Zinc alloy with excellent high-temperature strength as well as preparation method and application thereof

Abstract

The invention discloses a zinc alloy with excellent high-temperature strength as well as a preparation method and application thereof, and the zinc alloy with excellent high-temperature strength comprises the following components in percentage by mass: 39%-41% of Al, 1.0%-1.5% of Cu, 0.03%-0.06% of Mg, 0.1%-0.2% of Mn, 1.0%-1.5% of Si and Filt. 0.1%, Sn < lt >; 0.1%, with the balance being Zn; a rare earth alterant and an additive are also added; the addition amount of the rare earth alterant is 0.1%-0.3% of the total mass of the zinc alloy, and the addition amount of the additive is 0.8%-1.2% of the total mass of the zinc alloy. According to the zinc alloy with the excellent high-temperature strength, at the test temperature of 160 DEG C, the zinc alloy has obvious advantages, the abrasion loss and the abrasion rate of the zinc alloy are both smaller than those of ZA27-2, and it is indicated that in the high-temperature environment, the zinc alloy is more excellent in abrasion resistance. At the temperature of 160 DEG C, the average friction coefficient of the zinc alloy and the average friction coefficient of the ZA27-2 zinc alloy are both increased, and due to the fact that the alloy has better high-temperature performance, the average friction coefficient of the alloy is increased slightly and is only 0.078.

Description

Technical Field

[0001] This invention belongs to the field of zinc alloys, specifically a zinc alloy with excellent high-temperature strength, its preparation method, and its application. Background Technology

[0002] Zinc alloys have certain applications in the automotive parts manufacturing field due to their good casting performance, relatively low cost advantage, and certain mechanical properties. Traditional heavy-duty truck manual transmissions use copper alloys as shift fork lever blocks, as seen in the article "Improvement of HW Transmission Auxiliary Gearbox Synchronizer Shift Fork Lever Block" by Wang Hui et al. The invention "A Wear-resistant and High-temperature Resistant Zinc Alloy for Shift Fork Lever Blocks of Heavy-duty Truck Transmissions" proposes to use zinc alloy ZA27-2 material and improve the wear resistance of copper alloys through micro-alloying technology.

[0003] Currently, heavy-duty truck transmissions are transitioning from mechanically intensive to electronically controlled and intelligent systems. This means moving from an era dominated by manual transmissions (MT) to a more diversified and intelligent era encompassing automated manual transmissions (AMT) and automatic transmissions (AT), which necessitates higher performance requirements for components. In AMTs, due to the continuous operation of the control unit (TCU) and actuators, and the potential for extended clutch friction time caused by automatic shifting strategies, the operating temperature of AMTs is typically 10-20°C higher than that of manual transmissions. In some mountainous areas or harsh working conditions, the operating temperature can rise instantaneously, reaching 160°C or higher. This increased temperature can lead to a decrease in strength, resulting in problems such as gear shifting failures. Figure 2 As shown, this severely impacts the reliability and lifespan of the transmission. Currently, there are no materials in AMT products that meet these requirements. Summary of the Invention

[0004] This invention provides a zinc alloy with excellent high-temperature strength, its preparation method, and its application. While ensuring the wear resistance of the shift fork lever block parts, it improves the high-temperature strength of the shift fork lever block parts, thus solving the problem of AMT shifting failure caused by insufficient high-temperature strength of ZA27-2 zinc alloy.

[0005] To solve the above problems, the technical solution adopted by the present invention includes:

[0006] A zinc alloy with excellent high-temperature strength, wherein the zinc alloy has the following mass percentage content: Al 39%–41%, Cu 1.0%–1.5%, Mg 0.03%–0.06%, Mn 0.1%–0.2%, Si 1.0%–1.5%, Fe<0.1%, Sn<0.1%, and balance Zn;

[0007] Rare earth modifiers and additives are also added;

[0008] The rare earth modifier is added at a rate of 0.1% to 0.3% of the total mass of the zinc alloy, and the rare earth modifier is cerium and lanthanum, with a mass ratio of cerium to lanthanum of 7:3.

[0009] The amount of the additive is 0.8 to 1.2% of the total mass of the zinc alloy, and the additive is boron and titanium, with a mass ratio of boron to titanium of 1:1.

[0010] Optionally, the zinc alloy contains the following percentages by mass: Al: 40%, Cu: 1.25%, Mg: 0.045%, Mn: 0.15%, Si: 1.25%, Fe: <0.1%, Sn: <0.1%, rare earth modifier: 0.2%, B-Ti composite salt: 1.0%, and the balance is Zn.

