Stirring method for optimizing aluminum alloy microstructure and stirring head and stirring device used by stirring method

Abstract

The invention provides a stirring method for optimizing an aluminum alloy microstructure and a stirring head and a stirring device used in the stirring method, the face, making contact with a stirring needle, of a shaft shoulder is a bottom face, the edge of the bottom face of the shaft shoulder is circular, and the diameter of the circle of the bottom face is marked as L1; the surface, close to the shaft shoulder, of the stirring needle is an upper surface, the working radius formed by the upper surface of the stirring needle during operation is marked as an upper surface circumcircle, the diameter of the upper surface circumcircle is marked as L2, and the ratio of L1 to L2 is (2-3): 1; the stirring needle is of a conical table structure, and the diameter of a circumcircle of the cross section of the conical table structure is gradually reduced in the direction from the position close to the shaft shoulder to the position away from the shaft shoulder. According to the invention, the problem of poor processing performance of the aluminum alloy caused by a thick Al2Cu brittle phase in the casting process of the high-Cu-content aluminum alloy can be solved.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloy manufacturing, and in particular to a stirring method for optimizing the microstructure of an aluminum alloy and a stirring head and a stirring device used therein. Background Art

[0002] Low melting point aluminum silicon brazing filler metal is widely used in aluminum alloy brazing due to its good wettability, fluidity, machinability and corrosion resistance of brazed joints. The development of low melting point aluminum-based brazing filler metal has been a problem that has plagued the industry for decades. The low melting point means that brazing operations can be performed at relatively low temperatures. This is crucial for many heat-sensitive materials, as it can reduce the extent of thermal deformation and heat-affected zones and avoid damage to the properties of the parent material due to high-temperature welding. At the same time, lower welding temperatures can shorten heating and cooling times, thereby improving production efficiency. This advantage is particularly evident in large-scale production industries such as automobile manufacturing and electronic equipment production.

[0003] By adding alloying elements such as Cu, Si, Ni and rare earth elements to Al-Si based solder, the melting temperature of the solder can be reduced. Studies have found that the effect of Cu on reducing the liquidus temperature is more significant, and the order of influence of each element content on the liquidus temperature of the solder is Cu, Ni, Si, and Re. Through a large number of experiments and analyses, researchers have continuously optimized the formula of low-melting-point aluminum-silicon solder to obtain a solder with a lower melting point, a narrower melting temperature range, better brazing performance and higher joint strength.

[0004] At present, Al-Si alloy with high copper content is the mainstream alloy. For example, the Al-Si-Cu-Ni-Re brazing filler metal developed by (reference basis) mainly consists of α (Al) phase, Si phase, θ (Al2Cu) phase, and the distribution of phase components changes with the addition of alloy elements. Among them, the melting point of Al-8.5Si-25Cu-1Ni-0.45Re brazing filler metal is 530.15℃, which has the characteristics of low melting point, narrow melting temperature range, good brazing performance and high joint strength, and is suitable for 6063 aluminum alloy brazing.

[0005] However, during the casting process of this high copper content Al-Si alloy, a large amount of concentrated and coarse Al2Cu brittle phase will inevitably be produced, resulting in extremely poor processing performance of the alloy. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a stirring method for optimizing the microstructure of aluminum alloy and a stirring head and a stirring device used therein, which can solve the problem in the prior art that due to the high content of alloying elements in the high-copper content Al-Si alloy, the coarse Al2Cu brittle phase in the material leads to a decrease in machinability, and provides a method for refining the coarse Al2Cu brittle phase.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In the first aspect, the present invention provides a stirring head for a stirring device for optimizing the microstructure of aluminum alloy, the stirring head comprising a stirring needle and a shoulder arranged on the stirring needle, the side of the shoulder contacting the stirring needle is a bottom surface, the edge of the bottom surface of the shoulder is circular, and the circular diameter of the bottom surface is denoted as L1; the side of the stirring needle close to the shoulder is an upper surface, the working radius formed by the upper surface of the stirring needle during operation is denoted as an upper surface circumscribed circle, and the diameter of the upper surface circumscribed circle is denoted as L2, wherein the ratio of L1 to L2 is 2 to 3:1, for example, it can be 2:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1 or 3:1, etc.

[0009] The invention mechanism of the present invention is to use the friction stir welding technology in non-welding usage scenarios and improve the stirring head of the common friction stir welding device to solve the technical problems faced by the prior art. When the friction stir welding device has a high-speed rotating stirring head with a certain initial temperature, when the stirring head rotates semi-solidly on the surface of the material, the material in the stirring zone undergoes severe plastic deformation, so that the coarse Al2Cu brittle phase is split into fine phases.

[0010] The effective contact area between the shoulder and the sample to be processed is the largest. The heat generated by the mutual friction is an important source of heat for softening the sample. At the same time, the shoulder is also used to press the workpiece to prevent the overflow of the plastic material. The stirring needle is used to insert the material, and through rotation, the material flows, the microstructure is changed, and a small amount of heat is generated through friction to soften the material. The larger the ratio of the shoulder diameter to the diameter of the upper surface of the stirring needle, the greater the heat generated; if the shoulder diameter is too small, the heat input is insufficient, resulting in insufficient heating of the sample and plastic deformation, so that holes are formed in the stirring zone, and the stirring friction improvement fails; in the actual operation process, heat control is crucial. If the shoulder diameter is too large and the heat input is too high, it will trigger the secondary growth of the Al2Cu brittle phase, resulting in uneven hardness inside the sample.

