A method for producing a metallic material having a multiphase heterogeneous structure

Abstract

The application provides a preparation method of a metal material with a multiphase heterogeneous structure. According to the composition of the metal material, metal raw materials are taken to smelt and obtain a metal liquid. The metal liquid is subjected to electric pulse treatment to obtain a melt. The melt is subjected to directional crystallization to obtain a cast ingot with an inclined-eights-shaped columnar crystal organization. The cast ingot is subjected to hot working to obtain a blank. The blank is subjected to cold working treatment to obtain a cold worked piece. Finally, the cold worked piece is subjected to micro-area electric treatment to obtain the metal material with the multiphase heterogeneous structure. The application realizes hard outside and tough inside through hot working to obtain a core columnar crystal+edge equiaxed crystal organization. More dislocations and deformation twins are obtained through large deformation cold working treatment. Finally, the material is subjected to partition treatment through micro-area electric treatment to obtain a structure with alternating softening zones and hardening zones to realize alternating strong and tough phases. Under the cooperation of the above processes, the metal material with the multiphase heterogeneous structure has excellent mechanical properties, is hard outside and tough inside, and has alternating strong and tough phases.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of metal material preparation and processing, and particularly relates to a preparation method of a metal material with a multiphase heterogeneous structure. BACKGROUND

[0002] Metal materials are key structural and functional materials in many high-tech fields due to their good mechanical, electrical, magnetic and thermal properties, and have been widely used in electronic communication, aerospace, petroleum and chemical industry, marine engineering, new energy and other high-tech fields in China. In particular, copper alloys, aluminum alloys, titanium alloys, magnesium alloys and other materials are widely used in the manufacture of integrated circuit lead frames, precision electronic components, connectors and other aspects. With the rapid development of modern industry, especially in the high-precision industries of computers, semiconductors, instruments and meters, information communication, high load, high reliability and high service life have become the main development direction of conductor functional devices, which makes the service conditions of alloys used for signal transmission, structural support and thermal management systems more demanding, thus putting forward higher requirements on the comprehensive performance of materials.

[0003] At the same time, improving the strength and plasticity of metal materials is an important way to develop high-performance metals, and fine-grain strengthening and precipitation strengthening are important means to improve the mechanical properties of metal materials. Through the addition of modifiers during melting or rapid solidification, a cast ingot with fine grains can be prepared, and through equal channel angular extrusion, multi-directional compression, large deformation extrusion and other plastic deformation processing technologies, a microstructure with fine and uniform grains can be obtained. By refining the grains, the strength and plasticity of the material can be improved, but the degree of strengthening is limited. Therefore, the alloy usually needs to be subjected to appropriate heat treatment to form a large number of fine second-phase particles dispersedly distributed in the alloy.

[0004] There are many methods for preparing and processing high-performance metal materials at present, mainly focusing on the research of overall material preparation, and the research on micro-zone organization regulation process is rare. Patent No. ZL201210209072.8 discloses a CuNiSiMg alloy material and its preparation method and the method for preparing the alloy material into strip; Patent No. CN200810235978.0 discloses a modified preparation method of Cu-Cr-Zr alloy plate strip. The above two methods are both using the process of "semi-continuous casting-hot rolling-milling / polishing-cold rolling-(solid solution-cold rolling)-aging", which has problems of long process, low material yield, poor product quality, high production cost and so on in the production process; Patent No. CN107716885B discloses a short process production method of high-strength high-conductivity copper alloy strip, which uses the process of "hot and cold combined casting horizontal continuous casting-cold rolling-solid solution-cold rolling-aging" to produce the strip, which greatly reduces the process flow and has the characteristics of high material yield and low production cost; Patent No. CN111424224B discloses a preparation method of high-strength high-toughness conductive copper alloy strip, which uses the process route of "solid solution-cold rolling-electric pulse heat treatment-cold rolling-aging treatment", so that the alloy obtains a microstructure of small and uniform matrix grain, high density dislocation and dispersed distribution of precipitated phase, which greatly improves the mechanical properties of the alloy. However, the above methods still use deformation + traditional heat treatment process, which is limited by the size of the furnace cavity in the traditional heat treatment process, has long heat treatment time and low production efficiency; on the other hand, since the whole alloy is treated, only a single and uniformly distributed microstructure can be obtained. Patent No. CN110343993A discloses a hard alloy surface treatment method and application, which uses carburizing treatment or nitriding treatment on the surface of the alloy, which can effectively improve the mechanical properties of the alloy surface. However, this process has high requirements for the thickness of the alloy. If the thickness of the base material is too thin, the coating structure will be loose, resulting in coating failure or coating penetration. The above process cannot meet the increasing requirements of high life and high stability of the alloy during service. Therefore, it is very important to overcome the shortcomings of traditional production process of metal materials and develop a metal material preparation method that is not limited by material size and has specific performance requirements (such as hard outside and tough inside, strong and tough phases). SUMMARY

[0005] In view of the above-mentioned shortcomings, the purpose of the present invention is to provide a method for preparing a metal material with a multi-phase heterogeneous structure. First, a columnar crystal structure with an "oblique eight-shaped" structure is obtained through directional solidification, and then a structure of core columnar crystals + edge equiaxed crystals is obtained through hot working, so as to achieve hardness on the outside and toughness on the inside and improve the mechanical properties. Subsequently, more dislocations and deformation twins are obtained through large deformation cold working treatment, so that the material obtains more second-phase nucleation sites and better mechanical properties. Finally, the material is partitioned by micro-area current treatment to obtain a structure with periodic alternation of softening zones and hardening zones, so as to achieve strong and tough alternation in the micro-areas of the metal material. With the cooperation of the above-mentioned processes, a multi-phase heterogeneous structure metal material with hardness on the outside and toughness on the inside and strong and tough alternation with excellent comprehensive performance is obtained.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a preparation method of a metal material with a multi-phase heterogeneous structure. The method comprises the following steps: selecting metal raw materials according to the composition of the metal material and smelting them to obtain molten metal; subjecting the molten metal to electric pulse treatment to obtain a melt; subjecting the melt to directionally crystallization to obtain an ingot with an oblique eight-shaped columnar crystal structure; subjecting the ingot to hot processing to obtain a blank; further subjecting the ingot to cold processing to obtain a cold-processed part; and finally subjecting the cold-processed part to micro-area electrical processing to obtain the metal material with a multi-phase heterogeneous structure.

