A heteroalloy bar and a method for producing the same

Abstract

The application provides a heterogeneous alloy rod and a preparation method thereof, and belongs to the technical field of metal materials. The heterogeneous alloy rod is prepared by using a solid-liquid composite casting forming method, casting high-elasticity modulus metal / low-elasticity modulus magnesium alloy in a specific casting mold, and regulating the microstructure by specific deformation and heat treatment. The heterogeneous alloy rod with high-elasticity modulus is prepared. The solid-liquid composite casting can obtain a perfect original interface, has no oxidized inclusion and good interface combination, can prepare a large-size rod, and has simple and easy operation process, and can meet the demand of industrial application.

Description

Technical Field

[0001] This invention relates to the field of metallic materials technology, and in particular to a heterogeneous alloy rod and its preparation method. Background Technology

[0002] The modulus of elasticity is one of the important mechanical properties of metallic materials. In engineering, the modulus of elasticity is referred to as the stiffness of a material, characterizing its resistance to elastic deformation. The higher the value, the smaller the elastic deformation under the same stress. The stiffness of machine parts or components differs from the stiffness of the material itself; the former is expressed as the product of its cross-sectional area and the stiffness of the material used. Therefore, to improve the stiffness of machine parts, materials with a higher modulus of elasticity should be selected when the cross-sectional area cannot be increased. Existing research shows that the modulus of elasticity of metallic materials is a mechanical property that is insensitive to microstructure, and changes in external factors have a relatively small impact on it.

[0003] Magnesium alloys are currently the lightest metallic structural materials used in practical applications, and are widely used in defense, aerospace, automotive, and electronic communications, playing a significant role in achieving structural lightweighting and energy conservation and emission reduction. However, compared to other lightweight metallic structural materials such as aluminum and titanium alloys, magnesium alloys have a lower elastic modulus, thus limiting their applications. Therefore, improving the low elastic modulus of magnesium alloys is a key focus of magnesium alloy research, development, and industrialization. Existing research indicates that controlling process conditions such as temperature, strain rate, heat treatment, and plastic deformation has a very limited effect on improving the elastic modulus of magnesium alloys.

[0004] A literature review of existing technologies revealed that adding alloying elements can improve the elastic modulus of magnesium alloys. In their paper "Effects of Si addition on microstructure and mechanical properties of Mg-8Gd-4Y-Nd-Zr alloy," published in *Materials and Design*, 2013, 43, 74-79, Zhang et al. introduced high-elastic-modulus second-phase particles using an alloying method. Adding 1% Si to the Mg-8Gd-4Y-1Nd-1Zr alloy increased the elastic modulus from 44 GPa to 51 GPa. This increase in elastic modulus is attributed to the formation of a large number of high-modulus particles within the alloy. However, with increasing Si content, the melt fluidity of the alloy significantly decreases, which is detrimental to the preparation of alloys with even higher elastic modulus. In their article "Microstructures and mechanical properties of the Mg-8Gd-4Y-Nd-Zn-3Si (wt%) alloy," published in *Materials Science and Engineering: A*, 2013, 571, 19-24, Hu Jilong et al. demonstrated that adding a small amount of Zn to the Mg-8Gd-4Y-Nd-3Si alloy improved the melt's fluidity. Alloying studies have shown that adding certain amounts of alloying elements or rare earth elements can improve the elastic modulus to some extent, mainly because these elements react with other elements in the magnesium alloy matrix to generate a second, high-elastic-modulus particle-reinforcing phase. However, the addition of these elements reduces the alloy's strength, and more importantly, it further worsens the already poor plasticity of the magnesium alloy.

[0005] Further research in existing technical literature reveals that adding reinforcements to a magnesium alloy matrix to prepare magnesium-based composites is also a commonly used method to improve the elastic modulus. Compared to alloying methods, magnesium-based composites reinforced with particulate, whisker, fiber, or carbon nanotube phases show further improvements in elastic modulus. In their article "Interfacial Microstructure and Mechanical Properties of Aluminum Silicate Short Fiber Reinforced AZ91D Composites," published in *Acta Matericae Compositae Sinica*, 2008, 6, 156-159, Liu Guanjun et al. prepared (Al2O3-SiO2) / AZ91D magnesium-based composites via extrusion infiltration, increasing the elastic modulus from 38.5 GPa to 61 GPa, an increase of approximately 58%. While composite methods can effectively improve the strength and elastic modulus of materials, they significantly reduce plasticity. Furthermore, high-modulus reinforcement phases are expensive and their processing is relatively complex, hindering industrial applications. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a heterogeneous alloy rod and its preparation method. The heterogeneous alloy rod prepared by the forming method of solid-liquid composite casting of high elastic modulus metal / low elastic modulus alloy has high elastic modulus, the preparation process is simple, and the cost of high modulus reinforcing phase is low.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] This invention provides a method for preparing heterogeneous alloy rods, comprising the following steps:

[0009] Zinc plating is applied to the surface of a metal with a high elastic modulus to obtain a pretreated metal.

