Method for enabling Mg element component of 6-series alloy to be more stable

Abstract

The invention relates to the technical field of alloy stabilization, in particular to a method for enabling Mg element components of a 6-series alloy to be more stable, which comprises the following steps: in a 6-series alloy smelting stage, adding cerium and lanthanum into a melt according to a ratio, reacting with the alloy to generate a magnesium hydroxide stable phase, adding zirconium in a smelting process stage, and carrying out heat treatment to obtain the 6-series alloy. Carrying out extrusion forming on the alloy with uniformly distributed magnesium, carrying out stepped aging treatment, carrying out heat preservation at 120 DEG C for 8 hours to promote eta'phase precipitation, raising the temperature to 180 DEG C, carrying out heat preservation for 4 hours, and carrying out comprehensive performance detection on the alloy to ensure that the magnesium element is stable and the performance of the alloy reaches the standard so as to obtain a high-quality alloy product. The method solves the problems that the strength is unstable due to segregation of the magnesium element in the 6-series alloy, the corrosion resistance is reduced due to oxidation loss, the thermal responsiveness is reduced after T6 aging due to recrystallization abnormal diffusion (the hardness improvement amplitude is small), and the magnesium element stability and the alloy comprehensive performance optimization are difficult to realize by the existing process.

Description

Technical Field

[0001] This invention belongs to the field of alloy stabilization technology, specifically relating to a method for making the Mg element composition of 6-series alloys more stable. Background Technology

[0002] Despite extensive research and practice in the production and application of 6-series aluminum alloys (Al-Mg-Si system), several critical issues remain to be addressed. Magnesium segregation is a common problem. During alloy solidification, magnesium is difficult to distribute uniformly, resulting in significant local compositional differences, directly leading to unstable alloy strength. Tests conducted according to ASTM E8 standards show significant strength fluctuations, severely impacting the alloy's reliability in various applications. Oxidation loss is equally prominent. During smelting and processing, magnesium is chemically reactive and readily reacts with oxygen in the air, causing oxidation loss. This not only reduces the actual magnesium content in the alloy, disrupting the intended alloy composition ratio, but also significantly decreases the alloy's corrosion resistance. Salt spray tests show that the corrosion resistance test time is reduced by 30% compared to ideal conditions, greatly shortening the alloy's service life and limiting its application in harsh environments. Abnormal recrystallization diffusion is also a significant concern. During heat treatment and other processing, recrystallization behavior is difficult to control precisely, leading to abnormal diffusion, which in turn affects the alloy's microstructure and properties. Especially under T6 aging conditions, the alloy's thermal responsiveness decreases significantly, and the hardness increase after aging is less than 85%, failing to achieve the expected strengthening effect and making it difficult to meet the demands of high-strength applications. Currently, existing 6-series aluminum alloy production technologies lack effective means to address key issues such as magnesium segregation, oxidation loss, and abnormal recrystallization diffusion, making it difficult to simultaneously achieve high strength, good corrosion resistance, and stable thermal response performance. Therefore, developing a new technology that can stabilize magnesium and improve the overall performance of the alloy is of significant practical importance. Summary of the Invention

[0003] To address the aforementioned issues, this invention provides a method for stabilizing the Mg element composition of 6-series alloys. This method solves the problems of unstable strength due to magnesium segregation, reduced corrosion resistance due to oxidation loss, decreased thermal responsiveness (small increase in hardness) after T6 aging due to abnormal recrystallization diffusion, and the difficulty of achieving magnesium element stabilization and overall alloy performance optimization using existing processes. To achieve the above objectives, this invention adopts the following technical solution:

[0004] The method for stabilizing the Mg element composition of a 6-series alloy includes the following steps: During the smelting stage of the 6-series alloy, cerium and lanthanum are added to the melt in proportion, reacting with the alloy to generate a stable magnesium hydroxide phase, resulting in a melt with impaired magnesium migration; Zirconium is added during the smelting process, interacting with the alloy to form an Al3Zr-Ti composite dispersed phase with an average particle size of 50 to 80 nanometers, resulting in an alloy melt with enhanced magnesium stability; the melt after smelting and element addition is cast into a casting, and the casting is homogenized to ensure uniform alloy composition distribution, resulting in a casting with uniform composition; the homogenized composition is further processed before extrusion molding. The castings undergo a two-stage solution treatment. In the first stage, stress is relieved by holding at 520-530℃ for 2 hours. In the second stage, the temperature is raised to 550-560℃ and held for 1.5 hours to obtain an alloy with uniform magnesium distribution. The alloy with uniform magnesium distribution is then extruded and subjected to a stepped aging treatment. The η′ phase is precipitated by holding at 120℃ for 8 hours, and the temperature is raised to 180℃ and held for 4 hours to promote the formation of the Mg-Si reinforcing phase, resulting in an alloy with optimized performance. The alloy undergoes comprehensive performance testing, including testing tensile strength, yield strength, elongation, and corrosion resistance, to ensure magnesium stability and that the alloy performance meets the standards, resulting in a high-quality alloy product.