[0011] It should be noted that the three-dimensional structure of the shoulder is not specifically required or limited in the present invention, and it is sufficient to achieve the compression of the aluminum alloy plate. The bottom surface of the shoulder, that is, the side that contacts the stirring needle, has a circular edge shape. The side of the shoulder of the existing stirring friction device that contacts the stirring needle usually needs to be set with a circular edge to ensure that the heat-softened zone is always under the pressure of the shoulder during the stirring process. Otherwise, during the processing, the heat-softened zone is easy to flow to the edge of the shoulder, causing serious material loss and flash. The present invention does not limit the bottom surface of the shoulder to be a plane or a non-plane, and those skilled in the art can refer to the existing design methods and intentions of the stirring friction device for adjustment.

[0012] As a preferred technical solution, the stirring needle is a conical structure, and the diameter of the circumscribed circle of the cross section of the conical structure gradually decreases from close to the shaft shoulder to away from the shaft shoulder.

[0013] The stirring needle has a conical table structure. This conical table, which is wide at the top and narrow at the bottom, allows the material to be gradually stirred and mixed along the conical surface during stirring. Compared with a cylindrical stirring needle, the material in the processing area will also be subject to the downward pressure of the conical surface, resulting in longitudinal movement, which can better refine the large-sized Al2Cu phase.

[0014] As a preferred technical solution, the side of the stirring needle away from the shaft shoulder is recorded as the lower surface, the working radius formed by the lower surface of the stirring needle during operation is recorded as the circumscribed circle of the lower surface, the diameter corresponding to the circumscribed circle of the lower surface is recorded as L3, and the ratio of L2 to L3 is 1.4 to 1.8:1. For example, it can be 1.4:1, 1.45:1, 1.49:1, 1.54:1, 1.58:1, 1.63:1, 1.67:1, 1.72:1, 1.76:1 or 1.8:1, etc.

[0015] The present invention sets the ratio of L2 to L3 within the above range. When the ratio of L2 to L3 is too large, a vortex is easily formed during the stirring process, and the vortex will draw in air, leaving defects such as holes in the material. When the ratio of L2 to L3 is too small, the stirring needle is close to the same width at the top and bottom, the longitudinal flow effect of the material is weakened, and the refinement effect is reduced.

[0016] In a specific embodiment, the size of the stirring head can be set as follows: L3 of the stirring needle is 5 mm, L2 is 9 mm, the height is 9.5 mm, and L1 of the shoulder is 18 mm. This size is suitable for processing samples with a plate thickness of 10-12 mm. The present invention does not limit the size of the stirring head as long as it matches the appropriate plate thickness.

[0017] As a preferred technical solution, any cross section of the stirring needle is a polygon, and the number of sides of the polygon is 3 to 8, for example, 3, 4, 5, 6, 7 or 8. When the number of sides is greater than 8, its cross section is close to a circle, the flow is insufficient, and the refinement effect is reduced.

[0018] As a preferred technical solution, the polygon is a curved-edge polygon, and the sides of the curved-edge polygon are arc-shaped curved sides.

[0019] Preferably, the arc-shaped curved edge protrudes toward the center direction of the polygon, and the central angle corresponding to the arc-shaped curved edge is 30° to 90°, for example, it can be 30°, 37°, 44°, 50°, 57°, 64°, 70°, 77°, 84° or 90°, etc.

[0020] The side length of the stirring needle of the present invention is concave, and the concave design increases the complexity of the stirring needle, increases the side area, and increases the contact area between the stirring needle and the material, so that the stirring needle can produce a stronger stirring effect on the material during the rotation process, enhances the stirring effect and the refinement effect, and makes the Al2Cu phase more refined. The present invention sets the center angle corresponding to the arc curve within the above range. When the center angle is too large, the stirring resistance is large and the processing cannot be carried out; when the center angle is too small, the arc of the curved edge is too small, close to a straight edge, and the refinement effect is not good.

[0021] As a preferred technical solution, the apex angles of the polygon are evenly distributed on the circumscribed circle corresponding to the working radius of the polygon. When the apex angles of the polygon are unevenly distributed or one or more apex angles are within the circumscribed circle, there is a problem of insufficient refinement of large-sized Al2Cu phases.

[0022] In a second aspect, the present invention provides a stirring device for optimizing the microstructure of aluminum alloy, wherein the stirring device comprises a driving system, a clamp, a body and a control system, and the stirring device also comprises the stirring head described in the first aspect.

[0023] The drive system in the present invention is used to provide the power for the rotation of the mixing head and the relative movement of the mixing head relative to the plate to be processed, including a motor, a reducer and a transmission shaft. The control system is used to control the operating parameters, such as the forward speed v and the rotation speed ω of the mixing head. The fixture is used to fix the workpiece to ensure that the workpiece does not move or deform during the mixing process. The fuselage is the main structure, which is used to support and install other components.

[0024] In a third aspect, a stirring method for optimizing the microstructure of an aluminum alloy is provided, which is performed using a friction stir welding device.

[0025] Preferably, the stirring method is carried out using the stirring device for optimizing the microstructure of the aluminum alloy described in the second aspect.

[0026] Preferably, the stirring method comprises:

[0027] The stirring needle is arranged to be perpendicular to the surface of the aluminum alloy plate and vertically inserted into the aluminum alloy plate, and the shaft shoulder is arranged to contact the upper surface of the aluminum alloy plate and press the aluminum alloy plate.

[0028] The stirring device is started to make the stirring head move back and forth along the longitudinal direction of the aluminum alloy plate, wherein the stirring belts formed by two adjacent working paths are connected to each other until the entire aluminum alloy plate is processed;

[0029] Wherein, in terms of mass percentage, the Cu content in the aluminum alloy sheet is ≥10wt%, and the aluminum alloy sheet contains an Al2Cu brittle phase with an average equivalent circular diameter ≥25μm.

