Alloy multi-scale strengthening phase in-situ precipitation regulation method and alloy casting

Abstract

This invention discloses a method for controlling the in-situ precipitation of multi-scale strengthening phases in alloys and an alloy casting, belonging to the field of metal preparation technology. The method involves placing molten alloy in a crucible of a casting equipment, with a liquid cooling medium filling the area around and below a substrate. The molten alloy is ejected from the crucible outlet and impacts the substrate. Under the spreading and flowing action of the melt, and the cooling effect of the substrate and the liquid cooling medium, submicron-level precipitates are controlled, and a solidified alloy layer is formed. The substrate is then moved downwards towards the liquid cooling medium by a certain distance. This process is repeated, allowing the molten alloy to continuously accumulate and form on the solidified alloy layer. This ensures that the solidified alloy layer undergoes a certain temperature and number of thermal cycles before entering the liquid cooling medium, achieving the control of nanoscale strengthening phases and the formation of the alloy casting. This invention controls the solidification and solid-state phase transformation process of the alloy through a layering method. The process is short, the strengthening phase control effect is good, and high-quality, high-performance alloy castings can be obtained.

Description

Technical Field

[0001] This invention belongs to the field of metal preparation technology, specifically relating to a method for controlling the in-situ precipitation of multi-scale strengthening phases in alloys and alloy castings. Background Technology

[0002] Second-phase strengthening is an important strengthening mechanism for alloys. The strengthening phases of an alloy typically include discontinuously distributed fine submicron-sized precipitates and diffusely distributed nanoscale strengthening phases. Fine submicron-sized precipitates usually form during alloy solidification under the influence of solute redistribution, and are mostly located at grain boundaries, increasing grain boundary stability and thus improving the alloy's room temperature and high temperature strength. Nanoscale strengthening phases within grain boundaries typically precipitate from the supersaturated matrix during solid-state phase transformations, hindering dislocation movement during deformation and improving the alloy's overall mechanical properties.

[0003] Due to the limitations of traditional solidification processes and solid-state phase transformation processes for alloys, such as slow solidification rates and uneven heating and cooling rates, submicron-sized precipitates in the alloy tend to grow excessively and form a continuous network distribution. This also results in larger, fewer, and unevenly distributed nanoscale reinforcing phases, which negatively impacts both the strength and plasticity of the alloy.

[0004] Currently, the control of alloy strengthening phases mainly involves separately controlling the submicron-sized precipitates and nano-sized strengthening phases. Specifically, methods include refining, reducing, or breaking down coarse, continuous submicron-sized precipitates by improving solidification processes or adding solution treatment and plastic deformation processes; and improving aging processes to ensure uniform precipitation of nano-sized strengthening phases from the matrix, while controlling aging temperature and time to reduce the size and increase the quantity of nano-sized strengthening phases. While these methods can control both submicron-sized and nano-sized strengthening phases, they also have the following drawbacks:

[0005] (1) The existing control of the strengthening phase of alloys, especially the control of the nanoscale strengthening phase, is mostly achieved by heat treatment after the alloy solidifies and forms. There is a lack of methods for in-situ control of the strengthening phase during the solidification and forming process of alloys, and the process is relatively long.

[0006] (2) Existing methods for controlling the strengthening phase of alloys mostly involve controlling the submicron-scale precipitates and the nanoscale strengthening phases separately, lacking an integrated control method for multi-scale strengthening phases, resulting in poor control effect of the strengthening phase.

[0007] Therefore, it is of great significance to develop a method for controlling the in-situ precipitation of multi-scale strengthening phases in alloys with a short process flow and good effect on strengthening phase regulation, so as to obtain high-quality and high-performance alloy castings. Summary of the Invention

[0008] This invention addresses the problems of traditional alloy strengthening phase control, such as the lack of an integrated in-situ control method for multi-scale strengthening phases during alloy solidification and forming, long process flow, and poor strengthening phase control effect. It proposes an in-situ precipitation control method for multi-scale strengthening phases in alloys and an alloy casting, thereby achieving in-situ precipitation control of multi-scale strengthening phases in alloys.