[0005] Furthermore, in the smelting stage of the 6-series alloy, cerium and lanthanum are added to the melt in proportion to react with the alloy to generate a stable magnesium hydroxide phase, thereby obtaining a melt with inhibited magnesium migration. This includes the following steps: using a high-precision batching system, 0.15 to 0.3 wt% cerium and 0.08 to 0.12 wt% lanthanum are weighed according to the total alloy ratio; the weighed cerium and lanthanum are added sequentially to the preheated 720-750°C 6-series alloy melt using a vacuum conveying device; the melt is stirred at a speed of 300-500 r / min for 15-20 minutes using an electromagnetic stirring device; through the chemical reaction between cerium and lanthanum and the alloy, a stable magnesium hydroxide phase with a lattice constant a = 0.662 nm is extracted and generated from the reaction products, thereby obtaining a melt with inhibited magnesium migration.

[0006] Furthermore, the addition of zirconium during the smelting process, through interaction with the alloy, forms an Al3Zr-Ti composite dispersed phase with an average particle size of 50 to 80 nanometers, resulting in an alloy melt with enhanced magnesium stability. This includes the following steps: In the smelting process, the temperature of the melt with hindered magnesium migration is stabilized at 760-780℃, and 0.15 to 0.25 wt% zirconium is slowly added; the zirconium is fully dispersed by continuous stirring for 15-20 minutes; the temperature is raised to 800-820℃ and held for 30-40 minutes to allow the zirconium to fully interact with the melt with hindered magnesium migration, forming an Al3Zr-Ti composite dispersed phase with an average particle size of 50 to 80 nanometers, resulting in an alloy melt with enhanced magnesium stability.

[0007] Furthermore, the process of casting the melt after smelting and element addition into a casting, and then homogenizing the casting to ensure uniform alloy composition, results in a casting with uniform composition. This includes the following steps: rapidly pouring the magnesium-stabilized alloy melt into a metal mold preheated to 200-250°C, controlling the pouring speed to ensure the melt smoothly fills the mold, thus obtaining an initial casting; placing the casting in a heat treatment furnace, raising the temperature to 460-480°C at a heating rate of 50-80°C / h; and holding at this temperature for 8-10 hours for homogenization to ensure uniform alloy composition, resulting in a casting with uniformly distributed internal alloy composition.

[0008] Furthermore, the process of performing a two-stage solution treatment on the uniformly composed casting before extrusion molding involves: firstly, holding at 520-530℃ for 2 hours to relieve stress; and secondly, raising the temperature to 550-560℃ and holding for 1.5 hours to obtain an alloy with uniform magnesium distribution. This includes the following steps: placing the uniformly composed casting stably on a refractory brick support in a high-temperature resistance furnace, leaving a 10-15mm gap around it; raising the furnace temperature to 520-530℃ at a rate of 40℃ / h using an intelligent temperature control system and holding it uniformly for 2 hours to complete the first stage treatment; raising the temperature to 550-560℃ at a rate of 25℃ / h and holding it for 1.5 hours to complete the second stage treatment; and finally, after the holding period, using a forced air cooling fan to cool the temperature to below 200℃ to obtain an alloy with uniform magnesium distribution.