[0011] The method for preparing the zinc alloy with excellent high-temperature strength according to the present invention includes:

[0012] 1) Smelting: After melting the zinc ingots at 550-580℃, aluminum, copper, magnesium, manganese, silicon, iron and tin alloying elements are added in sequence. At this time, the temperature is controlled at 550-580℃ and held for 30-45 minutes to obtain the alloy melt.

[0013] 2) Add rare earth modifiers and additives: Add rare earth modifiers and additives to the alloy melt, stir the melt thoroughly for 10-15 minutes, and then keep it at the temperature for 20-30 minutes.

[0014] 3) Semi-solid billet preparation: The alloy melt treated in step 2) is rapidly cooled to 520-540℃ and stirred for 15-25 minutes to form a semi-solid slurry. The semi-solid slurry is then poured into a mold, and the pouring time is controlled within 5 minutes to make a semi-solid billet.

[0015] 4) Semi-solid secondary remelting extrusion casting: The semi-solid billet is heated to 530-550℃ for secondary remelting and then extruded; during extrusion casting, the temperature of the extrusion casting mold is 350-400℃, the semi-solid billet after secondary remelting is quickly transferred to the extrusion casting mold, and extrusion casting is carried out at 100-150MPa for holding pressure for 10-15S.

[0016] Optional, including:

[0017] 1) Smelting: Heat the zinc ingot to 560℃ to melt it, and add Al, Cu, Mg, Mn, Si, Fe and Sn in sequence. Maintain the temperature at 560±10℃ and hold for 35 minutes to allow the alloying elements to fully dissolve and form a homogeneous melt.

[0018] 5. The method for preparing zinc alloy with excellent high-temperature strength according to claim 3, characterized in that, 2) rare earth modifier and additives are added: rare earth modifier and additives are added to the alloy melt, and the melt is stirred thoroughly for 12 minutes and then kept at the temperature for 25 minutes.

[0019] Optionally, 3) Semi-solid billet preparation: The alloy melt treated in step 2) is rapidly cooled to 530°C and stirred for 20 minutes to form a semi-solid slurry. The semi-solid slurry is then poured into a mold, and the pouring time is controlled within 5 minutes to make a semi-solid billet.

[0020] 4) Semi-solid secondary remelting extrusion casting: The semi-solid billet is heated to 530-550℃ for secondary remelting and then extruded; during extrusion casting, the temperature of the extrusion casting mold is 350-400℃, the semi-solid billet after secondary remelting is quickly transferred to the extrusion casting mold, and extrusion casting is carried out at 120MPa for 12S.

[0021] The zinc alloy with excellent high-temperature strength described in this invention is used in the manufacture of shift fork lever blocks.

[0022] Optionally, the machining method for the shift fork rocker block includes the following steps:

[0023] 1) Smelting: After melting the zinc ingots at 550-580℃, aluminum, copper, magnesium, manganese, silicon, iron and tin alloying elements are added in sequence. At this time, the temperature is controlled at 550-580℃ and held for 30-45 minutes to obtain the alloy melt.

[0024] 2) Add rare earth modifiers and additives: Add rare earth modifiers and additives to the alloy melt, stir the melt thoroughly for 10-15 minutes, and then keep it at the temperature for 20-30 minutes.

[0025] 3) Semi-solid billet preparation: The alloy melt treated in step 2) is rapidly cooled to 520-540℃ and stirred for 15-25 minutes to form a semi-solid slurry. The semi-solid slurry is then poured into a mold, and the pouring time is controlled within 5 minutes to make a semi-solid billet.

[0026] 4) Semi-solid secondary remelting extrusion casting: The semi-solid billet is heated to 530-550℃ for secondary remelting and then extruded; during extrusion casting, the temperature of the extrusion casting mold is 350-400℃, the semi-solid billet after secondary remelting is quickly transferred to the extrusion casting mold, and extrusion casting is carried out at 100-150MPa for holding pressure for 10-15S.

[0027] Optional, also includes:

[0028] 5) Demolding and cleaning: After the extrusion casting is completed, wait for the parts to cool to a certain temperature, open the mold, remove the parts, and clean the parts;

[0029] 6) Heat treatment aging: Place the cleaned zinc alloy parts into a heat treatment furnace for aging treatment. The process parameters for aging treatment are: hold at 160-180℃ for 4-6 hours.

[0030] Optional, 6) Heat treatment aging: Place the cleaned zinc alloy parts into a heat treatment furnace for aging treatment. The process parameters for aging treatment are: hold at 170℃ for 5 hours.

