Preparation method of CoCrNi medium entropy alloy / 316L stainless steel composite sheet

Abstract

The present invention provides a method for preparing a CoCrNi medium-entropy alloy / 316L stainless steel composite sheet, belonging to the field of metal-based composite material forming. The preparation method comprises: preparing a CoCrNi medium-entropy alloy / 316L stainless steel composite thick plate by explosive welding; cutting a blank with good interface bonding from the composite thick plate; then performing multiple-pass hot rolling; annealing the hot-rolled plate and then performing multiple-pass cold rolling; stress relief annealing after cold rolling, and air cooling to obtain the medium-entropy alloy / stainless steel composite sheet. The CoCrNi medium-entropy alloy / 316L stainless steel composite sheet obtained by this method has uniform thickness, a flat bonding surface, excellent mechanical properties, a simple production process, and is suitable for industrial production.

Description

Technical Field

[0001] The invention relates to a preparation method of a CoCrNi medium entropy alloy / 316L stainless steel composite sheet, and belongs to the field of metal-based composite material forming. Background Art

[0002] The equiatomic ratio CoCrNi medium-entropy alloy, with its high hardness, strength, high-temperature oxidation resistance, corrosion resistance, and radiation resistance, is a promising new structural and functional integrated material. However, its high raw material prices and manufacturing costs have limited its widespread application. By combining the CoCrNi medium-entropy alloy with inexpensive 316L stainless steel, the resulting layered composite plate not only retains the excellent properties of the CoCrNi medium-entropy alloy but also significantly reduces manufacturing costs.

[0003] Currently, the main methods for preparing layered composite materials on the market include rolling lamination, solid-liquid lamination, diffusion lamination, explosive lamination, and explosive lamination combined with rolling. Rolling lamination typically requires a first-pass deformation greater than 50%, placing high demands on the rolling mill's rolling force and requiring the rolled material to possess good plasticity and low deformation resistance. While hot rolling can address these issues, it can lead to severe oxidation, resulting in low interfacial bonding or bond strength. Solid-liquid lamination typically requires a large melting point difference between the materials being composited. A smaller melting point difference can result in melt-through of the solid-phase sheet. Diffusion lamination is primarily suitable for joining dissimilar metals of smaller dimensions and complex shapes. Explosive lamination is more suitable for thicker materials. Explosive lamination combined with rolling combines the advantages of both processes and is currently the predominant method for preparing layered metal composite sheets. Because the explosive welding process already achieves metallurgical bonding at the interface of the dissimilar materials, the rolling process eliminates the need for large deformations and the concerns about interfacial oxidation associated with hot rolling, significantly reducing manufacturing costs and complexity.

[0004] Existing patents report on the use of explosive bonding and rolling to produce layered composite sheets from various materials. However, due to the significant differences in material properties, the technical parameters for the explosive welding and rolling processes vary significantly, and each of these parameters can affect the other. Furthermore, to ensure the performance of the final composite sheet, the interface structural characteristics of the explosive welding process and the microstructural control of the rolling process must also be considered. Therefore, the technical processes and parameters provided by existing patents are unlikely to be universally applicable.

[0005] Since there is currently no reference for the preparation technology of CoCrNi medium entropy alloy / 316L stainless steel composite thin plates, it is urgent to develop a technology that can meet the requirements of explosive welding + rolling of CoCrNi medium entropy alloy and 316L stainless steel to prepare composite thin plates. Summary of the Invention

[0006] To address the shortcomings of the prior art, the present invention provides a method for preparing a CoCrNi medium-entropy alloy / 316L stainless steel composite sheet. The composite sheet is produced using explosive welding and rolling techniques, has a thickness of 0.5 to 2 mm, and the thickness of the CoCrNi medium-entropy alloy is 0.15 to 0.25 mm, with a flat interface.