[0008] The preparation method of the present invention comprises the following steps: preparing various metal raw materials according to a designed ratio, placing them into an electric pulse directional solidification crucible in descending order of melting point, placing a covering agent on the surface of the crucible to melt the metal, and subjecting the molten metal liquid to an electric pulse treatment to obtain a melt with uniform composition and purity, and then subjecting the melt to directional crystallization to obtain an ingot with uniform composition and an "oblique eight-shaped" slender columnar crystal structure; then placing the ingot with uniform composition into a box-type resistance furnace for heating and heat preservation, and then subjecting the ingot to a heat treatment to eliminate internal looseness, pores, The defects such as microcracks are eliminated and a structure of columnar crystals in the center and equiaxed crystals at the edges is formed to achieve hardness on the outside and toughness on the inside. Then the hot-processed material is subjected to large deformation cold processing to introduce a large number of dislocations, which provide more driving force and nucleation sites for the precipitation of the second phase. Finally, the designated positions of the plate and strip after large deformation cold processing are subjected to micro-area electrical treatment to regulate the multiphase heterogeneous structure in the material microstructure and obtain a structure with periodic alternation of softening zone and hardening zone, thereby obtaining a multiphase heterogeneous structure metal material with hardness on the outside and toughness on the inside, strong and tough alternation and excellent comprehensive performance.

[0009] In a preferred embodiment, the metal material is one of copper alloy, iron alloy, aluminum alloy, magnesium alloy, zinc alloy and titanium alloy.

[0010] In the present invention, the shape of the metal material is not subject to too many restrictions, such as plates, strips, wires, tubes, special-shaped materials, etc.

[0011] A preferred solution is to place the metal raw materials into a crucible in descending order of melting point, place a covering agent on the surface of the crucible, and smelt them at 500-2000°C to obtain molten metal, wherein the covering agent is selected from at least one of sodium carbonate, borax, sodium fluoride, cryolite, and graphite powder.

[0012] In a preferred embodiment, the pulse current frequency of the electric pulse treatment is 200-5000 Hz, and the current density is 0.1-10 A / cm 3 .

[0013] Further preferably, the pulse current frequency of the electric pulse treatment is 400-2000 Hz, and the current density is 0.5-5 A / cm 3 .

[0014] By applying electric pulse treatment during the smelting process, the melt composition can be made more uniform.

[0015] In a preferred embodiment, the directional crystallization process is to use a casting speed of 1 to 100 mm / s to make the molten metal pass through the rapid cooling section and the slow cooling section of the water-cooled crystallizer in sequence, the length of the rapid cooling section is 50 to 200 mm, the length of the slow cooling section is 20 to 80 mm, the cooling water flow rate of the rapid cooling section is 600 to 2000 L / h, preferably 600-1000 L / h, and the cooling water flow rate of the slow cooling section is 100 to 400 L / h.

[0016] In the present invention, by controlling the water flow rate of the water-cooled crystallizer, a cooling temperature gradient of first rapid cooling and then slow cooling is achieved, so that the grains form "epitaxial oblique eight-shaped" columnar crystals. Based on this structure, subsequent heat treatment is carried out to allow the "eight-shaped foot" columnar crystals in the outermost circle to be recrystallized, and a structure of core columnar crystals + edge equiaxed crystals is achieved (the inside of the eight-shaped is columnar crystals, and the outside of the eight-shaped is equiaxed crystals). This structure has higher mechanical properties than single equiaxed crystals or parallel columnar crystals, achieving "hard outside and tough inside".

[0017] In a preferred embodiment, the hot working process is as follows: first, the ingot is heated to 400-1200°C, preferably 600-1100°C, and kept warm for 1-60 minutes, preferably 30-60 minutes, and then multiple hot working passes are performed, and the deformation of each pass is controlled to be 5%-60%, preferably 10%-30%, and heat treatment is performed between passes. The heat treatment temperature is 400-1200°C, preferably 600-1100°C, and the holding time is 30 minutes, preferably 5-10 minutes.

[0018] In actual operation, the ingot is placed in a box-type resistance furnace for heating and insulation, and then subjected to heat treatment (such as hot rolling) to eliminate defects such as internal porosity, pores, and microcracks.

[0019] In a preferred embodiment, during the thermal processing, the processing direction is controlled to be the temperature gradient direction. In the present invention, by processing along the temperature gradient direction, the internal stress of the sample on the processed surface is in a uniform state.

[0020] In a preferred embodiment, the hot working is selected from one of hot rolling, hot drawing, hot forging, hot rotary forging, hot radial forging, hot extrusion and hot upsetting, preferably hot rolling.

[0021] Preferably, the direction of the cold working treatment is consistent with the direction of the hot working treatment.

[0022] In a preferred embodiment, the cold working treatment is selected from one of cold rolling, cold drawing, cold forging, cold rotary forging, cold radial forging, cold extrusion and cold heading, preferably cold rolling.

[0023] In a preferred solution, during the cold working treatment, the deformation of a single pass is controlled to be 5-30%, and the total deformation is controlled to be 70-99%.

[0024] In the present invention, after obtaining the structure of core columnar crystals + edge equiaxed crystals through hot working, more dislocations and deformation twins are obtained through cold working with a large deformation amount, so that the material obtains more second phase nucleation sites and better mechanical properties.

[0025] In a preferred embodiment, the process of micro-area electrical treatment is to divide the metal material into several parallel hardening zones and softening zones along the length direction or the width direction, wherein the hardening zones and the softening zones are distributed alternately in a periodic manner, and a blank zone is provided between the hardening zones and the softening zones. Then, the hardening zones and the softening zones are subjected to micro-area electrical treatment in turn, wherein the micro-area electrical treatment parameters of the hardening zone are: voltage 0.01~8V, current 100~500A; the micro-area electrical treatment parameters of the softening zone are: voltage 8~20V, current 800~2000A.

