A high-strength, high-toughness, lightweight heterogeneous composite cable and its preparation method

Abstract

This invention relates to a high-strength, high-toughness, lightweight heterogeneous composite cable and its preparation method. The method includes the following steps: (1) Rotary forging: Forging steel rods at room temperature; forging magnesium alloy rods at high temperature; (2) Twisting: Grinding and cleaning several heterogeneous steel and magnesium alloy rods of equal length prepared in step (1), arranging them in a circumferentially alternating pattern, and feeding them into a twisting machine to form a heterogeneous steel-magnesium alloy composite cable. This invention utilizes the different deformation mechanisms of steel and magnesium alloy during rotary forging to produce different grain refinement effects in the radial direction of the two different rods, thereby obtaining heterogeneous steel and heterogeneous magnesium alloy rods with completely opposite grain size distribution characteristics in the radial direction. Finally, the two rods, arranged in a circumferentially alternating pattern, are mechanically combined through twisting to obtain a structurally controllable high-strength, high-toughness, lightweight heterogeneous steel-magnesium alloy composite cable.

Description

Technical Field

[0001] This invention belongs to the field of materials preparation, specifically relating to a high-strength, high-toughness, lightweight heterogeneous composite cable and its preparation method. Background Technology

[0002] In today's era, resource scarcity is becoming increasingly serious, hindering the rapid development of human society. On the other hand, with the advancement of science and technology, traditional metallic materials can no longer meet the needs of human society, making the development of high-performance lightweight metallic materials an urgent priority. Heterogeneous metallic materials are proposed in contrast to traditional homogeneous materials. They are characterized by non-uniform distribution of spatial structure and composition. Due to their unique structural features, heterogeneous metallic materials possess excellent mechanical properties, and their emergence has driven new developments in traditional metallic materials.

[0003] In their paper "Effect of post-deformation annealing on the microstructure and micro-mechanical behavior of Zn–Mg hybrids processed by High-Pressure Torsion," published in Materials Science & Engineering A [J], 2020, 771: 138578, David Hernández-Escobar et al. introduced a process for preparing heterogeneous zinc-magnesium composite materials using high-pressure torsion. The microstructure and mechanical properties of the materials were controlled through high-pressure torsion deformation and heat treatment. This technology has the following characteristics: (1) The heterogeneous materials obtained through high-pressure torsion have good interfacial bonding, achieving excellent interfacial metallurgical bonding; (2) The mechanical properties of the materials are significantly improved by controlling the microstructure through post-deformation heat treatment. However, this technology also has the following problems: (1) Due to the limitations of equipment and processing technology, this method is difficult to prepare large-sized heterogeneous materials and cannot meet the needs of industrialization; (2) This method has high requirements for the thickness and surface cleanliness of materials, which increases processing costs and difficulty and greatly reduces production efficiency.

[0004] In their paper "Additive manufacturing of multi-scale heterostructured high-strength steels" published in Materials Research Letters, 2021, 9: 291-299, Tan Chaolin et al. introduced a process for preparing layered heterostructured high-strength steels using additive manufacturing. This technology has the following characteristics: (1) the prepared layered heterostructured materials achieve atomic-level bonding between heterostructure interfaces, resulting in stable mechanical properties; (2) the prepared heterostructured high-strength steels exhibit hierarchical heterostructure characteristics at the layer, molten pool, and grain scales, demonstrating a good strength-ductility combination. However, this technology also has the following problems: (1) due to limitations in equipment and processing technology, the process flow is complex, the manufacturing cost is high, and it is not suitable for large-scale industrial promotion; (2) the raw materials for this technology are powder materials, which can easily lead to material waste and environmental pollution. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a high-strength, high-toughness, lightweight heterogeneous steel-magnesium alloy composite cable. First, steel rods and magnesium alloy rods are sequentially subjected to rotary forging deformation to obtain heterogeneous steel rods and heterogeneous magnesium alloy rods with a polycrystalline scale. Oil and oxide films are removed from the surfaces of the heterogeneous steel and magnesium alloy rods. Several heterogeneous steel and magnesium alloy rods of equal length are arranged in an alternating circumferential pattern and fed into a stranding machine for stranding to obtain a high-strength, high-toughness, lightweight heterogeneous steel-magnesium alloy composite cable.

