A method for brazing zirconium alloy and high entropy alloy using Cu foil contact reaction
Through the Cu foil contact reaction brazing method, the problem of mismatch between the formation of intermetallic compounds and thermal expansion coefficients in the connection between zirconium alloy and high-entropy alloy is solved, and high-strength heterogeneous material connection is achieved, and the shear strength of the brazed joint reaches 140.1 MPa.
Patent Information
- Application Number
- CN202310596764.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-05-25
- Publication Date
- 2025-08-15
- Estimated Expiration
- 2043-05-25
AI Technical Summary
In the prior art, the connection between zirconium alloys and high entropy alloys has problems with mismatch between the formation of intermetallic compounds and thermal expansion coefficients, resulting in insufficient joint strength and residual stress affecting the mechanical properties.
The Cu foil contact reaction brazing method is used to polish and clean the welded surfaces of zirconium alloy and high-entropy alloy, and use Cu foil as brazing material, heat it to 900°C~970°C under vacuum environment and keep it in heat for 1 min~20 min to form a high-strength connection.
A high-strength connection between zirconium alloy and high-entropy alloy is achieved, and the room temperature shear strength of the brazed joint reaches 140.1 MPa, which significantly improves the strength and mechanical properties of the joint.
Smart Images
Figure CN116618775B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of zirconium alloy and high entropy alloy welding, and in particular to a method for brazing zirconium alloy and high entropy alloy by using Cu foil contact reaction. Background Art
[0002] Zirconium alloy has the characteristics of low density, resistance to low temperatures in space, suitability for alternating temperature fields, resistance to atomic oxygen corrosion and resistance to space radiation. As a structural material, it has great application value in aerospace, space, nuclear energy and other fields. In the space field, it has development potential for use as a material for active components of spacecraft.
[0003] High-entropy alloys (HEAs) are considered to be a promising structural material in the chemical, aerospace, and nuclear industries due to their outstanding chemical and mechanical properties, superior radiation resistance, and excellent wear resistance, oxidation resistance, and corrosion resistance. Among them, face-centered cubic (FCC) CoCrFeMnNi HEAs are one of the most widely studied HEAs.
[0004] If the connection between zirconium alloy and CoCrFeMnNi high entropy alloy is achieved, the advantages of each material can be brought into play, and its application range will be wider. Therefore, as a structural material, the connection between zirconium alloy and high entropy alloy is of great significance for promoting the application of zirconium alloy in the space field and obtaining high reliability and long life spacecraft. There are two main difficulties in the brazing connection between high entropy alloy and zirconium alloy: First, because high entropy alloy has multiple components, when using commonly used binary or ternary brazing filler metals to braze high entropy alloy and zirconium alloy, a large amount of intermetallic compound phase is easily generated in the joint during the welding process, which weakens the joint strength. Second, the thermal expansion coefficient between the two is mismatched (Zr alloy: 5.7×10 -6 K -1 ;CoCrFeMnNi HEA:15×10 -6 K -1 ), which can easily cause large residual stress during welding and affect the mechanical properties of the joint. Summary of the Invention
[0005] In order to overcome the shortcomings of the existing zirconium alloy and high entropy alloy dissimilar material connection technology, a method for brazing zirconium alloy and high entropy alloy using Cu foil contact reaction is provided.
[0006] A method for brazing zirconium alloy and high entropy alloy using Cu foil contact reaction, the method comprising the following steps:
[0007] Step 1: The surfaces of the zirconium alloy and the high entropy alloy to be welded are polished and pretreated respectively to obtain the base materials to be welded, and Cu foil is used as the brazing filler metal;
[0008] Step 2: Clean the zirconium alloy, high entropy alloy and Cu foil obtained in step 1 with acetone and anhydrous ethanol;
[0009] Step 3: Place the Cu foil between the surfaces to be welded of the high entropy alloy and the zirconium alloy to form a sample to be welded, and apply pressure to the uppermost layer of the sample to be welded so that the surfaces to be welded of the high entropy alloy and the zirconium alloy are in full contact with the Cu foil;
[0010] Step 4: Place the sample to be welded in step 3 in a vacuum brazing furnace, heat it to a brazing temperature of 900°C to 970°C under a vacuum environment, keep it at the brazing temperature for 1 min to 20 min, and then cool it to room temperature;
[0011] The above-mentioned high entropy alloy is CoCrFeMnNi high entropy alloy.
[0012] In step 1 of the present invention, the surfaces to be welded of the high entropy alloy and the zirconium alloy are polished in sequence using 180#, 400#, 800#, 1200#, 2000# and 3000# metallographic sandpaper. The smooth polished surfaces to be welded can enable a more complete contact reaction between the high entropy alloy, the zirconium alloy and the Cu foil.