[0009] Furthermore, the process of extruding a uniformly magnesium-distributed alloy, followed by a stepped aging treatment, involves holding the alloy at 120°C for 8 hours to induce the precipitation of the η′ phase, then raising the temperature to 180°C and holding for 4 hours to promote the formation of the Mg-Si reinforcing phase, resulting in an alloy with optimized performance. This process includes the following steps: placing the uniformly magnesium-distributed alloy in an extrusion cylinder preheated to 420-450°C, and applying a constant pressure of 35-40 MPa using a 3000-ton extruder for forward extrusion; controlling the die temperature at 400-420°C and setting the extrusion speed to 2-3 mm / s; holding the profile at 120°C for 8 hours in an intelligent temperature-controlled furnace to induce solute atom segregation and form the η′ phase nucleus; and raising the temperature to 180°C at a rate of 10°C / min and holding for 4 hours to form a fine and dispersed Mg-Si reinforcing phase, resulting in an alloy with optimized performance.

[0010] Furthermore, the comprehensive performance testing of the alloy, including testing tensile strength, yield strength, elongation, and corrosion resistance, ensures magnesium stability and alloy performance meets standards, resulting in a high-quality alloy product. This process includes the following steps: obtaining a performance-optimized alloy test sample; loading the sample at a constant rate of 2 mm / min using a universal testing machine and extracting load-displacement curve data; calculating and obtaining tensile strength and yield strength indices; accurately measuring sample deformation using an extensometer and analyzing elongation parameters; placing the sample in a 3.5% NaCl salt spray chamber and conducting a 72-hour continuous spray test, observing and recording surface corrosion morphology, and extracting corrosion rate data; and comprehensively evaluating the test results to determine the stability of magnesium distribution and the overall alloy performance, thus obtaining a high-quality alloy product.

[0011] Furthermore, the process of rapidly pouring the magnesium-stabilized alloy melt into a metal mold preheated to 200-250°C, and controlling the pouring speed to ensure the melt smoothly fills the mold and yields the initial casting, includes the following steps: using a hoisting device to smoothly move the crucible containing the magnesium-stabilized alloy melt directly above the metal mold; confirming the mold preheating temperature is within the 200-250°C range using an infrared thermometer, and opening the controllable flow rate gate at the bottom of the crucible; precisely controlling the pouring speed to 0.8-1.2 kg / s by adjusting the gate valve to ensure the melt flows continuously and stably into the mold cavity; using a level to monitor the mold tilt in real time to ensure uniform filling of the melt; waiting for the melt to completely solidify, opening the mold, and removing the part to obtain the initial casting.

[0012] Furthermore, the step of placing the castings into the heat treatment furnace and raising the temperature to 460-480℃ at a heating rate of 50-80℃ / h includes the following steps: using a lifting device to stably place the castings on the heat-resistant support of the heat treatment furnace, ensuring that the spacing between the castings is not less than 50mm; setting the heating program through the intelligent temperature control system, adopting a segmented heating mode: raising the furnace temperature to 200℃ at a rate of 50℃ / h and holding it at that temperature for 30 minutes; adjusting the heating power to raise the temperature to 460-480℃ at a rate of 80℃ / h; and monitoring the furnace temperature in real time through thermocouples, extracting data, and providing feedback for adjustment to obtain a stable heat treatment environment with a furnace temperature uniformity error of ≤±5℃.

[0013] In the technical solution provided by this invention, during the smelting stage of the 6-series alloy, cerium and lanthanum are added to the melt in proportion, reacting with the alloy to generate a stable magnesium hydroxide phase, resulting in a melt with hindered magnesium migration. During the smelting process, zirconium is added, interacting with the alloy to form an Al3Zr-Ti composite dispersed phase with an average particle size of 50 to 80 nanometers, resulting in an alloy melt with enhanced magnesium stability. The melt after smelting and element addition is cast into castings, which are then homogenized to ensure uniform alloy composition, resulting in a uniformly composed casting. Before extrusion molding, the uniformly composed casting undergoes a two-stage solidification process. The process involves solution treatment, with the first stage at 520-530℃ for 2 hours to relieve stress, and the second stage at 550-560℃ for 1.5 hours to obtain an alloy with uniform magnesium distribution. This alloy is then extruded and subjected to a stepped aging treatment. Holding at 120℃ for 8 hours promotes the precipitation of the η′ phase, followed by raising the temperature to 180℃ and holding for 4 hours to promote the formation of the Mg-Si reinforcing phase, resulting in an alloy with optimized performance. Comprehensive performance testing of the alloy is performed, including testing tensile strength, yield strength, elongation, and corrosion resistance, to ensure magnesium stability and that the alloy performance meets standards, resulting in a high-quality alloy product. This invention solves the problems of magnesium segregation leading to unstable strength in 6-series alloys, oxidation loss reducing corrosion resistance, abnormal recrystallization diffusion causing decreased thermal responsiveness after T6 aging (small increase in hardness), and the difficulty of achieving magnesium stability and comprehensive alloy performance optimization in existing processes. Attached Figure Description

[0014] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention.

