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

Abstract

The invention provides a preparation method of a CoCrNi medium-entropy alloy / 316L stainless steel composite sheet, and belongs to the field of metal matrix composite material forming. The preparation method comprises the following steps: preparing the CoCrNi medium-entropy alloy / 316L stainless steel composite thick plate by adopting an explosive welding method; cutting a blank with good interface bonding from the composite thick plate; then multi-fire and multi-pass hot rolling is carried out; performing multi-pass cold rolling on the hot-rolled plate after annealing; and stress relief annealing is conducted after cold rolling, and the medium-entropy alloy / stainless steel composite sheet is obtained after air cooling. The CoCrNi medium-entropy alloy / 316L stainless steel composite sheet obtained by the method is uniform in thickness, flat and straight in joint surface, excellent in mechanical property, simple in production process and 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 thin plate, and belongs to the field of metal matrix composite material forming. Background Art

[0002] The equiatomic ratio CoCrNi medium entropy alloy has the advantages of high hardness, high strength, high temperature oxidation resistance, corrosion resistance and radiation resistance. It is a new type of structural and functional integrated material with great application prospects, but its high raw material prices and manufacturing costs have limited its wide application to a certain extent. After the CoCrNi medium entropy alloy is compounded with the inexpensive 316L stainless steel, the prepared layered composite plate can not only retain the excellent properties of the CoCrNi medium entropy alloy, but also significantly reduce the manufacturing cost.

[0003] At present, the preparation methods of layered composite materials on the market mainly include rolling compounding, solid-liquid compounding, diffusion compounding, explosive compounding, explosive compounding + rolling and other methods. Rolling compounding usually requires that the deformation of the first pass is greater than 50%, so not only the rolling force of the rolling mill is required to be high, but also the material to be rolled needs to have good plasticity and low deformation resistance. Although the above problems can be solved by hot rolling, the material will undergo severe oxidation, resulting in low interface bonding rate or low bonding strength. Solid-liquid compounding usually requires that the composite material has a large melting point difference. When the melting point difference of the composite material is small, it may cause the solid phase plate to melt through. Diffusion compounding is mainly suitable for connecting dissimilar metals with small size and complex shape. Explosive compounding is more suitable for materials with larger thickness. Explosive compounding + rolling combines the advantages of the two processes and is currently the most important method for preparing layered metal composite sheets. Because the explosive welding process has achieved the metallurgical bonding of the interface of dissimilar materials, the rolling process does not need to use a large deformation, nor does it need to consider the interface oxidation problem of the hot rolling process, which significantly reduces the manufacturing cost and difficulty.

[0004] Existing patents report the technology of preparing layered composite sheets using explosive composite + rolling of various materials. However, due to the great differences in the properties of various materials, the technical parameters of the explosive welding process and the rolling process are very different, and the technical parameters will also affect each other. In addition, in order to ensure the performance of the final composite sheet, the interface structure characteristics of the explosive welding and the microstructure control of the rolling process must also be considered. Therefore, the technical processes and parameters provided by the existing patents are difficult to be universal.

[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] In view of the shortcomings of the prior art, the object of the present invention is to provide a method for preparing a CoCrNi medium entropy alloy / 316L stainless steel composite sheet. The composite sheet of the present invention is prepared by explosive welding + rolling technology, and its thickness is 0.5~2mm, wherein the thickness of the CoCrNi medium entropy alloy is 0.15~0.25mm, and the bonding interface is a straight interface.

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

[0008] The invention discloses a preparation method of a CoCrNi medium entropy alloy / 316L stainless steel composite thin plate, comprising the steps of: performing explosion welding on 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 performing hot rolling to obtain a hot rolled plate, performing a first annealing on the hot rolled plate, and then performing cold rolling on 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 straight interface.