[0006] The technical solution for achieving the objective of this invention is: a method for preparing a high-strength, high-toughness, lightweight heterogeneous composite cable, comprising the following steps:

[0007] Step (1): Rotary forging: The steel bar is rotary forged at room temperature to obtain a heterogeneous steel bar. The surface of the steel bar is a softer coarse-grained phase, and the core is a harder fine-grained phase. The radial hardness of the heterogeneous steel bar is distributed in an inverted V-shape.

[0008] Magnesium alloy bars are forged under high temperature conditions to obtain heterogeneous magnesium alloy bars. The structure of the heterogeneous magnesium alloy is: the surface is a harder fine-grained phase along the radial direction, and the core is a softer coarse-grained phase. The radial hardness of the heterogeneous magnesium alloy is distributed in a positive V-shape.

[0009] Step (2): Twisting: Take several heterogeneous steel rods and heterogeneous magnesium alloy rods of the same length prepared in step (1), grind and clean them to remove oil and oxide scale from the surface, and then arrange the heterogeneous steel rods and heterogeneous magnesium alloy rods in a circumferentially alternating pattern and feed them into a twisting machine to twist them into a heterogeneous steel-magnesium alloy composite cable.

[0010] Furthermore, the steel bar rotary forging process parameters in step (1) are as follows: deformation temperature: room temperature, spindle speed: 80-205 rpm, feeding speed: 3 m / min, equivalent variable per pass: 1%-10%, and total equivalent variable: 20%-150%.

[0011] The parameters for the magnesium alloy rotary forging process are as follows: deformation temperature is 150-300℃, spindle speed is 80-205rpm, feeding speed is 3m / min, equivalent variable per pass is 1%-10%, and total equivalent variable is 20%-150%.

[0012] Furthermore, the twisting process parameters in step (2) are: deformation temperature of 25-300℃; rotation speed of 3-10 rpm; and feeding speed of 6 m / min.

[0013] Furthermore, the steel bars and magnesium alloy bars have the same diameter, which is 15-25mm.

[0014] Furthermore, the rotary forging in step (1) is carried out on a rotary forging machine, which is equipped with a heating coil device. The heating coil device is controlled to heat the bar to be rotary forged at different temperatures.

[0015] A high-strength, high-toughness, lightweight heterogeneous composite cable is prepared using the method described above.

[0016] Furthermore, the steel bars are made of 304 stainless steel or 316L stainless steel.

[0017] Furthermore, the magnesium alloy rods are made of AZ80 magnesium alloy, Mg-Li alloy, or AZ31 magnesium alloy.

[0018] Compared with the prior art, the significant advantages of this invention are:

[0019] (1) This invention can produce high-strength, high-toughness, lightweight heterogeneous steel-magnesium alloy composite cables. It is applicable to a wide range of materials, including 304 stainless steel / AZ80 magnesium alloy, 316L stainless steel / Mg-Li alloy, carbon steel / AZ31 magnesium alloy, and other alloys.

