A high-rigidity high-plasticity magnesium alloy and a forming method for large-scale complex components thereof

Abstract

This invention discloses a forming method for high-stiffness, high-ductility magnesium alloys and their large, complex components. The composition and weight percentage of the magnesium alloy are as follows: rare earth elements (RE): 10.0–25.0%, aluminum (Al): 5.0–15.0%, lithium (Li): 0–10%, silicon (Si): 1.0–2.0%, manganese (Mn): 0–2.0%, with the balance being magnesium (Mg). First, a billet is obtained through casting and upsetting. Then, wires or powders are prepared by extrusion, drawing, or atomization. Finally, large, complex high-stiffness magnesium alloy components are formed using additive manufacturing. The wire (powder) preparation and additive manufacturing processes effectively refine the size of the high-modulus reinforcing phase particles and improve their distribution uniformity, thereby enhancing the plasticity of the component. This invention effectively solves the problem of the mutual constraint between high modulus and plasticity of magnesium alloys, and between high modulus and the forming of complex components.

Description

Technical Field

[0001] This invention belongs to the field of magnesium alloy technology, and relates to a high-rigidity and high-ductility magnesium alloy. More specifically, it relates to a high-rigidity and high-ductility magnesium alloy and a forming method for its large and complex components. Background Technology

[0002] Magnesium alloys are the lightest metallic structural materials used in practical applications, with a density of only 1.7 g / cm³. 3 Furthermore, it possesses characteristics such as high specific strength and specific stiffness, good damping and vibration reduction properties, and excellent electromagnetic shielding performance. Moreover, the tensile strength of newly developed cast magnesium rare earth alloys has exceeded 400 MPa, and the tensile strength of wrought magnesium rare earth alloys has exceeded 500 MPa. Therefore, lightweight and high-strength magnesium alloys demonstrate great application potential in the meticulously controlled aerospace field.

[0003] Despite this, the elastic modulus of magnesium alloys is mostly 40–45 GPa, only 2 / 3 of that of aluminum alloys (above 70 GPa), 2 / 5 of that of titanium alloys (above 110 GPa), and 1 / 4 of that of steel (above 200 GPa), resulting in generally low stiffness in magnesium alloy components. Therefore, magnesium alloy components are highly susceptible to elastic deformation under heavy loads, which not only severely reduces the working accuracy of equipment but also affects the reliability of components in service. Clearly, as future weapon service environments continue to evolve towards extreme conditions such as hypersonic, high-pressure, and high-speed particle erosion, the low elastic modulus has gradually become a technical bottleneck restricting the application of magnesium alloys in high-end products. Therefore, developing magnesium alloys with high elastic modulus is of great significance.

[0004] Alloying and composite formation are two main methods for improving the elastic modulus of magnesium alloys. Alloying refers to introducing alloying elements into magnesium, thereby changing the lattice constant of the magnesium matrix and strengthening the bonding force between atoms to increase the modulus. Composite formation refers to introducing a reinforcing phase into the magnesium alloy through external application or in-situ self-generation. When the matrix is ​​subjected to external force, the load is transferred to the high-modulus reinforcing phase through the metallurgical interface between the matrix and the reinforcing phase, causing elastic deformation to be hindered, thus increasing the alloy modulus. The literature "Simultaneously improving elastic modulus and damping capacity of extruded Mg-Gd-Y-Zn-Mn alloy via alloying with Si" (Journal of Alloys and Compounds, 2019, Vol. 810, No. 151857) describes how adding 0.8% by mass of Si to magnesium alloys introduces high-modulus Gd5Si3 and SiY reinforcing phases, thereby increasing the elastic modulus of the alloy to 49.3 GPa. Besides introducing a high-modulus Si-containing phase, the paper "Development of a novel Mg-Y-Zn-Al-Li alloy with high elastic modulus and damping capacity" (Materials Science and Engineering: A, 2020, Vol. 790, No. 139744) reports the formation of a high-modulus Al2RE phase in magnesium alloys by adding Al, achieving an elastic modulus of 52.9 GPa. These studies demonstrate that introducing a high-modulus second phase into magnesium rare-earth alloys using Si or Al alloying is an effective method to improve the stiffness of magnesium alloy components.

[0005] However, the addition of Si or Al in existing magnesium rare earth alloys is relatively low, resulting in a low content of the introduced high-modulus second phase and limited stiffness improvement: the elastic modulus of most currently developed magnesium alloys does not exceed 55 GPa. The main reason for this is that existing high-modulus magnesium alloys are primarily formed by casting, and high-modulus reinforcing phase particles tend to agglomerate in the alloy melt, severely deteriorating the alloy's plasticity and affecting its fluidity, thus reducing its casting process performance. Therefore, the content of high-modulus particles should not be too high. In short, the elastic modulus and plasticity / toughness of high-modulus magnesium alloys, as well as the elastic modulus and processing performance, are mutually restrictive and even contradictory. For example, the Mg-10wt%Gd-8wt%Y-2wt%Si-1wt%Zn alloy prepared by Chinese invention patent CN202210533327.X (A high-stiffness magnesium alloy containing metal silicides and its preparation method) achieves a stiffness of 53 GPa, but its elongation is only 2.5%. For example, the literature "Effects of Si addition on microstructure and mechanical properties of Mg-8Gd-4Y-Nd-Zr alloy" (Materials & Design, 2013, Vol. 43, pp. 74-79) records that as the Si content increases, the alloy's elastic modulus increases, but the alloy's fluidity decreases significantly, which is detrimental to alloy forming. Chinese invention patent CN202210212489.3 (A high-modulus magnesium alloy and its preparation method) discloses a method for preparing high-stiffness magnesium alloys by alloying rare earth elements, Al, and Si. However, this method also uses conventional melt casting processes and does not provide technical guidance on how to avoid the agglomeration of the high-modulus second phase during casting.