[0026] In the present invention, by cold working a metal material with more dislocations and deformation twins, the metal material is divided into hardened and softened zones. High current is applied to the alloy, resulting in a significant thermal effect. This results in a higher instantaneous temperature in the metal region, causing intense recovery and recrystallization at locations where dislocations accumulate, resulting in a softened zone. Low current, on the other hand, results in a lower instantaneous temperature in the alloy region, causing recovery and second phase precipitation at locations where dislocations accumulate, resulting in a hardened zone.

[0027] Furthermore, preferably, the width of the blank area is greater than 5mm, preferably 5-15mm. A certain spacing must be set between the hardened and softened zones, and this spacing must be controlled. If the spacing is too low, heat conduction may cause thermal overlap in the target area, leading to excessive precipitation and growth of the second phase in the hardened area, weakening the strengthening effect of the hardened area and even causing recrystallization. If the spacing is too large, the ultimate strengthening effect is weakened.

[0028] In a preferred solution, the current in the micro-area electrical treatment process is in the form of any one of pulse current, constant current, alternating current, and direct current, preferably pulse current.

[0029] In a preferred embodiment, the micro-area electrical treatment process applies current to the metal material through a movable electronic probe, first placing the movable electronic probe at a certain point in any hardened zone or softened zone of the metal material, applying current once within the area of ​​the electronic probe, and then moving the electronic probe in parallel to apply current to the next area of ​​the electronic probe. After the treatment of one hardened zone or softened zone is completed, the electronic probe is moved to another untreated hardened zone or softened zone to repeat the above process; when current is applied to the hardened zone, the treatment time of any single point is 5 to 60 seconds, and when current is applied to the softened zone, the treatment time of any single point is 10 to 300 seconds.

[0030] Further preferably, the shape of the electronic probe is any one of rectangular, circular, elliptical and linear.

[0031] Further preferably, the area of ​​the electronic probe is 0.01 to 10 mm 2 .

[0032] In the prior art, for example, when applying electric pulses to materials, only the entire material can be processed. However, the present invention utilizes a movable electron probe to control the area of ​​the electron probe to achieve micro-regional current application on the metal material. In actual operation, for ease of operation, the electron probe is first placed at the starting point of a hardened or softened zone. Once current application within a certain electron probe area is complete, the electron probe is moved to apply current within the next electron probe area. After the treatment path for that zone is completely completed, the electron probe is moved to the starting point of another zone for further operation. This allows for the controlled and gradual application of current to each zone through the movement of the electron probe, thereby achieving the desired heterogeneous phase structure. Of course, in actual operation, the movement of the electron probe is relative, either directly or by moving the material to be processed, effectively changing the position of the electron probe relative to the material being processed.

[0033] Principles and advantages

[0034] The preparation method of the present invention comprises the following steps: preparing various metal raw materials according to a designed proportion, placing them into an electric pulse directional solidification crucible in order of their melting points from high to low, placing a covering agent on the surface of the crucible to melt the metal, and subjecting the molten metal liquid to electric pulse treatment to obtain a melt with uniform composition and purity, and then subjecting it to directional crystallization to obtain an ingot with uniform composition and an "oblique eight-shaped" slender columnar crystal structure; then placing the ingot with uniform composition into a box-type resistance furnace for heating and heat preservation, and then subjecting it to heat treatment to eliminate internal defects such as porosity, pores, and microcracks, and forming a structure of core columnar crystals + edge equiaxed crystals to achieve "hard outside and tough inside", and then subjecting the hot-treated material to large deformation cold working to introduce a large number of dislocations, thereby providing more driving force and nucleation sites for the precipitation of the second phase; finally, subjecting the designated positions of the plate and strip material after large deformation cold working to micro-area electrical treatment to regulate the multiphase heterogeneous structure in the material microstructure, and obtaining a structure in which softening zones and hardening zones are periodically alternatingly distributed, thereby obtaining a multiphase heterogeneous structure metal material with hard outside and tough inside and alternating strength and toughness.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) Compared with the existing technology, the present invention uses electric pulse directional solidification technology to prepare an ingot with a uniformly distributed "oblique eight-shaped" slender columnar crystal structure, replacing the equiaxed crystal structure in the traditional process. At the same time, the electric pulse directional solidification melting and micro-area electrical processing are organically combined. The electric pulse directional solidification is used to eliminate the agglomeration of the metal during the melting process, accelerate the atomic diffusion, and obtain a metal liquid with uniform composition; at the same time, the segregation phenomenon generated during the cooling and solidification process is suppressed; through subsequent hot processing and large deformation cold processing, the defects such as looseness, pores, and microcracks in the ingot are further eliminated, and a large number of dislocations are introduced to provide more driving force and nucleation sites for the precipitation of the second phase; finally, by using micro-area electrical processing at different metal material positions to change the input energy, the precipitation of multiple second phases is greatly promoted, forming a "soft / hardening alternating, soft and hard coating" heterogeneous structure, realizing the precise design of material microstructure guided by performance requirements.

[0037] (2) Compared with the existing metal material preparation process, the present invention organically combines electric pulse directional solidification, hot rolling, large deformation cold processing and micro-area electrical treatment, which greatly shortens the heat treatment and processing steps in the existing metal material preparation process of "hot-cold combined casting horizontal continuous casting - cold rolling - solid solution - cold rolling - aging" and "semi-continuous casting - solid solution - cold rolling - electric pulse treatment - cold rolling - aging". At the same time, since the traditional aging process is to place the material in a heat treatment furnace for insulation to promote the precipitation of second phase particles. However, due to the limitation of the furnace chamber size and the long heat treatment time, the production flow time is increased, which seriously reduces the production efficiency. At the same time, since the material is processed as a whole, only a single distribution of structure can be obtained. Some specific performance requirements can only be processed through surface treatment, which greatly increases the production cost. The micro-area electrical treatment process proposed in the present invention aims to precisely control different microstructures in local areas or tiny areas, thereby realizing mass production of metal materials with specific performance requirements (such as hard outside and tough inside, alternating strength and toughness) that are not restricted by material size, solving the problems of complex and cumbersome existing process flows, difficult processing, and high costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a process flow chart of the present invention.

[0039] Figure 2 This is the microstructure diagram of the alloy ingot in Example 1. The oblique S-shaped columnar crystal structure can be clearly observed in the figure.

