A high cycle fatigue aluminum alloy and method of making, a part, an end product

Abstract

The application relates to a high-cycle fatigue aluminum alloy and a preparation method, a part and an end product, and belongs to the field of aluminum alloys, and contains, in percentage by mass, Si 7.0-8.5%, Mg 0.8-1.2%, Cu 1.5-2.2%, Zn 0.5-0.8%, Mn 0.3-0.6%, Ti 0.15-0.25%, Zr 0.08-0.12%, and the balance of Al and inevitable impurities. The high-cycle fatigue aluminum alloy provided by the application is optimized in terms of the composition elements of the aluminum alloy, the high-cycle fatigue performance of the aluminum alloy is significantly improved under the premise that the strength meets the requirements, the problems of insufficient strength of an ordinary aluminum alloy crank, easy deformation and fracture and poor fatigue resistance are solved, the crank is greatly lightened, super-high structural strength, fatigue resistance and wear resistance stability are considered, and the long-term stable operation demand of a high-speed heavy-load industrial sewing machine is met.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloys, specifically to a high-cycle fatigue aluminum alloy and its preparation method, parts, and end products. Background Technology

[0002] Currently, high cyclic fatigue refers to the phenomenon that a structure may fail due to fatigue when subjected to more than 10 cycles of stress alternation within its service life. This phenomenon is common in mechanical components such as crankshafts and connecting rods, as well as components of aero-engines. For example, the crank of an industrial sewing machine is a core reciprocating transmission component that undertakes the core functions of motor power transmission and connecting rod reciprocating drive. It is subjected to high-speed reciprocating motion, alternating loads, and high-frequency vibration conditions for a long time, which places extremely high demands on the structural strength, fatigue resistance, and dimensional stability of the components.

[0003] For example, CN209243342U discloses a sewing machine including a main shaft, a connecting rod, a crank, and a drive shaft. The main shaft and the drive shaft are rotatably mounted on the body of the sewing machine. One end of the connecting rod is connected to the main shaft, and the other end of the connecting rod is connected to one end of the crank through a universal joint. The other end of the crank is connected to the drive shaft, and the end of the drive shaft is also connected to a needle assembly.

[0004] Currently, the mainstream materials used for industrial sewing machine cranks are low-carbon alloy steel and ductile iron. These traditional materials have significant technical shortcomings: First, their weight is relatively large, resulting in a large inertial torque during high-speed operation. This leads to delayed start-stop response, high energy consumption, and loud vibration and noise. Long-term high-speed operation can also cause transmission jamming and stitch deviation, affecting sewing accuracy and equipment stability. Second, steel cranks have limited wear resistance. Long-term friction at the shaft hole mating position can easily cause wear and hole enlargement, and excessive clearance, resulting in abnormal transmission noise, reduced transmission efficiency, and frequent parts replacement. Third, cast iron cranks have poor toughness, are prone to micro-cracks under alternating loads, and have weak impact resistance, making them unsuitable for the upgrade requirements of high-speed industrial sewing equipment.

[0005] Existing lightweight improvement solutions mostly use ordinary die-cast aluminum alloys to make cranks. Although this achieves weight reduction, ordinary aluminum alloys have defects such as low tensile strength, poor fatigue resistance, and insufficient rigidity. Under the high-frequency alternating load conditions of industrial sewing machines, they are prone to bending deformation and fatigue fracture. The wear rate at the shaft hole position is fast, and the service life is much shorter than that of steel cranks. They cannot meet the usage standards of high-speed, heavy-duty industrial sewing machines. At the same time, the forming process is rough, with many internal defects such as air holes and shrinkage, which further reduces the overall performance of the parts and restricts the technological upgrade of sewing machines towards lightweight, high-speed, and low-energy consumption. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of the present invention is to provide a high-cyclic fatigue aluminum alloy and its preparation method, parts, and end products, so as to solve the defects of the current aluminum alloys, which have poor fatigue resistance, are prone to bending deformation and fatigue fracture under the high-frequency alternating load conditions of industrial sewing machines, have a fast wear rate at the shaft hole position, and have a service life far lower than that of steel cranks, and cannot meet the use standards of high-speed, heavy-duty industrial sewing machines.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a high-cycle fatigue aluminum alloy, wherein the high-cycle fatigue aluminum alloy comprises, by weight percentage:

[0009] Si 7.0-8.5%, Mg 0.8-1.2%, Cu 1.5-2.2%, Zn 0.5-0.8%, Mn 0.3-0.6%, Ti 0.15-0.25%, Zr 0.08-0.12%, with the balance being Al and unavoidable impurities.