[0006] To improve the uniformity of high-modulus reinforcing phase particle distribution in cast alloys, numerous studies have explored plastic deformation of ingots using processes such as extrusion. Under pressure, the high-modulus reinforcing phase particles break down and disperse, improving their distribution uniformity. However, plastic deformation methods can only form profiles such as tubes, bars, and wires, and are insufficient for forming large, complex components. Therefore, this method cannot meet the practical application requirements of aerospace and other fields for large, complex components.

[0007] In summary, the inventors believe that to address the limitations of existing magnesium alloys in terms of stiffness and plasticity, and the difficulty of forming large and complex components with existing high-modulus magnesium alloys, it is essential to increase the content of reinforcing phase particles in magnesium alloys while ensuring particle dispersion, thereby achieving a synergistic improvement in both stiffness and plasticity. Therefore, this invention aims to develop a high-stiffness magnesium alloy with a higher content of reinforcing phase particles; simultaneously, it develops a novel forming process for high-modulus magnesium alloys that can improve the uniformity of reinforcing phase particle distribution in the magnesium alloy and can also be used for forming large and complex components. Developing this high-stiffness, high-plasticity magnesium alloy and its forming method for large and complex components has significant practical implications for promoting the further application of magnesium alloys in high-end fields. Summary of the Invention

[0008] To improve the stiffness of magnesium alloy components, existing methods mainly involve introducing high-modulus reinforcing phase particles into the alloy through alloying or composite processes. However, because these reinforcing phase particles tend to agglomerate, deteriorating the alloy's ductility and toughness, their content must be controlled at a low level, resulting in very limited stiffness improvements in existing magnesium alloys. Large plastic deformation can improve the uniformity of reinforcing phase particle distribution, but it cannot form large and complex components. Therefore, to address the aforementioned shortcomings of existing technologies, this invention provides a method for forming high-stiffness, high-ductility magnesium alloys and their large and complex components. On the one hand, it develops novel high-stiffness magnesium alloy materials, synergistically optimizing the stiffness, ductility, toughness, and forming process performance of magnesium alloys from a formulation optimization perspective. On the other hand, it innovatively adopts a process route of melting casting-upsetting extrusion-wire (powder) production-additive manufacturing to solve the problem of preparing large and complex high-stiffness magnesium alloy components.

[0009] To achieve the aforementioned technical effects, this invention first proposes a "composite stiffening" approach. This involves adding elements such as RE, Al, and Si to simultaneously form various high-modulus reinforcing phase particles in the magnesium alloy, such as Al₂RE particles, Mg₂Si particles, and RE-Si phase particles, thereby comprehensively improving the alloy's stiffness. "Composite stiffening" avoids the problem of single high-modulus particles easily coarsening and reducing the alloy's ductility and toughness during the casting process due to solute enrichment.

[0010] Secondly, regarding the alloy formulation, the RE and Al content in this invention is significantly higher than that in existing magnesium alloys. Li, as a highly reactive element, preferentially reacts with atmospheric oxygen during casting, avoiding the oxidation loss of reactive elements such as RE and Mg. This ensures a high content of Al2RE reinforcing phase particles in the alloy, greatly improving stiffness. Simultaneously, Li and Mn alloying can reduce the c / a ratio of the Mg lattice, improving the stiffness and plasticity of the matrix.

[0011] Furthermore, reciprocating upsetting breaks down and disperses the reinforcing phase particles formed in the billet without significantly altering the billet size. More importantly, the reciprocating upsetting creates a "strain aging" effect in the alloy matrix, promoting the supersaturated precipitation of nanoscale high-modulus reinforcing phase particles in the Mg matrix. This significantly increases stiffness while avoiding stress concentration, thus ensuring the ductility and toughness of the matrix.

[0012] Finally, unlike traditional forming processes such as melting and casting, this invention utilizes non-equilibrium solidification under rapid cooling conditions in arc additive manufacturing to suppress the coarsening of high-modulus particles in the wire or powder during the solidification process in the molten pool. This enables the forming of large and complex magnesium alloy components with high reinforcing phase content, resolving the constraints between the elastic modulus, ductility, toughness, and forming process performance of magnesium alloys. This invention provides a novel approach for the forming of high-stiffness, high-ductility magnesium alloys and their large and complex components.

[0013] Specifically, this is achieved through the following technical solutions:

[0014] This invention provides a high-stiffness, high-ductility magnesium alloy, comprising the following components by weight percentage:

[0015] Rare earth elements (RE): 10.0-25.0%, aluminum (Al): 5.0-15.0%, lithium (Li): 0-10%, silicon (Si): 1.0-2.0%, manganese (Mn): 0-2.0%, other individual impurity elements: ≤0.1%, total other impurity elements: ≤0.2%, balance is magnesium (Mg).