[0020] (2) The heterogeneous steel rods and heterogeneous magnesium alloy rods prepared by the present invention both have the characteristic of uneven distribution of grain size along the radial direction, and the distribution characteristics are completely opposite in the radial direction in the two different rods. Therefore, the alternating combination of the two materials can achieve a synergistic improvement in material strength and plasticity. The "soft outside, hard inside" structure of heterogeneous steel effectively prevents crack initiation and propagation. When subjected to external stress, the harder core components preferentially experience stress concentration, leading to microcracks that tend to propagate radially outward. However, the stress generated at the microcrack tip is alleviated and released by the softer external components, hindering rapid crack propagation and delaying necking and fracture of the heterogeneous steel. Similarly, the "hard outside, soft inside" structure of heterogeneous magnesium alloys also effectively prevents crack initiation and propagation. When subjected to external stress, the harder external components preferentially experience stress concentration, leading to microcracks that tend to propagate radially inward. However, the stress generated at the microcrack tip is alleviated and released by the softer internal components, hindering rapid crack propagation and delaying necking and fracture of the heterogeneous magnesium alloy. Furthermore, the refinement of the surface grains of heterogeneous magnesium alloy rods, forming nanocrystals / ultrafine grains, effectively improves their surface wear resistance and corrosion resistance.

[0021] (3) The heterogeneous steel-magnesium alloy composite cable prepared by the present invention achieves material lightweighting. Compared with steel cables of the same tensile strength, the heterogeneous composite cable prepared by the present invention is lighter and has better economic advantages in terms of cost saving. Compared with steel cables of the same weight, the heterogeneous composite cable prepared by the present invention has higher tensile strength and has stronger practical advantages in terms of industrial service.

[0022] (4) According to the actual needs of industrial applications, the arrangement order and proportion of alloys, the number of arrangement layers, etc. can be adjusted. It has great microstructure orientation and combination ratio flexibility, and can prepare high-strength, high-toughness, lightweight heterogeneous steel-magnesium alloy composite cables that meet the needs of diversified practical applications.

[0023] (5) The entire processing flow of the present invention does not require the addition of protective gas, has no pollutant emissions, has a low deformation temperature, no material loss, low production cost, and high feasibility.

[0024] (6) The present invention can directly process bar stock, with a simple process flow, high production efficiency, and strong industrial applicability. Attached Figure Description

[0025] Figure 1 This is a process flow diagram for preparing a high-strength, high-toughness, lightweight heterogeneous steel-magnesium alloy composite cable according to the present invention; wherein (a) is a schematic diagram of the rotary forging deformation process, and (b) is a schematic diagram of the stranding process.

[0026] Figure 2This is a schematic diagram of the radial strain distribution and microstructure evolution of steel during the rotary forging process of the present invention; wherein (a1) is a schematic diagram of the strain distribution of steel before deformation, (a2) is a schematic diagram of the strain distribution of steel after small deformation, (a3) ​​is a schematic diagram of the strain distribution of steel after deformation, and (b1), (b2), and (b3) are schematic diagrams of the microstructure of steel in the corresponding states of (a1), (a2), and (a3), respectively.

[0027] Figure 3 This is a schematic diagram of the radial strain distribution and microstructure evolution of magnesium alloy during the rotary forging process of the present invention; wherein (a1) is a schematic diagram of the strain distribution of magnesium alloy before deformation, (a2) is a schematic diagram of the strain distribution of magnesium alloy after small deformation, (a3) ​​is a schematic diagram of the strain distribution of magnesium alloy after deformation, and (b1), (b2), and (b3) are schematic diagrams of the microstructure of magnesium alloy in the corresponding states of (a1), (a2), and (a3), respectively.

[0028] Figure 4 These are radial microstructure evolution photographs of the heterogeneous steel and heterogeneous magnesium alloy rods prepared according to the present invention; wherein (a) is a grain size evolution diagram of the heterogeneous steel from the surface to the core, and (b) is a grain size evolution diagram of the heterogeneous magnesium alloy rod from the surface to the core.

[0029] Figure 5 The images show the radial Vickers microhardness distribution of the heterogeneous steel and heterogeneous magnesium alloy rods prepared according to the present invention; wherein (a) is the radial Vickers microhardness distribution of the heterogeneous steel and (b) is the radial Vickers microhardness distribution of the heterogeneous magnesium alloy rod.