[0010] The high-cycle fatigue aluminum alloy provided by this invention significantly improves the high-cycle fatigue performance of aluminum alloys while ensuring that the strength meets the requirements through optimized design of the constituent elements of the aluminum alloy. It solves the technical problems of excessive weight, high energy consumption, and high vibration and noise of traditional steel cranks, as well as insufficient strength, easy deformation and fracture, and poor fatigue resistance of ordinary aluminum alloy cranks. While achieving a significant reduction in crank weight, it also takes into account ultra-high structural strength, fatigue resistance and wear resistance stability, and is suitable for the long-term stable operation requirements of high-speed heavy-duty industrial sewing machines.

[0011] As a preferred embodiment of the present invention, the mass percentage content of the impurities is ≤0.1%.

[0012] Preferably, the impurities include: Fe impurities.

[0013] Preferably, the mass percentage of Fe impurities in the high-cycle fatigue aluminum alloy is ≤0.05%.

[0014] In a second aspect, the present invention provides a method for preparing a high-cycle fatigue aluminum alloy as described in the first aspect, the method comprising:

[0015] The ingredients are prepared according to the mass percentage formula, and then smelted and refined to obtain aluminum alloy melt;

[0016] The aluminum alloy melt is cast to obtain a billet, which is then subjected to solution treatment and aging treatment in sequence to obtain a high-cycle fatigue aluminum alloy.

[0017] As a preferred technical solution of the present invention, the smelting includes: sequentially melting aluminum and melting alloys.

[0018] Preferably, the aluminum is melted at a temperature of 720-750°C.

[0019] Preferably, the alloy is melted at a temperature of 740-760°C.

[0020] Preferably, the stirring speed is controlled at 300-500 r / min for 15-20 min during the alloy melting process.

[0021] As a preferred technical solution of the present invention, the casting method includes: low-pressure precision casting.

[0022] Preferably, the casting pressure is controlled at 0.35-0.45 MPa in the low-pressure precision casting.

[0023] Preferably, the filling speed in the low-pressure precision casting is controlled at 40-50 mm / s.

[0024] Preferably, the holding time in the low-pressure precision casting is controlled to be 80-100s.

[0025] As a preferred embodiment of the present invention, the solution treatment temperature is 490-510℃.

[0026] Preferably, the heat treatment time is 90-120 minutes.

[0027] Preferably, the cooling method for the solution treatment includes water cooling.

[0028] As a preferred technical solution of the present invention, the aging treatment temperature is 160-180℃.

[0029] Preferably, the heat preservation time for the aging treatment is 6-8 hours.

[0030] Preferably, the cooling method for the aging process includes air cooling.

[0031] Thirdly, the present invention provides a part, which is processed from a high-cycle fatigue aluminum alloy as described in the first aspect or a high-cycle fatigue aluminum alloy obtained by the preparation method described in the second aspect.

[0032] As a preferred technical solution of the present invention, the part is subjected to hard anodizing treatment.

[0033] Preferably, the thickness of the oxide film obtained by the hard anodizing treatment is 15-20 μm.

[0034] Fourthly, the present invention provides a terminal product, the terminal product comprising the parts described in the third aspect.

[0035] Compared with existing technical solutions, the present invention has the following beneficial effects:

[0036] (1) Significant weight reduction effect, reducing equipment energy consumption and vibration: The present invention adopts modified ultra-high strength aluminum alloy integral molding, which reduces the overall weight by 55-60% and high-speed vibration by 25-30% compared with the traditional 20Cr steel crank, greatly reducing the inertial torque of the crank at high speed, effectively reducing the energy consumption of sewing machine start-up and shutdown, machine vibration and operating noise, improving sewing accuracy and equipment response speed, and adapting to the working conditions of high-speed automated industrial sewing machines.

[0037] (2) Excellent strength and fatigue resistance, long service life: By optimizing the alloy ratio of aluminum alloy, adding trace amounts of Ti and Zr grain refining elements, and combining it with graded solid solution aging heat treatment, the mechanical properties and cyclic fatigue performance of aluminum alloy are significantly improved, far exceeding those of ordinary die-cast aluminum alloys, such as YL113.

[0038] (3) Strong wear resistance and low maintenance cost: The whole hard anodizing treatment is corrosion and wear resistant, which greatly reduces the frequency of parts replacement and equipment maintenance costs.