[0016] Existing magnesium alloys often have low content of high-modulus reinforcing phase particles, and these particles are of a single type, making them prone to coarsening during solidification. This results in minimal stiffness improvement and low plasticity. However, the magnesium alloy prepared using the formulation of this invention significantly increases the content of high-modulus reinforcing phase particles and simultaneously yields Al2RE, Mg2Si, Si-RE compounds, and a Li-supersaturated high-modulus Mg matrix. By combining different types of high-modulus reinforcing phase particles and a high-modulus matrix, a "composite stiffening" effect is achieved in the magnesium alloy. This avoids the problem of single-phase reinforcing particles easily coarsening during solidification due to solute enrichment and low enthalpy of formation, thus reducing the alloy's plasticity and toughness.

[0017] As one embodiment of the present invention, the rare earth elements include two or more of the elements selected from gadolinium (Gd), yttrium (Y), neodymium (Nd), ytterbium (Yb), and scandium (Sc).

[0018] As one embodiment of the present invention, the Al element content is 0.3-0.7 times the RE element content.

[0019] The reason for strictly limiting the Al to RE ratio is that it directly affects the quantity and type of Al₂RE formed. When the Al to RE ratio is too low, a eutectic Al₂RE phase is more likely to form, which is mainly needle-shaped, and therefore its strengthening effect is not as good as that of nascent granular Al₂RE. When the Al to RE ratio is too high, the strengthening effect is insufficient.

[0020] As one embodiment of the present invention, the alloy phase of the high-stiffness and high-plasticity magnesium alloy contains Al2RE reinforcing phase particles, Mg2Si reinforcing phase particles, and RE-Si reinforcing phase particles.

[0021] This invention also provides a method for forming large, complex components of high-stiffness and high-ductility magnesium alloys, comprising the following steps:

[0022] S1. Additive manufacturing: Prepare wires or powders according to the chemical element composition of high-rigidity and high-ductility magnesium alloys, and carry out additive manufacturing on the prepared wires or powders to obtain additively manufactured components.

[0023] S2, Hot Isostatic Pressing: The additive manufacturing component obtained in step S1 is subjected to hot isostatic pressing.

[0024] S3. Heat treatment: The additive manufacturing component obtained in step S2 is subjected to solution treatment and aging treatment to finally obtain a large and complex magnesium alloy component with high stiffness and high plasticity.

[0025] As one embodiment of the present invention, in step S1, the additive manufacturing specifically includes: arc melting additive manufacturing of the filament and powder bed melting additive manufacturing of the powder.

[0026] The arc-wire additive manufacturing includes single-wire arc-wire additive manufacturing or dual-wire arc-wire additive manufacturing, preferably dual-wire arc-wire additive manufacturing. Most existing magnesium alloy arc-wire additive manufacturing processes are single-wire, meaning they directly use wire with the same composition as the target component. However, high-modulus magnesium alloys have a high content of reinforcing phase particles and low plasticity, making the preparation of continuous, fine-diameter wires more difficult than that of magnesium alloys with low particle content. To address this contradiction, this invention innovatively proposes a novel approach for preparing high-modulus magnesium alloys using dual-wire arc-wire additive manufacturing. Specifically, in addition to the magnesium alloy wire, Al alloying relies on a separate second pure aluminum wire or aluminum alloy wire for feeding, avoiding the problems of alloy plasticity deterioration and wire preparation difficulties caused by excessively high Al2RE content during single-wire arc-wire additive manufacturing. In this way, Al2RE is generated in the molten pool during the arc additive manufacturing process, rather than being pre-formed during the billet preparation before wire extrusion. This avoids the problems associated with the preparation of high-particle-content magnesium alloy wires. At the same time, since the plasticity of pure Al or Al alloys is far superior to that of magnesium alloys, the process difficulty of preparing dual wires is significantly reduced.

[0027] As one embodiment of the present invention, in the dual-wire arc welding additive manufacturing process, the alloy composition range of the resulting additively manufactured component meets the chemical element composition requirements of a high-rigidity, high-ductility magnesium alloy, wherein the specific compositions of wire one and wire two are as follows:

[0028] Wire material one includes all rare earth elements RE, lithium Li, manganese Mn, silicon Si, magnesium Mg, and part of aluminum Al in the magnesium alloy; wire material two includes the remaining aluminum Al.

[0029] Alternatively, wire material one includes all rare earth elements RE, lithium Li, manganese Mn, magnesium Mg, some aluminum Al, and some silicon Si in the magnesium alloy; wire material two includes the remaining aluminum Al and silicon Si.

[0030] Alternatively, wire material one includes all rare earth elements RE, lithium Li, manganese Mn, magnesium Mg, and part of aluminum Al in the magnesium alloy; wire material two includes the remaining aluminum Al and all of silicon Si.

[0031] Wire material one: Mg-RE-Al(-Li-Si-Mn), Wire material two: Al(-Si). The elements in parentheses indicate that they may or may not be present. Si reduces the plasticity of the alloy and affects the wire-making process. Therefore, since wire material one already contains Al2RE particles, which are detrimental to the plasticity of the alloy, the Si content in wire material one should not be too high.

[0032] The weight percentage of Al in the first filament of the double filament is 0.5-2%.

[0033] The diameter ratio of wire one to wire two is 1:1 to 3:1; the wire feeding speed ratio is 1:1 to 9:1. By controlling the diameter and wire feeding speed of the two wires, the alloy composition range of the additively manufactured components meets the requirements of high-stiffness and high-ductility magnesium alloys.

