Device and method for improving distribution uniformity of particles in metal-based composite material

Abstract

The invention discloses a device and a method for improving distribution uniformity of particles in a metal-based composite material, and a method for controlling fluidity of semi-solid slurry during semi-solid rheoforming, and relates to the field of preparation of metal-based composite materials and the field of metal semi-solid forming. The invention aims to solve the problems that particle distribution is not uniform when a metal-based composite material is prepared by a stirring casting method and the fluidity of semi-solid slurry is difficult to control when a large casting is prepared by a rheoforming technology. The device is composed of a crucible and a pore plate assembly, the pore plate assembly is formed by connecting a fixing rod and a pore plate, the outer edge of the pore plate is completely attached to the inner wall of the crucible, the pore plate assembly linearly reciprocates in the crucible through external pressure, and the liquid metal matrix composite or the semi-solid slurry continuously passes through small through holes in the pore plate. The method is mainly used for improving the uniformity of particle distribution in the metal-based composite material or controlling the fluidity of semi-solid slurry.

Description

Technical Field

[0001] The invention relates to the fields of preparation of metal matrix composite materials and semi-solid forming, and in particular to a process for preparing particle-reinforced metal matrix composite materials by a stirring casting method and a rheological forming process. Background Art

[0002] Metal-matrix composites (MMCs) are made of ceramics as reinforcements and metals as the matrix. Due to their exceptional physical and mechanical properties, such as high specific strength, specific modulus, wear resistance, low thermal expansion coefficient, and good dimensional stability, MMCs have experienced remarkable development over the past half century and have become a key area of ​​high-tech research and development worldwide. Particle-reinforced aluminum-matrix composites, characterized by their isotropy, high dimensional stability, diverse preparation methods, good machinability, and low cost, are widely used in high-end applications such as aerospace, automotive, and military industries.

[0003] The stirring casting method is a liquid-state method for preparing metal-based composite materials. It relies on vigorously stirring the alloy melt to form a vortex, and uses the negative pressure suction effect of the vortex to draw particles into the matrix alloy liquid. The advantages of this method are simple process, low equipment investment, high production efficiency, low manufacturing cost, and suitability for large-scale production. However, when preparing particle-reinforced metal-based composite materials using the stirring casting method, the particles tend to aggregate in the melt due to factors such as poor wettability between the particles and the melt and easy air absorption. When the composite melt is left to stand, there is a problem that high-density particles tend to settle to the bottom of the melt, while low-density particles tend to float to the surface of the melt. The uneven distribution of particles in the metal-based composite material can easily lead to unstable physical and mechanical properties of the same batch of composite materials. Therefore, whether the particles can be evenly distributed in the metal-based composite melt has become one of the key issues of metal-based composite materials, and a low-cost solution is urgently needed.

[0004] Semi-solid rheoforming is an advanced forming technology that lies between liquid casting and solid forging. Its core principle is to leverage the high atomic diffusion capacity and non-Newtonian fluid properties of alloys in the semi-solid phase (solid fraction 30%-60%) to achieve grain refinement and near-net-net shape, significantly improving the density and mechanical properties of castings. It is primarily used in magnesium and aluminum alloys. In recent years, semi-solid rheoforming has gradually shifted towards industrial application, particularly in the automotive, aerospace, and consumer electronics sectors, where lightweighting is a pressing need. However, the technology currently suffers from the following challenges: 1. Slurry preparation is difficult to control, resulting in uneven solid phase distribution, segregation or agglomeration, and a sharp decrease in fluidity with prolonged dwell time in the semi-solid temperature range. 2. Process equipment limitations, such as the tendency for mechanical stirring to entrain gases and the low stirring efficiency of electromagnetic stirring for highly conductive alloys. 3. Stirring coverage of large crucibles is difficult, due to poor melt fluidity in the crucible wall and bottom regions. Especially for large high-alloy ingots (diameter > 500mm) or integrated large die castings, when applying semi-solid rheoforming technology, how to control all aluminum alloys in the crucible to achieve uniform flow and no agglomeration within the semi-solid temperature range is one of the key issues and urgently needs a low-cost solution.

[0005] In view of the above technical problems, this application is specially filed. Summary of the Invention

[0006] The present invention aims to address the problems of uneven particle distribution in metal matrix composites produced by stir casting and the difficulty in controlling the fluidity of semi-solid slurries when producing large castings using rheoforming techniques. The present invention provides a device and method for improving the uniformity of particle distribution in metal matrix composites. The device can also be used to control the fluidity of semi-solid slurries during alloy rheoforming.

[0007] The implementation of the present invention can be achieved like this:

[0008] First, to improve the uniformity of particle distribution in a metal-based composite material, the present invention provides an inventive device comprising a crucible and an orifice plate assembly, wherein the shape and size of the crucible inner wall are consistent from top to bottom, and the orifice plate assembly comprises a fixing rod and an orifice plate connected by a nut; the orifice plate is inside the crucible, a portion of the fixing rod is inside the crucible, and another portion is outside the crucible, the outer edge of the orifice plate is completely in contact with the inner wall of the crucible, and the orifice plate assembly is capable of linear reciprocating motion in the crucible. Because the device has a simple structure, it is suitable for matching the appropriate crucible size according to the production batch, and the outer edge of the orifice plate should increase with the size of the crucible inner wall to ensure contact.