[0039] The present invention will now be described in further detail. However, the examples described below are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims. Detailed Implementation

[0040] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows:

[0041] Existing lightweight improvement schemes mostly use ordinary die-cast aluminum alloys to make cranks. Although this achieves weight reduction, ordinary aluminum alloys have defects such as low tensile strength, poor fatigue resistance, and insufficient rigidity. Under the high-frequency alternating load conditions of industrial sewing machines, they are prone to bending deformation and fatigue fracture. The wear rate at the shaft hole is fast, and the service life is much shorter than that of steel cranks, which cannot meet the usage standards of high-speed, heavy-duty industrial sewing machines. At the same time, the forming process is rough, with many internal porosity and shrinkage defects, which further reduces the overall performance of the components and restricts the technological upgrade of sewing machines towards lightweight, high-speed, and low-energy consumption. Based on this, this invention significantly improves the high-cycle fatigue performance of aluminum alloys by optimizing the aluminum alloy composition while ensuring that the strength meets the requirements, as detailed below:

[0042] I. This embodiment provides a high-cycle fatigue aluminum alloy, which comprises, by weight percentage:

[0043] Si 7.0-8.5%, Mg 0.8-1.2%, Cu 1.5-2.2%, Zn 0.5-0.8%, Mn 0.3-0.6%, Ti 0.15-0.25%, Zr 0.08-0.12%, with the balance being Al and unavoidable impurities.

[0044] In this invention, the Si element in the high-cycle fatigue aluminum alloy is 7-8.5% by mass percentage, for example, it can be 7%, 7.15%, 7.3%, 7.45%, 7.6%, 7.75%, 7.9%, 8.05%, 8.2%, 8.35% or 8.5%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0045] In this invention, the Mg element in the high-cycle fatigue aluminum alloy is 0.8-1.2% by mass, for example, it can be 0.8%, 0.84%, 0.88%, 0.92%, 0.96%, 1%, 1.04%, 1.08%, 1.12%, 1.16%, or 1.2%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0046] In this invention, the Cu element in the high-cycle fatigue aluminum alloy is 1.5-2.2% by mass percentage, for example, it can be 1.5%, 1.57%, 1.64%, 1.71%, 1.78%, 1.85%, 1.92%, 1.99%, 2.06%, 2.13%, or 2.2%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0047] In this invention, the Zn element in the high-cycle fatigue aluminum alloy is 0.5-0.8% by mass percentage, for example, it can be 0.5%, 0.53%, 0.56%, 0.59%, 0.62%, 0.65%, 0.68%, 0.71%, 0.74%, 0.77% or 0.8%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0048] In this invention, the Mn element in the high-cycle fatigue aluminum alloy is 0.3-0.6% by mass percentage, for example, it can be 0.3%, 0.33%, 0.36%, 0.39%, 0.42%, 0.45%, 0.48%, 0.51%, 0.54%, 0.57% or 0.6%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0049] In this invention, the Ti element in the high-cycle fatigue aluminum alloy is 0.15-0.25% by mass percentage, for example, it can be 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24% or 0.25%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0050] In this invention, the Zr element in the high-cycle fatigue aluminum alloy is 0.08-0.12% by mass, for example, it can be 0.08%, 0.084%, 0.088%, 0.092%, 0.096%, 0.1%, 0.104%, 0.108%, 0.112%, 0.116%, or 0.12%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0051] In this invention, the mass percentage of the impurities is ≤0.1%, for example, it can be 0.1%, 0.091%, 0.082%, 0.073%, 0.064%, 0.055%, 0.046%, 0.037%, 0.028%, 0.019%, or 0.01%, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0052] In this invention, impurities include elements such as Fe and O that have an adverse effect on the properties of aluminum alloys.

[0053] In this invention, the impurities include Fe impurities.

[0054] In this invention, the mass percentage of Fe impurities in the high-cycle fatigue aluminum alloy is ≤0.05%, for example, it can be 0.05%, 0.046%, 0.042%, 0.038%, 0.034%, 0.03%, 0.026%, 0.022%, 0.018%, 0.014%, or 0.01%, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0055] II. This embodiment provides a method for preparing a high-cycle fatigue aluminum alloy, the method comprising:

[0056] The ingredients are prepared according to the mass percentage formula, and then smelted and refined to obtain aluminum alloy melt;

[0057] The aluminum alloy melt is cast to obtain a billet, which is then subjected to solution treatment and aging treatment in sequence to obtain a high-cycle fatigue aluminum alloy.

[0058] In this invention, the smelting process includes sequentially melting aluminum and melting an alloy.