[0034] Considering the significant grain-refining effect of Al2RE particles on magnesium alloys, the plasticity of Mg-RE alloys improved by adding a small amount of Al. Therefore, the alloy system selected for wire material one is Mg-RE-Al(-Li-Si-Mn) alloy, with an Al content of 0.5-2.0%. This achieves both grain refinement and improved plasticity and toughness while avoiding the negative impact of excessive Al2RE particle formation. Wire material two is an Al(-Si) alloy because Al-Si alloys have a lower melting point and better fluidity, which is beneficial for controlling the processing properties of wire material two.

[0035] As one embodiment of the present invention, the filament is prepared by the following method:

[0036] A1: Casting ingot: According to the chemical element composition ratio of the wire, the raw materials are prepared, smelted and cast to obtain the ingot;

[0037] A2: Reciprocating upsetting: The billet obtained in step A1 is homogenized and then reciprocated upsetting.

[0038] A3: Wire making or powder making: The ingot obtained in step A2 is made into wire by extrusion or drawing processes to obtain wire material.

[0039] In step A2, the homogenization treatment of the filament lasts for 10–30 hours, with parameters ranging from 450–550℃. The number of reciprocating upsetting cycles is 2–20.

[0040] As one embodiment of the present invention, the electric arc additive manufacturing process is any one of GTAW electric arc additive manufacturing, GMAW electric arc additive manufacturing, PAW electric arc additive manufacturing, and CMT electric arc additive manufacturing.

[0041] In one embodiment of the present invention, the current used in arc additive manufacturing is a pulsed arc with a pulse frequency of 1-100Hz. The oscillation effect of the pulsed current on the molten pool can further disperse the high-modulus reinforcing phase particles, improve their uniformity of distribution, and enhance the alloy's plasticity.

[0042] In one embodiment of the present invention, the interlayer dwell time in arc additive manufacturing is 10-200 s. By controlling the interlayer dwell time, heat accumulation during the arc additive manufacturing process is avoided, which leads to coarsening of the reinforcing phase particles and ensures the ductility and toughness of the alloy component.

[0043] In one embodiment of this invention, during powder bed melting additive manufacturing, the alloy powder used can be a single powder or a mixture of two or more powders, ensuring that the alloy composition of the arc additive component meets the chemical element composition requirements of high-stiffness, high-ductility magnesium alloys. Powder preparation differs from wire preparation. Wire preparation requires consideration of the alloy's ductility; if the alloy's ductility is too poor, it cannot be wire-made. This is the main reason why this invention uses dual-wire additive manufacturing to prepare magnesium alloys with high Al2RE particle content. Because the powder preparation process is completely different from wire preparation, powder preparation does not require consideration of alloy ductility; alloys of almost any composition can be powdered. Therefore, powder preparation differs from wire preparation.

[0044] As one embodiment of the present invention, the powder is prepared by the following method:

[0045] T1: Casting ingot: Raw materials are prepared according to the chemical element composition ratio of the powder, and then melted and cast to obtain ingot;

[0046] T2: Reciprocating upsetting: The billet obtained in step T1 is homogenized and reciprocated upsetting is performed.

[0047] T3: Filament making or powder making: The ingot blank obtained in step T2 is powdered using an atomization method to obtain powder material;

[0048] In step T1, the homogenization treatment time is 10–30 h, and the parameters are 450–550 °C. The number of reciprocating upsetting cycles is 2–20.

[0049] In one embodiment of the present invention, in step S2, the hot isostatic pressing parameters are: temperature 450-550℃, pressure 30-200MPa, and time 1-8h.

[0050] In one embodiment of the present invention, in step S3, the solution treatment temperature is 480-550°C and the time is 1-10 hours; the aging treatment temperature is 200-250°C and the time is 8-20 hours.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] (1) The magnesium alloy prepared by this invention contains different high modulus reinforcing phase particles and high modulus Mg matrix, which realizes the effect of "composite stiffening", avoiding the problem that single high modulus particles are easy to coarsen during the melting and casting process, thus reducing the alloy's plasticity and toughness. The prepared magnesium alloy has excellent elastic modulus and plasticity and toughness.

[0053] (2) The present invention adopts the process of melting casting-upsetting extrusion-fiber (powder)-additive manufacturing to form large and complex high-rigidity magnesium alloy components. At the same time, the distribution uniformity of high modulus reinforcing phase particles is improved in the extrusion, drawing and additive manufacturing process of the wire, which improves the plasticity and toughness of the components. It can effectively solve the problem of mutual restriction between high modulus and plasticity and toughness of magnesium alloy, and between high modulus and the forming of complex components.

[0054] (3) The novel approach to preparing high-modulus magnesium alloys by dual-wire arc welding additive manufacturing proposed in this invention can avoid the problems of alloy plasticity deterioration and wire preparation difficulties caused by excessive Al2RE content during single-wire arc welding additive manufacturing, and reduce the forming difficulty of complex high-modulus magnesium alloy components. Detailed Implementation

[0055] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0056] Example 1

[0057] First, magnesium rare earth alloy ingots were prepared: the chemical composition and mass percentage of the prepared ingots were as follows: Gd: 7.0%, Y: 3.0%, Al: 5.0%, Si: 1.0%, Mg: balance.