[0009] According to a first aspect of the present invention, a method for controlling the in-situ precipitation of multi-scale strengthening phases in alloys is provided, comprising the following steps:

[0010] Step 1: Fill the crucible of the casting equipment with the alloy melt, and fill the area around and below the substrate of the casting equipment with liquid cooling medium;

[0011] Step 2: The alloy melt is ejected from the outlet of the crucible and impacts the substrate to form an alloy solidification layer; after the alloy melt impacts the surface of the substrate, it spreads rapidly and is cooled by the substrate and the liquid cooling medium, which ultimately refines the alloy melt and causes the submicron-sized precipitates to be discontinuously distributed.

[0012] Step 3: Move the substrate downward toward the liquid cooling medium and perform online precise displacement control so that the distance between the liquid surface of the liquid cooling medium and the upper surface of the formed alloy solidified layer is always maintained at 20-90mm.

[0013] Step 4: Repeat the forming process of the alloy melt in Step 2 to Step 3, so that the alloy melt continuously solidifies and stacks on the alloy solidified layer; the formed alloy solidified layer undergoes multiple thermal cycles before entering the liquid cooling medium; finally, an alloy casting of the required thickness is obtained.

[0014] Furthermore, in the first step, the temperature of the alloy melt is maintained at 10-200°C above the liquidus temperature of the alloy; the temperature of the liquid cooling medium is maintained at 50-800°C, and the distance between the liquid surface of the liquid cooling medium and the upper surface of the substrate is 20-90 mm.

[0015] Furthermore, in the second step, the alloy melt is ejected from the outlet of the crucible at a speed of 6000 to 10000 mm / s and impacts the substrate, and an alloy solidification layer with a thickness of 0.5 to 50 mm is formed by additive manufacturing or by the outlet “on-off-…-on-off” method.

[0016] Furthermore, in the second step, the alloy melt is cooled at a rate of 1000 to 10000 °C / s.

[0017] Furthermore, in the second step, the average size of the submicron-sized precipitated phase is 0.1–0.5 μm.

[0018] Furthermore, in the third step, the substrate moves downwards towards the liquid cooling medium by a distance of 0.5 to 50 mm.

[0019] Furthermore, the substrate is a mold with a certain complex shape.

[0020] Furthermore, the maximum temperature of the thermal cycle is maintained below the solidus temperature of the alloy.

[0021] Furthermore, the liquid cooling medium includes water or a low-melting-point alloy; the low-melting-point alloy has a melting point of 10 to 100°C and is at least one of gallium-indium alloy, gallium-indium-tin alloy, and indium-tin-bismuth-lead alloy.

[0022] According to a second aspect of the technical solution of the present invention, an alloy casting is provided, characterized in that the alloy casting is prepared by the in-situ precipitation control method of multi-scale strengthening phases of alloys according to any of the above aspects.

[0023] This invention has the following advantages:

[0024] 1. The method of the present invention makes full use of the annular flow field generated at the front of the alloy solid-liquid interface when the alloy melt impacts the low-temperature substrate or the alloy solidified layer and spreads rapidly. This causes the alloy melt to solidify under the combined action of rapid cooling and melt flow stirring, which promotes the nucleation of submicron-sized precipitates and inhibits their growth, thereby refining and discontinuously distributing the submicron-sized precipitates.

[0025] 2. The method of the present invention makes full use of the thermal cycling effect under conformal temperature control, in which each solidified alloy layer undergoes thermal cycling at a temperature lower than the solidus temperature of the alloy and the number of cycles is controllable, thereby enabling the fine nanoscale reinforcing phase to be diffused and precipitated in a controllable manner from the solidified alloy matrix.