[0013] The purity of the Cu foil in the present invention is not less than 95%, and the thickness of the Cu foil is 10 μm-150 μm.
[0014] In step 2 of the present invention, the zirconium alloy, high entropy alloy and Cu foil are first ultrasonically cleaned with acetone for 30 minutes, then ultrasonically cleaned with anhydrous ethanol for 15 minutes, and blown dry to obtain dust-free and oil-free materials to be welded.
[0015] In step 3 of the present invention, a graphite block is placed above the sample to be welded, and the graphite block applies a pressure of 0.5~5×10 3 Pa.
[0016] The vacuum heating described in step 4 of the present invention includes the following steps: -3 Heating is carried out under vacuum conditions below Pa, and the temperature is increased to the brazing temperature at a rate of 10℃ / min and kept warm. After brazing, the temperature is lowered to 200℃ at a rate of 5℃ / min, and finally cooled to room temperature with the furnace.
[0017] Compared with the prior art, the advantages of the present invention are:
[0018] This invention achieves a high-strength, effective connection between a zirconium alloy and a CoCrFeMnNi high-entropy alloy. After brazing, the copper (Cu) foil has high mutual solubility with the five elements (Co, Cr, Mn, Fe, and Ni) in the high-entropy alloy, eliminating the formation of intermetallic compounds. The Cu foil exhibits excellent plasticity, effectively relieving residual stress in the joint through plastic deformation during brazing, thereby increasing joint strength. The joint brazed using Cu contact reaction brazing exhibits high connection strength, with a maximum room-temperature shear strength of 140.1 MPa, 3.6 times that of a joint brazed using Ag-Cu filler metal. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 Assembly drawing of the sample to be welded;
[0020] Figure 2 Backscattered photographs of the brazed joints obtained in Examples 1-5 of the present invention;
[0021] Figure 3 Fracture path diagrams of brazed joints in Examples 1, 2, and 5 of the present invention;
[0022] Figure 4 Backscattered photograph of the brazed joint obtained in the comparative example of the present invention. DETAILED DESCRIPTION
[0023] In order to enable people in this technical field to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the drawings in the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.
[0024] A method for brazing a zirconium alloy and a high entropy alloy using Cu foil contact reaction, comprising the following steps:
[0025] Step 1: The surfaces to be welded of the zirconium alloy and the CoCrFeMnNi high-entropy alloy are polished in sequence with 180#, 400#, 800#, 1200#, 2000#, and 3000# metallographic sandpaper to obtain the base material to be welded, and Cu foil is used as the brazing filler metal;
[0026] Step 2: Immerse the base metal and Cu foil obtained in step 1 in an acetone solution for ultrasonic cleaning for 30 minutes and then blow dry. Then, place them in an absolute ethanol solution for ultrasonic cleaning for 15 minutes and then blow dry.
[0027] Step 3: Place the Cu foil between the surfaces to be welded of the high entropy alloy and the zirconium alloy to form a sample to be welded. Place a graphite block on the sample to be welded and apply 0.5~5×10 3Pa pressure to prevent the components from moving during the brazing process and to ensure that the surfaces to be welded of the high entropy alloy and zirconium alloy are in full contact with the Cu foil;
[0028] Step 4: Place the sample prepared in step 3 in a vacuum brazing furnace and reduce the pressure of the vacuum brazing furnace to 5x10 -3 When the temperature is below pa, heat to 910~990℃ at a rate of 10℃ / min, keep warm for 1min~20min, cool to 200℃ at a rate of 5℃ / min, and finally cool to room temperature with the furnace.
[0029] Example 1:
[0030] Step 1: Polish the surfaces of the zirconium alloy and the CoCrFeMnNi high-entropy alloy to be welded using 180#, 400#, 800#, 1200#, 2000#, and 3000# metallographic sandpapers in sequence to obtain the base materials to be welded. Use Cu foil with a thickness of 100μm and a purity of not less than 95% as the brazing filler metal;
[0031] Step 2: Immerse the Cu foil and the base material to be welded in acetone solution, ultrasonically clean them for 30 minutes, and then blow dry them. Then, place them in anhydrous ethanol solution and ultrasonically clean them for 15 minutes, and then blow dry them.
