Cu-Cr-Zr-TiB2 copper-based composite material as well as preparation method and application thereof

Abstract

The invention discloses a Cu-Cr-Zr-TiB2 copper-based composite material and a preparation method and application thereof. A blank containing TiB2 particles is subjected to rotary forging to obtain a rotary forging piece, the rotary forging piece is subjected to primary aging treatment and then subjected to electric pulse drawing to obtain a drawing piece, and then the drawing piece is subjected to secondary aging treatment to obtain the Cu-Cr-Zr-TiB2 copper-based composite material. According to the Cu-Cr-Zr-TiB2 copper-based composite material prepared through the preparation method, the copper matrix is of a gradient structure with the surface layer being a nanocrystalline layer of 50-200 nm and the core part being fine grains of 0.5-1 micron, TiB2 particle reinforced phases are distributed in the copper matrix in a fibrous mode in the axial direction, and Cr / Zr nano precipitated phases are distributed in gaps of the TiB2 particle reinforced phases and in crystals of the copper matrix in a dispersed mode; therefore, the high-hardness, high-strength, high-conductivity, high-softening-temperature, excellent high-temperature performance and excellent arc extinguishing performance are achieved.

Description

Technical Field

[0001] The present invention relates to the field of metal matrix composites, and particularly to a Cu-Cr-Zr-TiB2 copper matrix composite material, a preparation method thereof and an application thereof. Background Art

[0002] Copper-based materials are widely used in the fields of electronics, electric power, aerospace, etc. due to their excellent electrical conductivity, thermal conductivity and processing performance. At present, high-performance copper materials mainly include copper alloys (such as Cu-Cr-Zr, Cu-Ni-Co-Si, etc.) and copper matrix composites (such as A12O3 / Cu, TiB2 / Cu, CNTs / Cu, etc.). Among them, copper alloys will show the coarsening and re-solution of precipitation phases with the increase of service temperature, resulting in inevitable deterioration of electrical and mechanical properties, and poor high-temperature performance of copper alloys. In addition, high-performance copper alloys have strict requirements for the selection of alloying elements: they require a relatively high solid solubility at high temperatures and a relatively low solid solubility at low temperatures to ensure sufficient precipitation of other phases while improving the electrical conductivity and strength. However, the upper limit of the solid solubility of most alloying elements that meet such requirements in copper is relatively low, resulting in insufficient content of precipitation phases, and their performance has reached a bottleneck. In addition, existing research mainly focuses on single-reinforcement-phase composites or alloy systems, so the improvement of performance is limited. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the first object of the present invention is to provide a preparation method of a Cu-Cr-Zr-TiB2 copper matrix composite material. The preparation method of the present invention is simple and controllable, and is suitable for large-scale industrial production.

[0004] The second object of the present invention is to provide a Cu-Cr-Zr-TiB2 copper matrix composite material prepared by the above preparation method. The Cu-Cr-Zr-TiB2 copper matrix composite material provided by the present invention realizes synergistic strengthening through nano-ceramic particle reinforcement phases and nano-precipitation phases, and has high hardness, high strength, high electrical conductivity, high softening temperature, excellent high-temperature performance and excellent arc extinguishing performance.

[0005] The third object of the present invention is to provide an application of the Cu-Cr-Zr-TiB2 copper matrix composite material prepared by the above preparation method.

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

[0007] A preparation method of a Cu-Cr-Zr-TiB2 copper matrix composite material of the present invention comprises subjecting a blank containing TiB2 particles to rotary forging to obtain a rotary forging piece, subjecting the rotary forging piece to a first aging treatment, then performing electro-pulse drawing to obtain a drawn piece, and then subjecting the drawn piece to a second aging treatment to obtain a Cu-Cr-Zr-TiB2 copper matrix composite material;

[0008] During rotary swaging, a conical die is used, the single-pass deformation amount is 4-8%, the total deformation amount is 75-90%, and the strain rate is 200-400 s -1 , the die rotation speed is 800-1200 rpm, and the feed rate is 0.2-0.5 mm / pass;

[0009] The Cu-Cr-Zr-TiB2 copper matrix composite material includes a copper matrix, as well as a TiB2 particle reinforcement phase and a Cr / Zr nano-precipitation phase. The copper matrix has a gradient structure with a surface layer of 50-200 nm nanocrystalline layer and a core of 0.5-1 μm fine crystal. The TiB2 particle reinforcement phase is distributed in the copper matrix in a fibrous shape along the axial direction, and the Cr / Zr nano-precipitation phase is dispersed in the gaps between the TiB2 particle reinforcement phases and within the copper matrix crystal grains;

[0010] In the Cu-Cr-Zr-TiB2 copper matrix composite material, by mass percentage, the composition is as follows: TiB2: 0.3-3%, Cr: 0.3-2.5%, Zr: 0.05-0.2%, M: 0-0.5%, and the balance is Cu. The M is selected from at least one of Fe, Y, Mg, Zn, Sc, La, Ag, Yb, In, Te. The TiB2 particles are formed by in-situ reaction of Ti element and B element.

[0011] For the Cu-Cr-Zr-TiB2 copper matrix composite material provided by the present invention, first, the billet containing TiB2 particles is rotary swaged. During the rotary swaging process, TiB2, as a hard particle, forms a fibrous distribution (aspect ratio >10) by flowing along the axial direction under the high-strain shear force of rotary swaging, providing anisotropic strengthening; at the same time, TiB2 hinders the movement of dislocations, generating a high dislocation density region, providing more nucleation sites for subsequent aging precipitation. More importantly, in the present invention, a conical die (entrance angle 15°, exit angle 3°) is used during rotary swaging; a gradient strain field is generated. The surface layer metal undergoes shear-dominated deformation (shear strain ratio >70%); the core is mainly in compressive strain (axial strain ratio >60%), and the strain rate is 200-400 s - ¹ (the local strain rate of the surface layer can reach 800 s - ¹); the die rotation speed: 800-1200 rpm (the flow velocity of the surface layer metal is 3-5 times higher than that of the core); the feed rate: 0.2-0.5 mm / pass (the cumulative true strain of the surface layer reaches 4-5, and that of the core is only 2-3); under the coordination of the above parameters, the rotary swaging die and the material experience intense friction to generate a shear stress >800 MPa, and the surface layer metal undergoes shear folding + compression composite deformation (true strain reaches 4-5), and the dislocation density breaks through 10 16 m -2The critical value triggers dynamic recrystallization. The hard TiB2 particles act as strain concentration points, generating a large amount of distortion energy at the interface, promoting discontinuous dynamic recrystallization to form nanocrystals. The Cr / Zr precipitation phase pins the subgrain boundaries, inhibiting the growth of nanograins. The effective strain in the core is only 1 / 2 - 1 / 3 of that in the surface layer (ε≈2 - 3), and the dislocation density maintains 10 14 -10 15 m -2 , not reaching the complete recrystallization threshold, thus retaining part of the original equiaxed crystal structure. Therefore, a gradient nanostructure with a nanocrystalline layer on the surface and fine grains in the core is formed by rotary swaging. The surface layer acts as a diffusion barrier, raising the anti-softening temperature to above 600 °C.