[0059] In this invention, the melting temperature of aluminum is 720-750℃, for example, it can be 720℃, 723℃, 726℃, 729℃, 732℃, 735℃, 738℃, 741℃, 744℃, 747℃ or 750℃, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0060] In this invention, the melting temperature of the alloy is 740-760℃, for example, it can be 740℃, 742℃, 744℃, 746℃, 748℃, 750℃, 752℃, 754℃, 756℃, 758℃ or 760℃, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0061] In this invention, the stirring speed during alloy melting is controlled at 300-500 r / min for 15-20 min. The stirring speed can be, for example, 300 r / min, 310 r / min, 320 r / min, 330 r / min, 340 r / min, 350 r / min, 360 r / min, 370 r / min, 380 r / min, 390 r / min, 400 r / min, 410 r / min, 420 r / min, or 430 r / min. 440 r / min, 450 r / min, 460 r / min, 470 r / min, 480 r / min, 490 r / min or 500 r / min, etc., and stirring time can be, for example, 15 min, 15.5 min, 16 min, 16.5 min, 17 min, 17.5 min, 18 min, 18.5 min, 19 min, 19.5 min or 20 min, etc., but not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0062] In this invention, the source of all alloying elements in the alloy melting process can be selected from pure metals or commercially available intermediate alloys, etc., and the specific selection can be made reasonably according to the conventional requirements in the field of aluminum alloy preparation.

[0063] In this invention, the casting method includes: low-pressure precision casting.

[0064] In this invention, low-pressure precision casting can effectively eliminate internal porosity and shrinkage defects in castings, ensuring structural density.

[0065] In this invention, the casting pressure is controlled at 0.35-0.45 MPa during low-pressure precision casting. For example, it can be 0.35 MPa, 0.36 MPa, 0.37 MPa, 0.38 MPa, 0.39 MPa, 0.4 MPa, 0.41 MPa, 0.42 MPa, 0.43 MPa, 0.44 MPa, or 0.45 MPa, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0066] In this invention, the filling speed in the low-pressure precision casting is controlled to be 40-50 mm / s, for example, it can be 40 mm / s, 41 mm / s, 42 mm / s, 43 mm / s, 44 mm / s, 45 mm / s, 46 mm / s, 47 mm / s, 48 ​​mm / s, 49 mm / s or 50 mm / s, etc., but is not limited to the listed values, and other unlisted values ​​within this range also meet the requirements.

[0067] In this invention, the holding time in the low-pressure precision casting is controlled to be 80-100s, for example, it can be 80s, 82s, 84s, 86s, 88s, 90s, 92s, 94s, 96s, 98s or 100s, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0068] In this invention, the mold is preheated to 220-250°C during low-pressure precision casting. For example, it can be 220°C, 223°C, 226°C, 229°C, 232°C, 235°C, 238°C, 241°C, 244°C, 247°C, or 250°C, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements. At the same time, a release agent is sprayed to ensure the integrity of the casting and the surface finish.

[0069] In this invention, the release agent can be reasonably selected according to the conventional requirements in the field, as long as it does not affect the demolding and the performance of the aluminum alloy.

[0070] In this invention, the solution treatment temperature is 490-510℃, for example, it can be 490℃, 492℃, 494℃, 496℃, 498℃, 500℃, 502℃, 504℃, 506℃, 508℃ or 510℃, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also acceptable.

[0071] In this invention, the heat treatment holding time is 90-120 min, for example, it can be 90 min, 93 min, 96 min, 99 min, 102 min, 105 min, 108 min, 111 min, 114 min, 117 min or 120 min, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0072] In this invention, the cooling method for the solution treatment includes water cooling.

[0073] In this invention, the aging treatment temperature is 160-180℃, for example, it can be 160℃, 162℃, 164℃, 166℃, 168℃, 170℃, 172℃, 174℃, 176℃, 178℃ or 180℃, etc., but is not limited to the listed values, and other unlisted values ​​within this range also meet the requirements.

[0074] In this invention, the heat preservation time for the aging treatment is 6-8 hours, for example, it can be 6 hours, 6.2 hours, 6.4 hours, 6.6 hours, 6.8 hours, 7 hours, 7.2 hours, 7.4 hours, 7.6 hours, 7.8 hours or 8 hours, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0075] In this invention, the cooling method for the aging process includes air cooling.

[0076] III. This embodiment provides a part, which is processed using the high-cycle fatigue aluminum alloy described above or the high-cycle fatigue aluminum alloy obtained by the preparation method described above.

[0077] In this invention, a part refers to a part used under cyclic loads (stress), such as mechanical components like crankshafts and connecting rods, and components of aircraft engines.

[0078] The part undergoes hard anodizing treatment.

[0079] The thickness of the oxide film obtained by the hard anodizing treatment is 15-20 μm, for example, it can be 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm, 18.5 μm, 19 μm, 19.5 μm or 20 μm, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0080] In this invention, hard anodizing treatment can further improve the surface wear resistance and corrosion resistance, thereby extending the service life of the parts.