[0058] Melting and casting: Pure Mg ingots, Mg-Gd master alloy, Mg-Y master alloy, pure Al ingots, and Al-Si master alloy are melted in a melting furnace at a melting temperature of 740℃, and castings are obtained by refining and casting in metal molds.

[0059] Next, magnesium rare earth alloy wire or powder is prepared: the ingot is first homogenized and annealed at 450℃ for 30 hours, and then upsetting is performed three times. The wire is obtained by extrusion and drawing, with an extrusion ratio of 10:1, a single drawing area reduction rate of 10%, and a drawing temperature of 200℃. At the same time, powder is prepared by atomization.

[0060] Magnesium rare earth alloy arc additive manufacturing and post-treatment: Arc melting was performed using CMT equipment and the prepared wire material, with a pulse current frequency of 1Hz and an interlayer dwell time of 10s. Simultaneously, selective laser melting (SLM) was used with the prepared powder material for laser additive manufacturing, with a laser power of 1500W. The resulting two sets of deposited parts were then subjected to hot isostatic pressing (HIP) and heat treatment. HIP was performed at 450℃, 200MPa, and for 1 hour. Solution treatment was performed at 480℃ for 10 hours, and aging was performed at 200℃ for 20 hours.

[0061] Experimental results: The hardness of magnesium rare earth alloy formed by arc welding wire additive manufacturing is 58 GPa and the elongation is 9%; the hardness of magnesium rare earth alloy formed by selective laser melting is 60 GPa and the elongation is 10%.

[0062] Example 2

[0063] First, magnesium rare earth alloy ingots were prepared. The chemical composition and mass percentage of the prepared ingots were as follows: Gd: 10.0%, Nd: 5.0%, Al: 5.0%, Li: 3.0%, Si: 1.5%, Mn: 1.0%, Mg: balance. Pure Mg ingots, Mg-Gd master alloys, Mg-Nd master alloys, pure Al ingots, pure Li ingots, Al-Si master alloys, and Al-Mn master alloys were melted in a melting furnace at a melting temperature of 740℃. Castings were obtained through refining and metal mold casting.

[0064] Next, magnesium rare earth alloy wire or powder is prepared: the ingot is first homogenized and annealed at 470℃ for 25 hours, and then reciprocated upsetting is performed 5 times. The wire is obtained by extrusion and drawing, with an extrusion ratio of 10:1, a single drawing area reduction rate of 10%, and a drawing temperature of 200℃. At the same time, powder is prepared by atomization.

[0065] Magnesium rare earth alloy arc additive manufacturing and post-treatment: Arc welding was performed using GTAW equipment and the prepared wire material, with a pulse current frequency of 10Hz and an interlayer dwell time of 50s. Simultaneously, selective laser melting (SLM) was used with the prepared powder material for laser additive manufacturing, with a laser power of 1500W. The resulting two sets of deposited parts were then subjected to hot isostatic pressing (HIP) and heat treatment. The HIP temperature was 470℃, the pressure was 180MPa, and the time was 2h. The solution temperature was 490℃, the solution time was 10h, and the aging temperature was 210℃, the aging time was 18h.

[0066] Experimental results: The hardness of magnesium rare earth alloy formed by arc welding wire additive manufacturing is 60 GPa and the elongation is 8%; the hardness of magnesium rare earth alloy formed by selective laser melting is 62 GPa and the elongation is 9%.

[0067] Example 3

[0068] First, magnesium rare earth alloy ingots were prepared. The chemical composition and mass percentage of the prepared ingots were as follows: Gd: 15.0%, Yb: 5.0%, Al: 14.0%, Li: 7.0%, Si: 1.5%, Mn: 1.5%, Mg: balance. Pure Mg ingots, Mg-Gd master alloys, Mg-Yb master alloys, pure Al ingots, pure Li ingots, Al-Si master alloys, and Al-Mn master alloys were melted in a melting furnace at a melting temperature of 740℃. Castings were obtained through refining and metal mold casting.

[0069] Next, magnesium rare earth alloy wire or powder is prepared: the ingot is first homogenized and annealed at 480℃ for 22 hours, and then reciprocated upsetting is performed 8 times. The wire is obtained by extrusion and drawing, with an extrusion ratio of 10:1, a single drawing area reduction rate of 10%, and a drawing temperature of 200℃. At the same time, powder is prepared by atomization.

[0070] Magnesium rare earth alloy arc additive manufacturing and post-treatment: Arc welding was performed using GMAW equipment and the prepared wire material, with a pulse current frequency of 50Hz and an interlayer dwell time of 100s. Simultaneously, selective laser melting (SLM) was used with the prepared powder material for laser additive manufacturing, with a laser power of 1500W. The resulting two sets of deposited parts were then subjected to hot isostatic pressing (HIP) and heat treatment. HIP was performed at 480℃, 160MPa, and for 3 hours. Solution treatment was performed at 500℃ for 9 hours, and aging was performed at 210℃ for 18 hours.

[0071] Experimental results: After testing, the hardness of magnesium rare earth alloy formed by arc welding wire additive manufacturing was 62 GPa and the elongation was 7%; the hardness of magnesium rare earth alloy formed by selective laser melting was 64 GPa and the elongation was 8%.