[0012] After the first aging treatment, the fibrous distribution of TiB2 and the nanoscale dispersion distribution of the precipitation phase jointly hinder dislocation slip, achieving the dual strengthening of "the precipitation phase pins the dislocations within the crystal, and TiB2 hinders grain boundary migration". The two jointly form a composite structure of "fiber channels + dislocation walls". Then, through electropulse drawing, the diffusion ability of Cr / Zr atoms is activated, enabling the incomplete precipitation of Cr / Zr to rapidly nucleate during the pulse interval to form ultrafine precipitation phases. As a good conductive phase, TiB2 evenly disperses the pulse current, preventing local overheating of the matrix from causing coarsening of the precipitation phase or damage to the TiB2 / matrix interface. Finally, through the second aging treatment, the residual supersaturated solid solution of Cr / Zr further precipitates, increasing the conductivity and supplementing the nanoscale precipitation phases. The Cr / Zr precipitation phases preferentially distribute along the surface of the TiB2 fibers, filling the gaps between TiB2 particles to form a dense dislocation hindrance network.

[0013] Under the synergy of the above processes and compositions, a gradient structure with a 50 - 200 nm nanocrystalline layer on the surface and 0.5 - 1 μm fine grains retained in the core is formed in the matrix. TiB2 is distributed in the matrix in a fibrous shape along the axis, and the Cr / Zr precipitation phases are dispersed in the fiber gaps and within the crystal. The two jointly constitute a synergistic strengthening network of "the precipitation phase pins the dislocations within the crystal, and TiB2 divides the grain boundaries"; thus, the material provided by the present invention has both high strength (≥600 MPa), high conductivity (≥80% IACS), and high-temperature anti-softening ability.

[0014] In the invention, the synergy between the composition and the process is crucial. If only relying on the precipitation strengthening of Cr / Zr, the coarsening of the precipitation phase at high temperatures leads to performance degradation; TiB2, as a thermally stable phase, provides persistent strengthening, and its interface induces the refinement of the precipitation phase. More importantly, only under the synergy of (TiB2 + Cr / Zr) and the rotary swaging parameters of the present invention, can a 50 - 200 nm nanocrystalline layer be formed on the surface of the material through rotary swaging, and fine grains (0.5 - 1 μm) be retained in the core. In the absence of TiB2 in the traditional process, even with the same rotary swaging parameters, only uniform micron-sized grains (3 - 5 μm) can be obtained.

[0015] In addition, during the experimental exploration process, attempts were also made to in-situ generate ceramic particles such as Al2O3, TiO2, TiC, and ZrB2. However, the properties of the finally obtained composite materials were all lower than those of the composite materials obtained in this invention.

[0016] Of course, in this invention, the contents of each component need to be controlled within the scope of this invention to achieve better synergy. If too much Cr, Zr, and other trace elements are added, not only will the strength increase be limited, but the conductivity will also be reduced. If the addition amount of TiB2 is too large, it will lead to particle agglomeration, increased porosity, and weakened interfacial bonding. Stress concentration is likely to occur at the interface between the agglomerates and the matrix, becoming the crack source, and the interfacial bonding becomes worse, resulting in premature fracture of the material. In addition, the addition of excessive TiB2 will also lead to a significant attenuation of the electrical / thermal conductivity. Excessive TiB2 will also consume Cr or Zr atoms through interfacial adsorption, inhibiting its solid solution-precipitation strengthening effect.

[0017] In a preferred embodiment, the process for obtaining the blank containing TiB2 particles is as follows: pure copper, a Cr source, a Zr source, a Ti source, a B source, and an M source are proportioned as raw materials according to the designed composition, melted to obtain an alloy liquid containing TiB2 particles, the alloy liquid is cast into an ingot, the ingot is subjected to homogenization treatment to obtain a homogenized blank, the homogenized blank is hot-extruded to obtain a hot-extruded blank, the hot-extruded blank is subjected to solution treatment to obtain a solution-treated blank, and the solution-treated blank is subjected to pre-aging treatment to obtain the blank containing TiB2 particles.

[0018] In this invention, pure copper, a Cr source, a Zr source, a Ti source, a B source, and an M source are proportioned as raw materials respectively. During the melting process, the Ti source and the B source will in-situ form nano-sized TiB2 ceramic particles with a particle size of only 50 - 200 nm. During this process, the Cr / Zr elements and the microalloying element M synergistically assist in the in-situ generation of TiB2, refine the particle size of TiB2, and improve its distribution, laying a foundation for the synergistic distribution of the subsequent Cr / Zr-based precipitation phase and TiB2 ceramic particles.

[0019] After melting is completed, the obtained ingot is subjected to homogenization treatment. Through the homogenization treatment, the Cr / Zr elements are fully diffused and homogenized, while TiB2 remains stable during the homogenization process due to its high-temperature stability. TiB2 inhibits the migration of grain boundaries at high temperatures, hinders grain growth, and induces recrystallization of the matrix near the interface, refining the grains and avoiding local grain coarsening.