[0040] Figure 3 This is a microstructure diagram of the metal material with a multiphase heterogeneous structure provided in Example 1. As can be seen from the figure, the left area is a second phase with a large amount of dispersed distribution, the right side is the original structure, the right side is the softening zone, and the left side is the hardening zone. DETAILED DESCRIPTION

[0041] In order to make the present invention easier to understand, the present invention is further described below with reference to specific examples. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in 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. Unless otherwise defined, the professional terms used below have the same meaning as understood by professional and technical personnel in this field; unless otherwise specified, the raw materials and equipment involved in this article can be purchased from the market or prepared by known methods.

[0042] Example 1

[0043] A method for preparing a metal material with a multiphase heterogeneous structure, the process flow is as followsFigure 1 As shown, the following steps are included:

[0044] This embodiment uses Cu-Ni-Sn alloy as the object.

[0045] (1) Electric pulse directional solidification: Prepare electrolytic copper sheets, nickel sheets and tin blocks with a purity of 99.99% or above according to the mass ratio of Ni: Sn: Cu = 15: 8: 77, and put Ni, Cu and Sn into the electric pulse directional solidification crucible in descending order according to their melting points, and then put 20g of graphite powder with a particle size of 5 mesh to cover the metal surface. The crucible is induction heated by an electromagnetic coil, and the heating temperature is controlled at 1350℃. After the metal block in the crucible is melted into liquid metal, the electromagnetic stirrer is turned on for mechanical stirring. The magnetic field strength of the electromagnetic stirring is set to 2500Gs and the stirring speed is 200r / min. Then the temperature is lowered to 1180℃ for insulation. After insulation for 5 minutes, the pulse power supply is turned on and the pulse frequency is set to 1200Hz and the current density is set to 2.0A / cm through the central controller. 3 After 5 minutes of processing time, the pulse power supply is turned off to obtain molten metal with uniform composition. Then, the molten metal is pulled out from the center hole of the crystallizer at a speed of 1 mm / s using a robotic arm-linked traction rod. During the pulling process, the molten metal passes through a 150 mm rapid cooling section and a 50 mm slow cooling section in sequence. Among them, the crystallizer circulating water flow rate in the rapid cooling section is 800 L / h, and the crystallizer circulating water flow rate in the slow cooling section is 400 L / h, forming a 60×20 mm alloy ingot with "oblique eight-shaped" slender columnar crystals.

[0046] (2) Hot rolling: The ingot is placed in a box-type resistance furnace for heating with the furnace, and the temperature is controlled at 820℃. After keeping warm for 30 minutes, it is taken out and rolled along the temperature gradient direction. The total deformation is 50%, and the deformation of a single pass is 20%. After each pass is completed, it is quickly placed in a box-type resistance furnace for continued insulation. After keeping warm for 10 minutes, it is taken out for the next rolling deformation. After multiple rolling, the thickness of the slab reaches 10 mm.

[0047] (3) Large deformation cold processing: The hot-rolled slab is placed in a six-roll rolling mill for cold rolling. The deformation direction is consistent with the hot rolling direction. The total deformation is 90%, the single-pass deformation is 10%, and the plate thickness reaches 1 mm after multiple rolling.

[0048] (4) Micro-area electrical processing: The metal material is divided into parallel hardening zones and softening zones along the X-axis direction. The hardening zones and softening zones are alternately distributed. At the same time, a blank area is set between the hardening zones and softening zones. The width of the hardening zone and softening zone is the width of the probe, and the width of the blank area is 10mm. Then, the cold-rolled alloy plate is subjected to micro-area electrical processing using an oxygen-free copper electronic probe. The probe uses a linear contactor with a contact area of ​​0.1mm. 2, select a low-frequency, high-peak pulse power supply, move the electronic probe linearly along the X direction (relative movement, or moving metal materials) to gradually perform micro-area scanning electrical treatment. In the hardening area, apply an equivalent voltage of 8V, a current of 200A, and a single treatment time of 30s. After the X-direction treatment is completed, move the electronic probe parallel to the Y axis for 10mm, and then continue to move the electronic probe horizontally along the X direction for micro-area scanning electrical treatment, applying an equivalent voltage of 8V, a current of 1000A, and a treatment time of 30s. Repeat the above process until the entire material is treated.

[0049] The performance indicators of the alloy plates and strips in this implementation case are:

[0050] Tensile strength: 1680MPa

[0051] Elongation at break: 10.6%

[0052] Electrical conductivity: 15.4% IACS

[0053] Example 2:

[0054] A method for preparing a metal material with a multiphase heterogeneous structure, the process flow is as follows Figure 1 As shown, the following steps are included:

[0055] This embodiment takes silicon steel alloy as the object.

[0056] (1) Electric pulse directional solidification: Prepare iron particles and silicon wafers with a purity of 99.99% or more according to the mass ratio of Fe:Si=96:4, and put Cu and Zn into the electric pulse directional solidification crucible in descending order according to the melting point, and then put 20g of graphite powder with a particle size of 5 mesh to cover the metal surface. The crucible is induction heated by an electromagnetic coil, and the heating temperature is controlled at 1580℃. After the metal block in the crucible is melted into liquid metal, the electromagnetic stirrer is turned on for mechanical stirring. The magnetic field strength of the electromagnetic stirring is set to 1500Gs and the stirring speed is 200r / min. Then the temperature is lowered to 1520℃ for insulation. After insulation for 5 minutes, the pulse power supply is turned on and the pulse frequency is set to 1200Hz and the current density is 1.0A / cm through the central controller. 3 After 5 minutes of processing time, the pulse power supply is turned off to obtain molten metal with uniform composition. Then, the molten metal is pulled out from the center hole of the crystallizer at a speed of 10 mm / s by using a robotic arm linked to a traction rod. During the pulling process, the molten metal passes through an 80 mm rapid cooling section and a 50 mm slow cooling section in sequence. Among them, the crystallizer circulating water flow rate in the rapid cooling section is 600 L / h, and the crystallizer circulating water flow rate in the slow cooling section is 300 L / h, forming a 60×20 mm alloy ingot with "oblique eight-shaped" slender columnar crystals.

[0057] (2) Hot rolling: The ingot is placed in a box-type resistance furnace for heating with the furnace, and the temperature is controlled at 880℃. After keeping warm for 30 minutes, it is taken out and rolled along the temperature gradient direction. The total deformation is 70%, and the deformation of a single pass is 30%. After each pass is completed, it is quickly placed in a box-type resistance furnace for continued insulation. After keeping warm for 10 minutes, it is taken out for the next rolling deformation. After multiple rolling, the thickness of the slab reaches 10 mm.