[0081] In this invention, the surface of the part is treated before hard anodizing to ensure the effect of the anodizing process, such as deburring and polishing.

[0082] IV. This embodiment provides a terminal product, which includes the aforementioned components.

[0083] In this invention, the end product includes a semi-finished product or a finished product containing the parts, such as a semi-finished component connected to the parts, and a product assembled from the semi-finished component and other accessories. The semi-finished product is such as a crank rocker mechanism, and the finished product is such as an industrial sewing machine.

[0084] V. To illustrate the superior performance of the high-cyclic fatigue aluminum alloy provided by this invention, the following examples are used for explanation:

[0085] In the following examples, the mechanical properties were tested according to GB / T 228.1 Tensile testing of metallic materials; the high-cycle fatigue test was conducted according to GB / T 3075 Method for controlling axial force during fatigue of metallic materials; and the high-speed vibration test was conducted according to the industrial sewing machine industry testing standard QB / T 4299.

[0086] Example 1

[0087] This embodiment provides a high-strength, fatigue-resistant, lightweight sewing machine crank. The modified ultra-high-strength aluminum alloy is composed of the following components by mass percentage: Si 7.8%, Mg 1%, Cu 1.8%, Zn 0.6%, Mn 0.45%, Ti 0.2%, Zr 0.1%, Fe 0.01%, with the balance being Al and unavoidable impurities.

[0088] Preparation method:

[0089] (1) Alloy smelting: aluminum ingots are melted at 730℃, alloy auxiliary materials are added in sequence, stirred at 750℃ for 18 minutes, refined and impurities removed, and then allowed to stand for 30 minutes;

[0090] (2) Preheat the mold to 230°C and spray with release agent (K6301).

[0091] (3) Low-pressure casting: pressure 0.4MPa, filling speed 45mm / s, holding pressure 90s;

[0092] (4) Solution treatment and aging: Solution treatment at 500℃ for 100 min followed by water cooling, and aging at 170℃ for 7 h followed by air cooling;

[0093] (5) Precision machining ensures the tolerance of mating holes is ±0.005mm, followed by deburring and polishing;

[0094] The crank prepared in this embodiment has an overall weight reduction of 58% compared to a steel crank.7 No deformation or cracks under alternating loads, and vibration is reduced by 26% during high-speed operation, making it compatible with 6000r / min high-speed industrial sewing machines.

[0095] Example 2

[0096] This embodiment describes a high-strength, fatigue-resistant, lightweight sewing machine crank. The modified ultra-high-strength aluminum alloy is composed of the following components by mass percentage: Si 8.2%, Mg 1.1%, Cu 2%, Zn 0.7%, Mn 0.5%, Ti 0.22%, Zr 0.11%, Fe 0.01%, with the balance being Al and unavoidable impurities.

[0097] The preparation method is the same as in Example 1. Solution treatment and aging: solution treatment at 505℃ for 110 min, and aging at 175℃ for 7.5 h.

[0098] The crank prepared in this embodiment has a weight reduction ratio of 59%, 10 7 No deformation or cracks under alternating loads, vibration reduced by 26%, suitable for long-term high-intensity operation of heavy-duty industrial sewing machines with thick materials.

[0099] Example 3

[0100] This embodiment provides a high-strength, fatigue-resistant, lightweight sewing machine crank. The modified ultra-high-strength aluminum alloy is composed of the following components by mass percentage: Si 7%, Mg 0.8%, Cu 2.2%, Zn 0.8%, Mn 0.3%, Ti 0.25%, Zr 0.08%, Fe 0.02%, with the balance being Al and unavoidable impurities.

[0101] Preparation method:

[0102] (1) Alloy smelting: aluminum ingots are melted at 720℃, alloy auxiliary materials are added in sequence, stirred at 740℃ for 15 minutes, refined and impurities removed, and then allowed to stand for 30 minutes;

[0103] (2) Preheat the mold to 230°C and spray with release agent (K6301).

[0104] (3) Low-pressure casting: pressure 0.35MPa, filling speed 40mm / s, holding pressure 80s;

[0105] (4) Solution treatment and aging: Solution treatment at 490℃ for 90 min followed by water cooling, and aging at 160℃ for 6 h followed by air cooling;

[0106] (5) Precision machining ensures the tolerance of mating holes is ±0.005mm, followed by deburring and polishing;

[0107] (6) The thickness of the hard anodized film is 18 μm.