[0020] After homogenization treatment, hot extrusion is carried out to induce dynamic recrystallization (the TiB2 hard particles hinder the movement of dislocations, increase the deformation resistance, and force more external energy to be used for grain refinement), and the grains are refined to 5 - 20 μm; TiB2 is arranged along the deformation direction to form a preliminary fiber structure. Subsequently, solution treatment is carried out to fully dissolve Cr / Zr to form a supersaturated solid solution, while TiB2 is insoluble in the Cu matrix. Through the Zener pinning effect, it inhibits grain boundary migration and coarsening, ensuring that the grains are uniformly fine, providing a fine-grained matrix for the high-temperature solid solution of Cr / Zr, and avoiding the blocking of solute diffusion channels by coarse grain boundaries; at the same time, due to the large difference in thermal expansion coefficients between TiB2 and the Cu matrix, a local stress field is generated during cooling, inducing dislocation multiplication. The dislocation structure induced by TiB2 guides the pre-enrichment of Cr / Zr atoms, avoiding the uneven distribution and size of precipitation phases caused by random nucleation, and promoting the uniform nucleation of fine precipitation phases during the subsequent pre-aging process.

[0021] During the pre-aging process, the surface of TiB2 serves as a low-energy nucleation site, inducing the preferential precipitation of Cr / Zr precipitation phases (5 - 20 nm) around it to form a TiB2 - precipitation phase "pinning - bearing" composite strengthening structure. The precipitation phases are smaller in size and more densely distributed, enhancing the strengthening effect.

[0022] Further optimization: The Cr source is selected from Cu - Cr master alloy, the Zr source is selected from Cu - Zr master alloy, the Ti source is selected from Cu - Ti master alloy, and the B source is selected from Cu - B master alloy; in the prepared raw materials, the molar ratio of Ti to B is 1:2.

[0023] Even further optimization: In the Cu - Ti master alloy, the mass fraction of Ti ≤ 50%, preferably 20 - 30%; in the Cu - B master alloy, the mass fraction of B ≤ 6%, preferably 4 - 5%.

[0024] Experiments have found that using master alloys with the above composition contents can minimize the burning loss rate of each metal.

[0025] Even further optimization: The pure copper is electrolytic copper, and the purity of the pure copper ≥ 99.9 wt.%.

[0026] Further optimization: The melting process is as follows: First, melt the pure copper, then raise the temperature to 1200 - 1300 °C. After adding the Cu - Ti master alloy and completely melting it, lower the temperature to 1100 - 1180 °C, preferably 1100 - 1150 °C, add the Cu - B master alloy, stir for 0.5 - 5 min, then raise the temperature to 1200 - 1400 °C, add the M source, Cu - Cr master alloy, and Cu - Zr master alloy, and keep warm for 1 - 5 min to obtain the melt. After the melting is completed, continue to cool down to 1150 - 1300 °C, preferably 1170 - 1230 °C, while stirring, and then cast it into a water-cooled mold.

[0027] In the present invention, after the Cu-Ti alloy is completely melted, the temperature of the melt is cooled to 1100-1180 °C, preferably in the range of 1100-1150 °C, and then the Cu-B alloy is added. Within the above range, it can not only ensure the formation of TiB2 particles, but also ensure the fineness of TiB2 particles, enhancing the strengthening effect. Then, after the TiB2 particles are formed, other metal raw materials are added in sequence, so as to ensure the uniform dispersion of TiB2 particles in the ingot finally. After the melting is completed, it is cooled to the range of the present invention for casting to obtain an ingot with uniformly dispersed TiB2 particles. In the present invention, the casting temperature cannot be too high. If casting at too high a temperature, it will affect the capture of TiB2 particles at the front of the liquid-solid interface, which is not conducive to particle dispersion. While casting at too low a temperature will affect the melt fluidity and it is difficult to ensure the continuity of the casting process.

[0028] During the solidification process of the copper-based alloy, TiB2 mainly improves the tissue properties through heterogeneous nucleation and grain refinement. Pure copper has a face-centered cubic (FCC) structure, while TiB2 has a hexagonal crystal system. The lattice misfit degree of the low-index crystal planes of the two (such as Cu(111) and TiB2(0001)) is about 3%-4%, which is an effective heterogeneous nucleation core. During the solidification of copper, TiB2 particles can be adsorbed on the solid-liquid interface, hinder the extension of the dendrite trunk, promote the formation of equiaxed crystals. The refined equiaxed crystal structure can enhance the melt feeding ability, reduce the segregation tendency of low-melting eutectic phases such as Cu-O and Cu-S, and reduce the porosity of the cast copper alloy by 40%-60%. TiB2 improves the high-temperature stability. The melting point of TiB2 particles is as high as 3225 °C and remains stable in the copper matrix. By pinning the grain boundaries, it inhibits the grain coarsening at high temperatures (>500 °C), and increases the high-temperature strength retention rate of the material by 30%-50%.

[0029] Further preferably, the melting is non-vacuum melting. During the non-vacuum melting process, graphite is covered on the melt. Using non-vacuum melting can not only reduce costs, but also be more suitable for industrial production, and covering graphite can reduce the burning loss rate.

[0030] Further preferably, the temperature of the homogenization treatment is 920-980 °C, the time of the homogenization treatment is 2-12 h, and water quenching is carried out after the homogenization treatment is completed.

[0031] Further preferably, before the hot extrusion, it is kept at 880-920 °C for 1-4 h, and then hot extrusion is carried out, controlling the extrusion ratio to be 9-17, and air cooling is carried out after the hot extrusion.

[0032] Under the action of high temperature and high pressure through hot extrusion, casting pores and microcracks are welded together, and the material density is increased to more than 99.5%. During the hot extrusion process, strain-induced dynamic recrystallization generates fine equiaxed grains. The TiB2 particles inhibit grain growth through the Zener pinning effect, and the grain size is reduced by 50-80% compared with the as-cast state. The flow of the matrix metal elongates the TiB2 particles along the extrusion direction, forming oriented strengthening fibers, which increases the longitudinal (extrusion direction) strength by 20-30% while reducing the loss of transverse properties.

[0033] Further preferably, the solution treatment temperature is 940-960 °C, the solution treatment time is 2-4 h, and water quenching is carried out after the solution treatment is completed.

[0034] Further preferably, the pre-aging treatment temperature is 425-475 °C, and the pre-aging treatment time is 30-240 min.