[0015] Figure 1 This is a schematic diagram of a first embodiment of a method for making the Mg element composition of 6-series alloys more stable according to an embodiment of the present invention.

[0016] Figure 2 This is a schematic diagram of a second embodiment of a method for making the Mg element composition of 6-series alloys more stable according to an embodiment of the present invention.

[0017] Figure 3 This is a schematic diagram of a third embodiment of a method for making the Mg element composition of 6-series alloys more stable according to the present invention.

[0018] Figure 4 This is a schematic diagram of the fourth embodiment of a method for making the Mg element composition of 6-series alloys more stable according to the present invention.

[0019] Figure 5 This is a schematic diagram of the fifth embodiment of a method for making the Mg element composition of 6-series alloys more stable according to the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0022] A method to stabilize the Mg elemental composition of 6-series alloys, such as Figure 1 As shown, the process includes the following steps: In the smelting stage of the 6-series alloy, cerium and lanthanum are added to the melt in proportion, and through reaction with the alloy, a magnesium hydroxide stable phase is generated, resulting in a melt with hindered magnesium migration; Zirconium is added in the smelting process stage, and through interaction with the alloy, an Al3Zr-Ti composite dispersed phase with an average particle size of 50 to 80 nanometers is formed, resulting in an alloy melt with enhanced magnesium stability; the melt after smelting and element addition is cast into castings, and the castings are homogenized to ensure uniform alloy composition distribution, resulting in castings with uniform composition; before extrusion molding, the castings with uniform composition undergo two-stage solution treatment. The process involves two stages: first, stress relief is achieved by holding the alloy at 520-530℃ for 2 hours; second, the temperature is raised to 550-560℃ and held for 1.5 hours to obtain an alloy with uniform magnesium distribution. This alloy is then extruded and subjected to a stepped aging treatment. Holding at 120℃ for 8 hours promotes the precipitation of the η′ phase, followed by raising the temperature to 180℃ and holding for 4 hours to promote the formation of the Mg-Si reinforcing phase, resulting in an alloy with optimized performance. Comprehensive performance testing is then performed on the alloy, including testing tensile strength, yield strength, elongation, and corrosion resistance, to ensure magnesium stability and that the alloy performance meets standards, resulting in a high-quality alloy product.

[0023] like Figure 2 As shown, in this embodiment, a high-precision batching system is used to weigh 0.15 to 0.3 wt% cerium and 0.08 to 0.12 wt% lanthanum according to the total alloy ratio. The weighed cerium and lanthanum are added sequentially to the preheated 720-750°C molten 6 series alloy using a vacuum conveying device. The molten 6 series alloy is stirred at a speed of 300-500 r / min for 15-20 minutes using an electromagnetic stirring device. Through the chemical reaction between cerium, lanthanum and the alloy, a stable phase of magnesium hydroxide with a lattice constant a = 0.662 nm is extracted and generated from the reaction products, resulting in a melt with hindered magnesium migration.

[0024] A high-precision batching system is employed to precisely control the cerium and lanthanum content, ensuring stable composition. Cerium and lanthanum are added to the preheated 6-series alloy melt via a vacuum conveying device, and stirred at an appropriate speed using an electromagnetic stirrer to ensure thorough mixing and reaction of the elements. Utilizing the chemical reaction between cerium, lanthanum, and the alloy, a magnesium hydroxide stable phase with a specific lattice constant is successfully extracted and generated, effectively hindering magnesium migration.

[0025] like Figure 3 As shown, in this embodiment, during the smelting process, the temperature of the melt with hindered magnesium migration is stabilized at 760-780℃, and 0.15 to 0.25 wt% zirconium is slowly added; by continuous stirring for 15-20 minutes, the zirconium is fully dispersed; the temperature is raised to 800-820℃ and held for 30-40 minutes to allow the zirconium and the melt with hindered magnesium migration to fully interact, forming an Al3Zr-Ti composite dispersed phase with an average particle size of 50 to 80 nanometers, thus obtaining an alloy melt with enhanced magnesium stability.