[0030] There is a ternary eutectic point in the Al-Si-Cu ternary system, and its eutectic temperature is 524°C. It is often used as an aluminum-based low-melting point solder and is widely studied. The present invention is suitable for solving the coarse Al2Cu brittle phase of Al-Si-Cu system aluminum alloy materials with a Cu content greater than or equal to 10wt%. When the Cu content in the system is greater than or equal to 10wt%, a large number of network-aggregated Al2Cu brittle phases will be formed, and there will be Al2Cu phases with an average equivalent circular diameter of ≥25μm inside the plate. Such large-sized Al2Cu phases are the source of the brittleness of the material. The formation of network-distributed Al2Cu makes the ingot plasticity poor, the rolling process is difficult to carry out, and the forming rate is low. The inventor found that this network-aggregated second phase can be significantly refined after stir friction treatment.

[0031] Moreover, when the Cu content in the system is less than 10wt% and greater than or equal to 2wt%, a massive Al2Cu phase will be formed in the system and distributed between α-Al dendrites. The refinement effect of this massive Al2Cu phase during the stirring process is not obvious. When the Cu content is less than 2wt%, the Cu in the system exists in the form of solid solution in the Al matrix, and there is no Al2Cu phase that needs to be refined.

[0032] In the present invention, the stirring zones formed by two adjacent working paths are connected to each other, that is, there is no gap between the stirring zones.

[0033] Specifically, measured in percentage by mass, the Cu content in the aluminum alloy plate is ≥10wt%, for example, it may be 10wt%, 10.7wt%, 11.4wt%, 12wt%, 12.7wt%, 13.4wt%, 14wt%, 14.7wt%, 15.4wt% or 16wt%, etc.

[0034] The aluminum alloy sheet contains an Al2Cu brittle phase with an average equivalent circular diameter ≥25 μm, for example, it can be 25 μm, 27 μm, 28 μm, 29 μm, 30 μm, 31 μm, 32 μm, 33 μm, 34 μm or 35 μm.

[0035] Preferably, the ratio v / ω of the forward speed v of the stirring head to the rotational speed ω is greater than or equal to 0.13, for example, it can be 0.13, 0.16, 0.19, 0.22, 0.25, 0.27, 0.3, 0.33, 0.36 or 0.37, etc.

[0036] When the ratio of forward speed to rotation speed v / ω is less than 0.13, the excessive heat input caused by the high rotation speed leads to the secondary growth of Al2Cu brittle phase, resulting in no improvement in the material's formability.

[0037] Preferably, the ratio v / ω of the forward speed v of the stirring head to the rotational speed ω is less than or equal to 0.37, for example, it can be 0.13, 0.16, 0.19, 0.22, 0.25, 0.27, 0.3, 0.33, 0.36 or 0.37, etc.

[0038] When the ratio of forward speed to rotation speed v / ω is greater than 0.37, the Al2Cu phase is not sufficiently refined because the forward speed is too fast and the rotation speed is too low.

[0039] The length of the stirring needle of the present invention should be determined according to the thickness of the plate to be treated so that the stirring needle can almost penetrate the plate to be treated, and the almost penetration means that it is not actually penetrated, but there is still 0.5-1mm remaining from the bottom, that is, the distance between the bottom of the stirring needle and the bottom of the aluminum alloy plate is 0.5~1mm, for example, it can be 0.5mm, 0.56mm, 0.62mm, 0.67mm, 0.73mm, 0.78mm, 0.84mm, 0.89mm, 0.95mm or 1mm, etc.

[0040] Those skilled in the art will appreciate that the aluminum alloy plate is a square plate, that is, the plate made of the high copper content Al-Si alloy of the present invention suitable for conventional friction stir processing devices is usually required to be a square plate, not a special-shaped plate.

[0041] As a preferred technical solution of the present invention, the stirring method comprises:

[0042] Step 1: Prepare a square aluminum alloy plate, wherein the Cu content in the aluminum alloy plate is ≥10wt%, and the aluminum alloy plate contains an Al2Cu brittle phase with an average equivalent circular diameter of ≥25μm.

[0043] Step 2: Setting the processing parameters on the control system, that is, setting the ratio of the forward speed v and the rotation speed ω of the stirring device.

[0044] Step 3: Fix the plate to be processed with a clamp.

[0045] Step 4: Adjust the position of the stirring head so that it is perpendicular to the surface of the plate, and vertically insert it into the aluminum alloy plate, and the shoulder is in contact with the upper surface of the aluminum alloy plate to press the aluminum alloy plate.

[0046] Step 5: Start the stirring device to make the stirring head move back and forth along the longitudinal direction of the aluminum alloy plate, wherein the stirring belts formed by two adjacent working paths are connected to each other until the entire aluminum alloy plate is processed.

[0047] Step 6: After the processing is completed, the upper and lower surfaces are milled off by 1-3 mm respectively to obtain a high copper content Al-Si alloy with refined phase size.

[0048] Compared with the prior art, the present invention has at least the following beneficial effects:

[0049] (1) The stirring head for a stirring device for optimizing the microstructure of aluminum alloy provided by the present invention, when performing semi-solid rotation on the surface of the material, the material in the stirring zone undergoes severe plastic deformation, so that the coarse Al2Cu brittle phase is split into fine phases, wherein for high copper content, the equivalent circle diameter of the Al2Cu phase is reduced from more than 25 μm to within 5.0 μm, preferably, to within 3.0 μm;

[0050] (2) The stirring method for optimizing the microstructure of aluminum alloy provided by the present invention can significantly reduce the peak stress of high copper content Al-Si alloy during hot compression by more than 18% compared with that before treatment, preferably, by more than 30%. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a three-dimensional schematic diagram of a stirring head for a stirring device for optimizing the microstructure of an aluminum alloy provided in a specific embodiment of the present invention.