[0007] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0008] The present invention provides a preparation method of a CoCrNi medium-entropy alloy / 316L stainless steel composite thin plate, comprising the steps of: explosively welding a CoCrNi medium-entropy alloy plate and a 316L stainless steel plate to obtain a CoCrNi medium-entropy alloy / 316L stainless steel composite thick plate; preheating the CoCrNi medium-entropy alloy / 316L stainless steel composite thick plate, and then hot-rolling the plate to obtain a hot-rolled plate; performing a first annealing on the hot-rolled plate; cold-rolling the annealed hot-rolled plate to obtain a cold-rolled plate; and finally performing a second annealing on the cold-rolled plate to obtain the CoCrNi medium-entropy alloy / 316L stainless steel composite thin plate.

[0009] The bimetallic interface of the CoCrNi medium entropy alloy / 316L stainless steel composite thick plate is a flat interface.

[0010] The preparation method of the present invention first obtains a CoCrNi medium-entropy alloy / 316L stainless steel composite thick plate having a straight bimetallic interface by explosion welding. The straight interface can ensure uniformity of layer thickness during the rolling process. During the rolling process, since the plastic deformation ability of the CoCrNi medium-entropy alloy is lower than that of 316L stainless steel, that is, the CoCrNi medium-entropy alloy has a stronger work hardening ability, the present invention first performs hot rolling, utilizes the dynamic softening behavior existing in the hot rolling process to alleviate part of the work hardening, and then performs annealing treatment to convert the CoCrNi medium-entropy alloy / 316L stainless steel composite thick plate into a soft state, thereby facilitating cold rolling. After further cold rolling, a CoCrNi medium-entropy alloy / 316L stainless steel composite thin plate with excellent mechanical properties can be obtained.

[0011] In a preferred embodiment, the process of explosively welding the CoCrNi medium-entropy alloy plate and the 316L stainless steel plate to obtain the CoCrNi medium-entropy alloy / 316L stainless steel composite thick plate is as follows: annealing the CoCrNi medium-entropy alloy plate, solution treating the 316L stainless steel plate, and then laying sand, anvils, 316L stainless steel plates, support columns, CoCrNi medium-entropy alloy plates, corrugated paper, and explosives in sequence from bottom to top on the explosion field, and finally explosively welding them to obtain the plate.

[0012] Further preferably, the CoCrNi medium-entropy alloy plate is annealed at a temperature of 1000-1100°C for 1-2 hours. By completely softening and annealing the medium-entropy alloy plate within the above parameter range, the alloy has good plasticity, ensuring that the explosion process easily achieves metallurgical bonding of the material without cracking.

[0013] Further preferably, the 316L stainless steel plate is subjected to a solution treatment at a temperature of 1100-1150° C. for 1.5-2 hours. In actual operation, after the solution treatment is completed, rapid cooling, such as water cooling, is performed.

[0014] Through the above-mentioned solution treatment, the stainless steel plate is softened and has good plasticity, ensuring that the metallurgical bonding of the materials can be easily achieved without cracking during the explosion process.

[0015] In a preferred embodiment, the explosives used for the explosive welding are composed, by mass percentage, of 50-55% antimony-free rock ammonium nitrate explosive, 12-15% calcium carbonate powder, 8-10% silicon carbide powder, 10-12% perlite powder, 10-12% sawdust, and 8-10% sodium chloride.

[0016] The inventors found that, by adjusting the ratio of the explosive components, the obtained explosive has a low detonation velocity, and the interface of the CoCrNi medium entropy alloy / 316L stainless steel composite thick plate obtained by explosive welding is a straight interface.

[0017] Further preferably, the explosive used for the explosive welding is composed of the following by mass percentage: 51% antimony-free rock ammonium nitrate explosive, 12% calcium carbonate powder, 9% silicon carbide powder, 10% perlite powder, 10% sawdust, and 8% sodium chloride.

