co-V-Ga-Ni high-temperature shape memory alloy and a preparation method thereof. Background Art

[0002] High-temperature shape memory alloys (HTSMA) refer to shape memory alloys with a martensitic transformation start temperature (Ms) higher than 100 °C, and can be used in applications such as aerospace aircraft, fire alarm systems, health care and vehicle engineering, satellite substrates, and drive devices in nuclear power plants. It has always been a research hotspot in the field of shape memory alloys.

[0003] In recent years, as the requirements for material properties in complex service environments have become increasingly stringent, it is required that the alloy has a high shape memory effect and phase transformation temperature, and it is also expected to have more excellent mechanical properties, thermal cycle stability, oxidation resistance, and strong corrosion resistance and high-temperature creep resistance. Therefore, continuously exploring and developing HTSMAs with excellent mechanical properties, high phase transformation temperature, and stable recoverability has extremely important practical value.

[0004] Co-V-Ga-based shape memory alloys, as a new type of intelligent high-temperature shape memory material, have a relatively wide adjustable martensitic transformation temperature (0 - 500K) and excellent thermal stability. They stand out due to their excellent corrosion resistance, elastocaloric properties, and physical characteristics, and are a highly potential HTSMA.

[0005] Due to the intrinsic brittleness and low strength of Co-V-Ga-based shape memory alloys, etc., it greatly restricts the application and development of such alloy materials in actual engineering. Therefore, how to enhance the strength and plasticity of Co-V-Ga-based alloys, reduce brittleness, thereby improving their mechanical properties, and obtaining a high phase transformation temperature and excellent mechanical properties has become the main research direction for the application and development of high-temperature memory alloys. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the present invention provides a high-plasticity, high-strength Co-V-Ga-Ni high-temperature shape memory alloy and a preparation method thereof. This method is to introduce nickel into the Co-V-Ga alloy, so that the prepared Co-V-Ga-Ni alloy material has excellent high-temperature resistance, and at the same time significantly improves the compressive strength and plasticity of the Co-V-Ga-based alloy, reduces its brittleness, and improves its mechanical properties.

[0007] The present invention is realized by adopting the following technical solutions:

[0008] A preparation method of a high-plasticity and high-strength Co-V-Ga-Ni high-temperature shape memory alloy, comprising the following steps:

[0009] Step 1: Weigh Co, V, Ga, and Ni according to the atomic ratio in the alloy, where x is 5; 55 V 29 Ga 16-x Ni x Weigh Co, V, Ga, and Ni according to the atomic ratio in the alloy, where x is 5;

[0010] Step 2: Put the weighed raw materials into a crucible, and use a vacuum non-consumable arc melting furnace to carry out vacuum arc melting to obtain an alloy ingot;

[0011] Step 3: Cut the alloy ingot into a cylindrical shape;

[0012] Step 4: After surface impurity removal and cleaning of the cut alloy ingot, obtain a cylindrical sample;

[0013] Step 5: Place the cylindrical sample in a quartz tube for vacuum pumping and then seal the tube to obtain a sealed tube sample;

[0014] Step 6: Place the sealed tube sample in a heat treatment furnace for homogenization treatment, where the treatment temperature is 1100 °C and the treatment time is 24 hours; finally, perform water quenching to obtain a high-plasticity and high-strength Co-V-Ga-Ni high-temperature shape memory alloy.

[0015] Preferably, in Step 2, the weighed Ga raw material is placed on the top layer of the crucible.

[0016] Preferably, in Step 2, the vacuum arc melting is to first carry out vacuum pumping to make the vacuum degree -0.05 MPa, then adjust the melting current to 200 A after arc ignition for melting to remove residual oxygen, and then adjust the current to 270 A - 300 A for repeated melting treatment.

[0017] More preferably, in Step 2, the vacuum arc melting is carried out 5 - 10 times at a current of 270 A - 300 A, each melting time is 1 min, and the alloy ingot needs to be turned over after each single melting.

[0018] Preferably, in Step 3, the alloy ingot is cut into a cylinder with a diameter of 3 mm and a length of 7 mm.

[0019] Preferably, in Step 4, the cut alloy ingot is subjected to wire cutting and mechanical polishing to remove surface impurities, and the obtained cylindrical sample is obtained after cleaning.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention introduces nickel into the Co-V-Ga alloy, thereby significantly and effectively improving the compressive strength and plasticity of the Co-V-Ga series alloy, and at the same time endowing it with excellent high-temperature resistance performance. By introducing nickel, the present invention further reduces the dosage of Ga in the Co-V-Ga series alloy, thereby reducing the processing cost of the alloy and having high economic value. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 XRD diffraction patterns of the shape memory alloys prepared in Example 1 and Comparative Example 1 of the present invention;

[0023] Figure 2 Differential scanning calorimetry DSC of the shape memory alloys prepared in Example 1 and Comparative Example 1 of the present invention;

[0024] Figure 3 Microstructure diagram of the shape memory alloy prepared in Comparative Example 1;

[0025] Figure 4 Microstructure diagram of the shape memory alloy prepared in Example 1;

[0026] Figure 5 Compressive stress-strain curve diagrams of the shape memory alloys prepared in Example 1 and Comparative Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] In order to make the objectives, features, and advantages of the present invention more obvious and understandable, the following provides a detailed description of the specific embodiments of the present invention. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0028] Example 1

[0029] A preparation method of a high-plasticity and high-strength Co-V-Ga-Ni high-temperature shape memory alloy, the steps are as follows:

[0030] Step 1: Weigh Co, V, Ga, and Ni according to the atomic ratio in the Co 55 V 29 Ga 11 Ni5 alloy;

[0031] Step 2: Put the weighed raw materials into a crucible and perform vacuum arc melting using a vacuum non-consumable arc melting furnace to obtain an alloy ingot. The weighed Ga raw material is placed on the top layer of the crucible. The vacuum arc melting is to first perform a vacuum pumping process to make the vacuum degree -0.05 MPa, then adjust the melting current to 200 A after striking an arc to remove the residual oxygen by melting, and then adjust the current to 280 A for repeated melting 6 times, with each melting time being 1 min. After each single melting, the alloy ingot needs to be turned over.