[0035] By performing a pre-aging treatment once before deformation, the precipitation of the Cr-rich phase can be made more sufficient, and the precipitation strengthening effect is more significant. Finally, combined with subsequent deformation and aging treatments, a better precipitation effect can be obtained. During the pre-aging process, the TiB2 surface serves as a low-energy nucleation site, inducing the preferential precipitation of Cr / Zr precipitation phases (5-20 nm) around it, forming a TiB2-precipitation phase "pinning-bearing" composite strengthening structure, which improves the interfacial bonding strength between the precipitation phase and TiB2 and avoids the debonding of hard particles and the matrix during subsequent deformation. During subsequent high-strain processing (such as rotary forging and drawing) of the material, the dislocation can be pinned by the Cr / Zr precipitation phase, and the integrity of the fiber structure can be maintained by using TiB2, realizing the synergistic improvement of strength and plasticity.

[0036] During the pre-aging process, the temperature needs to be effectively controlled. If the pre-aging temperature is too low: the diffusion ability of Cr / Zr atoms is insufficient, and it is difficult to break through the nucleation barrier, resulting in a small number of precipitation phases and uneven sizes. The size of the pre-precipitation phase is too small or not formed, and a longer time or higher temperature is required for compensation during the subsequent first aging, resulting in an increased risk of grain coarsening; if the pre-aging temperature is too high, the diffusion rate of Cr / Zr atoms increases sharply, resulting in the rapid nucleation and excessive growth (size > 50 nm) of precipitation phases (such as CrCu2 and ZrCu3) at the TiB2 interface, losing the nano-strengthening effect; over-aging causes the premature depletion of Cr / Zr solute atoms, and no precipitation can be replenished during the subsequent first aging treatment, resulting in limited strength improvement.

[0037] In a preferred solution, during rotary forging, the single-pass deformation amount is 5-6%, the total deformation amount is 80-85%, and the strain rate is 300-350 s -1. The rotational speed of the die is 1000 - 1100 rpm, and the feed rate is 0.3 - 0.4 mm per pass. By using the rotary forging parameters within this preferred range, the properties of the final composite material are better.

[0038] In a preferred embodiment, the temperature of the first aging treatment is 425 - 475 °C, the time of the first aging treatment is 30 - 360 min, and water quenching is performed after the first aging treatment.

[0039] By controlling the aging temperature within the above range, the properties of the final material are optimal. If the aging temperature is too low, the precipitation driving force is insufficient, and Cr / Zr cannot be effectively precipitated, and the conductivity and strength of the material cannot reach excellent levels after aging. If the aging temperature is too high, recrystallization and grain growth of the matrix will occur before the solid solution elements are completely precipitated, and the work hardening and grain boundary strengthening effects will decrease sharply.

[0040] In a preferred embodiment, during the electro - pulse drawing, the electro - pulse frequency is controlled to be 100 - 300 Hz, the current density is 50 - 200 A / mm², and the pulse width is 0.6 - 3 ms.

[0041] During electro - pulse drawing, the electro - pulse frequency and current density need to be effectively controlled. The electro - pulse frequency used is slightly higher than the dislocation relaxation frequency (200 - 300 Hz) to ensure that the pulse interval is shorter than the dislocation re - annihilation period, continuously promoting dislocation slip. If the electro - pulse frequency is too high, heat accumulation will occur and grain boundaries will be weakened; if the electro - pulse frequency is too low (<50 Hz), dislocation motion cannot be effectively activated. The current density is controlled at 50 - 200 A / mm 2 ² to balance the Joule heat and the electron wind force effect, avoid interface damage, and at the same time drive the electron - dislocation interaction and reduce the flow stress. If the current density is too large, the interface will overheat and the precipitated phase will coarsen; if the current density is too low, the energy cannot activate dynamic precipitation, resulting in insufficient strengthening effect.

[0042] During electro - pulse drawing, the pulse width is controlled to match the dislocation slip time scale of the Cu matrix to achieve efficient local energy utilization. If the pulse width is too short, the dislocation response is insufficient; if the pulse width is too long, the temperature rise range will be too large, increasing the risk of grain coarsening.

[0043] In the present invention, it is crucial to use electro - pulse drawing. If cold drawing is performed directly after aging, lacking the reduction of the matrix flow stress by electro - pulse and the pinning of dislocations by the dynamically precipitated Cr / Zr nano - phase, deformation is extremely likely to localize and the wire is prone to fracture.

[0044] In a preferred embodiment, the electro - pulse drawing is multi - pass drawing, the total number of passes is 12 - 16, the total deformation is 60% - 90%, and the drawing speed is 5 - 20 m / min.

[0045] In the present invention, a forming strategy of small deformation amount and multi-pass accumulation is adopted. By gradually introducing strain and combining with the dynamic regulation effect of electric pulse, the gradient optimization of the microstructure and the synergistic improvement of the performance are realized. The dislocation density is gradually increased by small deformation in each pass, avoiding excessive entanglement of dislocations. The combination of high strain rate and small deformation amount triggers discontinuous dynamic recrystallization at the TiB2 particle interface, refining the grains. At the same time, through multi-pass drawing, the TiB2 particles are distributed axially to form a continuous fiber network, strengthening the anisotropy. And a short diffusion window is provided for Cr / Zr during the pulse intermittent period of each pass, promoting the precipitation of the Cr / Zr nano-precipitates that have not been completely precipitated before at the TiB2 interface. At the same time, the combination of multi-pass small deformation and the pulse intermittent period reduces the residual stress, avoiding the risk of interface debonding.

[0046] Further preferably, during the electric pulse drawing, the current density in the initial passes is 150 - 200 A / mm², and the current density in the later passes is 50 - 100 A / mm². The number of initial passes is 50 - 60% of the total number of passes. In this preferred scheme, a high current density is adopted in the initial passes to quickly activate the dislocation source and break through the pinning at the TiB2 interface; while in the later passes (the passes after the initial passes), the current density is reduced to inhibit the temperature rise and refine the precipitates.

[0047] In a preferred scheme, the temperature of the second aging treatment is 400 - 450 °C, the time of the second aging treatment is 30 - 360 min, and water quenching is carried out after the second aging treatment.

[0048] In a preferred scheme, in the Cu-Cr-Zr-TiB2 copper matrix composite, by mass percentage, the component composition is as follows: TiB2: 0.5 - 1%, Cr: 0.5 - 1%, Zr: 0.05 - 0.1%, M 0 - 0.3%, and the balance is Cu.

[0049] In a preferred scheme, the particle size of the TiB2 particle reinforcement phase is 50 - 200 nm, and the size of the Cr / Zr nano-precipitate is <20 nm.