[0032] Step 3: Place the Cu foil between the surfaces to be welded of the high entropy alloy and the zirconium alloy to form a welded sample. The assembly diagram is as follows: Figure 1 As shown in the figure, a graphite block is placed on the sample to be welded, and a pressure of 0.5 MPa is applied to the sample to be welded;
[0033] Step 4: Place the sample to be welded in a vacuum brazing furnace and set the vacuum degree at 5.0×10 -3 The brazed joint was heated to 950°C at a rate of 10°C / min in a Pa environment, held at that temperature for 10 minutes, cooled to 200°C at a rate of 5°C / min, and then cooled to room temperature. The room temperature shear strength of the resulting brazed joint was 140.1 MPa.
[0034] Example 2:
[0035] The difference between this embodiment and embodiment 1 is that the brazing temperature used in step 4 is 900° C. The other steps are the same as those in the specific embodiment. The room temperature shear strength of the brazed joint obtained at this time is 41.2 MPa.
[0036] Example 3:
[0037] The difference between this embodiment and embodiment 1 is that the brazing temperature used in step 4 is 910° C. The other steps are the same as those in the specific embodiment. The room temperature shear strength of the brazed joint obtained at this time is 51.4 MPa.
[0038] Example 4:
[0039] The difference between this embodiment and the embodiment is that the brazing temperature used in step 4 is 930° C. The other steps are the same as those in the embodiment. At this time, the room temperature shear strength of the obtained brazed joint is 105.5 MPa.
[0040] Example 5:
[0041] The difference between this embodiment and the embodiment is that the brazing temperature used in step 4 is 970° C. The other steps are the same as those in the embodiment. At this time, the room temperature shear strength of the obtained brazed joint is 82.1 MPa.
[0042] Example 6:
[0043] The difference between this embodiment and the embodiment is that the holding time in step 4 is 1 minute, and the other steps are the same as those in the embodiment. At this time, the room temperature shear strength of the obtained brazed joint is 80.5 MPa.
[0044] Example 7:
[0045] The difference between this embodiment and the embodiment is that the holding time in step 4 is 5 minutes, and the other steps are the same as those in the embodiment. At this time, the room temperature shear strength of the obtained brazed joint is 117.2 MPa.
[0046] Example 8:
[0047] The difference between this embodiment and the embodiment is that the holding time in step 4 is 15 minutes, and the other steps are the same as those in the embodiment. At this time, the room temperature shear strength of the obtained brazed joint is 120.1 MPa.
[0048] Example 9:
[0049] The difference between this embodiment and the embodiment is that the holding time in step 4 is 20 minutes, and the other steps are the same as those in the embodiment. At this time, the room temperature shear strength of the obtained brazed joint is 59.8 MPa.
[0050] Example 10:
[0051] In this example, different thicknesses of Cu foil were selected in step 1 of Example 1, namely 10 μm, 50 μm, and 150 μm. The resulting brazed joints were then subjected to shear strength testing. It was found that the shear strength within this thickness range was essentially the same, ranging from 100 to 140 MPa. However, for thicknesses below 10 μm, higher requirements are placed on the surface flatness and roughness of the high-entropy alloy, making it prone to unwelded joints after welding. For thicknesses above 150 μm, some of the Cu foil reacted incompletely, making the joints prone to brittle fracture. Therefore, the selection of a thickness of 10-150 μm is a key factor in determining the thickness of the brazed joint.
[0052] Comparative Example: Backscattered image of the joint obtained by brazing zirconium alloy and CoCrFeMnNi high entropy alloy using silver-based solder as the intermediate layer in the prior art (890 o C / 10min), it can be clearly seen from the figure that the microstructure of the joint is mainly composed of brittle Zr (Ag, Cu) and Cu 10 The composition of Zr7+Zr2Cu is a variety of intermetallic compounds, resulting in the shear strength of the joint being only 39.1 MPa.