[0010] The pretreated metal is placed in the mold cavity and preheated to obtain preheated metal.

[0011] Low elastic modulus molten metal is poured into the mold cavity, and after pouring, it is kept at a constant temperature for solid-liquid composite casting to obtain heterogeneous magnesium alloy ingots.

[0012] The heterogeneous magnesium alloy ingot is subjected to deformation and heat treatment in sequence to obtain heterogeneous alloy rods.

[0013] Preferably, the ratio of the elastic modulus of the high elastic modulus metal to the elastic modulus of the low elastic modulus metal is ≥2, and the low elastic modulus metal includes aluminum alloy, titanium alloy or magnesium alloy.

[0014] Preferably, the high elastic modulus metal is in the shape of a helical spring or a disc spring.

[0015] Preferably, the thickness of the zinc plating is 0.1 to 50 μm.

[0016] Preferably, the diameter of the high elastic modulus metal is 1-99% of the mold cavity diameter, and the mold cavity diameter is 10-100cm.

[0017] Preferably, the preheating temperature is 500–800°C and the time is 1–10 hours.

[0018] Preferably, the pouring temperature is 650–1000°C.

[0019] Preferably, the insulation temperature is 500–800℃ and the time is 2–8 hours.

[0020] Preferably, the deformation temperature is 100–500°C; the heat treatment method is vacuum solution treatment, the temperature of the vacuum solution treatment is 400–900°C, and the solution treatment time is 1–12 hours.

[0021] The present invention also provides heterogeneous alloy rods prepared by the above preparation method.

[0022] Beneficial technical effects:

[0023] This invention provides a heterogeneous alloy rod and its preparation method. A solid-liquid composite casting method is used to cast a high-elastic-modulus metal / low-elastic-modulus magnesium alloy in a specific casting mold. Specific deformation and heat treatment are then employed to control the microstructure, resulting in a high-elastic-modulus heterogeneous alloy rod. This invention utilizes solid-liquid composite casting to obtain a perfect native interface, free of oxide inclusions and with good interfacial bonding. It can produce large-size rods, and the process is simple and easy to operate, better meeting the needs of industrial applications. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the pretreatment process in the embodiment; where a is a schematic diagram of the mold cross-section; b is a schematic diagram of the shape of a single solid mold; c is a schematic diagram of the shape of multiple solid molds; 1-solid metal; 2-riser; 3-liquid metal; 4-mold; 5-heating jacket; 6-positioning mold; 7-gate; 8-positioning hole;

[0025] Figure 2 This is a schematic diagram of the casting process for an embodiment; where 9 is the ingot and 10 is the finished ingot.

[0026] Figure 3 This is a schematic diagram of the ingot casting and deformation in an embodiment; where 11-extrusion press; 12-extruded product; 13-high temperature vacuum furnace;

[0027] Figure 4 This is a schematic diagram of the heat treatment process in an embodiment.

[0028] Figure 5 The mechanical properties diagram is shown in the example diagram. Detailed Implementation

[0029] This invention provides a method for preparing heterogeneous alloy rods, comprising the following steps:

[0030] Zinc plating is applied to the surface of a metal with a high elastic modulus to obtain a pretreated metal.

[0031] The pretreated metal is placed in the mold cavity and preheated to obtain preheated metal.

[0032] Low elastic modulus molten metal is poured into the mold cavity, and after pouring, it is kept at a constant temperature for solid-liquid composite casting to obtain heterogeneous magnesium alloy ingots.

[0033] The heterogeneous magnesium alloy ingot is subjected to deformation and heat treatment in sequence to obtain heterogeneous alloy rods.

[0034] This invention involves zinc plating on the surface of a high elastic modulus metal to obtain a pretreated metal.

[0035] In this invention, the ratio of the elastic modulus of the high elastic modulus metal to the elastic modulus of the low elastic modulus metal is ≥2; the high elastic modulus metal preferably includes VCoNi, CoCrNi or other high entropy alloys, more preferably VCoNi; the shape of the high elastic modulus metal is a helical spring or a disc spring.