[0050] The present invention also provides a Cu-Cr-Zr-TiB2 copper matrix composite prepared by the above preparation method.

[0051] The present invention also provides an application of the Cu-Cr-Zr-TiB2 copper matrix composite prepared by the above preparation method, and the Cu-Cr-Zr-TiB2 copper matrix composite is applied to one of resistance welding electrodes, heat dissipation devices, and aerospace wires.

[0052] Beneficial effects

[0053] (1)Multi-scale collaborative strengthening mechanism: On the one hand, TiB2 particles are generated through in-situ reaction to achieve a tight interfacial bond with the Cu matrix (lattice misfit degree ≈ 3% - 4%), reducing the electron scattering barrier. While enhancing the strength, high electrical conductivity is maintained (electrical conductivity ≥ 80% IACS), realizing the optimization of the interface of the nano-ceramic reinforcement phase. On the other hand, Cr / Zr alloying elements form nano-precipitates (size < 20nm) through multi-stage aging, which synergistically interact with sub-micron / nano-scale TiB2 particles. Through the Orowan bypass mechanism and dislocation pinning effect, the coupling dual-scale strengthening of the precipitate phase and particles is achieved.

[0054] (2)High-temperature stability regulation: Through rotary swaging combined with multi-stage deformation heat treatment, a gradient nanostructure with a 50 - 200 nm nanocrystalline layer on the material surface and 0.5 - 1 μm fine grains retained in the core is formed. The surface layer acts as a diffusion barrier, raising the anti-softening temperature to above 600°C.

[0055] (3)Low-energy consumption processing technology: Through electro-pulse assisted drawing, the electron wind effect promotes dislocation slip, eliminates dislocation tangles, reduces the processing energy consumption by 40%, and at the same time retains a high density of mobile dislocations (density > 10 14 m -2 ), realizing the collaborative optimization of strength and electrical conductivity.

[0056] In summary, through the collaboration of processes and preparation methods, the present invention breaks through the inverted relationship of "strength - electrical conductivity - thermal stability" of copper-based composites. The final product is applicable to extreme working conditions such as resistance welding electrodes (the arc extinction performance is improved by 30%), high-power heat dissipation devices (thermal conductivity ≥ 350 W / m·K), and aerospace wires, and the service life is increased by 3 - 5 times compared with traditional materials. Brief Description of the Drawings

[0057] Figure 1 Scanning images of the as-cast sample of the Cu-Cr-Zr-TiB2 copper-based composite material prepared in Example 1 of the present invention at different magnifications. Among them, Figure 1 (a)is at a lower magnification; Figure 1 (b)is at a higher magnification.

[0058] Figure 2 Macrophotograph of the sample after hot extrusion in Example 1 of the present invention.

[0059] Figure 3 Macrophotograph of the sample after rotary swaging in Example 1 of the present invention.

[0060] Figure 4 Scanning images of the sample after secondary aging in Example 1 of the present invention at different magnifications. Among them, Figure 4 (a)is at a lower magnification, Figure 4 (b)is at an intermediate magnification, Figure 4(c) is at a higher magnification.

[0061] Figure 5 This is a transmission image of the sample after secondary aging in Example 1 of the present invention, where Figure 5 (a) is a transmission image of the surface area of the sample, Figure 5 (b) is a transmission image of the core area of the sample.

[0062] Figure 6 This is a distribution map of TiB2 particles and Cr / Zr precipitation phases of the sample after secondary aging in Example 1 of the present invention, where Figure 6 (a) is a distribution map of the TiB2 particle reinforcement phase, Figure 6 (b) is a distribution map of the Cr / Zr precipitation phase.

[0063] Figure 7 This is a scanning electron micrograph of the fracture surface of the wire after secondary aging in Example 1 of the present invention.

[0064] Figure 8 This is a macroscopic photograph of the wire after cleaning after secondary aging in Example 1 of the present invention. Specific Embodiments

[0065] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0066] Example 1:

[0067] The Cu-Cr-Zr-TiB2 copper matrix composite material, by mass percentage, includes TiB2: 0.5%, Cr: 0.5%, Zr: 0.1%, Zn: 0.03%, In: 0.03%, Mg: 0.05%, and the balance is Cu.

[0068] The preparation process includes:

[0069] Step (1): Use an intermediate frequency induction melting furnace for non-vacuum melting and in-situ reaction to obtain an ingot. The raw materials added during melting include electrolytic copper (99.9 wt.%), Cu-10 wt.% Cr master alloy, Cu-30 wt.% Zr master alloy, Cu-25 wt.% Ti master alloy, Cu-4 wt.% B master alloy, and pure Mg (99.9 wt.%). Before melting, the raw materials, crucible, and mold are dried. During the melting process, first melt the pure copper (1083 °C). When the melt temperature reaches 1300 °C, add the Cu-Ti master alloy. After it is fully melted, cool down to 1150 °C and add the Cu-B master alloy. Stir the melt thoroughly to ensure that Ti and B undergo a sufficient in-situ reaction for about 3 minutes. Then raise the temperature to 1350 °C, add the Cu-Cr master alloy in 3 batches, stir for 30 s after holding for 2.5 minutes. Subsequently, add pure Zn, pure In, pure Mg, and Cu-Zr master alloy, continue to hold for 1 minute while stirring, and reduce the power of the induction furnace. When the melt temperature drops to 1200 °C, pour the melt into a cylindrical water-cooled mold to solidify. The diameter of the ingot is about 90 mm and the height is about 200 mm.

[0070] Step (2): Homogenize the ingot at a homogenization temperature of 960 °C for 8 h, and the cooling method is water quenching. Then, machine process to remove the surface defects of the ingot to ensure that there is no oxide layer, shrinkage cavity, etc. on the ingot surface.

[0071] Step (3): Hot extrude the homogenized billet with a hot extrusion ratio of 17:1. Before hot extrusion, the billet is held at a temperature of 900 °C for 1 h, and the extrusion die is held at a temperature of 450 °C for 1 h. During the extrusion process, the average pressure of the press is 700 MPa and the maximum pressure is 900 MPa. After hot extrusion, air cooling is carried out. The diameter of the bar is about 21 mm.

[0072] Step (4): Solution treat the bar after blooming at a solution temperature of 960 °C for 4 h, and the cooling method is water quenching.