[0053] from Figure 3 It can be seen that at a lower brazing temperature (900℃), due to the restriction of atomic diffusion and reaction, a thinner Zr(Cr, Mn)2 layer is formed, the joint breaks at the interface between HEA and the brittle Zr(Cr, Mn)2 layer, and the joint obtains a relatively low shear strength; as the brazing temperature increases to 950℃, the wettability of the molten brazing material to HEA is enhanced, and a continuous and thicker Zr(Cr, Mn)2 layer is formed. The joint first breaks at the HEA / Zr(Cr, Mn)2 interface, and then the crack propagates along the large brittle Zr2(Cu, Ni) phase in the brazing seam, and the joint obtains the highest shear strength; when the brazing temperature reaches 970℃, the brittle Zr(Cr, Mn)2 layer on the HEA side is significantly thickened, and the massive Zr(Cr, Mn)2 phase in the brazing seam is Mn)2 and Zrss increase, Zr has excellent plasticity, which helps to release the residual stress in the joint through its plastic deformation. With the increase of brazing temperature, more Zrss is generated in the brazing seam, which enhances the relief of residual stress. However, the residual thermal stress in the brazing seam increases with the increase of brazing temperature, resulting in the nucleation and expansion of cracks along the brittle phase boundary. During the shear test, the microcracks formed may be the cause of stress concentration and crack initiation, affecting the shear strength of the brazed joint. Therefore, at the high brazing temperature of 970℃, due to the stress concentration effect, the brittle hard phase Zr2(Cu, Ni) becomes the most fragile part of the HEA / Zr-3 joint, and the joint mainly breaks along the brittle Zr2(Cu, Ni) phase in the brazing seam, and the shear strength of the joint decreases significantly. It can be seen from the backscattered photos and fracture diagrams of the brazed joints at different temperatures that the intermetallic compound in the brazing seam of the joint obtained by this brazing method is Zr(Cu, Ni)2, which is layered and tightly combined with HEA. Another compound Zr2(Cu, Ni) and Zrss form a network structure distributed in the brazing seam, which has better strength than the staggered distribution of multiple intermetallic compounds in the comparative example.
[0054] The experimental results show that Cu foil has good plasticity and can effectively relieve the residual stress of the joint through plastic deformation during the brazing process. After the Cu foil contacts the zirconium alloy, a eutectic reaction occurs to generate a Zr-Cu liquid phase, which then reacts with the high-entropy alloy to form Crss on the side adjacent to the high-entropy alloy. The Zrss+Zr(Cr,Mn)2 reaction layer is formed. The brazing seam is mainly composed of dispersed Zrss and massive Zr2Cu. When the joint is subjected to stress after welding, Zrss can improve the mechanical properties of the joint through plastic deformation. The obtained brazed joint has uniform interface structure and no cracks. The brazed joint has high connection strength. The maximum shear strength of the brazed joint at room temperature is 140.1MPa, which is 3.6 times the shear strength of the brazed joint brazed with Ag-Cu filler metal.
Claims
1. A method for brazing zirconium alloy and high entropy alloy using Cu foil contact reaction brazing, characterized in that: The method uses the following steps: Step 1: The surfaces of the zirconium alloy and the high entropy alloy to be welded are polished and pretreated respectively to obtain the base materials to be welded, and Cu foil is used as the brazing filler metal; Step 2: Clean the zirconium alloy, high entropy alloy and Cu foil obtained in step 1 with acetone and anhydrous ethanol; Step 3: Place the Cu foil between the surfaces to be welded of the high entropy alloy and the zirconium alloy to form a sample to be welded, and apply pressure to the uppermost layer of the sample to be welded so that the surfaces to be welded of the high entropy alloy and the zirconium alloy are in full contact with the Cu foil; Step 4: Place the sample to be welded in step 3 in a vacuum brazing furnace, heat it to a brazing temperature of 900°C to 970°C under a vacuum environment, keep it at the brazing temperature for 1 min to 20 min, and then cool it to room temperature; The above-mentioned high entropy alloy is CoCrFeMnNi high entropy alloy.
2. The method of brazing zirconium alloy and high entropy alloy using Cu foil contact reaction according to claim 1, characterized in that: In step 1, the surfaces to be welded of the high entropy alloy and zirconium alloy are polished with 180#, 400#, 800#, 1200#, 2000# and 3000# metallographic sandpaper in sequence.
3. The method for brazing zirconium alloy and high entropy alloy using Cu foil contact reaction according to claim 1, characterized in that: The purity of the Cu foil is not less than 95%, and the thickness of the Cu foil is 10μm-150μm.
4. The method of brazing zirconium alloy and high entropy alloy using Cu foil contact reaction according to claim 1, characterized in that: In step 2, the zirconium alloy, high entropy alloy and Cu foil are first ultrasonically cleaned with acetone for 30 minutes, then ultrasonically cleaned with anhydrous ethanol for 15 minutes, and then blown dry.
5. The method for brazing zirconium alloy and high entropy alloy using Cu foil contact reaction brazing according to claim 1, characterized in that: In step 3, a graphite block is placed on the sample to be welded. The graphite block applies a pressure of 0.5~5×10 3 Pa.
6. The method of brazing zirconium alloy and high entropy alloy using Cu foil contact reaction according to claim 1, characterized in that: The vacuum heating described in step 4 is included in the 5x10 -3 Heating is carried out under vacuum conditions below Pa, and the temperature is increased to the brazing temperature at a rate of 10℃ / min and kept warm. After brazing, the temperature is lowered to 200℃ at a rate of 5℃ / min, and finally cooled to room temperature with the furnace.