[0026] The temperature of the magnesium migration-impeded melt was stabilized at 760-780℃, and 0.15-0.25 wt% zirconium was added and stirred for 15-20 minutes to ensure thorough dispersion of zirconium. After heating to 800-820℃ and holding for 30-40 minutes, an Al3Zr-Ti composite dispersed phase with an average particle size of 50-80 nanometers was successfully formed. Testing showed that the resulting magnesium-stabilized alloy melt exhibited a 15%-20% increase in tensile strength, a 10%-15% increase in elongation, and significantly enhanced stability at high temperatures, effectively expanding the alloy's application range.

[0027] like Figure 4 As shown, in this embodiment, the magnesium-stabilized alloy melt is rapidly poured into a metal mold preheated to 200-250°C. By controlling the pouring speed, the melt smoothly fills the mold to obtain an initial casting. The casting is then placed in a heat treatment furnace, and the temperature is raised to 460-480°C at a heating rate of 50-80°C / h. The casting is held at this temperature for 8-10 hours for homogenization treatment to ensure uniform distribution of the alloy composition, resulting in a casting with uniformly distributed internal alloy composition.

[0028] Magnesium-stabilized alloy melt is rapidly poured into a preheated metal mold at 200-250℃, with precise control of the pouring speed to ensure the melt smoothly fills the mold. This effectively avoids defects such as porosity and inclusions inside the casting, increasing the casting yield to over 95%. The casting is then homogenized by heating at 50-80℃ / h to 460-480℃ and holding for 8-10 hours to ensure uniform alloy composition distribution. Testing shows that the treated casting exhibits a 10%-15% increase in hardness and approximately a 20% improvement in fatigue resistance, significantly enhancing the overall performance of the casting.

[0029] like Figure 5 As shown, in this embodiment, a uniformly composed casting is placed stably on a refractory brick support of a high-temperature resistance furnace, with a 10-15mm gap around it. The furnace temperature is raised to 520-530℃ at a rate of 40℃ / h using an intelligent temperature control system and held at that temperature for 2 hours to complete the first stage of treatment. The temperature is then raised to 550-560℃ at a rate of 25℃ / h and held for 1.5 hours to complete the second stage of treatment. After the holding period ends, forced air cooling is performed using a fan to cool the temperature to below 200℃, resulting in an alloy with uniform magnesium distribution.

[0030] The uniformly composed castings were placed in a high-temperature resistance furnace with a 10-15mm gap around them to facilitate uniform heat transfer. The alloy was then treated in stages using an intelligent temperature control system: first, the temperature was increased at 40℃ / h to 520-530℃ and held for 2 hours; then, it was increased at 25℃ / h to 550-560℃ and held for 1.5 hours, precisely controlling the microstructure transformation of the alloy. Finally, forced cooling with a fan was used to bring the temperature below 200℃. Testing showed that the uniformity of magnesium distribution in the treated alloy increased by more than 30%, and the tensile strength reached 350-380MPa, an increase of 15%-20% compared to before treatment.

[0031] In this embodiment, a magnesium-uniformly distributed alloy is placed in an extrusion cylinder preheated to 420-450°C and subjected to a constant pressure of 35-40 MPa using a 3000-ton extruder for forward extrusion. The die temperature is controlled at 400-420°C during the extrusion process, and the extrusion speed is set to 2-3 mm / s. The profile is then held at 120°C for 8 hours in an intelligent temperature-controlled furnace, where the long-term low-temperature action promotes the segregation of solute atoms to form η′ phase nuclei. The temperature is then increased to 180°C at a rate of 10°C / min and held for 4 hours to form a fine and dispersed Mg-Si reinforcing phase, resulting in an alloy with optimized performance.

[0032] The magnesium-uniformly distributed alloy is placed in a preheated extrusion cylinder and extruded under a constant pressure of 35-40 MPa using a 3000-ton extruder. Simultaneously, the die temperature is precisely controlled at 400-420℃ and the extrusion speed at 2-3 mm / s, ensuring the dimensional accuracy and surface quality of the extruded profiles, with a product qualification rate exceeding 98%. Subsequently, the alloy undergoes staged processing in an intelligent temperature-controlled furnace: first, it is held at 120℃ for 8 hours, then increased to 180℃ at a rate of 10℃ / min and held for 4 hours. This process forms a fine, dispersed Mg-Si reinforcing phase, increasing the alloy's tensile strength to 420-450 MPa and elongation by 10%-15%, resulting in significantly optimized performance.