[0073] Step (5): Pre-age the bar after solution treatment at a pre-ageing temperature of 450 °C for 60 min, and the cooling method is water quenching.

[0074] Step (6): Cold rotary forging is carried out on the bar after pre-ageing treatment. A conical die (entrance angle 15°, exit angle 3°) is used during rotary forging. The single-pass deformation amount is 5%, and the total rotary forging deformation amount is 80%. The strain rate is 300 s -1 , the die rotation speed is 1000 rpm, and the feed rate is 0.4 mm / pass. After rotary forging, the bar is aged at a temperature of 450 °C for 60 min, and the cooling method is water quenching. The diameter of the bar is about 5 mm.

[0075] Step (7): Perform electro-pulse assisted drawing. The final state wire is achieved through multiple passes, with a total deformation of 80%. Pulse parameters: frequency 200 Hz (matched with the relaxation time of dislocation movement), current density 60 A / mm 2 , pulse width 1 ms (ensuring the balance between dislocation slip and dynamic recovery). The drawing is carried out in 14 passes, from 5 mm to 0.2 mm. The specific drawing passes are as follows: 5 mm → 4.2 mm → 3.5 mm → 2.9 mm → 2.4 mm → 2.0 mm → 1.6 mm → 1.3 mm → 1.0 mm → 0.8 mm → 0.6 mm → 0.5 mm → 0.4 mm → 0.3 mm → 0.2 mm. Use lubricant to reduce friction and prevent surface defects. The drawing speed is 10 m / min.

[0076] Step (8): Perform aging treatment on the wire after electro-pulse assisted drawing under a protective atmosphere. The aging temperature is 400 °C, the aging time is 120 min, and the cooling method is water quenching. After cleaning the wire after secondary aging, the finished product is obtained.

[0077] Figure 1 This is the scanning image of the as-cast sample of the Cu-Cr-Zr-TiB2 composite material prepared in Example 1 of the present invention at different magnifications. From Figure 1 it can be seen that the TiB2 particles are dispersed and distributed finely. The average size of the TiB2 particles is 126 nm, presenting regular hexagons or approximate circles, with a uniform size distribution and no obvious agglomeration phenomenon.

[0078] Figure 2 This is the macroscopic photograph of the sample after hot extrusion in Example 1 of the present invention. From Figure 2 it can be seen that there are no obvious cracks or defects on the surface of the sample. There are slight extrusion lines, linearly distributed along the extrusion direction. The cross-section is a regular circle, with clear edges, no obvious deformation or burrs.

[0079] Figure 3 This is the macroscopic photograph of the sample after rotary forging in Example 1 of the present invention. From Figure 3 it can be seen that the surface of the sample is smooth, showing a metallic luster, without obvious cracks, scratches or defects. The sample is cylindrical, with uniform dimensions, clear edges, no burrs or warping. The overall color of the sample is uniform, without oxide scale or discolored areas.

[0080] Figure 4 This is the scanning image of the sample after secondary aging in Example 1 of the present invention at different magnifications. From Figure 4It can be seen that TiB2 particles are clearly visible in the matrix, presenting regular hexagons or approximate circles, and the size distribution is more uniform than that in the as-cast state. The interface between the particles and the matrix is well bonded, and no obvious interface cracks or debonding phenomena are observed.

[0081] Figure 5 This is the transmission image of the sample after secondary aging in Example 1 of the present invention. In the figure, TiB2 particles are clearly visible in the matrix, presenting regular hexagons or approximate circles, with a uniform size distribution. The interface between the particles and the matrix is tightly bonded, and no obvious interface reactions or defects are observed. A certain number of dislocations and substructures are observed, the dislocation density is moderate, and no excessive dislocation tangles or pile-ups are observed; from Figure 5 (a), it can be seen that the grain size of the copper matrix in the surface region is 50 - 200 nm; from Figure 5 (b), it can be seen that the grain size in the core region is 0.5 - 1 μm, showing a gradient structure.

[0082] Figure 6 This is the distribution map of TiB2 particles and Cr / Zr precipitation phases of the sample after secondary aging in Example 1 of the present invention, where Figure 6 (a) is the distribution map of the TiB2 particle reinforcement phase. From Figure 6 (a), it can be seen that the TiB2 particle reinforcement phase is distributed in the matrix along the axial direction in a fibrous shape. From Figure 6 (b), it can be seen that the Cr / Zr nano-precipitation phases (black parts) are diffusely distributed in the fiber gaps and within the matrix grains, and their average size < 20 nm.

[0083] Figure 7 This is the fracture surface scanning image of the wire after secondary aging in Example 1 of the present invention. From the figure, it can be seen that the interface between the particles and the matrix is well bonded, and no obvious debonding or interface cracks are observed, indicating that the TiB2 particles play a good strengthening role on the material. The fracture surface morphology is mainly ductile fracture, and the dimple characteristics are obvious, indicating that the material has experienced significant plastic deformation during the fracture process. A small amount of cleavage planes may be observed in local areas, but the overall is dominated by ductile fracture, the fracture surface morphology is uniform, and the distribution of dimples and TiB2 particles is consistent, reflecting the uniformity of the material and the good interface bonding performance.

[0084] Figure 8 This is the macroscopic photograph of the wire after cleaning after secondary aging in Example 1 of the present invention. From Figure 8 it can be seen that the surface of the wire is smooth, presenting a uniform metallic luster, without obvious scratches, cracks or defects. The diameter of the wire is uniform, without obvious uneven thickness or deformation phenomena, indicating that the processing technology is well controlled.

[0085] Example 2:

[0086] Other preparation processes and parameters are the same as those in Example 1, except for the current density parameter in step (7). Specifically: the current density in the initial passes (5 mm → 4.2 mm → 3.5 mm → 2.9 mm → 2.4 mm → 2.0 mm → 1.6 mm → 1.3 mm) is 160 A / mm², and the current density in the later passes (1.3 mm → 1.0 mm → 0.8 mm → 0.6 mm → 0.5 mm → 0.4 mm → 0.3 mm → 0.2 mm) is 70 A / mm².

[0087] Comparative Example 1:

[0088] Other preparation processes and parameters are the same as those in Example 1. Only in step (7), traditional cold drawing is used for processing, and the drawing passes and total deformation amount are the same as those in Example 1.