[0036] In this invention, the thickness of the zinc plating is preferably 0.1–50 μm, more preferably 1–40 μm, and most preferably 10–20 μm; the zinc plating method is preferably electroplating, hot-dip galvanizing, thermal spraying, or vapor deposition. In this invention, if the zinc layer is too thin, it will vaporize before casting, and the surface will subsequently oxidize, failing to provide protection; if it is too thick, the zinc layer will completely dissolve into the casting material, preventing the formation of a metallurgical bond, or causing zinc accumulation at the metallurgical bond interface. Zinc accumulation affects the performance of the composite material. This invention, by setting the zinc plating thickness, prevents oxidation of the alloy surface. Zinc has a low melting point, easily melts, and reacts or diffuses in a liquid state at the interface, which is more conducive to the formation of metallurgical and chemical bonds, allowing the heterogeneous material to obtain a high-quality metallurgical interface and preventing the formation of oxide inclusions at the interface, thus avoiding damage to the bond between the heterogeneous materials. Furthermore, zinc resources are relatively abundant and the cost is relatively low. Its physical properties are similar to those of magnesium or aluminum alloys, making it an ideal intermediate layer metal for magnesium alloy solid-liquid composite casting.

[0037] This invention also includes cleaning the high elastic modulus metal before galvanizing. The cleaning method is not particularly limited; any method sufficient to remove oil and oxides from the surface of the high elastic modulus metal is acceptable.

[0038] After obtaining the pretreated metal, the present invention places the pretreated metal in the mold cavity for preheating to obtain the preheated metal.

[0039] In this invention, the preheating temperature is preferably 500-800℃, more preferably 600-700℃, and most preferably 650-670℃; the preheating time is preferably 1-10h, more preferably 2-8h, and most preferably 5-7h; the diameter of the high elastic modulus metal is preferably 1-99% of the mold cavity diameter, more preferably 10-80%, and most preferably 30-50%; the mold cavity diameter is preferably 10-100cm, more preferably 20-80cm, and most preferably 30-50cm.

[0040] After obtaining the preheated metal, the present invention pours a low elastic modulus metal liquid into the mold cavity, and after pouring, heat preservation is carried out for solid-liquid composite casting to obtain a heterogeneous magnesium alloy ingot.

[0041] In this invention, the low elastic modulus metal preferably includes aluminum alloy, titanium alloy or magnesium alloy, more preferably magnesium alloy; the casting temperature is preferably 650-1000℃, more preferably 700-900℃; and most preferably 750-800℃.

[0042] The present invention preferably involves removing the outer heating jacket of the mold under an inert gas oxygen-free protective atmosphere before casting, and then quickly wrapping the heating jacket back on to keep it warm after casting.

[0043] In this invention, the heat preservation temperature is preferably 500–800℃, more preferably 550–750℃, and most preferably 600–700℃; the heat preservation time is preferably 2–8 hours, more preferably 3–5 hours. This invention achieves a perfect metallurgical bond at the solid-liquid interface through heat preservation.

[0044] After obtaining the heterogeneous magnesium alloy ingot, the present invention performs deformation and heat treatment on the heterogeneous magnesium alloy ingot in sequence to obtain heterogeneous alloy rods.

[0045] In this invention, the deformation temperature is preferably 100–500°C, more preferably 200–400°C, and most preferably 250–300°C; the deformation method is preferably extrusion, drawing, or rotary forging. This invention eliminates casting defects through deformation, further improving the interfacial bonding quality.

[0046] In this invention, the heat treatment method is preferably vacuum solution treatment, wherein the temperature of the vacuum solution treatment is preferably 400–900°C, with a reference temperature for metals with low elastic modulus, and the solution treatment time is 1–12 hours. This invention uses vacuum solution treatment on deformed heterogeneous metal rods to eliminate the influence of deformation on the material and to regulate the microstructure of different metals.

[0047] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0048] Example 1

[0049] Using solid VCoNi high-entropy alloy and liquid pure AZ31 alloy as examples, detailed implementation methods and specific operations are given. The following examples involve four steps: pretreatment, solid-liquid composite casting, deformation, and heat treatment, wherein:

[0050] (1) Preprocessing: such as Figure 1 As shown in -a, the surface of the spiral VCoNi high-entropy alloy 1 is chemically cleaned to remove oil and oxides, and then galvanized. The zinc layer is electroplated and has a thickness of 30μm. The treated spiral VCoNi high-entropy alloy is then passed through the positioning hole 8 of the positioning mold 6 and pre-placed in the cavity of the mold 4. A heating jacket 5 is then wrapped around the mold to preheat the solid spiral VCoNi high-entropy alloy and the mold at 800℃ for 2 hours.