[0058] (3) Large deformation cold processing: The hot-rolled slab is placed in a six-roll rolling mill for cold rolling. The deformation direction is consistent with the hot rolling direction. The total deformation is 90%, the single-pass deformation is 20%, and the slab thickness reaches 1 mm after multiple rolling.

[0059] (4) Micro-area electrical processing: The metal material is divided into parallel hardening zones and softening zones along the X-axis direction. The hardening zones and softening zones are alternately distributed. At the same time, a blank area is set between the hardening zones and softening zones. The width of the hardening zone and softening zone is the width of the probe, and the width of the blank area is 5mm. Then, the cold-rolled alloy plate is subjected to micro-area electrical processing using an oxygen-free copper electronic probe. The probe uses a linear contactor with a contact area of ​​0.1mm. 2 , select a low-frequency, high-peak pulse power supply, move the electronic probe linearly along the X direction and gradually perform micro-area scanning electrical treatment. In the hardening area, apply an equivalent voltage of 10V, a current of 250A, and a treatment time of 30s. After the X-direction treatment is completed, move the electronic probe parallel to the Y axis for 1mm, and then continue to move the electronic probe horizontally along the X direction for micro-area scanning electrical treatment, apply an equivalent voltage of 10V, a current of 1200A, and a treatment time of 30s. Repeat the above process until the entire material is treated.

[0060] The performance indicators of the alloy plates and strips in this implementation case are:

[0061] Tensile strength: 1450MPa

[0062] Elongation at break: 15.6%

[0063] Example 3:

[0064] A method for preparing a metal material with a multiphase heterogeneous structure, the process flow is as follows Figure 1 As shown, the following steps are included:

[0065] This embodiment uses Ti-6Al-4V alloy as the object.

[0066] (1) Electric pulse directional solidification: titanium particles and aluminum particles and vanadium blocks with purity of 99.99% and above are prepared according to the mass ratio of Ti:Al:V=90:6:4, and V, Ti, Al are sequentially placed in the electric pulse directional solidification crucible according to the melting point from high to low, and then 20g of graphite powder with a particle size of 5# is placed to cover the metal surface. The crucible is inductively heated by an electromagnetic coil, and the heating temperature is controlled at 1380°C. After the metal blocks in the crucible are melted into a metal liquid, the electromagnetic stirrer is turned on for mechanical stirring. The magnetic field strength of electromagnetic stirring is set to 2000Gs, and the stirring speed is 200r / min. Then the temperature is lowered to 1100°C for insulation, and after 5min of insulation, the pulse power is turned on. The pulse frequency is set to 1200Hz by the central controller, and the current density is 1.0A / cm 3 After 5min of treatment, the pulse power is turned off, and a uniform metal liquid is obtained. Then the metal liquid is pulled out from the center hole of the crystallizer at a speed of 2mm / s by using a mechanical arm linkage drag rod. In the process of pulling out, the metal liquid passes through a 100mm rapid cooling section and a 30mm slow cooling section in turn. The circulating water flow rate of the crystallizer in the rapid cooling section is 800L / h, and the circulating water flow rate of the crystallizer in the slow cooling section is 200L / h. A 60x20mm alloy billet with equiaxed crystal + fine elongated columnar crystal is formed.

[0067] (2) Hot rolling: the cast billet is placed in a box-type resistance furnace for in-furnace heating, and the temperature is controlled at 880°C. After 30min of insulation, it is taken out and rolled along the temperature gradient direction. The total deformation is 70%, and the single pass deformation is 30%. After each pass, it is quickly placed in a box-type resistance furnace for continuous insulation. After 10min of insulation, it is taken out for the next pass of rolling deformation. After multiple rolling, the plate blank thickness reaches 10mm.

[0068] (3) Large deformation cold working: the hot-rolled plate blank is placed in a six-roll rolling machine for cold rolling. The deformation direction is consistent with the hot rolling direction. The total deformation is 90%, and the single pass deformation is 20%. After multiple rolling, the plate blank thickness reaches 1mm.

[0069] (4) Micro-area electric treatment: the metal material is divided into parallel hardening zones and softening zones along the X-axis direction. The hardening zones and the softening zones are alternately distributed, and a blank zone is provided between the hardening zones and the softening zones. The width of the hardening zone and the softening zone is the width of the probe, and the width of the blank zone is 5mm. Then the cold-rolled alloy plate is treated by micro-area electric processing using an oxygen-free copper electronic probe. The probe selects a linear contactor with a contact area of 0.1mm 2, select a low-frequency, high-peak pulse power supply, move the electronic probe linearly along the X direction to gradually perform micro-area scanning electrical treatment. In the hardening area, apply an equivalent voltage of 6V, a current of 400A, and a treatment time of 30s. After the X direction is treated, move the electronic probe parallel to the Y axis for 1mm, and then continue to move the electronic probe horizontally along the X direction for micro-area scanning electrical treatment, apply an equivalent voltage of 10V, a current of 800A, and a treatment time of 30s. Repeat the above process until the entire material is treated.

[0070] The performance indicators of the alloy plates and strips in this implementation case are:

[0071] Tensile strength: 1320MPa

[0072] Elongation at break: 15.6%

[0073] Comparative Example 1

[0074] This comparative example uses a directional solidification process followed by hot rolling, large deformation cold working, and micro-area electrical treatment to process Cu-Ni-Sn alloy plates and strips based on the embodiment, including the following steps:

[0075] (1) Directional solidification: Prepare electrolytic copper sheets, nickel sheets, and tin blocks with a purity of 99.99% or above according to the mass ratio of Ni:Sn:Cu=15:8:77, and place Ni, Cu, and Sn into the directional solidification crucible in descending order according to their melting points. Turn on the water cooling circulation system and set the circulating water flow rate to 600L / h (rapid cooling section) and 400L / h (slow cooling section). Close the furnace door and air inlet valve, turn on the mechanical pump, vacuum gauge, and molecular pump to reduce the vacuum degree in the furnace (5×10 -4 Pa), induction heating of the graphite crucible is performed via an induction coil and an electromagnetic coil. The melting temperature is controlled at 1350°C. Once the metal block in the crucible has melted into liquid metal, an electromagnetic stirrer is activated for mechanical stirring. The magnetic field strength of the electromagnetic stirrer is set to 2500 Gs and the stirring speed is 200 r / min. The temperature is then lowered to 1180°C and held for 10 minutes. After this, a mechanical turbine is activated, driving a metal connector at an axial speed of 0.01 mm / s to pull the crucible from the induction coil to a condenser (16° gallium-indium alloy coolant) for cooling and forming, forming a 60×20 mm ingot with a columnar crystalline structure.