[0033] In this embodiment, an alloy test sample with optimized performance was obtained. Using a universal testing machine, the sample was loaded at a constant rate of 2 mm / min, and load-displacement curve data was extracted. Tensile strength and yield strength were calculated, and the sample deformation was precisely measured using an extensometer to analyze the elongation parameter. The sample was placed in a 3.5% NaCl salt spray chamber and subjected to a 72-hour continuous spray test. The surface corrosion morphology was observed and recorded, and corrosion rate data was extracted. Based on the comprehensive test results, the stability of magnesium element distribution and the overall performance of the alloy were determined, resulting in a high-quality alloy product.

[0034] Load-displacement curves obtained by applying load at a rate of 2 mm / min allow for accurate calculation of tensile strength and yield strength. Combined with extensometer measurements, the elongation parameter error is less than 1%. A 72-hour continuous spray test in a 3.5% NaCl salt spray chamber clearly observes the surface corrosion morphology and accurately extracts corrosion rate data. This comprehensive testing not only determines the stability of magnesium element distribution but also comprehensively evaluates the alloy's overall performance. Practice shows that high-quality alloy products assessed using this method exhibit a 20% improvement in corrosion resistance and a mechanical property stability exceeding 95%.

[0035] In this embodiment, a hoisting device is used to smoothly move the crucible containing the magnesium stability-enhancing alloy melt directly above the metal mold; the preheating temperature of the mold is confirmed to be in the range of 200-250℃ by an infrared thermometer, and the gate with controllable flow rate at the bottom of the crucible is opened; by adjusting the gate valve, the pouring speed is precisely controlled at 0.8-1.2 kg / s, so that the melt is injected into the mold cavity in a continuous and stable flow state; the mold tilt is monitored in real time using a level to ensure uniform filling of the melt; after the melt has completely solidified, the mold is opened and the part is removed to obtain the initial casting.

[0036] The crucible is moved smoothly using hoisting equipment to prevent molten material from sloshing and spilling. An infrared thermometer accurately confirms the mold preheating temperature is between 200-250℃, providing suitable conditions for good melt molding. The pouring speed is precisely controlled between 0.8-1.2 kg / s by adjusting the gating valve, ensuring continuous and stable injection of the molten material into the mold cavity, effectively reducing defects such as porosity and inclusions. A level is used to monitor the mold tilt in real time to ensure uniform molten material filling. Testing shows that the initial castings obtained using this method have an internal defect rate reduced to below 5%, and dimensional accuracy errors controlled within ±0.2 mm.

[0037] In this embodiment, a lifting device is used to place the castings stably on the heat-resistant support of the heat treatment furnace, ensuring that the spacing between the castings is not less than 50mm; the heating program is set through an intelligent temperature control system, and a segmented heating mode is adopted: the furnace temperature is raised to 200℃ at a rate of 50℃ / h and held for 30 minutes; by adjusting the heating power, the temperature is raised to 460-480℃ at a rate of 80℃ / h; the furnace temperature is monitored in real time by thermocouples, data is extracted and feedback is used for adjustment, and a stable heat treatment environment with a furnace temperature uniformity error of ≤±5℃ is obtained.

[0038] The castings are placed stably using lifting equipment, ensuring a minimum spacing of 50mm to facilitate uniform heat transfer and prevent interference between castings. The intelligent temperature control system employs a segmented heating mode: first, the temperature is raised to 200℃ at a rate of 50℃ / h and held for 30 minutes, then raised to 460-480℃ at a rate of 80℃ / h, reducing thermal stress in the castings. Thermocouples monitor and provide feedback adjustments in real time, ensuring that the temperature uniformity within the furnace is ≤±5℃. This treatment improves the uniformity of the casting microstructure by over 25%, reduces the standard deviation of hardness to within 3HV, and effectively enhances the quality stability and performance consistency of the castings.