[0052] Figure 2 It is a front view of a stirring head for a stirring device for optimizing the microstructure of aluminum alloy provided in a specific embodiment of the present invention.

[0053] Figure 3 It is a top view of a stirring needle used in a stirring device for optimizing the microstructure of aluminum alloy provided in a specific embodiment of the present invention.

[0054] Figure 4 It is a schematic diagram of a stirring device for optimizing the microstructure of aluminum alloy provided in a specific embodiment of the present invention.

[0055] Figure 5 It is a schematic diagram of the operation of a stirring head on an aluminum alloy plate in a stirring device for optimizing the microstructure of an aluminum alloy provided in a specific embodiment of the present invention.

[0056] Figure 6 It is a top view of a stirring needle used in a stirring device for optimizing the microstructure of aluminum alloy provided in Example 4 of the present invention.

[0057] In the figure: 1. stirring head; 1-1. stirring needle; 1-2. shoulder; 2. driving system; 3. control system; 4. fixture; 5. body; 6. aluminum alloy plate. DETAILED DESCRIPTION

[0058] For the convenience of understanding the present invention, the present invention lists the following embodiments. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0059] It should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "disposed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0060] Test method:

[0061] 1. Peak stress: The peak stress of the material is measured using a thermal simulation test machine, and an isothermal compression test is carried out at 450°C and a strain rate of 0.1s-1.

[0062] 2. Equivalent circle diameter of Al2Cu phase: Backscattered electron images were taken using a scanning electron microscope, and size analysis was performed using ImagePro plus.

[0063] The present invention provides a stirring head 1 for a stirring device for optimizing the microstructure of an aluminum alloy, see Figure 1-2 The stirring head 1 includes a stirring needle 1-1 and a shoulder 1-2 arranged on the stirring needle 1-1.

[0064] See also Figure 2The stirring head 1 includes a stirring needle 1-1 and a shoulder 1-2 arranged on the stirring needle 1-1, the side of the shoulder 1-2 contacting the stirring needle 1-1 is the bottom surface, the edge of the bottom surface of the shoulder 1-2 is circular, and the circular diameter of the bottom surface is recorded as L1; the side of the stirring needle 1-1 close to the shoulder 1-2 is the upper surface, the working radius formed by the upper surface of the stirring needle 1-1 during operation is recorded as the upper surface circumscribed circle, and the diameter of the upper surface circumscribed circle is recorded as L2, wherein the ratio of L1 to L2 is 2 to 3:1.

[0065] See also Figure 2 The stirring needle 1-1 is a conical structure, and the diameter of the circumscribed circle of the cross section of the conical structure gradually decreases from the direction close to the shoulder 1-2 to the direction away from the shoulder 1-2. The side of the stirring needle 1-1 away from the shoulder 1-2 is recorded as the lower surface, and the working radius formed by the lower surface of the stirring needle 1-1 during operation is recorded as the circumscribed circle of the lower surface. The diameter corresponding to the circumscribed circle of the lower surface is recorded as L3, and the ratio of L2 to L3 is 1.4 to 1.8:1.

[0066] See also Figure 3 , any cross section of the stirring needle 1-1 is a polygon, and the number of sides of the polygon is 3 to 8. The polygon is a curved polygon, and the side of the curved polygon is an arc-shaped curved side ( Figure 3 The curved side of the arc is convex toward the center of the polygon, and the central angle of the curved side is 30° to 90°. The vertex angles of the polygon are evenly distributed on the circumscribed circle corresponding to the working radius of the polygon.

[0067] Generally speaking, the central angles of the curved edges of the curved polygons on the lower and upper surfaces of the stirring needle 1 - 1 are the same.

[0068] The present invention provides a stirring device for optimizing the microstructure of aluminum alloy. The stirring device comprises a driving system, a clamp, a body and a control system. The stirring device also comprises the stirring head mentioned above.

[0069] It should be noted that there is no special restriction on the specific structure of the drive system, clamp, body and control system in the stirring device in the following embodiments and comparative examples, wherein the drive system can provide the stirring head with rotational motion and power for relative motion relative to the plate to be processed; the clamp can fix the aluminum alloy plate to ensure that it does not move or deform during the stirring process; the body can be used to support and install the drive system, clamp, control system and stirring head; the control system can set and control the stirring parameters of the stirring head and the running path of the stirring head.

[0070] Optionally, refer to Figure 4, the control system 3 includes a computer processing system connected to the drive system 2 through an electrical signal; the drive system 2 includes a motor, a reducer and a transmission shaft, the transmission shaft is connected to the stirring head 1, wherein the shoulder 1-2 is arranged close to the motor. The fixture 4 includes a first plate and a second plate arranged in a stacked manner, and a groove for fixing the aluminum alloy plate 6 is arranged inside the first plate. The fuselage 5 can be used to support and install the drive system, the fixture 4, the control system and the stirring head, for example, including a first bracket connected to the drive system, and a second bracket for supporting the fixture 4.

[0071] The present invention also provides a stirring method for optimizing the microstructure of an aluminum alloy, wherein the stirring method is performed using the stirring device for optimizing the microstructure of an aluminum alloy, and the stirring method comprises:

[0072] Step 1: Prepare a square aluminum alloy plate, wherein the Cu content in the aluminum alloy plate is ≥10wt%, and the aluminum alloy plate contains an Al2Cu brittle phase with an average equivalent circular diameter of ≥25μm.