[0018] The explosive composition of the present invention uses antimony-free rock ammonium nitrate as a basic explosive. Calcium carbonate, silicon carbide powder and sodium chloride are added to the basic explosive to reduce the detonation velocity of the explosive. Perlite powder and wood chips are added to increase the fluffiness, which is beneficial for detonation. Furthermore, through the synergistic effect of the above components, a flat interface can be obtained despite a low detonation velocity, laying a foundation for the interface to remain flat after subsequent rolling, and ultimately ensuring that the thickness of the obtained thin plate is uniform.

[0019] Although the wavy interface provides additional strength, the huge deformation force generated during the rolling process, coupled with the thermal effect, further strengthens the metallurgical bonding of the interface, and there is no need to rely on the wavy interface to provide additional strength. Therefore, the present invention uses the above-mentioned components to obtain a straight interface, so that the rolled thin plate has excellent layer thickness uniformity, thereby improving the quality of the thin plate.

[0020] In a preferred embodiment, the detonation velocity of the explosive is 1600-2100 m / s.

[0021] In a preferred embodiment, the thickness of the CoCrNi medium entropy alloy / 316L stainless steel composite thick plate is 7-45 mm, wherein the thickness of the CoCrNi medium entropy alloy layer is 2-5 mm, and the thickness of the 316L stainless steel layer is 5-40 mm.

[0022] During the actual operation, the parts with poor bonding around the explosively composite thick plate are removed, and the blank with good interface bonding in the middle is cut for rolling.

[0023] In a preferred embodiment, the preheating temperature is 820-850° C. and the holding time is 45-120 minutes. Hot rolling is performed directly after preheating.

[0024] In a preferred embodiment, the hot rolling is multi-pass hot rolling, the rolling speed of the hot rolling is 20-30 m / min, the deformation of the pass is 15-20%, the total deformation of each pass is 40-50%, and the hot rolling is completed when a hot-rolled plate of 2.5-5 mm is obtained.

[0025] The hot rolling of the present invention avoids the maximum shear stress surface during rolling being located at the bonding surface of the explosive composite thick plate by controlling the rolling speed and the deformation amount of each pass, thereby not only reducing the risk of separation of the two metals during rolling, but also ensuring the coordinated deformation of the two metals, which is more conducive to the thickness control of each layer of metal. In addition, the hot rolling of the present invention adopts multi-fire and multi-pass hot rolling. After multiple passes, the hot rolling is returned to the furnace for short-term heat preservation at the preheating temperature, thereby improving production efficiency.

[0026] In a preferred embodiment, the first annealing temperature is 780-800°C, and the holding time is 60-120 minutes. Annealing at these temperatures eliminates the work hardening from the hot rolling process, leaving both the base plate and the composite plate in a soft state, facilitating subsequent cold rolling. If the temperature is too low, complete softening will not occur; if the temperature is too high, the grains will grow, hindering the control of final properties.

[0027] In a preferred embodiment, the cold rolling process is performed at a speed of 15-20 m / min and a deformation per pass of 10-15%. These cold rolling process parameters can prevent warping of the sheet during the cold rolling process, ensure the flatness of the sheet, and provide a foundation for subsequent annealing to control the properties of the composite sheet.

[0028] In a preferred embodiment, the second annealing temperature is 650-700°C, and the holding time is 60-70 minutes. By controlling the second annealing temperature within this range, a fine recrystallized structure can be obtained. If the temperature is too low, the degree of recrystallization is low; if the temperature is too high, the grains will grow, both of which will reduce performance.

[0029] The CoCrNi medium-entropy alloy / 316L stainless steel composite thin plate prepared by the present invention has a room temperature yield strength of 1000-1150 MPa, a tensile strength of 1140-1260 MPa, and an elongation after fracture of 11-18%.