[0039] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for stabilizing the Mg element composition of 6-series alloys, characterized in that, The method for making the Mg element composition of 6-series alloys more stable includes the following steps: During the smelting stage of the 6-series alloys, cerium and lanthanum are added to the melt in proportion. Through the reaction with the alloy, a stable phase of magnesium hydroxide is generated, resulting in a melt in which magnesium migration is hindered. Adding zirconium during the smelting process allows it to interact with the alloy to form an Al3Zr-Ti composite dispersed phase with an average particle size of 50 to 80 nanometers, resulting in an alloy melt with enhanced magnesium stability. The melt that has been smelted and element added is cast into a casting. The casting is then homogenized to ensure that the alloy composition is evenly distributed, resulting in a casting with uniform composition. Before extrusion molding, the casting with uniform composition is subjected to two-stage solution treatment. In the first stage, the stress is relieved by holding at 520-530℃ for 2 hours. In the second stage, the temperature is raised to 550-560℃ and held for 1.5 hours to obtain an alloy with uniform magnesium distribution. The alloy with uniform magnesium distribution is extruded and then subjected to step aging treatment. The η′ phase is precipitated by holding at 120℃ for 8 hours. The temperature is then raised to 180℃ and held for 4 hours to promote the formation of the Mg-Si reinforcing phase, resulting in an alloy with optimized performance. Comprehensive performance testing of the alloy is conducted, including testing tensile strength, yield strength, elongation, and corrosion resistance, to ensure that the magnesium element is stable and the alloy performance meets the standards, resulting in high-quality alloy products.

2. The method for stabilizing the Mg element composition of 6-series alloys according to claim 1, characterized in that, In the smelting stage of the 6-series alloy, cerium and lanthanum are added to the melt in proportion, and through reaction with the alloy, a stable phase of magnesium hydroxide is generated, resulting in a melt in which magnesium migration is hindered. This includes the following steps: Using a high-precision batching system, weigh out 0.15 to 0.3 wt% cerium and 0.08 to 0.12 wt% lanthanum according to the total alloy ratio; Using a vacuum conveying device, the weighed cerium and lanthanum are added sequentially to the 6-series alloy melt, which has been preheated to 720-750°C. Stir with an electromagnetic stirrer at a speed of 300-500 r / min for 15-20 minutes; By reacting cerium and lanthanum with the alloy, a stable phase of magnesium hydroxide with a lattice constant of a = 0.662 nm is extracted from the reaction products, resulting in a melt with hindered magnesium migration.

3. The method for stabilizing the Mg element composition of 6-series alloys according to claim 1, characterized in that, The process of adding zirconium during the smelting stage, through its interaction with the alloy, forms an Al3Zr-Ti composite dispersed phase with an average particle size of 50 to 80 nanometers, resulting in an alloy melt with enhanced magnesium stability. This process includes the following steps: In the smelting process, the temperature of the melt where magnesium migration is hindered is stabilized at 760-780℃, and 0.15 to 0.25 wt% zirconium is slowly added; By continuously stirring for 15-20 minutes, the zirconium can be fully dispersed; Raise the temperature to 800-820℃ and hold for 30-40 minutes to allow the zirconium and magnesium-migrating melt to fully interact, forming an Al3Zr-Ti composite dispersed phase with an average particle size of 50 to 80 nanometers, thus obtaining an alloy melt with enhanced magnesium stability.

4. The method for stabilizing the Mg element composition of 6-series alloys according to claim 1, characterized in that, The process of converting the melt, after smelting and element addition, into a casting, and then homogenizing the casting to ensure a uniform distribution of alloy composition, resulting in a casting with homogeneous composition, includes the following steps: The magnesium-stabilized alloy melt is rapidly poured into a metal mold preheated to 200-250°C. By controlling the pouring speed, the melt is made to fill the mold smoothly, thus obtaining the initial casting. The casting is placed in a heat treatment furnace, and the temperature is raised to 460-480℃ at a heating rate of 50-80℃ / h. The alloy is kept at a high temperature for 8-10 hours for homogenization treatment, so that the alloy composition is evenly distributed, resulting in a casting with a uniformly distributed internal alloy composition.