[0073] Step 2: Setting the processing parameters on the control system, that is, setting the ratio of the forward speed v to the rotation speed ω of the stirring device to be greater than or equal to 0.13 and less than or equal to 0.37.

[0074] Step 3: Fix the plate to be processed with a clamp.

[0075] Step 4: Adjust the position of the stirring head so that it is perpendicular to the surface of the plate, and insert it vertically into the aluminum alloy plate, and the shoulder is in contact with the upper surface of the aluminum alloy plate and presses the aluminum alloy plate. The distance between the bottom of the stirring needle and the bottom of the aluminum alloy plate is 0.5 to 1 mm.

[0076] Step 5: Start the stirring device and make the stirring head move back and forth along the longitudinal direction of the aluminum alloy plate. Figure 5 The stirring zones formed by two adjacent working paths are connected to each other until the entire aluminum alloy plate is processed.

[0077] Step 6: After the processing is completed, the upper and lower surfaces are milled off by 1-3 mm respectively to obtain a high copper content Al-Si alloy with refined phase size.

[0078] The following is a detailed description with specific embodiments, comparative examples and application examples.

[0079] Example 1

[0080] This embodiment provides a stirring device for optimizing the microstructure of aluminum alloy, the stirring device includes a driving system, a clamp, a body and a control system, the stirring device also includes a stirring head, the stirring head includes a stirring needle and a shoulder arranged on the stirring needle.

[0081] The stirring head includes a stirring needle and a shoulder arranged on the stirring needle, the side of the shoulder contacting the stirring needle is the bottom surface, the edge of the bottom surface of the shoulder is circular, the circular diameter of the bottom surface is denoted by L1, L1=18mm; the side of the stirring needle close to the shoulder is the upper surface, the working radius formed by the upper surface of the stirring needle during operation is denoted by the upper surface circumscribed circle, the diameter of the upper surface circumscribed circle is denoted by L2, L2=9mm, wherein the ratio of L1 to L2 is 2:1.

[0082] The stirring needle is a conical structure, the height of the stirring needle is 9.2mm, and the diameter of the circumscribed circle of the cross section of the conical structure gradually decreases from the direction close to the shaft shoulder to the direction away from the shaft shoulder. The side of the stirring needle away from the shaft shoulder is recorded as the lower surface, and the working radius formed by the lower surface of the stirring needle during operation is recorded as the circumscribed circle of the lower surface. The diameter corresponding to the circumscribed circle of the lower surface is recorded as L3, L3=5mm, and the ratio of L2 to L3 is 1.8:1.

[0083] Any cross section of the stirring needle is a polygon, and the number of sides of the polygon is 5. The polygon is a curved polygon, and the side of the curved polygon is an arc-shaped curved side. The arc-shaped curved side protrudes toward the center of the polygon, and the central angle corresponding to the arc-shaped curved side is 60°. The vertex angles of the polygon are evenly distributed on the circumscribed circle corresponding to the working radius of the polygon.

[0084] Example 2

[0085] The present embodiment provides a stirring device for optimizing the microstructure of aluminum alloy, the stirring device comprising a driving system, a clamp, a body and a control system, the stirring device also comprising a stirring head, the stirring head comprising a stirring needle and a shoulder arranged on the stirring needle.

[0086] The stirring head includes a stirring needle and a shoulder arranged on the stirring needle, the side of the shoulder contacting the stirring needle is the bottom surface, the edge of the bottom surface of the shoulder is circular, the circular diameter of the bottom surface is denoted by L1, L1=21mm; the side of the stirring needle close to the shoulder is the upper surface, the working radius formed by the upper surface of the stirring needle during operation is denoted by the upper surface circumscribed circle, the diameter of the upper surface circumscribed circle is denoted by L2, L2=7mm, wherein the ratio of L1 to L2 is 3:1.

[0087] The stirring needle is a conical structure, the height of the stirring needle is 12mm, and the diameter of the circumscribed circle of the cross section of the conical structure gradually decreases from the direction close to the shaft shoulder to the direction away from the shaft shoulder. The side of the stirring needle away from the shaft shoulder is recorded as the lower surface, and the working radius formed by the lower surface of the stirring needle during operation is recorded as the circumscribed circle of the lower surface. The diameter corresponding to the circumscribed circle of the lower surface is recorded as L3, L3=5mm, and the ratio of L2 to L3 is 1.4:1.

[0088] Any cross section of the stirring needle is a polygon, and the number of sides of the polygon is 3. The polygon is a curved polygon, and the side of the curved polygon is an arc-shaped curved side. The arc-shaped curved side protrudes toward the center of the polygon, and the central angle corresponding to the arc-shaped curved side is 90°. The vertex angles of the polygon are evenly distributed on the circumscribed circle corresponding to the working radius of the polygon.

[0089] Example 3

[0090] This embodiment provides a stirring device for optimizing the microstructure of aluminum alloy, the stirring device comprising a driving system, a clamp, a body and a control system, the stirring device also comprising a stirring head, the stirring head comprising a stirring needle and a shoulder arranged on the stirring needle.

[0091] The stirring head includes a stirring needle and a shoulder arranged on the stirring needle, the side of the shoulder contacting the stirring needle is the bottom surface, the edge of the bottom surface of the shoulder is circular, the circular diameter of the bottom surface is denoted by L1, L1=30mm; the side of the stirring needle close to the shoulder is the upper surface, the working radius formed by the upper surface of the stirring needle during operation is denoted by the upper surface circumscribed circle, the diameter of the upper surface circumscribed circle is denoted by L2, L2=10mm, wherein the ratio of L1 to L2 is 3:1.