[0072] Example 4

[0073] First, magnesium rare earth alloy ingots were prepared. The chemical composition and mass percentage of the prepared ingots were as follows: Gd: 15.0%, Sc: 10.0%, Al: 14.0%, Li: 10.0%, Si: 2.0%, Mn: 2.0%, Mg: balance. Pure Mg ingots, Mg-Gd master alloys, Mg-Sc master alloys, pure Al ingots, pure Li ingots, Al-Si master alloys, and Al-Mn master alloys were melted in a melting furnace at a melting temperature of 740℃. Castings were obtained through refining and metal mold casting.

[0074] Next, magnesium rare earth alloy wire or powder is prepared: the ingot is first homogenized and annealed at 490℃ for 20 hours, and then reciprocated upsetting is performed 10 times. The wire is obtained by extrusion and drawing, with an extrusion ratio of 10:1, a single drawing area reduction rate of 10%, and a drawing temperature of 200℃. At the same time, powder is prepared by atomization.

[0075] Magnesium rare earth alloy arc additive manufacturing and post-treatment: Arc welding was performed using a PAW device and the prepared wire material, with a pulse current frequency of 100Hz and an interlayer dwell time of 200s. Simultaneously, selective laser melting (SLM) was used with the prepared powder material for laser additive manufacturing, with a laser power of 1500W. The resulting two sets of deposited parts were then subjected to hot isostatic pressing (HIP) and heat treatment. The HIP temperature was 490℃, the pressure was 150MPa, and the time was 4h. The solution temperature was 500℃, the solution time was 9h, and the aging temperature was 220℃, the aging time was 17h.

[0076] Experimental results: The hardness of magnesium rare earth alloy formed by arc welding wire additive manufacturing is 65 GPa and the elongation is 5%; the hardness of magnesium rare earth alloy formed by selective laser melting is 67 GPa and the elongation is 6%.

[0077] Example 5

[0078] First, two sets of magnesium rare earth alloy ingots were prepared: Ingot 1 had the following chemical composition and mass percentages: Gd: 10.0%, Y: 5.0%, Al: 0.5%, Si: 2.0%, Mg: balance. Ingot 2 was a pure aluminum ingot. The preparation process for Ingot 1 involved melting pure Mg ingots, Mg-Gd master alloy, Mg-Y master alloy, pure Al ingot, and Al-Si master alloy in a melting furnace at a melting temperature of 740℃, followed by refining and casting to obtain the casting. Ingot 2 was a commercially available pure aluminum ingot.

[0079] Next, the wire materials were prepared: the ingot was first homogenized and annealed at 500℃ for 18 hours, and then upsetting was performed in three passes. Wire material one and wire material two were obtained by extrusion and drawing, respectively, and were used for later use. Wire material one and wire material two had the same diameter. The extrusion ratio of the two wire materials was 10:1, the area reduction rate of a single drawing was 10%, and the drawing temperature was 200℃.

[0080] Magnesium rare earth alloy arc additive manufacturing and post-treatment: A dual-wire arc welding process was performed using CMT equipment and the prepared wires. The alloy composition of the arc additive component was adjusted by controlling the wire feed speed ratio of wire one to wire two to be 9:1. The arc pulse current frequency was 1Hz, and the interlayer residence time was 10s. The prepared deposited parts were then subjected to hot isostatic pressing (HIP) and heat treatment. The HIP temperature was 500℃, the pressure was 140MPa, and the time was 5h. The solution temperature was 510℃, the solution time was 8h, and the aging temperature was 230℃, the aging time was 12h.

[0081] Experimental results: The hardness of the magnesium rare earth alloy produced by arc-fused wire additive manufacturing is 63 GPa, and the elongation is 10%.

[0082] Example 6

[0083] First, two sets of magnesium rare earth alloy ingots were prepared: Ingot 1 had the following chemical composition and mass percentage: Gd: 15.0%, Nd: 5.0%, Al: 1.0%, Li: 10.0%, Si: 0.5%, Mn: 2.0%, Mg: balance. Ingot 2 had the following chemical composition and mass percentage: Si: 10.0%, Al: balance. The preparation process for Ingot 1 involved melting pure Mg ingots, Mg-Gd master alloy, Mg-Nd master alloy, pure Al ingots, pure Li ingots, Al-Si master alloy, and Al-Mn master alloy in a melting furnace at 740℃, followed by refining and casting to obtain the casting. Ingot 2 was prepared by melting pure aluminum ingots and Al-Si master alloy.

[0084] Next, the filaments are prepared: the billet is first homogenized and annealed, and then upsetting is performed 20 times. Fiber material 1 and filament material 2 are obtained by extrusion and drawing. The extrusion ratio of the two filaments is 10:1, the area reduction rate per drawing is 10%, and the drawing temperature is 200℃.

[0085] Magnesium rare earth alloy arc additive manufacturing and post-treatment: A dual-wire arc welding process was performed using GTAW equipment and the prepared wires. The alloy composition of the arc additive component was adjusted by controlling the wire feed speed ratio of wire one to wire two to be 9:1. The pulse current frequency was 50Hz, and the interlayer residence time was 100s. The prepared deposited parts were then subjected to hot isostatic pressing (HIP) and heat treatment. The HIP temperature was 520℃, the pressure was 120MPa, and the time was 4h. The solution temperature was 520℃, the solution time was 8h, and the aging temperature was 230℃, the aging time was 12h.