[0010] The preparation method of the present invention first obtains a CoCrNi medium entropy alloy / 316L stainless steel composite thick plate with a straight bimetallic interface by explosion welding. The straight interface can ensure the uniformity of layer thickness during rolling. During rolling, since the plastic deformation capacity 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 transform the CoCrNi medium entropy alloy / 316L stainless steel composite thick plate into a soft state, thereby facilitating cold rolling. After cold rolling, the CoCrNi medium entropy alloy / 316L stainless steel composite thin plate with excellent mechanical properties can be obtained.

[0011] A preferred solution is that 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 the plate 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 can easily achieve metallurgical bonding of the material without cracking.

[0013] Further preferably, the 316L stainless steel plate is subjected to a solution treatment, wherein the temperature of the solution treatment is 1100-1150° C. and the time of the solution treatment is 1.5-2 hours. In the actual operation process, 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 explosion process can easily achieve metallurgical bonding of the materials without cracking.

[0015] In a preferred embodiment, the explosive used for the explosive welding is 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% wood chips, and 8-10% sodium chloride.

[0016] The inventors found that, through the ratio of the above 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 explosion welding is a straight interface.

[0017] Further preferably, the explosive used for the explosive welding is composed, by mass percentage, of 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.

[0018] The explosive composition of the present invention uses antimony-free rock ammonium nitrate as the basic explosive. Adding calcium carbonate, silicon carbide powder and sodium chloride to the basic explosive can reduce the detonation velocity of the explosive. Adding perlite powder and crushed wood chips can improve the fluffiness and facilitate detonation. Moreover, through the synergy of the above components, although the detonation velocity is low, a straight interface can be obtained, which lays a foundation for the interface to remain straight after subsequent rolling, and finally makes the obtained thin plate layer thickness 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] In the actual operation process, the parts with poor bonding around the explosive composite thick plate are removed, and the billet 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 min. Hot rolling is directly performed after the preheating is completed.

[0024] In a preferred embodiment, the hot rolling is multi-fire and multi-pass hot rolling, the rolling speed of the hot rolling is 20-30 m / min, the deformation of each pass is 15-20%, the total deformation of each fire is 40-50%, and the hot rolling is terminated 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, and being more conducive to thickness control of each layer of metal. 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 solution, the first annealing temperature is 780-800°C and the holding time is 60-120 minutes. Annealing at the above temperature can eliminate the work hardening during the hot rolling process, so that both the substrate and the composite plate are in a soft state, which is convenient for subsequent cold rolling. If the temperature is too low, it will not fully soften; if the temperature is too high, the grains will grow, which is not conducive to the control of the final performance.

[0027] In a preferred solution, the cold rolling speed is 15-20 m / min, and the deformation per pass is 10-15%. The above cold rolling process parameters can avoid the warping of the thin plate during the cold rolling process, ensure the flatness of the plate, and provide an organizational basis for the subsequent annealing treatment to achieve performance control of the composite thin plate.

[0028] In a preferred embodiment, the temperature of the second annealing is 650-700°C and the holding time is 60-70 minutes. By controlling the temperature of the second annealing 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, which will reduce the performance.

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

[0030] Beneficial Effects

[0031] The present invention optimizes the explosive composition and controls the rolling process, and adopts the explosive welding + rolling technology to realize the preparation of the CoCrNi medium entropy alloy / 316L stainless steel composite thin plate. The composite plate has uniform thickness, a straight interface, and excellent mechanical properties. First, in the process of explosive welding, since the explosive composition has an important influence on the interface morphology, the present invention has explored an explosive composition after multiple experiments, which can achieve a straight interface of the thick plate after explosive welding, laying the foundation for the interface to remain straight 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 rolling and cold rolling and the selection of the cold rolling process are all set based on the different work hardening capabilities of the CoCrNi medium entropy alloy and the 316L stainless steel. The process parameters of the present invention can avoid the warping of the thin plate during the cold rolling process, ensure the flatness of the plate, and provide an organizational basis for the subsequent use of annealing treatment to achieve performance control of the composite thin plate.