[0092] The stirring needle is a conical structure, the height of the stirring needle is 10.5mm, and the diameter of the circumscribed circle of the cross section of the conical structure gradually decreases from the direction close to the shaft shoulder to the direction away from the shaft shoulder. The side of the stirring needle away from the shaft shoulder is recorded as the lower surface, and the working radius formed by the lower surface of the stirring needle during operation is recorded as the circumscribed circle of the lower surface. The diameter corresponding to the circumscribed circle of the lower surface is recorded as L3, L3=6mm, and the ratio of L2 to L3 is 1.7:1.

[0093] Any cross section of the stirring needle is a polygon, and the number of sides of the polygon is 8. The polygon is a curved polygon, and the side of the curved polygon is an arc-shaped curved side. The arc-shaped curved side protrudes toward the center of the polygon, and the central angle corresponding to the arc-shaped curved side is 30°. The vertex angles of the polygon are evenly distributed on the circumscribed circle corresponding to the working radius of the polygon.

[0094] Example 4

[0095] This embodiment provides a stirring device for optimizing the microstructure of aluminum alloy. Figure 6 , compared with Example 1, the difference is that the vertex angles of the polygon are not evenly distributed on the circumscribed circle corresponding to the working radius of the polygon, one of the five vertex angles of the polygon is distributed inside the circumscribed circle, and the angles between the lines connecting the five vertex angles and the center of the circumscribed circle are 73°, 68°, 74°, 70° and 75° respectively. The rest is exactly the same as Example 1.

[0096] Example 5

[0097] This embodiment provides a stirring device for optimizing the microstructure of aluminum alloy. Compared with Embodiment 1, the difference is that the central angle corresponding to the arc-shaped curved edge is 20°, and the rest is exactly the same as Embodiment 1.

[0098] Example 6

[0099] This embodiment provides a stirring device for optimizing the microstructure of aluminum alloy. Compared with Embodiment 1, the difference is that the number of sides of the polygon is 10, and the rest is exactly the same as Embodiment 1.

[0100] Example 7

[0101] This embodiment provides a stirring device for optimizing the microstructure of aluminum alloy. Compared with Embodiment 1, the difference is that any cross-section of the stirring needle is circular, and the rest is exactly the same as Embodiment 1.

[0102] Comparative Example 1

[0103] This comparative example provides a stirring device for optimizing the microstructure of aluminum alloy. Compared with Example 1, the difference is that the stirring needle is not a conical structure, and the diameter of the circumscribed circle of the cross section of the conical structure from close to the shoulder to away from the shoulder is the same, L3=9mm, the ratio of L2 to L3 is 1:1, and the rest is exactly the same as Example 1.

[0104] Comparative Example 2

[0105] This comparative example provides a stirring device for optimizing the microstructure of aluminum alloy. Compared with Example 1, the difference is that the edge of the bottom surface of the shoulder is circular, and the circular diameter of the bottom surface is denoted as L1, L1=30mm, so that the ratio of L1 to L2 is 10:3, and the rest is exactly the same as Example 1.

[0106] Application Example 1

[0107] This application example provides a stirring method for optimizing the microstructure of an aluminum alloy. The stirring method is performed using the stirring device for optimizing the microstructure of an aluminum alloy provided in Example 1. The stirring method includes:

[0108] Step 1: Prepare a square aluminum alloy plate, the thickness of the aluminum alloy plate is 10 μm, the Cu content in the aluminum alloy is 10 wt%, and the Si content is 8.5 wt%.

[0109] Step 2: Setting the processing parameters on the control system, that is, setting the ratio v / ω of the forward speed v and the rotation speed ω of the stirring device to 0.22.

[0110] Step 3: Fix the plate to be processed with a clamp.

[0111] Step 4: Adjust the position of the stirring head so that it is perpendicular to the surface of the plate, and insert it vertically into the aluminum alloy plate, and the shoulder is in contact with the upper surface of the aluminum alloy plate and presses the aluminum alloy plate. The distance between the bottom of the stirring needle and the bottom of the aluminum alloy plate is 0.8mm.

[0112] Step 5: Start the stirring device to make the stirring head move back and forth along the longitudinal direction of the aluminum alloy plate, wherein the stirring belts formed by two adjacent working paths are connected to each other until the entire aluminum alloy plate is processed.

[0113] Step 6: After the processing is completed, the upper and lower surfaces are milled off by 1.5 mm each to obtain a high copper content Al-Si alloy with refined phase size.

[0114] Application Example 2

[0115] This application example provides a stirring method for optimizing the microstructure of an aluminum alloy. The stirring method is performed using the stirring device for optimizing the microstructure of an aluminum alloy provided in Example 1. The stirring method includes:

[0116] Step 1: Prepare a square aluminum alloy plate, the thickness of the aluminum alloy plate is 13 μm, the Cu content in the aluminum alloy is 12 wt%, and the Si content is 7.8 wt%.

[0117] Step 2: Setting the processing parameters on the control system, that is, setting the ratio v / ω of the forward speed v and the rotation speed ω of the stirring device to 0.13.

[0118] Step 3: Fix the plate to be processed with a clamp.

[0119] Step 4: Adjust the position of the stirring head so that it is perpendicular to the surface of the plate, and insert it vertically into the aluminum alloy plate, and the shoulder is in contact with the upper surface of the aluminum alloy plate and presses the aluminum alloy plate. The distance between the bottom of the stirring needle and the bottom of the aluminum alloy plate is 1.0 mm.

[0120] Step 5: Start the stirring device to make the stirring head move back and forth along the longitudinal direction of the aluminum alloy plate, wherein the stirring belts formed by two adjacent working paths are connected to each other until the entire aluminum alloy plate is processed.