[0030] Beneficial effects

[0031] By optimizing explosive composition and controlling the rolling process, the present invention utilizes explosive welding combined with rolling technology to produce CoCrNi medium-entropy alloy / 316L stainless steel composite sheets. The resulting composite sheets exhibit uniform thickness, a flat interface, and excellent mechanical properties. First, during explosive welding, the explosive composition significantly influences the interface morphology. Through multiple experiments, the present invention has developed an explosive composition that achieves a flat interface on thick plates after explosive welding, paving the way for a consistent flat interface after subsequent rolling.

[0032] Secondly, when selecting the hot rolling process, based on the calculation results of rolling deformation mechanics, the rolling speed and pass deformation are limited at the same time to avoid the maximum shear stress surface during rolling being located at the bonding surface of the explosive composite thick plate. This not only reduces the risk of separation of the two metals during rolling, but also ensures the coordinated deformation of the two metals, which is more conducive to the thickness control of each layer of metal.

[0033] Finally, the annealing treatment between hot and cold rolling, as well as the selection of the cold rolling process, are based on the different work hardening capabilities of the CoCrNi medium-entropy alloy and 316L stainless steel. The process parameters of this invention prevent warping of the sheet during the cold rolling process, ensuring sheet flatness and providing a foundation for subsequent annealing to manipulate the properties of the composite sheet.

[0034] The above process and parameter selection ensure that the CoCrNi medium-entropy alloy / 316L stainless steel composite sheet prepared by the present invention has excellent mechanical properties, with a room temperature yield strength of 1000-1150 MPa, a tensile strength of 1140-1260 MPa, and an elongation after fracture of 11-18%. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The CoCrNi medium entropy alloy / 316L stainless steel composite sheet sample prepared in Example 1.

[0036] Figure 2 Interface morphology of the CoCrNi medium-entropy alloy / 316L stainless steel composite sheet prepared in Example 1.

[0037] Figure 3 Tensile mechanical curves of composite sheets after annealing at different temperatures. DETAILED DESCRIPTION

[0038] The following are preferred embodiments of the present invention, but not all embodiments. Without departing from the principle of this process innovation, any equivalent process transformation made by utilizing the contents of the present invention specification, or directly or indirectly applied in other related technical fields, shall be deemed to be within the scope of patent protection of this invention.

[0039] Example 1

[0040] CoCrNi medium entropy alloy sheet and 316L stainless steel sheet were selected as raw materials. First, the CoCrNi medium entropy alloy sheet was subjected to a complete softening annealing treatment at 1000℃ / 2h, and the 316L stainless steel was subjected to a solution treatment and rapid cooling treatment at 1100℃ / 2h. Then the following steps were followed:

[0041] S1. A stainless steel plate with dimensions of 300 mm × 500 mm in length × width and 5 mm in thickness was selected as the base plate, and a CoCrNi medium-entropy alloy with dimensions of 320 mm × 520 mm in length × width and 2 mm in thickness was selected as the composite plate. Sand, anvils, 316L stainless steel plates, support columns, CoCrNi medium-entropy alloy plates, corrugated paper, and explosives were laid in order from bottom to top on the blast field and explosively welded to obtain an explosive composite thick plate with a thickness of 7 mm (2 mm medium-entropy alloy + 5 mm stainless steel). The explosive composition and ratio of the explosives used for explosive welding were: 51% antimony-free rock ammonium nitrate explosive, 12% calcium carbonate powder, 9% silicon carbide powder, 10% perlite powder, 10% wood chips, and 8% sodium chloride. The detonation velocity of the explosives was 2000 m / s. The charge thickness during operation was 50 mm.

[0042] S2. Remove the poorly bonded parts around the explosively composite thick plate and cut a blank with a length × width of 200 mm × 400 mm in the middle and good interface bonding for rolling.

[0043] S3. Place the billet to be rolled in a heating furnace at 820°C and keep it at this temperature for 45 minutes.

[0044] S4. After the insulation is completed, hot rolling is carried out directly, with the rolling speed controlled at 30 m / min and the deformation per pass at 15%. When the billet thickness reaches 4 mm, it is returned to the furnace for insulation for 10 minutes. Then, a second hot rolling is carried out using the same rolling speed and deformation per pass. When the billet thickness reaches 2.5 mm, rolling is stopped.