[0108] The crank prepared in this embodiment has an overall weight reduction of 56% compared to a steel crank. 7 No deformation or cracks under alternating loads, and vibration is reduced by 25% during high-speed operation, making it compatible with 6000r / min high-speed industrial sewing machines.

[0109] Example 4

[0110] This embodiment provides a high-strength, fatigue-resistant, lightweight sewing machine crank. The modified ultra-high-strength aluminum alloy is composed of the following components by mass percentage: Si 8.5%, Mg 1.2%, Cu 1.5%, Zn 0.5%, Mn 0.6%, Ti 0.15%, Zr 0.12%, Fe 0.005%, with the balance being Al and unavoidable impurities.

[0111] Preparation method:

[0112] (1) Alloy smelting: aluminum ingots are melted at 750℃, alloy auxiliary materials are added in sequence, stirred at 760℃ for 20 minutes, refined and impurities removed, and then allowed to stand for 30 minutes;

[0113] (2) Preheat the mold to 230°C and spray with release agent (K6301).

[0114] (3) Low-pressure casting: pressure 0.45MPa, filling speed 50mm / s, holding pressure 100s;

[0115] (4) Solution treatment and aging: Solution treatment at 510℃ for 120 min followed by water cooling, and aging at 180℃ for 8 h followed by air cooling;

[0116] (5) Precision machining ensures the tolerance of mating holes is ±0.005mm, followed by deburring and polishing;

[0117] (6) The thickness of the hard anodized film is 18 μm.

[0118] The crank prepared in this embodiment has an overall weight reduction of 54% compared to a steel crank. 7 No deformation or cracks under alternating loads, and vibration is reduced by 23% during high-speed operation, making it compatible with 6000r / min high-speed industrial sewing machines.

[0119] Example 5

[0120] The only difference from Example 1 is that the solution treatment temperature is 530°C.

[0121] Example 6

[0122] The only difference from Example 1 is that the heat treatment time for solid solution treatment is 300 min.

[0123] Example 7

[0124] The only difference from Example 1 is that the aging treatment temperature is 155°C.

[0125] Example 8

[0126] The only difference from Example 1 is that the heat preservation time for aging treatment is 10 hours.

[0127] Comparative Example 1

[0128] The only difference from Example 1 is that the Si content in the high-cycle fatigue aluminum alloy is 10% by mass.

[0129] Comparative Example 2

[0130] The only difference from Example 1 is that the Si content in the high-cycle fatigue aluminum alloy is 1% by mass.

[0131] Comparative Example 3

[0132] The only difference from Example 1 is that the Mg content in the high-cycle fatigue aluminum alloy is 0.5% by mass.

[0133] Comparative Example 4

[0134] The only difference from Example 1 is that the Mg content in the high-cycle fatigue aluminum alloy is 2% by mass.

[0135] Comparative Example 5

[0136] The only difference from Example 1 is that the Cu content in the high-cycle fatigue aluminum alloy is 0.6% by mass.

[0137] Comparative Example 6

[0138] The only difference from Example 1 is that the Cu element in the high-cycle fatigue aluminum alloy is 3% by mass.

[0139] Comparative Example 7

[0140] The only difference from Example 1 is that the Zn content in the high-cycle fatigue aluminum alloy is 0.2% by mass.

[0141] Comparative Example 8

[0142] The only difference from Example 1 is that the Zn content in the high-cycle fatigue aluminum alloy is 1% by mass.

[0143] Comparative Example 9

[0144] The only difference from Example 1 is that the Mn content in the high-cycle fatigue aluminum alloy is 0.2% by mass.

[0145] Comparative Example 10

[0146] The only difference from Example 1 is that the Mn element in the high-cycle fatigue aluminum alloy is 1% by mass.

[0147] Comparative Example 11

[0148] The only difference from Example 1 is that the Ti element in the high-cycle fatigue aluminum alloy is 0.05% by mass.

[0149] Comparative Example 12

[0150] The only difference from Example 1 is that the Ti element in the high-cycle fatigue aluminum alloy is 0.3% by mass.

[0151] Comparative Example 13

[0152] The only difference from Example 1 is that the Zr content in the high-cycle fatigue aluminum alloy is 0.05% by mass.

[0153] Comparative Example 14

[0154] The only difference from Example 1 is that the Zr content in the high-cycle fatigue aluminum alloy is 0.14% by mass.

[0155] The performance of the cranks obtained in the above embodiments and comparative examples is detailed in Table 1.