[0121] Step 6: After the processing is completed, the upper and lower surfaces are milled off by 3 mm each to obtain a high copper content Al-Si alloy with refined phase size.

[0122] Application Example 3

[0123] This application example provides a stirring method for optimizing the microstructure of an aluminum alloy. The stirring method is performed using the stirring device for optimizing the microstructure of an aluminum alloy provided in Example 1. The stirring method includes:

[0124] Step 1: Prepare a square aluminum alloy plate, the thickness of the aluminum alloy plate is 11 μm, the Cu content in the aluminum alloy is 15wt%, and the Si content is 7.0wt%.

[0125] Step 2: Setting the processing parameters on the control system, that is, setting the ratio v / ω of the forward speed v and the rotation speed ω of the stirring device to 0.37.

[0126] Step 3: Fix the plate to be processed with a clamp.

[0127] Step 4: Adjust the position of the stirring head so that it is perpendicular to the surface of the plate, and insert it vertically into the aluminum alloy plate, and the shoulder is in contact with the upper surface of the aluminum alloy plate and presses the aluminum alloy plate. The distance between the bottom of the stirring needle and the bottom of the aluminum alloy plate is 0.5mm.

[0128] Step 5: Start the stirring device to make the stirring head move back and forth along the longitudinal direction of the aluminum alloy plate, wherein the stirring belts formed by two adjacent working paths are connected to each other until the entire aluminum alloy plate is processed.

[0129] Step 6: After the processing is completed, the upper and lower surfaces are milled off by 1.0 mm each to obtain a high copper content Al-Si alloy with refined phase size.

[0130] Application Examples 4 to 7 and Application Examples 8 to 9

[0131] Application Examples 4 to 7 and Application Examples 8 to 9 provide a stirring method for optimizing the microstructure of aluminum alloys. Compared with Application Example 1, the difference lies in that Application Examples 4 to 7 and Application Examples 8 to 9 respectively use the stirring devices for optimizing the microstructure of aluminum alloys provided in Examples 4 to 7 and Comparative Examples 1 to 2, and the rest is exactly the same as Application Example 1.

[0132] Application Example 10

[0133] This application example provides a stirring method for optimizing the microstructure of aluminum alloy. Compared with Application Example 1, the difference is that the ratio v / ω of the forward speed v of the stirring device to the rotational speed ω is 0.1, and the rest is exactly the same as Application Example 1.

[0134] Application Example 11

[0135] This application example provides a stirring method for optimizing the microstructure of aluminum alloy. Compared with Application Example 1, the difference is that the ratio v / ω of the forward speed v of the stirring device to the rotational speed ω is 0.4, and the rest is exactly the same as Application Example 1.

[0136] The peak stress and the equivalent circle diameter of the Al2Cu phase of the aluminum alloy sheet before and after optimization were tested, and the results are shown in Table 1.

[0137] Table 1

[0138]

[0139]

[0140] From Table 1, we can see the following points:

[0141] (1) It can be seen from the application examples 1 to 3 that the stirring method for optimizing the microstructure of aluminum alloy provided by the present invention can split the coarse Al2Cu brittle phase into fine phases by improving the structure of the stirring head and using the stir friction welding technology in the non-welding microstructure optimization process, thereby improving the machinability of the aluminum alloy plate. Specifically, the equivalent circle diameter of the Al2Cu phase can be reduced by more than 95.3%, and the peak stress can be reduced by more than 39.5%;

[0142] (2) Influence of the ratio of L1 to L2

[0143] Comparing Application Example 1 and Application Example 9, it can be seen that the ratio of L1 to L2 in Application Example 1 is 2:1, compared with the ratio of L1 to L2 in Application Example 9 of 10:3, the equivalent circular diameter and peak stress of the Al2Cu phase of the aluminum alloy plate after treatment in Application Example 9 are greatly increased compared with Application Example 1. This is because the diameter of the bottom edge of the shoulder is too large and the heat input is too high, which will trigger the secondary growth problem of the Al2Cu brittle phase. This shows that the present invention can better reduce the equivalent circular diameter of the Al2Cu phase and improve the processing performance of the aluminum alloy plate by controlling the ratio of L1 to L2 within a reasonable range.

[0144] (3) Conical structure of stirring needle

[0145] Comparing Application Example 1 and Application Example 8, it can be seen that the ratio of L2 to L3 in Application Example 1 is 1.8:1. Compared with the ratio of L2 to L3 in Application Example 8 of 1:1, the equivalent circular diameter and peak stress of the Al2Cu phase of the aluminum alloy plate after treatment in Application Example 8 have increased significantly compared with Application Example 1. This is because the conical table structure is used in Application Example 1. Compared with the cylindrical stirring needle, the material in the processing area will also be subject to the downward pressure of the cone surface, resulting in longitudinal movement, which can better refine the large-sized Al2Cu phase. This shows that the present invention can better reduce the equivalent circular diameter of the Al2Cu phase and improve the processing performance of the aluminum alloy plate by controlling the ratio of L2 to L3 within a reasonable range.

[0146] (4) Cross-sectional shape of the stirring needle

[0147] By comparing Application Example 1 with Application Examples 6-7, it can be seen that the cross-section in Application Example 1 is a pentagon. Compared with Application Examples 6-7 which are 10-gon and circular respectively, the equivalent circular diameter and peak stress of the Al2Cu phase of the aluminum alloy plate after treatment in Application Example 1 are relatively smaller. This is because when the number of sides in Application Example 6 is greater than 8, its cross-section has approached a circle, the flow is insufficient, and the refinement effect is poor, while in Application Example 7 it is a circle, and the refinement effect of the Al2Cu phase is worse than that in Application Example 6.