[0009] Preferably, the orifice plate of the device has small through holes evenly distributed, the center distance between every two small through holes is 1 to 4 mm, the aperture of the small through holes is 0.5 to 1.5 mm, and the thickness of the orifice plate is 5 to 10 mm.

[0010] Secondly, to improve the uniformity of particle distribution in a metal-matrix composite material, the present invention provides a method for improving the uniformity of particle distribution in a metal-matrix composite material. The method comprises placing a liquid or semi-solid metal-matrix composite melt into the crucible described herein, wherein the orifice plate assembly is subjected to linear reciprocating motion within the crucible, with the orifice plate always positioned below the liquid level of the metal-matrix composite melt. The liquid or semi-solid metal-matrix composite material continuously passes through small through-holes in the orifice plate, whereupon the metal-matrix composite melt forms turbulent flow within the small through-holes. After the process is completed, the orifice plate assembly is removed. Finally, the metal-matrix composite melt is cast into a part or into a billet for further forging, rolling, or extrusion.

[0011] Preferably, the speed of the linear reciprocating motion of the orifice plate assembly inside the crucible is 1 to 10 m / min.

[0012] On the third aspect, in response to the problem that it is difficult to control the fluidity of semi-solid slurry when preparing large castings using rheology molding technology, the present invention provides a method for controlling the fluidity of semi-solid slurry during rheology molding, the method comprising placing liquid alloy into the aforementioned crucible, then cooling the liquid alloy to a semi-solid temperature range to form a semi-solid slurry, then placing the aforementioned orifice plate assembly into the crucible, and utilizing external force to cause the orifice plate assembly to perform linear reciprocating motion, the orifice plate is always below the liquid level of the semi-solid slurry, the orifice plate travels from the bottom of the crucible to near the melt liquid surface, the semi-solid slurry continues to pass through the small through holes on the orifice plate, forming turbulence in the small through holes, and the linear reciprocating motion of the orifice plate assembly continues until the semi-solid slurry is cast.

[0013] The present invention improves the uniformity of particle distribution in metal-based composite materials by the following principle: an external force causes the orifice plate assembly to reciprocate linearly within the crucible. Under pressure, the melt rapidly passes through the small holes on the orifice plate, creating turbulent flow within the small holes. According to the volume flow formula Q = Av and the Reynolds number calculation formula Re = ρvd / μ, the melt flow rate Q1 through the orifice plate per unit time is equal to the flow rate Q2 that increases or decreases in the crucible. The sum of the cross-sectional areas A1 of all the orifice plates is less than the cross-sectional area A2 of the crucible's inner wall. Therefore, the melt flow rate v1 through the small holes is greater than the melt flow rate v2 within the crucible. d is the equivalent diameter of all the orifice plates, ρ is the density of the melt, and μ is the viscosity of the melt. When the Reynolds number Re is greater than 4000, the flow is turbulent. This invention transforms the aluminum alloy melt from laminar flow to micro-turbulent flow, thereby enhancing the mixing effect and achieving more uniform particle distribution.

[0014] The principle of controlling the fluidity of the semi-solid slurry in the present invention is as follows: the semi-solid slurry is a non-Newtonian fluid, and inputting energy into the semi-solid slurry can improve its fluidity. The present invention utilizes the mechanical energy of the orifice plate to input energy into the semi-solid slurry. The orifice plate can act on all parts inside the crucible, thereby improving the fluidity of all semi-solid slurries inside the crucible. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solution of the present invention, a brief description of the accompanying drawings is given below.

[0016] Figure 1 Schematic diagram of the structure of a device for improving the uniformity of particle distribution in metal matrix composites;

[0017] Figure 2 Schematic diagram of the structure of the orifice plate assembly;

[0018] Figure 3 For the use of SiC p Optical metallographic photograph of A356 aluminum matrix composite material, showing agglomeration of SiC particles;

[0019] Figure 4 For the use of SiC after the present invention p Optical metallographic photograph of A356 aluminum matrix composite material, showing a more uniform distribution of SiC particles.

[0020] Icon: 1-well plate assembly; 2-crucible. DETAILED DESCRIPTION

[0021] Example 1

[0022] This embodiment provides a device for improving the uniformity of particle distribution in a metal matrix composite material. The structure is as follows: Figure 1 As shown, the device consists of a crucible and a hole plate assembly. The shape and size of the inner wall of the crucible are consistent from top to bottom. The hole plate assembly consists of a fixed rod and a hole plate connected by nuts, as shown in FIG. Figure 2 As shown, the orifice plate is inside the crucible, with a portion of the fixing rod inside and the other portion outside. The outer edge of the orifice plate fits perfectly against the inner wall of the crucible, allowing the orifice plate assembly to perform linear reciprocating motion within the crucible. The orifice plate has evenly distributed small through-holes, with a center-to-center spacing of 4mm between each two small through-holes and a diameter of 1mm. The orifice plate is 5mm thick, and the inner wall of the crucible is cylindrical with an inner diameter of 40mm. The outer edge of the orifice plate has a diameter of 39mm and is chamfered to facilitate movement.