[0026] 3. The method of this invention utilizes rapid cooling and melt flow during the layer-by-layer solidification of the alloy to control the in-situ precipitation of submicron-sized precipitates, while simultaneously increasing the supersaturated solid solubility and dislocation content (density up to 1×10⁻⁶) of the solidified alloy matrix. 13 ~1×10 15 m -2 This provides a stronger driving force and nucleation sites for the precipitation of nanoscale strengthening phases during the subsequent layer-by-layer stacking process. Based on this, the in-situ precipitation of nanoscale strengthening phases in the alloy is controlled by the controllable thermal cycling during the layer-by-layer stacking process, thereby realizing the in-situ precipitation control of multi-scale strengthening phases in the alloy. It has the advantages of short process flow and good strengthening phase control effect, and can obtain high-quality high-performance alloy castings. Attached Figure Description

[0027] Figure 1 This is a process flow diagram of an in-situ precipitation control method for multi-scale strengthening phases in alloys according to the present invention. Detailed Implementation

[0028] The present invention will be described in detail below with reference to the embodiments. It should be noted that the embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments based on the above content of the present invention.

[0029] This invention provides a method for controlling the in-situ precipitation of multi-scale strengthening phases in alloys and an alloy casting. Based on the layer-by-layer solidification of molten metal, the method controls the strengthening phases of the alloy by regulating the solidification process and the solid-state phase transformation process of the solidified layers during layer stacking. This results in the development of a method to control submicron-scale precipitates generated during the solidification process of the alloy by rapidly spreading the molten metal after impacting a low-temperature base layer during solidification, and to control nanoscale strengthening phases generated during the solid-state phase transformation of the formed layers during subsequent layer stacking using conformal temperature control. Ultimately, this method achieves in-situ precipitation control of multi-scale strengthening phases in the alloy. This method not only fully utilizes the fact that when molten metal impacts a low-temperature base layer and spreads rapidly, the alloy melt solidifies under the combined effects of melt flow, stirring, and rapid cooling, promoting the nucleation of submicron-sized precipitates and inhibiting their growth. This refines and discontinuously distributes the submicron-sized precipitates while increasing the supersaturated solid solubility of the matrix and increasing the content of substructures such as dislocations, providing a stronger driving force and nucleation sites for the precipitation of nanoscale strengthening phases during subsequent layer-by-layer stacking; it also utilizes the fact that each solidified alloy layer undergoes a controllable thermal cycle at a temperature below the alloy solidus temperature during the layer-by-layer stacking process under conformal temperature control, thereby enabling the controllable dispersion and precipitation of fine nanoscale strengthening phases from the matrix. Ultimately, this achieves in-situ precipitation control of multi-scale strengthening phases in the alloy, resulting in high-quality, high-performance alloy castings.

[0030] like Figure 1 The method for controlling the in-situ precipitation of multi-scale strengthening phases in this alloy includes the following steps:

[0031] Step 1: Fill the crucible of the casting equipment with the alloy melt and maintain the temperature of the alloy melt at 10-200°C above the liquidus temperature of the alloy; fill the area around and below the substrate of the casting equipment with liquid cooling medium and maintain the temperature of the liquid cooling medium at 50-800°C, and keep the distance between the liquid surface of the liquid cooling medium and the upper surface of the substrate at 20-90 mm.

[0032] The substrate is a mold with a certain complex shape; the liquid cooling medium includes, for example, water or a low-melting-point alloy; the melting point of the low-melting-point alloy is 10 to 100°C, for example, at least one of gallium-indium alloy, gallium-indium-tin alloy, and indium-tin-bismuth-lead alloy.

[0033] Step 2: The alloy melt is ejected from the crucible outlet at a speed of 6000–10000 mm / s and impacts the substrate. An alloy solidification layer with a thickness of 0.5–50 mm is formed using additive manufacturing or an "on-off-…-on-off" outlet process. After the alloy melt impacts the substrate surface, it spreads rapidly, creating a high-speed annular flow field at the solid-liquid interface front formed by the impact of the alloy melt on the substrate. This allows for the full and abundant nucleation of submicron-sized precipitates. Under the cooling effect of the substrate and the liquid cooling medium, the alloy melt is continuously cooled at a rate of 1000–10000 °C / s, reducing the growth rate of the submicron-sized precipitates. Ultimately, the precipitates are refined and discontinuously distributed with an average size of 0.1–0.5 μm.