[0089] Perform performance tests on the Cu-0.5Cr-0.1Zr-0.5TiB2 copper matrix composites prepared in Example 1, Example 2, and Comparative Example 1. The test results are shown in Table 1.

[0090]

[0091] It can be seen from the table that Example 2 exhibits better performance than Example 1 and Comparative Example 1. The main reason is that Example 2 optimizes the electro-pulse current density in the initial passes and the later passes. A high current density is adopted in the initial passes to quickly activate the dislocation source and break through the TiB2 interface pinning; while the current density is reduced in the later passes to inhibit temperature rise, refine the precipitated phase, and improve the strengthening effect.

[0092] Example 3:

[0093] Cu-1Cr-0.1Zr-1TiB2 copper matrix composite material. In terms of mass percentage, the material components include TiB2: 1.0%, Cr: 1.0%, Zr: 0.1%, Mg: 0.05%, Sc: 0.03%, La: 0.03%, Y: 0.03%, and the balance is Cu.

[0094] The specific preparation process includes:

[0095] Step (1): Use an intermediate frequency induction melting furnace for non-vacuum melting and in-situ reaction to obtain an ingot. The raw materials added during melting include electrolytic copper (99.9 wt.%), Cu-10 wt.% Cr master alloy, Cu-30 wt.% Zr master alloy, Cu-25 wt.% Ti master alloy, Cu-4 wt.% B master alloy, pure Mg (99.9 wt.%), pure Sc (99.9 wt.%), pure La (99.9 wt.%), and pure Y (99.9 wt.%). Before melting, the raw materials, crucible, and mold are dried. During the melting process, first melt the pure copper (1083 °C). When the melt temperature reaches 1320 °C, add the Cu-Ti master alloy (the addition amount is 3.2 kg / 100 kg of raw materials). Wait for it to melt completely, then cool down to 1140 °C and add the Cu-B master alloy (the addition amount is 8.5 kg / 100 kg of raw materials). Stir the melt thoroughly to ensure sufficient in-situ reaction between Ti and B, with a duration of 3 min. Then raise the temperature to 1350 °C and add the Cu-Cr master alloy in 3 batches, and keep warm for 3 minutes. Subsequently, add pure Mg, pure Sc, pure La, pure Y, and Cu-Zr master alloy, continue to keep warm for 1.5 minutes, while stirring, and reduce the power of the induction furnace. When the melt temperature drops to 1250 °C, pour the melt into a cylindrical water-cooled mold to solidify. The diameter of the ingot is about 90 mm and the height is about 200 mm.

[0096] Step (2): Homogenize the ingot. The homogenization temperature is 960 °C, the homogenization time is 10 h, the cooling method is water quenching, and the surface oxide layer and defects are removed by machining.

[0097] Step (3): Perform hot extrusion to break the billet after homogenization. The extrusion ratio is 17:1. The ingot billet is kept warm at 900 °C for 1.5 h, the mold is kept warm at 450 °C for 1.5 h, the average pressure of the press is 750 MPa, the maximum pressure is 950 MPa, and the extruded material is air-cooled to obtain a bar with a diameter of about 21 mm.

[0098] Step (4): The solution treatment parameters are 960 °C × 4 h, and water quenching is used for cooling.

[0099] Step (5): The pre-aging process is 450 °C × 90 min, and water quenching is used for cooling.

[0100] Step (6): Cold rotary forging is performed on the bar after pre-aging treatment. A conical mold (entrance angle 15°, exit angle 3°) is used during rotary forging. The single-pass deformation amount is 5.5%, the total rotary forging deformation amount is 85%, the strain rate is 350 s -1 , the mold rotation speed is 1100 rpm, the feed rate is 0.35 mm / pass. After rotary forging, the bar is subjected to aging treatment. The aging temperature is 450 °C, the aging time is 90 min, and the cooling method is water quenching. The diameter of the bar is about 3 mm.

[0101] Step (7): Perform electro-pulse assisted drawing. The final state of the drawn wire is achieved through multiple passes, with a total deformation of 90%. Pulse parameters: frequency 220 Hz, current density 80 A / mm², pulse width 0.8 ms. The number of drawing passes is 16: 3 mm → 2.7 mm → 2.4 mm → 2.1 mm → 1.9 mm → 1.7 mm → 1.5 mm → 1.3 mm → 1.1 mm → 0.9 mm → 0.7 mm → 0.55 mm → 0.3 mm → 0.25 mm → 0.2 mm → 0.15 mm → 0.1 mm. Use lubricant to reduce friction and prevent surface defects. The drawing speed is 8 m / min.

[0102] Step (8): Perform aging treatment on the wire after electro-pulse assisted drawing under a protective atmosphere. The aging temperature is 400 °C, the aging time is 180 min, and the cooling method is water quenching. After cleaning the wire after secondary aging, the finished product is obtained.

[0103] Comparative Example 2:

[0104] Other preparation processes and parameters are the same as those in Example 2, except for a difference in Step (5). Specifically: Do not perform pre-aging treatment on the sample.

[0105] Example 4:

[0106] Other preparation processes and parameters are the same as those in Example 2, except for a difference in the cold rotary forging parameters in Step (6). Specifically: The strain rate is set to 200 s -1 , the die rotation speed is 800 rpm, and the feed rate is 0.2 mm / pass. Others are the same.

[0107] Example 5:

[0108] Other preparation processes and parameters are the same as those in Example 2, except for a difference in the current density parameter in Step (7). Specifically: The current density in the initial passes (3 mm → 2.7 mm → 2.4 mm → 2.1 mm → 1.9 mm → 1.7 mm → 1.5 mm → 1.3 mm → 1.1 mm) is 180 A / mm², and the current density in the later passes (1.1 mm → 0.9 mm → 0.7 mm → 0.55 mm → 0.3 mm → 0.25 mm → 0.2 mm → 0.15 mm → 0.1 mm) is 80 A / mm².

[0109] Perform performance tests on the Cu-Cr-Zr-TiB2 copper matrix composites prepared in Example 3, Example 4, Example 5, and Comparative Example 2. The test results are shown in Table 2.