[0051] (2) Solid-liquid composite casting: such as Figure 1 As shown in -b, the outer heating jacket 5 is removed, and casting is carried out under an oxygen-free and inert gas protective atmosphere. Liquid AZ31 is poured in from the gate 7 until it overflows from the riser 2. The pouring temperature is 800℃. After pouring, the heating jacket 5 is quickly wrapped around the liquid and kept at 500℃ for 2 hours to help form a perfect metallurgical bond at the solid-liquid interface.

[0052] (3) Deformation: such as Figure 2 As shown in -a, ingot 9 is formed, with a diameter of 15cm and a length of 50cm. Following the diagram, a rod 10 with a diameter of 15cm is cut from ingot 9 (as shown). Figure 2 -b). For example Figure 3 As shown in -a, the bar 10 is extruded and deformed along the axial direction by an extruder 11 at an extrusion temperature of 200℃ and an extrusion ratio of 1:2. After multiple extrusion passes, a bar 12 with a diameter of 1cm is obtained (e.g., ...). Figure 3 b).

[0053] (4) Heat treatment: such as Figure 4 As shown, the extruded rod 12 was solution treated at 500°C for 12 hours in a high-temperature vacuum furnace 13 under an argon protective atmosphere to eliminate the influence of deformation on the material, thus obtaining a heterogeneous magnesium alloy rod. Figure 5The mechanical properties of high-entropy alloy VCoNi and solution-treated AZ31 are shown. The elastic modulus of AZ31 is approximately 13 GPa, while that of VCoNi is as high as 207 GPa, indicating a significant difference in elastic modulus—VCoNi's is 16 times that of AZ31. Furthermore, the uniform elongation of AZ31 is approximately 19%, and that of VCoNi is close to 20%, exhibiting similar plasticity, which is beneficial for maintaining the overall plasticity of the heterogeneous rod. This embodiment successfully produced a magnesium alloy rod with a high elastic modulus through the aforementioned solid-liquid bonding and heat treatment alloying technology.

[0054] Example 2

[0055] Using multiple sets of solid CrCoNi high-entropy alloys and liquid pure AZ31 alloys as examples, detailed implementation methods and specific operations are given. The following examples involve four steps: pretreatment, solid-liquid composite casting, deformation, and heat treatment, wherein:

[0056] (1) Preprocessing: such as Figure 1 As shown in -c, multiple sets of spiral CrCoNi high-entropy alloy 1 are chemically cleaned to remove surface oil and oxides, and then galvanized. The zinc layer is electroplated and has a thickness of 30μm. The treated spiral CrCoNi high-entropy alloy is then passed through the positioning hole 8 of the positioning mold 6 and pre-placed in the cavity of the mold 4. A heating jacket 5 is then wrapped around the mold to preheat the solid spiral CrCoNi high-entropy alloy and the mold at 800℃ for 2 hours.

[0057] (2) Solid-liquid composite casting: such as Figure 1 As shown in -c, remove the outer heating jacket 5 and perform casting bonding under an oxygen-free and inert gas protective atmosphere. Liquid AZ31 is poured in from the gate 7 until it overflows from the riser 2. The pouring temperature is 800℃. After pouring, quickly cover the heating jacket 5 and keep it at 500℃ for 2 hours to help form a perfect metallurgical bond at the solid-liquid interface.

[0058] (3) Deformation: such as Figure 2 As shown in diagram -c, ingot 9 is formed, with a diameter of 30cm and a length of 50cm. Following the diagram, a bar 10 with a diameter of 30cm is cut from ingot 9 (e.g., ...). Figure 2 -b). For example Figure 3 As shown in Figure a, the bar 10 is extruded and deformed along the axial direction by an extruder 11 at an extrusion temperature of 200℃ and an extrusion ratio of 1:2. After multiple extrusion passes, a bar 12 with a diameter of 2cm is obtained. Figure 3 -b).

[0059] (4) Heat treatment: such as Figure 4As shown, the extruded rod 12 was solution treated at 500°C for 12 hours in a high-temperature vacuum furnace 13 under an argon protective atmosphere to eliminate the influence of deformation on the material, thus obtaining a heterogeneous magnesium alloy rod. Figure 5 The mechanical properties of high-entropy alloy CrCoNi and solution-treated AZ31 are shown. The elastic modulus of AZ31 is approximately 13 GPa, while that of CrCoNi is as high as 206 GPa, demonstrating a significant difference. CrCoNi's elastic modulus is 16 times that of AZ31. Furthermore, AZ31 has a uniform elongation of approximately 19%, while CrCoNi's exceeds 30%, exhibiting superior plasticity compared to low-elastic-modulus alloys, which is beneficial for maintaining the overall plasticity of the heterogeneous rod. In this embodiment, a high-elastic-modulus magnesium alloy rod was successfully prepared using an alloying technique involving solid-liquid bonding and heat treatment.