[0030] Explanation of reference numerals in the attached figures:

[0031] 1- Rotary forging machine housing, 2- Rotary forging die system, 3- Bar stock in rotary forging deformation, 4- Heating coil, 5- Heterogeneous AZ80 magnesium alloy bar stock, 6- Heterogeneous 304 stainless steel bar stock, 7- Twisting machine. Detailed Implementation

[0032] The present invention will now be described in further detail with reference to the accompanying drawings. This embodiment is implemented based on the technical solution of the present invention, providing detailed implementation methods and operating procedures; however, the scope of protection of the present invention is not limited to the following implementation content. The materials used in this embodiment are 304 stainless steel and AZ80 magnesium alloy.

[0033] The first step is rotary forging. Four 2.0m long, 20mm diameter 304 stainless steel bars and three AZ80 magnesium alloy bars of the same size are fed sequentially into the rotary forging mill at a feed rate of 3m / min. The stainless steel bars are forged at room temperature, while the magnesium alloy bars are forged after the heating coil of the rotary forging mill has reached and stabilized at 200℃. The spindle speed for both is 100rpm. The diameter reduction per pass is 1mm, until both the 304 stainless steel and AZ80 magnesium alloy bars reach a diameter of 15mm.

[0034] The second step, as Figure 1 As shown in (b), several heterogeneous steel and heterogeneous magnesium alloy bars of the same length are taken, ground and cleaned to remove oil and oxide scale from the surface. Then, the heterogeneous steel and heterogeneous magnesium alloy bars are arranged in a circumferentially alternating pattern and fed into a twisting machine at a speed of 6 m / min to form a heterogeneous steel-magnesium alloy composite cable.

[0035] The macroscopic compositional distribution of the obtained high-strength, high-toughness, lightweight heterogeneous steel-magnesium alloy composite cable is as follows: Figure 1 As shown in (b), the microstructure is as follows Figure 2 , Figure 3 , Figure 4 As shown. The crystal structure of 304 stainless steel is body-centered cubic (BCC) and face-centered cubic (FCC). This structure has a sufficient number of independent slip systems that can be activated under stress, thus exhibiting good processing and deformation capabilities. During rotary forging, the stress state on the circumferential surface of the 304 stainless steel bar is uniaxial compressive stress. Under the coordination of dislocation slip, the stress can be rapidly transferred from the surface of the bar to the core and continuously accumulate in the core. The stress on the core structure is three-dimensional multiaxial compressive stress. As the stress continuously accumulates in the core, the stress on the core grains continuously increases. Under sufficiently large three-dimensional multiaxial compressive stress... Under stress, the core grains refine to form nanocrystals or ultrafine grains. As stress accumulates, the interface between the fine and coarse grain layers gradually expands radially outward, and the area of ​​nanocrystals / ultrafine grains gradually increases until the dislocation density and grain refinement effect in the core of the bar reach saturation. Dislocations can no longer coordinate the inward transmission of stress, and the interface between the fine and coarse grain layers no longer expands outward. The area of ​​nanocrystals / ultrafine grains tends to stabilize, ultimately resulting in a 304 heterogeneous stainless steel bar composed of a coarse grain layer with a softer circumferential surface and a harder nanocrystal / ultrafine grain layer in the core. Its vertical axial microstructure distribution is as follows: Figure 4 As shown in (a), the microhardness distribution is as follows: Figure 5 As shown in (a).