[0045] S5. Place the hot-rolled plate in an annealing furnace at 780°C for 60 minutes and then air-cool.

[0046] S6. The annealed hot-rolled composite plate is subjected to multiple cold rolling passes at a controlled rolling speed of 15 m / min and a pass deformation of 10%. The rolling is stopped when the billet thickness reaches 0.5 mm.

[0047] S7. The cold-rolled sheet is subjected to stress relief annealing at 650°C for 60 min and then naturally cooled to obtain a medium-entropy alloy / stainless steel composite sheet.

[0048] The thickness of the CoCrNi medium-entropy alloy / 316L stainless steel composite plate obtained by this method is 0.5 mm, wherein the thickness of the CoCrNi medium-entropy alloy is 0.15 mm, the thickness of the 316L stainless steel is 0.35 mm, and the interface between the two metals is flat. The composite plate has a yield strength of 1102 MPa, a tensile strength of 1252 MPa, and an elongation at break of 11.2%.

[0049] Example 2

[0050] CoCrNi medium entropy alloy sheet and 316L stainless steel sheet were selected as raw materials. First, the CoCrNi medium entropy alloy sheet was subjected to a complete softening annealing treatment at 1000℃ / 2h, and the 316L stainless steel was subjected to a solution treatment and rapid cooling treatment at 1100℃ / 2h. Then the following steps were followed:

[0051] S1. A stainless steel plate with dimensions of 300 mm × 500 mm in length × width and 20 mm in thickness was selected as the base plate, and a CoCrNi medium-entropy alloy with dimensions of 320 mm × 520 mm in length × width and 3 mm in thickness was selected as the composite plate. Sand, anvils, 316L stainless steel plates, support columns, CoCrNi medium-entropy alloy plates, corrugated paper, and explosives were laid in order from bottom to top on the blast field and explosively welded to obtain an explosive composite thick plate with a thickness of 23 mm (3 mm medium-entropy alloy + 20 mm stainless steel). The explosive composition and ratio used for explosive welding were as follows: 51% antimony-free rock ammonium nitrate explosive, 12% calcium carbonate powder, 9% silicon carbide powder, 10% perlite powder, 10% wood chips, and 8% sodium chloride. The detonation velocity of the explosive was 2000 m / s. The charge thickness during operation was 60 mm.

[0052] S2. Remove the poorly bonded parts around the explosively composite thick plate and cut a blank with a length × width of 200 mm × 400 mm in the middle and good interface bonding for rolling.

[0053] S3. Place the billet to be rolled in a heating furnace at 830°C and keep it at this temperature for 60 minutes.

[0054] S4. After the insulation is completed, hot rolling is carried out directly, with the rolling speed controlled at 25 m / min and the deformation per pass at 18%. When the billet thickness reaches 12 mm, it is returned to the furnace for insulation for 10 minutes. Then, a second hot rolling is carried out using the same rolling speed and deformation per pass. When the billet thickness reaches 6.5 mm, it is returned to the furnace for insulation for 10 minutes. Then, a third hot rolling is carried out using the same rolling speed and deformation per pass. When the billet thickness reaches 4 mm, rolling is stopped.

[0055] S5. Place the hot-rolled plate in an annealing furnace at 790°C for 90 minutes and then air-cool.

[0056] S6. The annealed hot-rolled composite plate is subjected to multiple cold rolling passes at a controlled rolling speed of 18 m / min and a pass deformation of 12%. The rolling is stopped when the billet thickness reaches 1.5 mm.

[0057] S7. The cold-rolled sheet is subjected to stress relief annealing at 650°C for 60 min and then naturally cooled to obtain a medium-entropy alloy / stainless steel composite sheet.