[0156] Table 1

[0157]

[0158] As shown in Table 1, the solution provided by this invention achieves high strength and high fatigue life through the synergistic effect of the Si-Mg-Cu-Zn main strengthening system, Mn impurity modification, and Ti / Zr composite grain refinement. Any deviation of any element from the defined range will disrupt the microstructure balance and significantly shorten the fatigue life. The resulting aluminum alloy has a tensile strength ≥335MPa, a yield strength ≥268MPa, and a fatigue cycle count ≥2.8×10⁻⁶. 6 The optimal design has a tensile strength ≥386MPa, a yield strength ≥322MPa, and a fatigue cycle count ≥10. 7 The specific analysis is as follows:

[0159] (I) Failure Mechanism of Component Classification Comparative Examples (Comparative Examples 1-14)

[0160] ①Si content deviates

[0161] Excessive Si (10%, Comparative Example 1): Exceeding the reasonable range for eutectic silicon, large bulk primary silicon hard and brittle phases precipitate during casting, disrupting the continuity of the aluminum matrix. Under alternating loads, fatigue microcracks preferentially initiate at the hard silicon phase boundaries, resulting in a precipitous drop in tensile and yield strength, with a fatigue cycle limit of only 2.1 × 10⁻⁶. 6 Second-rate;

[0162] Low Si content (1%, Comparative Example 2): There is a severe shortage of silicon atoms that can participate in the formation of the Mg2Si nano-reinforcing phase. The matrix precipitation strengthening effect is essentially eliminated, the material lacks rigidity, is prone to deformation under cyclic stress, and has a fatigue life of only 1.6 × 10⁻⁶. 6 Second-rate.

[0163] ②Mg content deviates

[0164] Insufficient Mg (0.5%, Comparative Example 3): The number of precipitated strengthening phases of the Mg2Si strengthening phase core component is greatly reduced, the yield strength is significantly reduced, and the ability to resist alternating plastic deformation is worse.

[0165] Excess Mg (2%, Comparative Example 4): Excess Mg accumulates at grain boundaries to form coarse, Mg-rich, brittle intermetallic compounds, reducing grain boundary bonding strength. Cracks easily propagate along grain boundaries, leading to deterioration of fatigue resistance.

[0166] ③Cu content deviates

[0167] Cu plays a role in solid solution strengthening and improving high-temperature strength, making it suitable for the continuous high-speed heating conditions of sewing machines.

[0168] Low Cu content (0.6%, Comparative Example 5): Insufficient solid solution strengthening effect, low resistance to dislocation movement, easy plastic slip under cyclic loading, and shortened fatigue life.

[0169] Cu exceeding the standard (3%, Comparative Example 6): precipitation of a continuous network of brittle CuAl2 phase at grain boundaries significantly reduced the material's toughness. Under alternating stress, the network phase directly became a crack propagation channel.

[0170] ④Zn content deviates

[0171] Zn-assisted solid solution strengthening, synergistically with Cu to improve matrix strength;

[0172] Too low Zn (0.2%, Comparative Example 7): fewer solute atoms in the solid solution, resulting in insufficient matrix strength reserves;

[0173] Excessive Zn content (1%, Comparative Example 8): Low-melting-point Zn-rich phases form at grain boundaries, which easily generate micro-defects at grain boundaries during casting and heat treatment, accelerating fatigue failure.

[0174] ⑤Mn content deviates

[0175] The core function of Mn is to neutralize harmful Fe impurities, transform the acicular brittle Al-Fe phase into the spherical Al-Fe-Mn phase, and eliminate fatigue crack initiation sites.

[0176] Insufficient Mn (0.2%, Comparative Example 9): Fe impurities cannot be completely modified, a large number of acicular iron phases penetrate the matrix, and fatigue performance is greatly reduced;

[0177] Excess Mn (1%, Comparative Example 10): Generates large Mn-rich intermetallic inclusions, disrupting the matrix homogeneity and becoming stress concentration points.

[0178] ⑥Ti and Zr refinement element deviation

[0179] The addition of Ti and Zr composites forms nano-Al3(Ti,Zr) particles, which undergo heterogeneous nucleation to refine grains and inhibit grain growth, thus providing a core guarantee against high-cycle fatigue.

[0180] Insufficient Ti (0.05%, Comparative Example 11) / Insufficient Zr (0.05%, Comparative Example 13): Insufficient grain refinement effect, coarse as-cast grains, and slip band cracks are easily generated inside the coarse grains;

[0181] Excessive Ti (0.3%, Comparative Example 12) / Excessive Zr (0.14%, Comparative Example 14): Coarse, blocky Ti / Zr intermetallic compounds are formed, with sizes far exceeding the critical size, which in turn induces stress concentration and significantly reduces fatigue life.