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

[0035] Figure 1 The CoCrNi medium entropy alloy / 316L stainless steel composite thin plate 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 the process innovation, any equivalent process transformation made by using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, shall be deemed as the patent protection scope of the present invention.

[0039] Example 1

[0040] Select CoCrNi medium entropy alloy sheet and 316L stainless steel sheet as raw materials. First, the CoCrNi medium entropy alloy sheet is subjected to complete softening annealing at 1000℃ / 2h, and the 316L stainless steel is subjected to solid solution + rapid cooling at 1100℃ / 2h. Then the following steps are implemented:

[0041] S1. Select a stainless steel plate with a length × width of 300 mm × 500 mm and a thickness of 5 mm as a substrate, and a CoCrNi medium entropy alloy with a length × width of 320 mm × 520 mm and a thickness of 2 mm as a composite plate, and then lay sand, anvil, 316L stainless steel plate, support column, CoCrNi medium entropy alloy plate, corrugated paper, and explosives from bottom to top on the explosion field, and perform explosion welding to obtain an explosion composite thick plate with a thickness of 7 mm (2 mm medium entropy alloy + 5 mm stainless steel); the explosives used for explosive welding are composed of 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 is 2000 m / s; the charge thickness during operation is 50 mm.

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

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

[0044] S4. After the insulation is completed, hot rolling is carried out directly, and the rolling speed is controlled to be 30m / min and the deformation amount per pass is 15%. When the billet thickness reaches 4mm, it is returned to the furnace for insulation for 10min, and then the second hot rolling is carried out with the same rolling speed and deformation amount per pass. When the billet thickness reaches 2.5mm, the 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, with the rolling speed controlled to be 15 m / min and the deformation amount per pass being 10%. When the billet thickness is 0.5 mm, the rolling is stopped.

[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, the interface of the two metals is straight, the yield strength of the composite plate is 1102 MPa, the tensile strength is 1252 MPa, and the elongation after fracture is 11.2%.

[0049] Example 2

[0050] Select CoCrNi medium entropy alloy sheet and 316L stainless steel sheet as raw materials. First, the CoCrNi medium entropy alloy sheet is subjected to complete softening annealing at 1000℃ / 2h, and the 316L stainless steel is subjected to solid solution + rapid cooling at 1100℃ / 2h. Then the following steps are implemented:

[0051] S1. Select a stainless steel plate with a length × width of 300 mm × 500 mm and a thickness of 20 mm as a substrate, and a CoCrNi medium entropy alloy with a length × width of 320 mm × 520 mm and a thickness of 3 mm as a composite plate, and then lay sand, anvil, 316L stainless steel plate, support column, CoCrNi medium entropy alloy plate, corrugated paper, and explosives from bottom to top on the explosion field, and perform explosive welding 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 proportion selected for explosive welding are: antimony-free rock ammonium nitrate explosive 51%, calcium carbonate powder 12%, silicon carbide powder 9%, perlite powder 10%, crushed wood chips 10%, sodium chloride 8%; the detonation velocity of the explosive is 2000 m / s; the charge thickness during operation is 60 mm.

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

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

[0054] S4. After the insulation is completed, hot rolling is carried out directly, and the rolling speed is controlled to be 25m / min and the deformation amount of each pass is 18%. When the billet thickness reaches 12mm, return to the furnace for insulation for 10min, and then use the same rolling speed and deformation amount to carry out the second hot rolling. When the billet thickness reaches 6.5mm, return to the furnace for insulation for 10min, and then use the same rolling speed and deformation amount to carry out the third hot rolling. When the billet thickness reaches 4mm, stop rolling.

[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, with the rolling speed controlled to be 18 m / min and the deformation amount per pass being 12%. When the billet thickness reaches 1.5 mm, the rolling is stopped.