[0058] The thickness of the CoCrNi medium-entropy alloy / 316L stainless steel composite plate obtained by this method is 1.5 mm, of which the thickness of the CoCrNi medium-entropy alloy is 0.2 mm and the thickness of the 316L stainless steel is 1.3 mm. The interface between the two metals is flat. The composite plate has a yield strength of 1085 MPa, a tensile strength of 1207 MPa, and an elongation at break of 13.8%.

[0059] Example 3

[0060] CoCrNi medium entropy alloy sheet and 316L stainless steel sheet were selected as raw materials. First, the CoCrNi medium entropy alloy sheet was subjected to complete softening annealing treatment at 1000℃ / 2h, and the 316L stainless steel was subjected to solid solution + rapid cooling treatment at 1100℃ / 2h. Then the following steps were followed:

[0061] S1. A stainless steel plate with dimensions of 300 mm × 500 mm in length × width and 40 mm in thickness was selected as the base plate, and a CoCrNi medium-entropy alloy with dimensions of 320 mm × 520 mm in length × width and 5 mm in thickness was selected as the composite plate. Sand, anvils, 316L stainless steel plates, support columns, CoCrNi medium-entropy alloy plates, corrugated paper, and explosives were laid in order from bottom to top on the blast field and explosively welded to obtain an explosive composite thick plate with a thickness of 45 mm (5 mm medium-entropy alloy + 40 mm stainless steel). The explosive composition and ratio used for explosive welding were as follows: 51% antimony-free rock ammonium nitrate explosive, 12% calcium carbonate powder, 9% silicon carbide powder, 10% perlite powder, 10% wood chips, and 8% sodium chloride. The detonation velocity of the explosive was 2000 m / s, and the charge thickness during operation was 70 mm.

[0062] S2. Remove the poorly bonded parts around the explosively composite thick plate and cut a blank with a length × width of 200 mm × 400 mm in the middle and good interface bonding for rolling.

[0063] S3. Place the billet to be rolled in a heating furnace at 850°C and keep it at this temperature for 120 minutes.

[0064] S4. Hot rolling is carried out directly after the insulation is completed, with the rolling speed controlled at 30 m / min and the pass deformation at 20%. When the billet thickness reaches 25 mm, it is returned to the furnace for insulation for 10 minutes, and then the second hot rolling is carried out using the same rolling speed and pass deformation. When the billet thickness reaches 14 mm, it is returned to the furnace for insulation for 10 minutes, and then the third hot rolling is carried out using the same rolling speed and pass deformation. When the billet thickness reaches 8 mm, it is returned to the furnace for insulation for 10 minutes, and then the fourth hot rolling is carried out using the same rolling speed and pass deformation. When the billet thickness reaches 4.5 mm, rolling is stopped.

[0065] S5. Place the hot-rolled plate in an annealing furnace at 800°C for 120 minutes and then air-cool.

[0066] S6. The annealed hot-rolled composite plate is subjected to multiple cold rolling passes at a controlled rolling speed of 20 m / min and a pass deformation of 15%. The rolling is stopped when the billet thickness reaches 2 mm.

[0067] S7. The cold-rolled sheet is subjected to stress relief annealing at 700°C for 60 min and then naturally cooled to obtain a medium-entropy alloy / stainless steel composite sheet.

[0068] The thickness of the CoCrNi medium-entropy alloy / 316L stainless steel composite plate obtained by this method is 2 mm, wherein the thickness of the CoCrNi medium-entropy alloy is 0.25 mm, the thickness of the 316L stainless steel is 1.75 mm, and the interface between the two metals is flat. The composite plate has a yield strength of 1023 MPa, a tensile strength of 1152 MPa, and an elongation at break of 17.6%.