[0110]

[0111] It can be seen from Table 2 that Example 5 exhibits better performance than Example 3, Example 4, and Comparative Example 2. The main reason is that in Example 5, the electric pulse current density in the initial pass and the final pass is optimized. A high current density is adopted in the initial pass to quickly activate the dislocation source and break through the TiB2 interface pinning; while in the final pass, the current density is reduced to suppress the temperature rise, refine the precipitated phase, and improve the strengthening effect.

Claims

1. A method for preparing a Cu-Cr-Zr-TiB2 copper-based composite material, characterized in that: The blank containing TiB2 particles is subjected to rotary forging to obtain a rotary forging, the rotary forging is subjected to a first aging treatment, and then subjected to electric pulse drawing to obtain a drawn part, and the drawn part is subjected to a second aging treatment to obtain a Cu-Cr-Zr-TiB2 copper-based composite material; The rotary forging adopts a conical die, the deformation of a single pass is 4-8%, the total deformation is 75-90%, and the strain rate is 200-400 s -1 , die speed is 800-1200 rpm, feed rate is 0.2-0.5 mm / pass; The Cu-Cr-Zr-TiB2 copper-based composite material comprises a copper matrix, a TiB2 particle reinforcement phase and a Cr / Zr nano-precipitated phase, wherein the copper matrix has a gradient structure with a surface layer of 50-200 nm nano-crystalline layer and a core of 0.5-1 μm fine crystals, the TiB2 particle reinforcement phase is distributed in the copper matrix in a fibrous shape along the axial direction, and the Cr / Zr nano-precipitated phase is dispersed in the gaps between the TiB2 particle reinforcement phases and in the copper matrix crystals; The Cu-Cr-Zr-TiB2 copper-based composite material has the following components in mass percentage: TiB2: 0.3-3%, Cr: 0.3-2.5%, Zr: 0.05-0.2%, M: 0-0.5%, and the balance is Cu. The M is selected from at least one of Fe, Y, Mg, Zn, Sc, La, Ag, Yb, In, and Te. The TiB2 particles are generated by in-situ reaction of Ti element and B element.

2. The method for preparing a Cu-Cr-Zr-TiB2 copper-based composite material according to claim 1, characterized in that: The process of obtaining the billet containing TiB2 particles is as follows: pure copper, Cr source, Zr source, Ti source, B source, and M source are taken as raw materials according to the designed composition, smelted to obtain an alloy liquid containing TiB2 particles, the alloy liquid is cast to obtain an ingot, the ingot is homogenized to obtain a homogenized billet, the homogenized billet is hot-extruded to obtain a hot-extruded billet, the hot-extruded billet is solution-treated to obtain a solid solution billet, the solid solution billet is pre-aged to obtain a billet containing TiB2 particles.

3. The method for preparing a Cu-Cr-Zr-TiB2 copper-based composite material according to claim 2, characterized in that: The Cr source is selected from Cu-Cr master alloy, the Zr source is selected from Cu-Zr master alloy, the Ti source is selected from Cu-Ti master alloy, and the B source is selected from Cu-B master alloy. In the prepared raw materials, the molar ratio of Ti to B is 1:2; In the Cu-Ti master alloy, the mass fraction of Ti is ≤50%, and in the Cu-B master alloy, the mass fraction of B is ≤6%; The pure copper is electrolytic copper, and the purity of the pure copper is ≥99.9wt.%; The smelting process is as follows: firstly melt pure copper, then heat it to 1200-1300°C, add Cu-Ti master alloy and completely melt it, then cool it to 1100-1180°C, add Cu-B master alloy, stir for 0.5-5min, then heat it to 1200-1400°C, add M source, Cu-Cr master alloy and Cu-Zr master alloy, keep it warm for 1-5min, continue to cool it to 1150-1300°C while stirring after smelting, and then cast it into a water-cooled mold; The homogenization temperature is 920-980°C, the homogenization time is 2-12h, and the homogenization is completed by water quenching; Before hot extrusion, the material is kept at 880-920°C for 1-4 hours, and then hot extrusion is performed, the extrusion ratio is controlled to be 9-17, and air cooling is performed after hot extrusion; The temperature of the solution treatment is 940-960°C, the time of the solution treatment is 2-4h, and the solution treatment is completed and water quenched; The pre-aging treatment temperature is 425-475° C., and the pre-aging treatment time is 30-240 min.

4. The method for preparing a Cu-Cr-Zr-TiB2 copper-based composite material according to claim 1, characterized in that: The temperature of the first aging treatment is 425-475° C., the time of the first aging treatment is 30-360 min, and water quenching is performed after the first aging treatment.

5. The method for preparing a Cu-Cr-Zr-TiB2 copper-based composite material according to claim 1, characterized in that: During the electric pulse drawing, the electric pulse frequency is controlled to be 100-300 Hz, the current density is 50-200 A / mm², and the pulse width is 0.6-3 ms; The electric pulse drawing is a multi-pass drawing, the total number of passes is 12-16 passes, the total deformation is 60%-90%, and the drawing speed is 5-20 m / min.

6. The method for preparing a Cu-Cr-Zr-TiB2 copper-based composite material according to claim 5, characterized in that: During the electric pulse drawing, the current density of the initial pass is 150-200 A / mm², and the current density of the later pass is 50-100 A / mm². The number of initial passes is the first 50-60% of the total number of passes.

7. The method for preparing a Cu-Cr-Zr-TiB2 copper-based composite material according to claim 1, characterized in that: The temperature of the second aging treatment is 400-450° C., the time of the second aging treatment is 30-360 min, and water quenching is performed after the second aging treatment.

8. The method for preparing a Cu-Cr-Zr-TiB2 copper-based composite material according to claim 1, characterized in that: The Cu-Cr-Zr-TiB2 copper-based composite material has the following components in mass percentage: TiB2: 0.5-1%, Cr: 0.5-1%, Zr: 0.05-0.1%, M 0-0.3%, and the balance is Cu; The particle size of the TiB2 particle reinforcement phase is 50-200nm, and the size of the Cr / Zr nano-precipitation phase is less than 20nm.

9. The Cu-Cr-Zr-TiB2 copper-based composite material prepared by the preparation method according to any one of claims 1 to 8.

10. Application of the Cu-Cr-Zr-TiB2 copper-based composite material prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The Cu-Cr-Zr-TiB2 copper-based composite material is applied to one of resistance welding electrodes, heat dissipation devices, and aerospace wires.

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