[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, wherein the thickness of the CoCrNi medium entropy alloy is 0.2 mm, the thickness of the 316L stainless steel is 1.3 mm, the interface between the two metals is straight, the yield strength of the composite plate is 1085 MPa, the tensile strength is 1207 MPa, and the elongation after fracture is 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 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. Select a stainless steel plate with a length × width of 300 mm × 500 mm and a thickness of 40 mm as a substrate, and a CoCrNi medium entropy alloy with a length × width of 320 mm × 520 mm and a thickness of 5 mm as a composite plate, and then lay sand, anvil, 316L stainless steel plate, support column, CoCrNi medium entropy alloy plate, corrugated paper, and explosives from bottom to top on the explosion field, and perform explosive welding 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 proportion selected for explosive welding are: antimony-free rock ammonium nitrate explosive 51%, calcium carbonate powder 12%, silicon carbide powder 9%, perlite powder 10%, crushed wood chips 10%, and sodium chloride 8%; the detonation velocity of the explosive is 2000 m / s, and the charge thickness during operation is 70 mm.

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

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

[0064] S4. After the insulation is completed, hot rolling is carried out directly, and the rolling speed is controlled to be 30m / min and the deformation amount of each pass is 20%. When the billet thickness reaches 25mm, return to the furnace for insulation for 10min, and then use the same rolling speed and deformation amount of each pass to carry out the second hot rolling. When the billet thickness reaches 14mm, return to the furnace for insulation for 10min, and then use the same rolling speed and deformation amount of each pass to carry out the third hot rolling. When the billet thickness reaches 8mm, return to the furnace for insulation for 10min, and then use the same rolling speed and deformation amount of each pass to carry out the fourth hot rolling. When the billet thickness reaches 4.5mm, stop rolling.

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

[0066] S6. The annealed hot-rolled composite plate is subjected to multiple cold rolling passes, with the rolling speed controlled to be 20 m / min and the deformation amount per pass being 15%. When the billet thickness is 2 mm, the rolling is stopped.

[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, the interface between the two metals is straight, the yield strength of the composite plate is 1023 MPa, the tensile strength is 1152 MPa, and the elongation after fracture is 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 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 a length × width of 300 mm × 500 mm and a thickness of 30 mm was selected as a substrate, and a CoCrNi medium entropy alloy with a length × width of 320 mm × 520 mm and a thickness of 4 mm was selected as a composite plate for explosion welding to obtain an explosion composite thick plate with a thickness of 34 mm (4 mm medium entropy alloy + 30 mm stainless steel); the explosive composition and proportion selected for explosive welding are: antimony-free rock ammonium nitrate explosive 51%, calcium carbonate powder 12%, silicon carbide powder 9%, perlite powder 10%, wood chips 10%, sodium chloride 8%, and the detonation velocity of the explosive is 2000 m / s; the charge thickness during operation is 65 mm.

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

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

[0074] S4. After the insulation is completed, hot rolling is carried out directly, and the rolling speed is controlled to be 25m / min and the deformation amount of each pass is 18%. When the billet thickness reaches 18mm, return to the furnace for insulation for 10min, and then use the same rolling speed and deformation amount to carry out the second hot rolling. When the billet thickness reaches 10mm, return to the furnace for insulation for 10min, and then use the same rolling speed and deformation amount to carry out the third hot rolling. When the billet thickness reaches 5mm, stop rolling.

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

[0076] S6. The annealed hot-rolled composite plate is subjected to multiple cold rolling passes, with the rolling speed controlled to be 18 m / min and the deformation amount per pass being 12%. When the billet thickness is 1 mm, the rolling is stopped.

[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, wherein the thickness of the CoCrNi medium entropy alloy is 0.12 mm, the thickness of the 316L stainless steel is 0.88 mm, the interface between the two metals is straight, the yield strength of the composite plate is 1140 MPa, the tensile strength is 1250 MPa, and the elongation after fracture is 12.3%.

[0079] Comparative Example 1

[0080] The other conditions are the same as those in Example 1, except that the CoCrNi medium entropy alloy is not annealed before the explosive composite, that is, the composite plate material is a hard CoCrNi medium entropy alloy. Since the hard medium entropy alloy has high strength and poor plasticity, it is difficult to bear strong plastic deformation during the explosive composite process. Therefore, after the explosion, the medium entropy alloy composite plate is cracked due to the strong impact force generated by the explosives, and the composite fails.