[0069] Example 4

[0070] CoCrNi medium entropy alloy sheet and 316L stainless steel sheet were selected as raw materials. First, the CoCrNi medium entropy alloy sheet was subjected to complete softening annealing treatment at 1000℃ / 2h, and the 316L stainless steel was subjected to solid solution + rapid cooling treatment at 1100℃ / 2h. Then the following steps were followed:

[0071] S1. A stainless steel plate with dimensions of 300 mm × 500 mm in length × width and 30 mm in thickness was selected as the base plate, and a CoCrNi medium-entropy alloy with dimensions of 320 mm × 520 mm in length × width and 4 mm in thickness was selected as the cladding plate for explosive welding to obtain an explosively composite thick plate with a thickness of 34 mm (4 mm medium-entropy alloy + 30 mm stainless steel). The explosive composition and ratio used for explosive welding were as follows: 51% antimony-free rock ammonium nitrate explosive, 12% calcium carbonate powder, 9% silicon carbide powder, 10% perlite powder, 10% wood chips, and 8% sodium chloride. The detonation velocity of the explosive was 2000 m / s. The charge thickness during operation was 65 mm.

[0072] S2. Remove the poorly bonded parts around the explosively composite thick plate and cut a blank with a length × width of 200 mm × 400 mm in the middle and good interface bonding for rolling.

[0073] S3. Place the billet to be rolled in a heating furnace at 840°C and keep it at this temperature for 90 minutes.

[0074] S4. After the insulation is completed, hot rolling is carried out directly, with the rolling speed controlled at 25 m / min and the deformation per pass at 18%. When the billet thickness reaches 18 mm, it is returned to the furnace for insulation for 10 minutes, and then a second hot rolling is carried out using the same rolling speed and deformation per pass. When the billet thickness reaches 10 mm, it is returned to the furnace for insulation for 10 minutes, and then a third hot rolling is carried out using the same rolling speed and deformation per pass. When the billet thickness reaches 5 mm, rolling is stopped.

[0075] S5. Place the hot-rolled plate in an annealing furnace at 800°C for 100 minutes and then air-cool.

[0076] S6. The annealed hot-rolled composite plate is subjected to multiple cold rolling passes at a controlled rolling speed of 18 m / min and a pass deformation of 12%. The rolling is stopped when the billet thickness reaches 1 mm.

[0077] S7. The cold-rolled sheet is subjected to stress relief annealing at 650°C for 60 min and then naturally cooled to obtain a medium-entropy alloy / stainless steel composite sheet.

[0078] The thickness of the CoCrNi medium-entropy alloy / 316L stainless steel composite plate obtained by this method is 2 mm, of which the thickness of the CoCrNi medium-entropy alloy is 0.12 mm and the thickness of the 316L stainless steel is 0.88 mm. The interface between the two metals is flat. The composite plate has a yield strength of 1140 MPa, a tensile strength of 1250 MPa, and an elongation at break of 12.3%.

[0079] Comparative Example 1

[0080] All other conditions were the same as in Example 1, except that the CoCrNi medium-entropy alloy was not annealed before explosive cladding, meaning the composite plate material was a hard CoCrNi medium-entropy alloy. Because hard medium-entropy alloys have high strength but poor plasticity, they are unable to withstand the intense plastic deformation during explosive cladding. Therefore, after the explosion, the strong impact force generated by the explosives caused the medium-entropy alloy composite plate to rupture, resulting in composite failure.

[0081] Comparative Example 2

[0082] Other conditions were the same as in Example 1, except that the explosive composition was changed to: 72% antimony-free rock ammonium nitrate explosive, 10% perlite powder, 10% sawdust, and 8% sodium chloride. The calcium carbonate powder and silicon carbide powder used to reduce the detonation velocity were removed, and the detonation velocity of the explosive was increased to 2800 m / s. Due to the high detonation velocity, the interface waveform was disordered, and excessive melting zones appeared.

[0083] Comparative Example 3

[0084] Other conditions were the same as in Example 1, except that the rolling speed was increased to 40 m / min during hot rolling, and the per-pass deformation was adjusted to 30%. Although increasing the rolling speed and per-pass deformation can improve production efficiency, the interface of the original composite thick plate is a weak point in the entire billet. High rolling speeds and large per-pass deformations increase friction between the plate surface and the rollers, leading to gaping at the interface during rolling and rolling failure.