[0034] Step 3: Move the substrate downwards by 0.5 to 50 mm towards the liquid cooling medium, and perform precise online displacement control to keep the distance between the liquid surface of the liquid cooling medium and the upper surface of the solidified alloy layer always between 20 and 90 mm.

[0035] Step 4: Repeat the alloy melt forming process of steps 2 and 3, allowing the alloy melt to continuously solidify and stack on the alloy solidified layer; through precise control of the substrate downward movement distance, ensure that the formed alloy solidified layer undergoes 10 to 100 thermal cycles before entering the liquid cooling medium, so that the nanoscale reinforcing phase with an average particle size of 1 to 50 nm can be controllably dispersed and precipitated from the solidified alloy matrix; until a casting of alloy with the required thickness is obtained.

[0036] The highest temperature of the thermal cycle is maintained below the solidus temperature of the alloy to prevent the supersaturated solid solution in the solidified layer of the alloy from being destroyed and to prevent the growth of nano-reinforcing phases.

[0037] Example 1:

[0038] S1: 7075 aluminum alloy melt is placed in the crucible of the casting equipment and the temperature of the 7075 aluminum alloy melt is maintained at 730℃; Indium tin bismuth lead alloy is filled around and below the substrate of the casting equipment and the temperature of the indium tin bismuth lead alloy is maintained at 80℃, and the distance between the liquid surface of the indium tin bismuth lead alloy and the upper surface of the substrate is 40mm.

[0039] S2: Molten 7075 aluminum alloy is ejected from the crucible outlet at a speed of 6000 mm / s and impacts the substrate. An additive manufacturing method is used to form a 1 mm thick solidified layer of 7075 aluminum alloy. After the molten 7075 aluminum alloy impacts the substrate surface, it spreads rapidly. At the solid-liquid interface front of the spread molten 7075 aluminum alloy, there is a high-speed annular flow field formed by the impact of the molten 7075 aluminum alloy on the substrate. This allows for the full and large-scale nucleation of AlZnMgCu submicron precipitates. Under the cooling effect of the substrate and the indium tin bismuth lead alloy, the molten 7075 aluminum alloy is cooled at a rate of 5000 °C / s, which reduces the growth rate of the AlZnMgCu submicron precipitates. Finally, the AlZnMgCu submicron precipitates with an average size of 0.5 μm are refined and discontinuously distributed.

[0040] S3: Move the substrate down 1 mm into the indium tin bismuth lead alloy and perform online precise displacement control to keep the distance between the liquid surface of the indium tin bismuth lead alloy and the upper surface of the formed 7075 aluminum alloy solidified layer always at 40 mm.

[0041] S4: Repeat the forming process of the 7075 aluminum alloy melt in S2 and S3, allowing the 7075 aluminum alloy melt to continuously solidify and stack on the 7075 aluminum alloy solidified layer. By precisely controlling the downward movement distance of the substrate, ensure that the formed 7075 aluminum alloy solidified layer undergoes 40 thermal cycles before entering the indium tin bismuth lead alloy. The maximum temperature of the thermal cycles is maintained at 270℃ and the minimum temperature is maintained at 80℃, so that the MgZn nanoscale reinforcing phase with an average particle size of 9nm, coherent with the matrix, can be controllably dispersed and precipitated from the solidified alloy matrix; until the 7075 aluminum alloy billet of the required thickness is obtained.

[0042] Example 2:

[0043] S1: Fill the crucible of the casting equipment with molten 6061 aluminum alloy and maintain the temperature of the molten 6061 aluminum alloy at 800℃; fill the mold of the casting equipment with cooling water around and below, maintain the temperature of the cooling water at 50℃, and make the distance between the liquid level of the cooling water and the bottom of the mold 30mm.