[0023] Example 2

[0024] This embodiment provides a method for improving the uniformity of particle distribution in a metal matrix composite material by mixing liquid or semi-solid SiC pThe A356 composite material is placed in the crucible described in Example 1. The orifice plate assembly described in Example 1 is linearly reciprocated within the crucible at a speed of 10 m / min. The orifice plate is always below the liquid level of the metal matrix composite melt. The liquid or semi-solid metal matrix composite material continuously passes through the small through-holes in the orifice plate, where the metal matrix composite melt forms turbulent flow. After the process is completed, the orifice plate assembly is removed. Finally, the metal matrix composite melt is cast into parts or billets for further forging, rolling, or extrusion. Figure 3 and Figure 4 SiC before and after using this method p Optical metallographic photograph of the PTFE / A356 composite material shows that the SiC particles are more evenly distributed on the matrix after using the present invention.

[0025] Example 3

[0026] This embodiment provides a method for controlling the fluidity of semi-solid slurry during rheological molding. The device consists of a crucible and a perforated plate assembly, and its structure is as follows: Figure 1 As shown, the shape and size of the inner wall of the crucible are consistent from top to bottom, and the orifice plate assembly is composed of a fixed rod and an orifice plate connected by nuts, as shown in FIG. Figure 2 As shown, the orifice plate is inside the crucible, with one portion of the fixing rod inside and the other outside. The outer edge of the orifice plate fits perfectly against the inner wall of the crucible, allowing the orifice plate assembly to perform linear reciprocating motion within the crucible under external force. The orifice plate has evenly distributed small through-holes, with a center-to-center spacing of 4mm between each two small through-holes and a diameter of 1.5mm. The orifice plate is 5mm thick, and the inner wall of the crucible is cylindrical with an inner diameter of 40mm. The outer edge of the orifice plate has a diameter of 39mm and is chamfered to facilitate movement. A356 liquid alloy is placed in the crucible, then cooled to 590°C, within the semi-solid temperature range, to form a semi-solid slurry. The orifice plate assembly is then placed in the crucible and, using external force, causes the orifice plate assembly to perform linear reciprocating motion at a speed of 1 m / min. The orifice plate is always below the liquid level of the semi-solid slurry, traveling from the bottom of the crucible to near the melt surface. The semi-solid slurry continuously passes through the small through-holes in the orifice plate, creating turbulent flow in the small through-holes. This linear reciprocating motion of the orifice plate assembly continues until the semi-solid slurry is cast. The present invention maintains a well-flowing state for all semi-solid slurries in the crucible.

Claims

1. A device for improving the uniformity of particle distribution in a metal matrix composite material, characterized in that: The device consists of a crucible and a orifice plate assembly. The shape and size of the inner wall of the crucible are consistent from top to bottom. The orifice plate assembly is composed of a fixed rod and an orifice plate connected together. The orifice plate is inside the crucible, part of the fixed rod is inside the crucible, and the other part is outside the crucible. The outer edge of the orifice plate is completely fitted with the inner wall of the crucible, and the orifice plate assembly can perform linear reciprocating motion in the crucible.

2. The device for improving the uniformity of particle distribution in a metal matrix composite material according to claim 1, wherein: Small through holes are evenly distributed on the orifice plate of the device, the center distance between every two small through holes is 1 to 4 mm, the aperture of the small through holes is 0.5 to 1.5 mm, and the thickness of the orifice plate is 5 to 10 mm.

3. A method for improving the uniformity of particle distribution in a metal matrix composite material, characterized in that: A liquid or semi-solid metal-based composite material melt is placed into the crucible as described in claim 1, and then the orifice plate assembly as described in claim 1 moves back and forth linearly inside the crucible, and the orifice plate is always below the liquid level of the metal-based composite material melt. The liquid or semi-solid metal-based composite material continuously passes through the small through holes on the orifice plate, and the metal-based composite material melt forms turbulence in the small through holes. After the treatment is completed, the orifice plate assembly is removed.

4. A method for improving the uniformity of particle distribution in a metal matrix composite material according to claim 3, characterized in that: The speed of the linear reciprocating motion of the orifice plate assembly inside the crucible is 1 to 10 m / min.

5. A method for controlling the fluidity of a semi-solid slurry during semi-solid rheological molding, characterized in that: The liquid alloy is placed in the crucible as described in claim 1, and then the liquid alloy is cooled to a semi-solid temperature range to form a semi-solid slurry. Subsequently, the orifice plate assembly as described in claim 1 is placed inside the crucible, and an external force is used to make the orifice plate assembly perform linear reciprocating motion. The orifice plate is always below the liquid level of the semi-solid slurry. The stroke of the orifice plate is from the bottom of the crucible to near the melt liquid level. The semi-solid slurry continues to pass through the small through holes on the orifice plate, forming turbulence in the small through holes. The linear reciprocating motion of the orifice plate assembly continues until the semi-solid slurry is cast.

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