[0085] Comparative Example 4

[0086] All other conditions were the same as in Example 1, with the exception that the second annealing temperature and duration were the same as in the first annealing, namely 780°C / 60 min, which is higher than the 650-700°C specified in the present invention. Since this annealing step is intended to adjust material properties, increasing the annealing temperature increases the degree of recrystallization and reduces the alloy's strength. After annealing at this temperature, the final composite plate had a room temperature yield strength of 800 MPa, a tensile strength of 1050 MPa, and an elongation of 32%, which are below the strength range specified in the present invention.

Claims

1. A method for preparing a CoCrNi medium entropy alloy / 316L stainless steel composite sheet, characterized by: A CoCrNi medium entropy alloy plate and a 316L stainless steel plate are explosion-welded to obtain a CoCrNi medium entropy alloy / 316L stainless steel composite thick plate, the CoCrNi medium entropy alloy / 316L stainless steel composite thick plate is preheated, and then hot-rolled to obtain a hot-rolled plate, the hot-rolled plate is subjected to a first annealing, the annealed hot-rolled plate is then cold-rolled to obtain a cold-rolled plate, and finally the cold-rolled plate is subjected to a second annealing to obtain a CoCrNi medium entropy alloy / 316L stainless steel composite thin plate; The bimetallic interface of the CoCrNi medium entropy alloy / 316L stainless steel composite thick plate is a flat interface; The process of explosively welding a CoCrNi medium-entropy alloy plate and a 316L stainless steel plate to obtain a CoCrNi medium-entropy alloy / 316L stainless steel composite thick plate is as follows: annealing the CoCrNi medium-entropy alloy plate, solution treating the 316L stainless steel plate, and then laying sand, anvils, 316L stainless steel plates, support columns, CoCrNi medium-entropy alloy plates, corrugated paper, and explosives on the explosion field from bottom to top, and finally explosive welding to obtain the plate. The annealing temperature is 1000-1100°C and the annealing time is 1-2 hours; The temperature of the solution treatment is 1100-1150°C, and the time of the solution treatment is 1.5-2 hours; The explosives used in the explosive welding are composed of the following by mass percentage: 50-55% antimony-free rock ammonium nitrate explosive, 12-15% calcium carbonate powder, 8-10% silicon carbide powder, 10-12% perlite powder, 10-12% sawdust, and 8-10% sodium chloride; The detonation velocity of the explosive is 1600-2100 m / s; The preheating temperature is 820-850°C and the holding time is 45-120 minutes; The hot rolling is a multi-pass hot rolling process with a rolling speed of 20-30 m / min, a deformation of 15-20% per pass, and a total deformation of 40-50% per pass. The hot rolling is completed when a hot-rolled plate with a thickness of 2.5-5 mm is obtained. The cold rolling speed is 15-20 m / min, and the deformation per pass is 10-15%; The first annealing temperature is 780-800°C, and the holding time is 60-120 minutes; The temperature of the second annealing is 650-700° C., and the holding time is 60-70 minutes.

2. The method for preparing a CoCrNi medium entropy alloy / 316L stainless steel composite sheet according to claim 1, characterized in that: The thickness of the CoCrNi medium entropy alloy / 316L stainless steel composite thick plate is 7-45 mm, wherein the thickness of the CoCrNi medium entropy alloy layer is 2-5 mm, and the thickness of the 316L stainless steel layer is 5-40 mm.

3. The method for preparing a CoCrNi medium entropy alloy / 316L stainless steel composite sheet according to claim 1 or 2, characterized in that: The CoCrNi medium entropy alloy / 316L stainless steel composite sheet has a room temperature yield strength of 1000-1150 MPa, a tensile strength of 1140-1260 MPa, and an elongation after fracture of 11-18%.

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