[0044] S2: Molten 6061 aluminum alloy is ejected from the crucible outlet at a speed of 8000 mm / s and impacts the mold. A 2 mm thick solidified layer of 6061 aluminum alloy is formed by using an "open-close-...-open-close" outlet method. After the molten 6061 aluminum alloy impacts the bottom of the mold, it spreads rapidly. At the solid-liquid interface front of the spread molten 6061 aluminum alloy, there is a high-speed annular flow field formed by the impact of the molten 6061 aluminum alloy on the bottom of the mold. This allows the Mg2Si submicron precipitates to nucleate sufficiently and in large quantities. Under the cooling effect of the mold and cooling water, the molten 6061 aluminum alloy is cooled at a speed of 2000℃ / s, which reduces the growth rate of the Mg2Si submicron precipitates. Finally, the Mg2Si submicron precipitates with an average size of 0.9 μm are refined and discontinuously distributed.

[0045] S3: Move the mold down 2mm into the cooling water and perform online precise displacement control to keep the distance between the cooling water surface and the upper surface of the solidified 6061 aluminum alloy layer at 30mm.

[0046] S4: Repeat the forming process of the 6061 aluminum alloy melt in S2 and S3, allowing the 6061 aluminum alloy melt to continuously solidify and stack on the 6061 aluminum alloy solidified layer. By precisely controlling the downward movement distance of the mold, ensure that the formed 6061 aluminum alloy solidified layer undergoes 15 thermal cycles before entering the cooling water. The maximum temperature of the thermal cycles is maintained at 400℃ and the minimum temperature is maintained at 50℃, so that the β″ nanoscale reinforcing phase with an average particle size of 50nm, coherent with the matrix, can be controllably dispersed and precipitated from the solidified alloy matrix; until the 6061 aluminum alloy wheel hub is obtained.

[0047] Example 3:

[0048] S1: Fill the crucible of the casting equipment with copper-nickel-silicon alloy melt and maintain the temperature of the copper-nickel-silicon alloy melt at 1200℃; fill the area around and below the substrate of the casting equipment with gallium-indium-tin alloy, maintain the temperature of the gallium-indium-tin alloy at 200℃, and keep the distance between the liquid surface of the gallium-indium-tin alloy and the upper surface of the substrate at 20mm.

[0049] S2: The copper-nickel-silicon alloy melt is ejected from the crucible outlet at a speed of 7000 mm / s and impacts the substrate. An additive manufacturing method is used to form a 0.5 mm thick copper-nickel-silicon alloy solidified layer. After the copper-nickel-silicon alloy melt impacts the substrate surface, it spreads rapidly. At the solid-liquid interface front of the spread copper-nickel-silicon alloy melt, there is a high-speed annular flow field formed by the impact of the copper-nickel-silicon alloy melt on the substrate. This allows for the full and large-scale nucleation of Ni3Si submicron-sized precipitates. Under the cooling effect of the substrate and the gallium indium tin alloy, the copper-nickel-silicon alloy melt is cooled at a rate of 10000℃ / s, reducing the growth rate of the Ni3Si submicron-sized precipitates. This ultimately refines and discontinuously distributes the Ni3Si submicron-sized precipitates with an average size of 0.1 μm.

[0050] S3: Move the substrate down 0.5mm into the gallium indium tin alloy and perform online precise displacement control to keep the distance between the liquid surface of the gallium indium tin alloy and the upper surface of the formed copper nickel silicon alloy solidified layer always at 20mm.

[0051] S4: Repeat the forming process of the copper-nickel-silicon alloy melt in S2 and S3, allowing the copper-nickel-silicon alloy melt to continuously solidify and stack on the copper-nickel-silicon alloy solidified layer. By precisely controlling the substrate downward movement distance, ensure that the formed copper-nickel-silicon alloy solidified layer undergoes 40 thermal cycles before entering the gallium-indium-tin alloy. The maximum temperature of the thermal cycles is maintained at 500℃ and the minimum temperature is maintained at 200℃, so that the β″ nanoscale reinforcing phase with an average particle size of 2nm, coherent with the matrix, can be controllably dispersed and precipitated from the solidified alloy matrix; until the copper-nickel-silicon alloy lead frame is obtained.