[0086] Experimental results: The hardness of the magnesium rare earth alloy produced by arc-fused wire additive manufacturing is 64 GPa, and the elongation is 9%.

[0087] Example 7

[0088] First, two sets of magnesium rare earth alloy ingots were prepared: Ingot 1 had the following chemical composition and mass percentage: Gd: 20.0%, Yb: 5.0%, Al: 2.0%, Li: 8.0%, Si: 1.5%, Mn: 2.0%, Mg: balance. Ingot 2 had the following chemical composition and mass percentage: Si: 5.0%, Al: balance. The preparation process for Ingot 1 involved melting pure Mg ingots, Mg-Gd master alloy, Mg-Yb master alloy, pure Al ingots, pure Li ingots, Al-Si master alloy, and Al-Mn master alloy in a melting furnace at 740℃, followed by refining and casting to obtain the casting. Ingot 2 was prepared by melting pure aluminum ingots and Al-Si master alloy.

[0089] Next, the filaments are prepared: the billet is first homogenized and annealed, and then upsetting is performed 20 times. Fiber material 1 and filament material 2 are obtained by extrusion and drawing. The extrusion ratio of the two filaments is 10:1, the area reduction rate per drawing is 10%, and the drawing temperature is 200℃.

[0090] Magnesium rare earth alloy arc additive manufacturing and post-treatment: A dual-wire arc welding process was performed using GMAW equipment and the prepared wires. The alloy composition of the arc additive component was adjusted by controlling the wire feed speed ratio of wire one to wire two to be 9:1. The pulse current frequency was 100Hz, and the interlayer residence time was 200s. The resulting deposited part was then subjected to hot isostatic pressing (HIP) and heat treatment. The HIP temperature was 550℃, the pressure was 80MPa, and the time was 1h. The solution temperature was 550℃, the solution time was 2h, and the aging temperature was 250℃, the aging time was 6h.

[0091] Experimental results: The hardness of the magnesium rare earth alloy produced by arc-fused wire additive manufacturing is 68 GPa, and the elongation is 8%.

[0092] Dual-filament technology is primarily used to prepare continuous filaments because the low-plasticity particulate phase is mainly generated during additive manufacturing. Experiments showed that although the components prepared from single filaments in Examples 1-4 also exhibited good stiffness, the filaments were prone to breakage during fabrication, making it difficult to obtain continuous filaments. Furthermore, the arc was unstable during printing, easily causing filament jamming and reducing deposition efficiency. This is mainly due to the presence of a large amount of high-modulus second phase in the filament, which is prone to breakage during extrusion. Simultaneously, the difference in resistance between the high-modulus second phase and the matrix leads to filament breakage and jamming during CMT. The components prepared in Examples 5-7 showed slightly better performance, with only minor differences (for example, using the same chemical composition as in Example 5, the stiffness could also reach 57 GPa through single-filament fabrication), but continuous filaments could be prepared, and the aforementioned problems in the fabrication process were not present.

[0093] Comparative Example 1

[0094] The forming method of the high-rigidity and high-ductility magnesium alloy and its large and complex components described in this comparative example is basically the same as that in Example 1, except that: pure Mg ingots, Mg-Gd master alloys, Mg-Y master alloys, pure Al ingots, and Al-Si master alloys are directly melted in a melting furnace by casting, and castings with the same composition as those in Example 1 are obtained by melting, refining, and casting.

[0095] A casting with the same chemical composition as in Example 1 was obtained.

[0096] The experiment showed that the stiffness of the magnesium rare earth alloy casting was 50 GPa and the elongation was 3%. It can be seen that the stiffness and plasticity of the magnesium rare earth alloy are lower than those in Example 1. This is mainly because the high modulus reinforcing phase particles in the alloy formed by casting agglomerate in large quantities and are difficult to disperse, resulting in a lower composite stiffening effect and a serious reduction in the plasticity and toughness of the alloy.

[0097] Comparative Example 2

[0098] The forming method of the high-rigidity and high-ductility magnesium alloy and its large and complex components described in this comparative example is basically the same as that in Example 1, except that the chemical composition of the ingot does not contain Si.

[0099] After testing, the stiffness of the magnesium rare earth alloy formed by arc wire additive manufacturing was 53 GPa and the elongation was 8%. It can be seen that the stiffness of the magnesium rare earth alloy is lower than that in Example 1. This is mainly because there are only single Al2RE high modulus reinforcing phase particles in the alloy, which do not form a composite stiffening effect, thus reducing the stiffening effect.

[0100] Comparative Example 3

[0101] The forming method of the high-rigidity and high-ductility magnesium alloy and its large and complex components described in this comparative example is basically the same as that in Example 1, except that the billet is not reciprocated upsetting before the wire extrusion.

[0102] The experiment showed that the stiffness of the magnesium rare earth alloy produced by arc wire additive manufacturing was 54 GPa and the elongation was 7%. It can be seen that the stiffness of the magnesium rare earth alloy is lower than that in Example 1. This is mainly because the alloy billet was not subjected to reciprocating upsetting, resulting in the absence of nanoscale high-modulus particles in the billet, thus reducing the stiffness enhancement effect.

[0103] Comparative Example 4

[0104] The forming method of the high-rigidity and high-ductility magnesium alloy and its large and complex components described in this comparative example is basically the same as that in Example 1, except that the Al content of the ingot is only 0.1 of the RE element content, that is, the Al content is 1.0%.