[0032] Step 3: Cut the alloy ingot into cylinders with a diameter of 3 mm and a length of 7 mm.

[0033] Step 4: Remove the surface impurities from the cut alloy ingot by wire cutting and mechanical polishing, and obtain cylindrical specimens after cleaning.

[0034] Step 5: Place the cylindrical specimens in a quartz tube for vacuum pumping (vacuum degree is 10 -1 Pa) and seal the tube to obtain sealed tube samples.

[0035] Step 6: Place the sealed tube samples in a heat treatment furnace for homogenization treatment, where the treatment temperature is 1100 °C and the treatment time is 24 hours; finally, perform water quenching to obtain a high-plasticity and high-strength Co-V-Ga-Ni high-temperature shape memory alloy, namely Co 55 V 29 Ga 11 Ni5 alloy.

[0036] Comparative Example 1

[0037] A preparation method of a Co-V-Ga-based memory alloy is as follows:

[0038] Step 1: Weigh Co, V, and Ga according to the atomic ratio in the 55 V 29 Ga 16 alloy.

[0039] Steps 2 to 6 refer to Example 1 to obtain a Co 55 V 29 Ga 16 alloy.

[0040] It can be seen from Figure 1 that compared with Comparative Example 1, the memory alloy prepared in Example 1 of the present invention has a γ phase in addition to the martensite phase at room temperature.

[0041] It can be seen from Figure 2It can be seen that the initial temperature Ms of the martensitic transformation of the shape memory alloy prepared in Example 1 of the present invention is enhanced, the service temperature rises from 233 °C to 274 °C, and the range of its application in high-temperature scenarios is broadened. It is an excellent candidate material for high-temperature shape memory alloys.

[0042] From Figures 3 - 4 it can be seen that the main microstructure of the shape memory alloy prepared in Example 1 of the present invention consists of lath martensite and γ phase, and the main microstructure of the shape memory alloy prepared in Comparative Example 1 consists of large lath martensite structures.

[0043] From Figure 5 it can be seen that the shape memory alloy prepared in the present invention has a compressive strain of 30.7% and a compressive strength of 2490 MPa. Compared with Comparative Example 1, the shape memory alloy of Example 1 of the present invention has better strength and plasticity.

[0044] The above-described embodiments merely represent several implementation manners of the present invention, and the description thereof is relatively specific and detailed. However, it should not be construed as a limitation on the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the appended claims.

Claims

1. A preparation method of a high-plasticity and high-strength Co-V-Ga-Ni high-temperature shape memory alloy, characterized in that, It includes the following steps: Step 1: Follow Co 55 V 29 Ga 16-x Ni x The atomic ratios in the alloy are Co, V, Ga, and Ni, where x is 5; Step 2: Put the weighed raw materials into a crucible, and carry out vacuum arc melting by using a vacuum non-consumable arc melting furnace to obtain an alloy ingot; Step 3: Cut the alloy ingot into a cylindrical shape; Step 4: After surface impurity removal and cleaning of the cut alloy ingot, obtain a cylindrical sample; Step 5: Place the cylindrical sample in a quartz tube, carry out vacuum pumping treatment and then seal the tube to obtain a sealed tube sample; Step 6: Place the sealed tube sample in a heat treatment furnace for homogenization treatment, where the treatment temperature is 1100 °C and the treatment time is 24 hours; finally, carry out water quenching to obtain a high-plasticity and high-strength Co-V-Ga-Ni high-temperature shape memory alloy; In step 2, for vacuum arc melting, first carry out vacuum pumping treatment to make the vacuum degree -0.05 MPa, then after arc ignition, adjust the melting current to 200 A to carry out melting to remove residual oxygen, and then adjust the current to 270 A - 300 A for 5 - 10 times of repeated melting treatment, with each melting time being 1 min. After each single melting, it is necessary to turn over the alloy ingot.

2. The preparation method of the high-plasticity and high-strength Co-V-Ga-Ni high-temperature shape memory alloy according to claim 1, characterized in that In step 2, the weighed Ga raw material is placed on the top layer of the crucible.

3. The preparation method of the high-plasticity and high-strength Co-V-Ga-Ni high-temperature shape memory alloy according to claim 1, characterized in that, In step 3, the alloy ingot is cut into a cylinder with a diameter of 3 mm and a length of 7 mm.

4. The preparation method of the high-plasticity and high-strength Co-V-Ga-Ni high-temperature shape memory alloy according to claim 1, wherein, In step 4, the cut alloy ingot is subjected to wire cutting and mechanical polishing to remove surface impurities, and the obtained cylindrical sample is obtained after cleaning.

5. A high-plasticity, high-strength Co-V-Ga-Ni high-temperature shape memory alloy, characterized in that, Prepared by the method according to any one of claims 1 to 4.

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