[0052] Comparative Example 1:

[0053] The temperature of the 7075 aluminum alloy melt in the crucible was maintained at 730℃ by induction heating. Then, the 7075 aluminum alloy melt was directly poured into a water-cooled copper mold. The AlZnMgCu second phase of the 7075 aluminum alloy billet was finally prepared with an average size of 5μm and continuously distributed at the grain boundaries. After solidification at 470℃ for 2 hours and aging at 120℃ for 24 hours, the MgZn2 nanoscale strengthening phase with an average particle size of 100nm, which is incoherent with the matrix, was dispersed and precipitated.

[0054] The above are merely specific embodiments of the present invention, but the protection of the present invention is not limited thereto. Any equivalent variations or substitutions of the features of the present technical solution that can be conceived by those skilled in the art are covered within the protection scope of the present invention. The protection scope of the present invention should be determined by the scope of the claims.

Claims

1. A method for controlling the in-situ precipitation of multi-scale strengthening phases in alloys, characterized in that, Includes the following steps: Step 1: Fill the crucible of the casting equipment with molten 7075 aluminum alloy and fill the area around and below the substrate of the casting equipment with liquid cooling medium. Step 2: Molten 7075 aluminum alloy is ejected from the crucible outlet at a speed of 6000 mm / s and impacts the substrate. An additive manufacturing method is used to form a 1 mm thick solidified layer of 7075 aluminum alloy. After the molten 7075 aluminum alloy impacts the substrate surface, it spreads rapidly. At the solid-liquid interface front of the spread molten 7075 aluminum alloy, there is a high-speed annular flow field formed by the impact of the molten 7075 aluminum alloy on the substrate. This allows the AlZnMgCu submicron precipitates to nucleate sufficiently and in large quantities. Under the cooling effect of the substrate and the liquid cooling medium, the molten 7075 aluminum alloy is cooled at a rate of 5000ºC / s, which reduces the growth rate of the AlZnMgCu submicron precipitates. Ultimately, the AlZnMgCu submicron precipitates with an average size of 0.5μm are refined and discontinuously distributed. Step 3: Move the substrate 1 mm down into the liquid cooling medium and perform online precise displacement control to keep the distance between the liquid surface of the liquid cooling medium and the upper surface of the formed 7075 aluminum alloy solidified layer at 40 mm. Step 4: Repeat the forming process of the 7075 aluminum alloy melt in Steps 2 and 3, allowing the 7075 aluminum alloy melt to continuously solidify and stack on the 7075 aluminum alloy solidified layer; through precise control of the substrate downward movement distance, ensure that the formed 7075 aluminum alloy solidified layer undergoes 40 thermal cycles before entering the liquid cooling medium, with the highest temperature of the thermal cycles maintained at 270ºC and the lowest temperature maintained at 80ºC, so that the MgZn nanoscale reinforcing phase with an average particle size of 9 nm, coherent with the matrix, can be controllably dispersed and precipitated from the solidified alloy matrix; until a 7075 aluminum alloy billet of the required thickness is obtained.

2. The method for controlling in-situ precipitation of multi-scale strengthening phases in alloys according to claim 1, characterized in that, The substrate is a mold with a certain complex shape.

3. The method for controlling in-situ precipitation of multi-scale strengthening phases in alloys according to claim 1, characterized in that, The liquid cooling medium includes water or a low-melting-point alloy; the low-melting-point alloy has a melting point of 10~100 ºC and is at least one of gallium-indium alloy, gallium-indium-tin alloy, and indium-tin-bismuth-lead alloy.

4. An alloy casting, characterized in that, The alloy casting is prepared using the in-situ precipitation control method for multi-scale strengthening phases according to any one of claims 1 to 3.

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