[0105] After testing, the stiffness of the magnesium rare earth alloy formed by arc wire additive manufacturing was 48 GPa, and the elongation was 10%. It can be seen that the stiffness of the magnesium rare earth alloy is lower than that in Example 1. This is mainly because the Al2RE phase generated in the alloy is mainly a needle-like eutectic Al2RE phase, which reduces the stiffness-enhancing effect.

[0106] Comparative Example 5

[0107] The forming method of the high-rigidity, high-ductility magnesium alloy and its large and complex components described in this comparative example is basically the same as that in Example 5, except that the wire material does not contain Al.

[0108] The experiment revealed that the filament broke during the filament-making process of filament one, making subsequent shaping impossible. This was mainly due to the lack of sufficient heterogeneous nucleation sites during the solidification of ingot one, resulting in coarse grains and reduced plasticity and toughness.

[0109] Comparative Example 6

[0110] The forming method of the high-rigidity and high-ductility magnesium alloy and its large and complex components described in this comparative example is basically the same as that in Example 5, except that the Al content in wire one is 3.0%.

[0111] Through experiments, it was found that the length of a single wire decreased during the wire-making process of wire material one. This is mainly because a large number of Al2RE particles were formed during the solidification of billet one, and their agglomeration led to a decrease in the alloy's ductility and toughness.

[0112] Comparative Example 7

[0113] The forming method of the high-rigidity, high-ductility magnesium alloy and its large and complex components described in this comparative example is basically the same as that in Example 1, except that the interlayer dwell time is 5s during arc additive manufacturing.

[0114] The experiment showed that the stiffness of the magnesium rare earth alloy formed by arc wire additive manufacturing was 51 GPa and the elongation was 8%. It can be seen that the stiffness of the magnesium rare earth alloy is lower than that in Example 1. This is mainly due to the short interlayer residence time, which leads to heat accumulation and coarsening of the high modulus reinforcing phase particles, thus reducing the stiffening effect.

[0115] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A forming method for large, complex components made of high-stiffness and high-ductility magnesium alloy, characterized in that, Includes the following steps: S1. Additive manufacturing: Prepare wire according to the chemical element composition of high-rigidity and high-ductility magnesium alloy, and carry out additive manufacturing on the prepared wire to obtain additive manufacturing components. S2, Hot Isostatic Pressing: The additive manufacturing component obtained in step S1 is subjected to hot isostatic pressing treatment. S3. Heat treatment: The additive manufacturing component obtained in step S2 is subjected to solution treatment and aging treatment to finally obtain a large and complex magnesium alloy component with high stiffness and high plasticity. In step S1, the high-rigidity and high-ductility magnesium alloy comprises the following components by weight percentage: rare earth element RE: 10.0-25.0%, aluminum Al: 5.0-15.0%, lithium Li: 0-10%, silicon Si: 1.0-2.0%, manganese Mn: 0-2.0%, with the balance being magnesium Mg; the Al content is 0.3-0.7% of the RE content. In step S1, the filament is prepared by the following method: A1: Casting ingot: According to the chemical element composition ratio of the wire, the raw materials are prepared, smelted and cast to obtain the ingot; A2: Reciprocating upsetting: The billet obtained in step A1 is homogenized and reciprocated upsetting is performed. A3: Wire making: The ingot obtained in step A2 is made into wire by extrusion and drawing processes to obtain wire material; In step S1, the additive manufacturing specifically involves: performing arc-wire additive manufacturing on the filament; the arc-wire additive manufacturing is a dual-wire arc-wire additive manufacturing. In the dual-wire arc welding additive manufacturing process, the alloy composition range of the resulting additively manufactured components meets the chemical element composition requirements of high-rigidity, high-ductility magnesium alloys. The specific compositions of wire one and wire two are as follows: Wire material one includes all rare earth elements RE, lithium Li, manganese Mn, silicon Si, magnesium Mg, and part of aluminum Al in the magnesium alloy; wire material two includes the remaining aluminum Al. Alternatively, wire material one includes all rare earth elements RE, lithium Li, manganese Mn, magnesium Mg, some aluminum Al, and some silicon Si in the magnesium alloy; wire material two includes the remaining aluminum Al and silicon Si. Alternatively, wire material one includes all rare earth elements RE, lithium Li, manganese Mn, magnesium Mg, and part of aluminum Al in the magnesium alloy; wire material two includes the remaining aluminum Al and all silicon Si. The current used in arc-fused wire additive manufacturing is a pulsed arc with a pulse frequency of 1-100Hz; the interlayer dwell time of arc-fused additive manufacturing is 10-200s.

2. The forming method for large and complex high-stiffness and high-ductility magnesium alloy components according to claim 1, characterized in that, The rare earth element RE includes two or more of the elements gadolinium (Gd), yttrium (Y), neodymium (Nd), ytterbium (Yb), and scandium (Sc).

3. The forming method for large and complex high-stiffness and high-ductility magnesium alloy components according to claim 1, characterized in that, In step S2, the temperature of hot isostatic pressing is 450~550℃, the pressure is 30~200MPa, and the time is 1~8h.

4. The forming method for large and complex high-stiffness and high-ductility magnesium alloy components according to claim 1, characterized in that, In step S3, the solution treatment temperature is 480~550℃ and the time is 1~10h; the aging treatment temperature is 200~250℃ and the time is 8~20h.