5. The method for stabilizing the Mg element composition of 6-series alloys according to claim 1, characterized in that, The process of performing a two-stage solution treatment on a uniformly composed casting before extrusion molding includes the following steps: First, stress relief is achieved by holding the casting at 520-530℃ for 2 hours; second, the casting is heated to 550-560℃ and held for 1.5 hours to obtain an alloy with uniform magnesium distribution. Place the uniformly composed castings stably on the refractory brick support of the high-temperature resistance furnace, leaving a 10-15mm gap around them. The furnace temperature is raised to 520-530℃ at a rate of 40℃ / h using an intelligent temperature control system, and then kept at a uniform temperature for 2 hours to complete the first stage of processing. The temperature was increased to 550-560℃ at a rate of 25℃ / h, and held for 1.5 hours to complete the second stage of treatment. After the heat preservation is completed, a forced air cooling process is used to cool the temperature to below 200℃, resulting in an alloy with uniform magnesium distribution.

6. The method for stabilizing the Mg element composition of 6-series alloys according to claim 1, characterized in that, The process involves extruding a uniformly magnesium-distributed alloy, followed by a stepped aging treatment. The η′ phase is precipitated by holding at 120℃ for 8 hours, and the temperature is then increased to 180℃ and held for 4 hours to promote the formation of the Mg-Si reinforcing phase, resulting in an alloy with optimized performance. The process includes the following steps: The magnesium-uniformly distributed alloy is placed in an extrusion cylinder preheated to 420-450℃ and subjected to a constant pressure of 35-40MPa through a 3000-ton extruder for forward extrusion. The die temperature during the extrusion process is controlled at 400-420℃, and the extrusion speed is set to 2-3mm / s; The profiles are kept at 120℃ for 8 hours in an intelligent temperature-controlled furnace, and the long-term action of low temperature promotes the segregation of solute atoms to form η′ phase nuclei. The temperature was increased to 180℃ at a rate of 10℃ / min and held for 4 hours to form a fine and dispersed Mg-Si reinforcing phase, resulting in an alloy with optimized performance.

7. The method for stabilizing the Mg element composition of 6-series alloys according to claim 1, characterized in that, The comprehensive performance testing of the alloy, including testing tensile strength, yield strength, elongation, and corrosion resistance, ensures the stability of magnesium and that the alloy performance meets the standards, resulting in a high-quality alloy product. This process includes the following steps: To obtain alloy test samples with optimized performance, load-displacement curve data were extracted by loading the test samples at a constant rate of 2 mm / min using a universal testing machine. The tensile strength and yield strength indices are calculated and obtained. The deformation of the specimen is accurately measured using an extensometer, and the elongation parameter is analyzed. The sample was placed in a 3.5% NaCl salt spray chamber and subjected to a 72-hour continuous spray test. The surface corrosion morphology was observed and recorded, and the corrosion rate data was extracted. Based on the comprehensive test results, the stability of magnesium element distribution and the overall performance of the alloy were determined, resulting in a high-quality alloy product.

8. A method for stabilizing the Mg element composition of 6-series alloys according to claim 4, characterized in that, The process of rapidly pouring the magnesium-stabilized alloy melt into a metal mold preheated to 200-250°C, and controlling the pouring speed to ensure the melt smoothly fills the mold and yields the initial casting, includes the following steps: Using hoisting equipment, the crucible containing the magnesium stability-enhancing alloy melt was smoothly moved to a position directly above the metal mold; The preheating temperature of the mold was confirmed to be in the range of 200-250℃ by infrared thermometer, and the gate with controllable flow rate at the bottom of the crucible was opened. By adjusting the gate valve, the pouring speed is precisely controlled at 0.8-1.2 kg / s, so that the melt is injected into the mold cavity in a continuous and stable flow state; The mold tilt is monitored in real time using a level to ensure uniform melt filling; After the melt has completely solidified, the mold is opened and the part is removed to obtain the initial casting.

9. A method for stabilizing the Mg element composition of 6-series alloys according to claim 4, characterized in that, The step of placing the casting in a heat treatment furnace and raising the temperature to 460-480℃ at a heating rate of 50-80℃ / h includes the following steps: Use a lifting device to place the castings stably on the heat-resistant support of the heat treatment furnace, ensuring that the spacing between the castings is not less than 50mm; The heating program is set through an intelligent temperature control system, and a segmented heating mode is adopted: the furnace temperature is raised to 200℃ at a rate of 50℃ / h and held for 30 minutes. By adjusting the heating power, the temperature is raised to 460-480℃ at a rate of 80℃ / h; By monitoring the furnace temperature in real time with thermocouples, extracting data, and adjusting accordingly, a stable heat treatment environment with a furnace temperature uniformity error of ≤±5℃ is obtained.

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