[0076] (2) Hot rolling: The ingot is placed in a box-type resistance furnace for heating with the furnace, and the temperature is controlled at 820℃. After keeping warm for 30 minutes, it is taken out and rolled along the temperature gradient direction. The total deformation is 50%, and the deformation of a single pass is 20%. After each pass is completed, it is quickly placed in a box-type resistance furnace for continued insulation. After keeping warm for 10 minutes, it is taken out for the next rolling deformation. After multiple rolling, the thickness of the slab reaches 10 mm.

[0077] (3) Large deformation cold processing: The hot-rolled slab is placed in a six-roll rolling mill for cold rolling. The deformation direction is consistent with the hot rolling direction. The total deformation is 90%, the single-pass deformation is 10%, and the plate thickness reaches 1 mm after multiple rolling.

[0078] (4) Micro-area electrical processing: The metal material is divided into parallel hardening zones and softening zones along the X-axis direction. The hardening zones and softening zones are alternately distributed. At the same time, a blank area is set between the hardening zones and softening zones. The width of the hardening zone and softening zone is the width of the probe, and the width of the blank area is 10mm. Then, the cold-rolled alloy plate is subjected to micro-area electrical processing using an oxygen-free copper electronic probe. The probe uses a linear contactor with a contact area of ​​0.1mm. 2 , select a low-frequency, high-peak pulse power supply, move the electronic probe linearly along the X direction to gradually perform micro-area scanning electrical treatment. In the hardening area, apply an equivalent voltage of 8V, a current of 200A, and a single treatment time of 30s. After the X-direction treatment is completed, move the electronic probe parallel to the Y axis for 10mm, and then continue to move the electronic probe horizontally along the X direction for micro-area scanning electrical treatment, apply an equivalent voltage of 8V, a current of 1000A, and a treatment time of 30s. Repeat the above process until the entire material is treated.

[0079] The performance indicators of the alloy plates and strips in this implementation case are:

[0080] Tensile strength: 1520MPa

[0081] Elongation at break: 8.4%

[0082] Electrical conductivity: 13.4% IACS

[0083] Comparative Example 2

[0084] This comparative example uses an electric pulse conventional melting process followed by hot rolling, large deformation cold working, and micro-area electrical treatment to process Cu-Ni-Sn alloy plates and strips based on the embodiment, including the following steps:

[0085] (1) Electric pulse ordinary smelting: Use an industrial frequency induction furnace to carry out smelting in a non-vacuum environment. Prepare electrolytic copper sheets, nickel sheets and tin blocks with a purity of 99.99% or above according to the mass ratio of Ni:Sn:Cu=15:8:77, and put Ni, Cu, and Sn into the smelting crucible in descending order according to their melting points. The smelting temperature is 1350℃. After the metal blocks in the crucible are melted into molten metal, turn on the electromagnetic stirrer for mechanical stirring. The magnetic field strength of the electromagnetic stirring is set to 2500Gs and the stirring speed is 200r / min. Then lower the temperature to 1180℃ and keep warm. After keeping warm for 5 minutes, turn on the pulse power supply, set the pulse frequency to 1200Hz and the current density to 2.0A / cm3 through the central controller, and after 5 minutes of processing time, turn off the pulse power supply and start casting to form a 60×20mm alloy ingot.

[0086] (2) Hot rolling: The ingot is placed in a box-type resistance furnace for heating with the furnace, and the temperature is controlled at 820℃. After keeping warm for 30 minutes, it is taken out and rolled along the temperature gradient direction. The total deformation is 50%, and the deformation of a single pass is 20%. After each pass is completed, it is quickly placed in a box-type resistance furnace for continued insulation. After keeping warm for 10 minutes, it is taken out for the next rolling deformation. After multiple rolling, the thickness of the slab reaches 10 mm.

[0087] (3) Large deformation cold processing: The hot-rolled slab is placed in a six-roll rolling mill for cold rolling. The deformation direction is consistent with the hot rolling direction. The total deformation is 90%, the single-pass deformation is 10%, and the plate thickness reaches 1 mm after multiple rolling.

[0088] (4) Micro-area electrical processing: The metal material is divided into parallel hardening zones and softening zones along the X-axis direction. The hardening zones and softening zones are alternately distributed. At the same time, a blank area is set between the hardening zones and softening zones. The width of the hardening zone and softening zone is the width of the probe, and the width of the blank area is 10mm. Then, the cold-rolled alloy plate is subjected to micro-area electrical processing using an oxygen-free copper electronic probe. The probe uses a linear contactor with a contact area of ​​0.1mm. 2 , select a low-frequency, high-peak pulse power supply, move the electronic probe linearly along the X direction to gradually perform micro-area scanning electrical treatment. In the hardening area, apply an equivalent voltage of 8V, a current of 200A, and a single treatment time of 30s. After the X-direction treatment is completed, move the electronic probe parallel to the Y axis for 10mm, and then continue to move the electronic probe horizontally along the X direction for micro-area scanning electrical treatment, apply an equivalent voltage of 8V, a current of 1000A, and a treatment time of 30s. Repeat the above process until the entire material is treated.