[0060] Example 3

[0061] Using solid VCoNi high-entropy alloy and liquid pure Mg alloy as examples, detailed implementation methods and specific operations are given. The following examples involve four steps: pretreatment, solid-liquid composite casting, deformation, and heat treatment, wherein:

[0062] (1) Preprocessing: such as Figure 1 As shown in -a, the surface of the spiral VCoNi high-entropy alloy 1 is chemically cleaned to remove oil and oxides, and then galvanized. The zinc layer is electroplated and has a thickness of 30μm. The treated spiral VCoNi high-entropy alloy is then passed through the positioning hole 8 of the positioning mold 6 and pre-placed in the cavity of the mold 4. A heating jacket 5 is then wrapped around the mold to preheat the solid spiral VCoNi high-entropy alloy and the mold at 800℃ for 2 hours.

[0063] (2) Solid-liquid composite casting: such as Figure 1 As shown in -b, the outer heating jacket 5 is removed, and casting is carried out under an oxygen-free and inert gas protective atmosphere. Liquid Mg is poured in from the gate 7 until it overflows from the riser 2. The pouring temperature is 800℃. After pouring, the heating jacket 5 is quickly wrapped around the liquid and kept at 500℃ for 2 hours to help form a perfect metallurgical bond at the solid-liquid interface.

[0064] (3) Deformation: such as Figure 2 As shown in diagram a, ingot 9 is formed, with a diameter of 15cm and a length of 50cm. Following the diagram, a rod 10 with a diameter of 15cm is cut from ingot 9 (as shown in the diagram). Figure 2 -b). For example Figure 3 As shown in Figure a, the bar 10 is extruded and deformed along the axial direction by an extruder 11 at an extrusion temperature of 200℃ and an extrusion ratio of 1:2. After multiple extrusion passes, a bar 12 with a diameter of 1cm is obtained. Figure 3-b).

[0065] (4) Heat treatment: such as Figure 4 As shown, the extruded rod 12 was solution treated at 500°C for 12 hours in a high-temperature vacuum furnace 13 under an argon protective atmosphere to eliminate the influence of deformation on the material, thus obtaining a heterogeneous magnesium alloy rod. Figure 5 The mechanical properties of high-entropy alloy VCoNi and solution-treated Mg are shown. The elastic modulus of Mg is approximately 45 GPa, while that of VCoNi is as high as 207 GPa, demonstrating a significant difference. VCoNi's elastic modulus is five times that of Mg. Furthermore, Mg has a uniform elongation of approximately 20%, while VCoNi's is close to 20%, exhibiting similar plasticity, which is beneficial for maintaining the overall plasticity of the heterogeneous rod. This patent successfully produced magnesium alloy rods with high elastic modulus through the aforementioned solid-liquid bonding and heat treatment alloying technology.

[0066] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing heterogeneous alloy rods, characterized in that, Includes the following steps: Zinc plating is applied to the surface of a metal with a high elastic modulus to obtain a pretreated metal. The pretreated metal is placed in the mold cavity and preheated to obtain preheated metal. Low elastic modulus molten metal is poured into the mold cavity, and after pouring, it is kept at a constant temperature for solid-liquid composite casting to obtain heterogeneous magnesium alloy ingots. The heterogeneous magnesium alloy ingot was subjected to deformation and heat treatment in sequence to obtain heterogeneous alloy rods; The ratio of the elastic modulus of the high elastic modulus metal to the elastic modulus of the low elastic modulus metal is ≥2, and the low elastic modulus metal includes aluminum alloy, titanium alloy or magnesium alloy. The thickness of the zinc plating is 0.1–50 μm; The deformation temperature is 100–500℃; the heat treatment method is vacuum solution treatment, the temperature of the vacuum solution treatment is 400–900℃, and the solution treatment time is 1–12h.

2. The preparation method according to claim 1, characterized in that, The high elastic modulus metal is shaped like a helical spring or a disc spring.

3. The preparation method according to claim 1, characterized in that, The diameter of the high elastic modulus metal is 1 to 99% of the mold cavity diameter, and the mold cavity diameter is 10 to 100 cm.

4. The preparation method according to claim 1, characterized in that, The preheating temperature is 500–800℃, and the time is 1–10 hours.

5. The preparation method according to claim 1, characterized in that, The pouring temperature is 650–1000℃.

6. The preparation method according to claim 1, characterized in that, The insulation temperature is 500-800℃, and the time is 2-8 hours.

7. The heterogeneous alloy rod prepared by the preparation method according to any one of claims 1 to 6.

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