[0036] The crystal structure of AZ80 magnesium alloy is a hexagonal close-packed lattice (HCP), which has only 3 / 6 of the number of movable independent slip systems, far fewer than that of body-centered cubic (BCC) and face-centered cubic (FCC) lattices, resulting in poor machinability. During rotary forging, the circumferential surface of the AZ80 magnesium alloy bar experiences uniaxial compressive stress. Due to the limited number of movable independent slip systems and poor dislocation slip capability, the coordination effect on stress transmission is limited. Therefore, stress accumulates on the circumferential surface of the bar and cannot be effectively transmitted to the core. When the stress accumulates sufficiently, the grains in the surface region refine into nanocrystals / ultrafine grains under stress. As stress continues to accumulate, the interface between the fine and coarse grain layers gradually expands radially inward, the area of ​​the coarse grain layer in the core gradually shrinks while the area of ​​the nanocrystals / ultrafine grains on the surface gradually expands. This grain refinement phenomenon is completely opposite to the grain refinement pattern of steel, until the dislocation density and grain refinement effect on the surface of the bar reach saturation. At this point, the surface nanocrystals / ultrafine grains act like a "hard shell," surrounding the "soft core." This prevents external stress from being transmitted further inward, while simultaneously strengthening the core structure through HDI strengthening and HDI work hardening effects. Ultimately, this results in an AZ80 heterogeneous magnesium alloy rod composed of a harder circumferential surface layer of nanocrystals / ultrafine grains and a softer coarse grain layer in the core. Its vertical axial microstructure distribution is as follows: Figure 4 As shown in (b), the microhardness distribution is as follows Figure 5 As shown in (b).

[0037] In summary, this patent successfully prepared a high-strength, high-toughness, lightweight heterogeneous steel-magnesium alloy composite cable through the above-mentioned rotary forging and twisting processing methods.

Claims

1. A method for preparing a high-strength, high-toughness, lightweight heterogeneous composite cable, characterized in that, Includes the following steps: Step (1): Rotary forging: The steel bar is rotary forged at room temperature to obtain a heterogeneous steel bar. The surface of the steel bar is a softer coarse-grained phase, and the core is a harder fine-grained phase. The radial hardness of the heterogeneous steel bar is distributed in an inverted V-shape. Magnesium alloy bars are forged under high temperature conditions to obtain heterogeneous magnesium alloy bars. The structure of the heterogeneous magnesium alloy is: the surface is a harder fine-grained phase along the radial direction, and the core is a softer coarse-grained phase. The radial hardness of the heterogeneous magnesium alloy is distributed in a positive V-shape. Step (2): Twisting: Take several heterogeneous steel rods and heterogeneous magnesium alloy rods of the same length prepared in step (1), grind and clean them to remove oil and oxide scale from the surface, and then arrange the heterogeneous steel rods and heterogeneous magnesium alloy rods in a circumferentially alternating pattern and feed them into a twisting machine to twist them into a heterogeneous steel-magnesium alloy composite cable. The parameters for the rotary forging process of steel bars in step (1) are as follows: deformation temperature: room temperature, spindle speed: 80-205 rpm, feeding speed: 3 m / min, equivalent variable per pass: 1%-10%, and total equivalent variable: 20%-150%. The parameters for the magnesium alloy rotary forging process are as follows: deformation temperature is 150-300℃, spindle speed is 80-205rpm, feed rate is 3m / min, equivalent variable per pass is 1%-10%, and total equivalent variable is 20%-150%.

2. The method according to claim 1, characterized in that, The twisting process parameters in step (2) are: deformation temperature of 25-300℃, rotation speed of 3-10rpm, and feeding speed of 6m / min.

3. The method according to claim 2, characterized in that, The steel bars and magnesium alloy bars have the same diameter, which is 15-25mm.

4. The method according to claim 3, characterized in that, The rotary forging in step (1) is carried out on a rotary forging machine, which is equipped with a heating coil device. The heating coil device is controlled to heat the bar to be rotary forged at different temperatures.

5. A high-strength, high-toughness, lightweight heterogeneous composite cable, characterized in that, Prepared by the method described in any one of claims 1-4.

6. The composite cable according to claim 5, characterized in that, The steel bars are made of 304 stainless steel or 316L stainless steel.

7. The composite cable according to claim 6, characterized in that, The magnesium alloy rods are made of AZ80 magnesium alloy, Mg-Li alloy or AZ31 magnesium alloy.

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