[0089] The performance indicators of the alloy plates and strips in this implementation case are:

[0090] Tensile strength: 1360MPa

[0091] Elongation at break: 5.3%

[0092] Electrical conductivity: 10.6% IACS

[0093] Comparative Example 3

[0094] This comparative example uses a directional solidification process followed by hot rolling, large deformation cold working, and traditional aging process to process Cu-Ni-Sn alloy plates and strips on the basis of the embodiment, including the following steps:

[0095] (1) Electric pulse directional solidification: Prepare electrolytic copper sheets, nickel sheets, and tin blocks with a purity of 99.99% or above according to the mass ratio of Ni:Sn:Cu=15:8:77, and place Ni, Cu, and Sn into the electric pulse directional solidification crucible in descending order according to their melting points. Then, add 20g of graphite powder with a particle size of 5 mesh to cover the metal surface. The crucible is induction heated by an electromagnetic coil, and the heating temperature is controlled at 1350℃. After the metal block in the crucible is melted into metal liquid, the electromagnetic stirrer is turned on for mechanical stirring. The magnetic field strength of the electromagnetic stirring is set to 2500Gs, and the stirring speed is 200r / min. The temperature is then lowered to 1180°C for insulation. After 5 minutes of insulation, the pulse power supply is turned on, and the pulse frequency and current density are set to 1200Hz and 2.0A / cm3 through the central controller. After 5 minutes of processing, the pulse power supply is turned off to obtain molten metal with uniform composition. The molten metal is then pulled out of the center hole of the crystallizer at a speed of 1mm / s using a robotic arm-linked traction rod. During the pulling process, the molten metal passes through a 150mm rapid cooling section and a 50mm slow cooling section in turn. The circulating water flow rate of the crystallizer in the rapid cooling section is 800L / h, and the circulating water flow rate of the crystallizer in the slow cooling section is 400L / h, forming a 60×20mm alloy ingot with "oblique eight-shaped" slender columnar crystals.

[0096] (1) Hot rolling: The ingot is placed in a box-type resistance furnace for heating with the furnace, and the temperature is controlled at 820℃. After keeping warm for 30 minutes, it is taken out and rolled along the temperature gradient direction. The total deformation is 50%, and the deformation of a single pass is 20%. After each pass is completed, it is quickly placed in a box-type resistance furnace for continued insulation. After keeping warm for 10 minutes, it is taken out for the next rolling deformation. After multiple rolling, the thickness of the slab reaches 10 mm.

[0097] (2) Large deformation cold processing: The hot-rolled slab is placed in a six-roll rolling mill for cold rolling. The deformation direction is consistent with the hot rolling direction. The total deformation is 90%, and the single-pass deformation is 10%. After multiple rolling, the plate thickness reaches 1 mm.

[0098] (3) Traditional aging process: The plates and strips after large deformation and cold working are placed in a box-type resistance furnace for aging and heat preservation treatment. The heat preservation temperature is 400℃ and the heat preservation time is 2h.

[0099] The performance indicators of the alloy plates and strips in this implementation case are:

[0100] Tensile strength: 1360MPa

[0101] Elongation at break: 5.3%

[0102] Electrical conductivity: 10.6% IACS

[0103] Comparative Example 4

[0104] This comparative example uses a directional solidification process followed by hot rolling, large deformation cold working, and electric pulse aging process to process Cu-Ni-Sn alloy plates and strips on the basis of the embodiment, including the following steps:

[0105] (1) Electric pulse directional solidification: Prepare electrolytic copper sheets, nickel sheets and tin blocks with a purity of 99.99% or above according to the mass ratio of Ni: Sn: Cu = 15: 8: 77, and put Ni, Cu and Sn into the electric pulse directional solidification crucible in descending order according to their melting points, and then put 20g of graphite powder with a particle size of 5 mesh to cover the metal surface. The crucible is induction heated by an electromagnetic coil, and the heating temperature is controlled at 1350℃. After the metal block in the crucible is melted into liquid metal, the electromagnetic stirrer is turned on for mechanical stirring. The magnetic field strength of the electromagnetic stirring is set to 2500Gs and the stirring speed is 200r / min. Then the temperature is lowered to 1180℃ for insulation. After insulation for 5 minutes, the pulse power supply is turned on and the pulse frequency is set to 1200Hz and the current density is set to 2.0A / cm through the central controller. 3 After 5 minutes of processing time, the pulse power supply is turned off to obtain molten metal with uniform composition. Then, the molten metal is pulled out from the center hole of the crystallizer at a speed of 1 mm / s using a robotic arm-linked traction rod. During the pulling process, the molten metal passes through a 150 mm rapid cooling section and a 50 mm slow cooling section in sequence. Among them, the crystallizer circulating water flow rate in the rapid cooling section is 800 L / h, and the crystallizer circulating water flow rate in the slow cooling section is 400 L / h, forming a 60×20 mm alloy ingot with "oblique eight-shaped" slender columnar crystals.

[0106] (1) Hot rolling: The ingot is placed in a box-type resistance furnace for heating with the furnace, and the temperature is controlled at 820℃. After keeping warm for 30 minutes, it is taken out and rolled along the temperature gradient direction. The total deformation is 50%, and the deformation of a single pass is 20%. After each pass is completed, it is quickly placed in a box-type resistance furnace for continued insulation. After keeping warm for 10 minutes, it is taken out for the next rolling deformation. After multiple rolling, the thickness of the slab reaches 10 mm.

[0107] (2) Large deformation cold processing: The hot-rolled slab is placed in a six-roll rolling mill for cold rolling. The deformation direction is consistent with the hot rolling direction. The total deformation is 90%, and the single-pass deformation is 10%. After multiple rolling, the plate thickness reaches 1 mm.

[0108] (3) Electric pulse aging process: The plates and strips after large deformation cold working are placed in the electric pulse heat treatment circuit for electric pulse aging. A low-frequency high-peak pulse power supply is selected, with an equivalent voltage of 8V, a current of 200A, and a processing time of 5 minutes.

[0109] The performance indicators of the alloy plates and strips in this implementation case are:

[0110] Tensile strength: 1360MPa

[0111] Elongation at break: 5.3%

[0112] Electrical conductivity: 10.6% IACS

[0113] Comparative Example 5

[0114] This comparative example uses a conventional smelting process followed by hot rolling, large deformation cold working, and aging process to process Cu-Ni-Sn alloy plates and strips on the basis of the embodiment, including the following steps:

[0115] (1) Ordinary smelting: Use an industrial frequency induction furnace to carry out smelting in a non-vacuum environment. Prepare electrolytic copper sheets, nickel sheets and tin blocks with a purity of 99.99% or above according to the mass ratio of Ni:Sn:Cu=15:8:77. Put Ni, Cu and Sn into the smelting crucible in descending order according to their melting points. The smelting temperature is 1350℃. After the metal blocks in the crucible are melted into molten metal, turn on the electromagnetic stirrer for mechanical stirring. The magnetic field strength of the electromagnetic stirring is set to 2500Gs and the stirring speed is 200r / min. Then reduce the temperature to 1180℃ and keep warm. After the holding time is 10min, start casting to form a 60×20mm alloy ingot.