[0182] In summary, any single element exceeding the range defined in this invention will damage the microstructure, reduce strength by more than 20%, and reduce the number of fatigue cycles to less than 4 × 10⁻⁶. 6 Unable to meet 10 7 The second-highest cyclic fatigue condition, that is, the element ratio range in this invention has a strong synergistic effect, and is not a simple adjustment of conventional parameters.

[0183] (II) Deterioration Mechanism of Heat Treatment Process Deviating from Examples (Examples 5-8)

[0184] The solution treatment (490-510℃) × (90-120 min) + aging (160-180℃) × (6-8 h) designed in this invention is a dedicated heat treatment window for this alloy system. Deviating from this window will result in overheating, under-aging, or over-aging defects.

[0185] ① Excessive solution temperature (530℃, Example 5) and excessive solution time (300 min, Example 6) caused the alloy to overheat, resulting in localized melting of grain boundaries, coarsening and agglomeration of strengthening phases; a large amount of solute atoms were lost, and subsequent aging could not precipitate uniform and fine strengthening phases, leading to a 12-17% decrease in tensile and yield strength, and a fatigue life of only 2.8-3.2×10⁻⁶. 6 Second-rate.

[0186] ② The aging temperature was too low (155℃) (Example 7), and the aging time was too long (10 hours) (Example 8).

[0187] Low-temperature under-aging: Solute atoms are not fully precipitated, the number and size of the reinforcing phase are small, and the reinforcing effect is not fully realized; Over-aging: The nano-Mg2Si and Cu-Zn reinforcing phases continue to coarsen, the interphase spacing increases, the ability to hinder dislocations is greatly weakened, the material softens, and plastic deformation and fatigue cracking are prone to occur under alternating loads.

[0188] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0189] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0190] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A high-cycle fatigue aluminum alloy, characterized in that, The high-cyclic fatigue aluminum alloy comprises, by weight percentage: Si 7-8.5%, Mg 0.8-1.2%, Cu 1.5-2.2%, Zn 0.5-0.8%, Mn 0.3-0.6%, Ti 0.15-0.25%, Zr 0.08-0.12%, with the balance being Al and unavoidable impurities.

2. The high-cycle fatigue aluminum alloy as described in claim 1, characterized in that, The mass percentage of the impurity is ≤0.1%; Preferably, the impurities include: Fe impurities; Preferably, the mass percentage of Fe impurities in the high-cycle fatigue aluminum alloy is ≤0.05%.

3. A method for preparing a high-cyclic fatigue aluminum alloy as described in claim 1 or 2, characterized in that, The preparation method includes: The ingredients are prepared according to the mass percentage formula, and then smelted and refined to obtain aluminum alloy melt; The aluminum alloy melt is cast to obtain a billet, which is then subjected to solution treatment and aging treatment in sequence to obtain a high-cycle fatigue aluminum alloy.

4. The method for preparing high-cyclic fatigue aluminum alloy as described in claim 3, characterized in that, The smelting process includes sequentially melting aluminum and melting alloys; Preferably, the aluminum is melted at a temperature of 720-750°C; Preferably, the alloy melts at a temperature of 740-760°C; Preferably, the stirring speed is controlled at 300-500 r / min for 15-20 min during the alloy melting process.

5. The method for preparing high-cyclic fatigue aluminum alloy as described in claim 3, characterized in that, The casting method includes: low-pressure precision casting; Preferably, the casting pressure is controlled at 0.35-0.45 MPa in the low-pressure precision casting process; Preferably, the filling speed in the low-pressure precision casting is controlled at 40-50 mm / s; Preferably, the holding time in the low-pressure precision casting is controlled to be 80-100s.

6. The method for preparing high-cyclic fatigue aluminum alloy as described in claim 3, characterized in that, The solution treatment temperature is 490-510℃; Preferably, the heat treatment time is 90-120 min; Preferably, the cooling method for the solution treatment includes water cooling.

7. The method for preparing high-cyclic fatigue aluminum alloy as described in claim 3, characterized in that, The aging treatment temperature is 160-180℃; Preferably, the heat preservation time for the aging treatment is 6-8 hours; Preferably, the cooling method for the aging process includes air cooling.

8. A component, characterized in that, The part is processed using the high-cycle fatigue aluminum alloy as described in claim 1 or 2, or the high-cycle fatigue aluminum alloy obtained by the preparation method described in any one of claims 3-7.

9. The part as described in claim 8, characterized in that, The parts are subjected to hard anodizing treatment; Preferably, the thickness of the oxide film obtained by the hard anodizing treatment is 15-20 μm.

10. A terminal product, characterized in that, The end product includes the parts as described in claim 8 or 9.

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