[0148] By comparing Application Example 1 and Application Example 4, it can be seen that in Application Example 1, the vertices are evenly distributed on the circumscribed circle. Compared with Application Example 4, in which the vertices of the polygons are unevenly distributed and partly inside the circumscribed circle, the equivalent circle diameter and peak stress of the Al2Cu phase of the treated aluminum alloy plate in Application Example 1 are relatively smaller. This is because when the vertices of the polygons are unevenly distributed or one or more vertices are inside the circumscribed circle, there is a problem of insufficient refinement of the large-size Al2Cu phase.

[0149] Comparing Application Example 1 and Application Example 5, it can be seen that the central angle of the arc-shaped curved edge in Application Example 1 is 60°, compared with the central angle of the arc-shaped curved edge in Application Example 5 of 20°, the equivalent circular diameter and peak stress of the Al2Cu phase of the aluminum alloy plate after treatment in Application Example 1 are relatively smaller. This is because the design of the arc-shaped curved edge can increase the contact area between the stirring needle and the aluminum alloy plate, so that the stirring needle can produce a stronger stirring effect on the aluminum alloy plate during the rotation process, enhance the stirring effect and refinement effect, and make the Al2Cu phase more refined. When the central angle is small, the concave arc of the curved edge is too small, close to a straight edge, and the refinement effect is not good.

[0150] This shows that the present invention can better reduce the equivalent circle diameter of the Al2Cu phase, reduce the peak stress, and improve the processing performance of the aluminum alloy plate by controlling the central angle, polygon and number of edges corresponding to the arc-shaped curved edge in the cross section of the stirring needle within a reasonable range and evenly distributing the vertex angle.

[0151] The present invention illustrates the detailed features of the present invention through the above embodiments, but the present invention is not limited to the above detailed features, that is, it does not mean that the present invention must rely on the above detailed features to be implemented. Those skilled in the art should understand that any improvement to the present invention, equivalent replacement of the technical features selected by the present invention, addition of auxiliary technical features, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A stirring head for a stirring device for optimizing the microstructure of an aluminum alloy, the stirring head (1) comprising a stirring needle (1-1) and a shoulder (1-2) arranged on the stirring needle (1-1), characterized in that: The side of the shaft shoulder (1-2) contacting the stirring needle (1-1) is the bottom surface, the edge of the bottom surface of the shaft shoulder (1-2) is circular, and the circular diameter of the bottom surface is recorded as L1; the side of the stirring needle (1-1) close to the shaft shoulder (1-2) is the upper surface, the working radius formed by the upper surface of the stirring needle (1-1) during operation is recorded as the upper surface circumscribed circle, and the diameter of the upper surface circumscribed circle is recorded as L2, wherein the ratio of L1 to L2 is 2 to 3:1; The stirring needle (1-1) is a conical structure, and the diameter of the circumscribed circle of the cross section of the conical structure gradually decreases from the direction close to the shaft shoulder (1-2) to the direction away from the shaft shoulder (1-2).

2. The stirring head according to claim 1, characterized in that: The side of the stirring needle (1-1) away from the shaft shoulder (1-2) is recorded as the lower surface, the working radius formed by the lower surface of the stirring needle (1-1) during operation is recorded as the circumscribed circle of the lower surface, the diameter corresponding to the circumscribed circle of the lower surface is recorded as L3, and the ratio of L2 to L3 is 1.4 to 1.8:

1.

3. The stirring head according to claim 1, characterized in that: Any cross section of the stirring needle (1-1) is a polygon, and the number of sides of the polygon is 3 to 8.

4. The stirring head according to claim 3, characterized in that: The polygon is a curved-edge polygon, the sides of which are arc-shaped curved sides, and the arc-shaped curved sides protrude toward the center of the polygon.

5. The stirring head according to claim 4, characterized in that: The central angle of the arc-shaped curved edge is 30° to 90°.

6. The stirring head according to any one of claims 3 to 5, characterized in that: The vertex angles of the polygon are evenly distributed on the circumscribed circle corresponding to the working radius of the polygon.

7. A stirring device for optimizing the microstructure of an aluminum alloy, the stirring device comprising a drive system (2), a fixture (4), a body (5) and a control system (3), characterized in that: The stirring device further comprises a stirring head according to any one of claims 1 to 6.

8. A stirring method for optimizing the microstructure of aluminum alloy, characterized in that: The friction stir welding device is used.

9. The stirring method according to claim 8, characterized in that: The stirring method is carried out using the stirring device for optimizing the microstructure of the aluminum alloy as described in claim 7.

10. The stirring method according to claim 9, characterized in that: The stirring method comprises: The stirring needle (1-1) is arranged to be perpendicular to the surface of the aluminum alloy plate (6) and vertically inserted into the aluminum alloy plate (6), and the shaft shoulder (1-2) is arranged to contact the upper surface of the aluminum alloy plate (6) and press the aluminum alloy plate (6); Starting the stirring device so that the stirring head (1) moves back and forth along the longitudinal direction of the aluminum alloy plate (6), wherein the stirring belts formed by two adjacent working paths are connected to each other until the entire aluminum alloy plate (6) is processed; Wherein, in terms of mass percentage, the Cu content in the aluminum alloy plate (6) is ≥10wt%, and the aluminum alloy plate (6) contains an Al2Cu brittle phase with an average equivalent circular diameter of ≥25μm; Preferably, the ratio v / ω of the forward speed v of the stirring head (1) to the rotation speed ω is greater than or equal to 0.13; Preferably, the ratio v / ω of the forward speed v of the stirring head (1) to the rotation speed ω is less than or equal to 0.37.

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