[0081] Comparative Example 2

[0082] Other conditions were the same as those in Example 1, except that the explosive composition was changed to: 72% antimony-free rock ammonium nitrate explosive, 10% perlite powder, 10% wood chips, 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 too many melting zones appeared.

[0083] Comparative Example 3

[0084] The other conditions were the same as those in Example 1, except that the rolling speed was increased to 40 m / min during hot rolling, and the pass deformation was adjusted to 30%. Although increasing the rolling speed and pass deformation can improve production efficiency, the interface of the original composite thick plate is the weak position of the entire billet. High rolling speed and large pass deformation will increase the friction between the plate surface and the roller, resulting in opening at the interface during the rolling process and rolling failure.

[0085] Comparative Example 4

[0086] The other conditions are the same as those in Example 1, except that the temperature of the second annealing is the same as the temperature and time of the first annealing, i.e., 780°C / 60min, which is higher than the 650-700°C described in the present invention. Since the purpose of annealing in this step is to adjust the material properties, the increase in annealing temperature leads to an increase in the degree of recrystallization of the material and a decrease in the strength of the alloy. After annealing at this temperature, the final composite plate has a room temperature yield strength of 800MPa, a tensile strength of 1050MPa, and an elongation of 32%, and the strength is lower than the range of the present invention.

Claims

1. A method for preparing a CoCrNi medium entropy alloy / 316L stainless steel composite sheet, characterized in that: The CoCrNi medium entropy alloy plate and the 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 obtained, and 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 straight interface.

2. The method for preparing a CoCrNi medium entropy alloy / 316L stainless steel composite sheet according to claim 1, characterized in that: The process of explosive 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 in sequence from bottom to top on the explosion field, and finally explosive welding the plate.

3. The method for preparing a CoCrNi medium entropy alloy / 316L stainless steel composite sheet according to claim 2, characterized in that: The CoCrNi medium entropy alloy plate is annealed at a temperature of 1000-1100° C. for a time of 1-2 h; The 316L stainless steel plate is subjected to a solution treatment, wherein the temperature of the solution treatment is 1100-1150° C. and the time of the solution treatment is 1.5-2 h.

4. The method for preparing a CoCrNi medium entropy alloy / 316L stainless steel composite sheet according to claim 1 or 2, characterized in that: The explosive used for the explosive welding is 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% pearlite powder, 10-12% wood chips, and 8-10% sodium chloride; The detonation velocity of the explosive is 1600-2100 m / s.

5. The method for preparing a CoCrNi medium entropy alloy / 316L stainless steel composite sheet according to claim 1 or 2, 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.

6. The method for preparing a CoCrNi medium entropy alloy / 316L stainless steel composite sheet according to claim 1 or 2, characterized in that: The preheating temperature is 820-850°C, and the holding time is 45-120 minutes; The hot rolling is multi-fire and multi-pass hot rolling, the rolling speed of the hot rolling is 20-30 m / min, the deformation of each pass is 15-20%, the total deformation of each fire is 40-50%, and the hot rolling is ended when a 2.5-5 mm hot-rolled plate is obtained.

7. The method for preparing a CoCrNi medium entropy alloy / 316L stainless steel composite sheet according to claim 1 or 2, characterized in that: The first annealing temperature is 780-800° C., and the holding time is 60-120 min.

8. The method for preparing a CoCrNi medium entropy alloy / 316L stainless steel composite sheet according to claim 1 or 2, characterized in that: The cold rolling speed is 15-20 m / min, and the deformation amount per pass is 10-15%.

9. The method for preparing a CoCrNi medium entropy alloy / 316L stainless steel composite sheet according to claim 1 or 2, characterized in that: The temperature of the second annealing is 650-700° C., and the holding time is 60-70 minutes.

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

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