[0116] (2) Hot rolling: The ingot is placed in a box-type resistance furnace for heating with the furnace, and the temperature is controlled at 820℃. After keeping warm for 30 minutes, it is taken out and rolled. The total deformation is 50%, and the deformation of a single pass is 20%. After each pass is completed, it is quickly placed in a box-type resistance furnace for continued insulation. After keeping warm for 10 minutes, it is taken out and the next rolling deformation is carried out. After multiple rolling, the thickness of the slab reaches 10 mm.

[0117] (3) Large deformation cold processing: The hot-rolled slab is placed in a six-roll rolling mill for cold rolling. The deformation direction is consistent with the hot rolling direction. The total deformation is 90%, the single-pass deformation is 10%, and the plate thickness reaches 1 mm after multiple rolling.

[0118] (4) Traditional aging process: The plates and strips after large deformation and cold working are placed in a box-type resistance furnace for aging and heat preservation treatment. The heat preservation temperature is 400℃ and the heat preservation time is 2h.

[0119] The performance indicators of the alloy plates and strips in this implementation case are:

[0120] Tensile strength: 1220MPa

[0121] Elongation at break: 2.73%

[0122] Electrical conductivity: 7.6% IACS.

Claims

1. A method for preparing a metal material having a multiphase heterogeneous structure, characterized in that: According to the composition of the metal material, metal raw materials are selected and smelted to obtain molten metal, the molten metal is subjected to electric pulse treatment to obtain a melt, the melt is directionally crystallized to obtain an ingot with an oblique eight-shaped columnar crystal structure, the ingot is hot-processed to obtain a billet, the billet is then cold-processed to obtain a cold-processed part, and finally the cold-processed part is subjected to micro-area electrical treatment to obtain a metal material with a multi-phase heterogeneous structure; The process of micro-area electrical treatment is to divide the metal material into several parallel hardening zones and softening zones along the length direction or width direction, wherein the hardening zones and softening zones are distributed alternately in a periodic manner, and a blank zone is set between the hardening zones and softening zones. Then, the hardening zones and softening zones are subjected to micro-area electrical treatment in turn to achieve alternating strength and toughness in the micro-areas of the metal material.

2. The method for preparing a metal material having a multi-phase heterogeneous structure according to claim 1, characterized in that: Metal raw materials are placed into a crucible in descending order of melting point, a covering agent is placed on the surface of the crucible, and smelting is performed at 500-2000°C to obtain molten metal. The covering agent is selected from at least one of sodium carbonate, borax, sodium fluoride, cryolite, and graphite powder.

3. The method for preparing a metal material having a multi-phase heterogeneous structure according to claim 1, characterized in that: The pulse current frequency of the electric pulse treatment is 200~5000Hz, and the current density is 0.1~10A / cm 3 .

4. The method for preparing a metal material having a multi-phase heterogeneous structure according to claim 1, wherein: The directional crystallization process is to use a casting speed of 1~100mm / s to make the molten metal pass through the rapid cooling section and slow cooling section of the water-cooled crystallizer in sequence, the length of the rapid cooling section is 50~200mm, the length of the slow cooling section is 20~80mm, the cooling water flow rate of the rapid cooling section is 600~2000L / h, and the cooling water flow rate of the slow cooling section is 100~400L / h.

5. The method for preparing a metal material having a multi-phase heterogeneous structure according to claim 1, characterized in that: The process of the heat treatment is as follows: first, the ingot is heated to 400-1200°C, kept at this temperature for 1-60 minutes, and then multiple heat treatments are performed, with the deformation of each pass controlled at 5%-60%. Heat treatment is performed between passes at a temperature of 400-1200°C and a holding time of 30 minutes. During the thermal processing, the processing direction is controlled to be the direction of the temperature gradient; The hot working is selected from one of hot rolling, hot drawing, hot forging, hot rotary forging, hot radial forging, hot extrusion and hot upsetting.

6. The method for preparing a metal material having a multi-phase heterogeneous structure according to claim 1, characterized in that: The direction of the cold working treatment is consistent with the direction of the hot working; The cold working treatment is selected from one of cold rolling, cold drawing, cold forging, cold rotary forging, cold radial forging, cold extrusion and cold heading, During the cold working treatment, the deformation of a single pass is controlled to be 5-30%, and the total deformation is controlled to be 70-99.9%.

7. The method for preparing a metal material having a multi-phase heterogeneous structure according to claim 1, characterized in that: The micro-area electrical treatment parameters of the hardened zone are: voltage 0.01~8V, current 100~500A, and the micro-area electrical treatment parameters of the softened zone are: voltage 8~20V, current 800~2000A; The width of the blank area is greater than 5 mm.

8. The method for preparing a metal material having a multi-phase heterogeneous structure according to claim 1 or 7, characterized in that: The current form in the micro-area electrical treatment process is any one of pulse current, constant current, alternating current and direct current.

9. The method for preparing a metal material having a multi-phase heterogeneous structure according to claim 1 or 7, characterized in that: The micro-area electrical treatment process applies an electric current to the metal material through a movable electronic probe. The movable electronic probe is first placed at a certain point in any hardened zone or softened zone of the metal material, and a current is applied once within the area of ​​the electronic probe. Then, the electronic probe is moved parallel to apply current to the next area of ​​the electronic probe. After the treatment of one hardened zone or softened zone is completed, the electronic probe is moved to another untreated hardened zone or softened zone to repeat the above process. When current is applied to the hardened zone, the treatment time of any single point is 5 to 60 seconds, and when current is applied to the softened zone, the treatment time of any single point is 10 to 300 seconds.

10. The method for preparing a metal material having a multi-phase heterogeneous structure according to claim 9, characterized in that: The shape of the electronic probe is any one of rectangular, circular, elliptical and linear; The area of ​​the electronic probe is 0.01~10mm 2 .

Images