[0031] The advantages of this invention are:

[0032] The zinc alloy of this invention possesses excellent high-temperature strength and wear resistance comparable to ZA27-2 alloy. At a test temperature of 90°C, the wear amount and wear rate of the zinc alloy of this invention are comparable to those of ZA27-2. However, at a test temperature of 160°C, the zinc alloy of this invention exhibits a significant advantage, with both wear amount and wear rate being lower than ZA27-2. This indicates that the zinc alloy of this invention has superior wear resistance under high-temperature conditions. At a working temperature of 90°C, the average friction coefficients of the zinc alloy of this invention and ZA27-2 zinc alloy are 0.075 and 0.08, respectively, showing little difference. As the working temperature increases, at 160°C, the average friction coefficients of both the zinc alloy of this invention and ZA27-2 zinc alloy increase. This is mainly because the hardness of the zinc alloy decreases with increasing temperature, making the surface more susceptible to plastic deformation, leading to an increase in the friction contact area and thus an increase in the friction coefficient. However, due to the better high-temperature performance of the alloy of this invention, its average friction coefficient increases only slightly, by only 0.078. Attached Figure Description

[0033] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings:

[0034] Figure 1 A comparison of the porosity and pore size between the zinc alloy prepared in Example 1 of this invention and zinc alloy ZA27-2;

[0035] Figure 2 The disassembly results of the zinc alloy and zinc alloy ZA27-2 prepared in Example 1 of this invention after testing are shown. Detailed Implementation

[0036] The technical solution of the present invention will be further described below with reference to the embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0037] Zinc alloys have certain applications in the automotive parts manufacturing field due to their good casting performance, relatively low cost advantage, and certain mechanical properties. Traditional heavy-duty truck manual transmissions use copper alloys as shift fork lever blocks, as seen in the article "Improvement of HW Transmission Auxiliary Gearbox Synchronizer Shift Fork Lever Block" by Wang Hui et al. The invention "A Wear-resistant and High-temperature Resistant Zinc Alloy for Shift Fork Lever Blocks of Heavy-duty Truck Transmissions" proposes to use zinc alloy ZA27-2 material and improve the wear resistance of copper alloys through micro-alloying technology.

[0038] Currently, heavy-duty truck transmissions are transitioning from mechanically intensive to electronically controlled and intelligent systems. This means moving from an era dominated by manual transmissions (MT) to a more diversified and intelligent era encompassing automated manual transmissions (AMT) and automatic transmissions (AT), which necessitates higher performance requirements for components. In AMTs, due to the continuous operation of the control unit (TCU) and actuators, and the potential for extended clutch friction time caused by automatic shifting strategies, the operating temperature of AMTs is typically 10-20°C higher than that of manual transmissions. In some mountainous areas or harsh working conditions, the operating temperature can rise instantaneously, reaching 160°C or higher. Increased temperature leads to decreased strength, resulting in gear shifting failures and severely impacting the reliability and lifespan of the transmission. Currently, no materials in AMT products meet these requirements.

[0039] Based on this, this invention develops a zinc alloy with excellent high-temperature strength and its application in heavy-duty truck AMT transmissions. By increasing the aluminum content and adding other alloying elements, combined with semi-solid extrusion remelting casting and modification treatment processes, the overall performance of the alloy can be improved. Compared with ZA27-2 zinc alloy, increasing the alloying elements, especially aluminum, and adding B-Ti composite salts are beneficial to improving strength. Compared with gravity casting, semi-solid extrusion remelting produces a finer and more uniform grain structure, significantly reducing casting defects such as porosity, improving the density of the microstructure, further increasing the strength of the zinc alloy, and producing a high-quality zinc alloy. The composition of the high-temperature strength zinc alloy of this invention is as follows (by mass percentage): Al 39-41%, Cu 1.0-1.5%, Mg 0.03-0.06%, Mn 0.1-0.2%, Si 1.0-1.5%, Fe <0.1%, Sn <0.1%, balance Zn. The rare earth modifier is added at a rate of 0.1-0.3%, where the rare earth modifier refers to a cerium and lanthanum metal complex, and the B-Ti complex salt is 0.8-1.2%.

[0040] The advantages of this invention are that it provides a zinc alloy with excellent high-temperature strength for use in heavy-duty truck AMTs. It uses a high-alumina new alloy formula and a semi-solid extrusion remelting casting preparation method. Through optimal rare earth elements and B-Ti composite salt enhancement modification treatment and heat treatment, it can ensure both excellent wear resistance of the shift fork and improve the high-temperature strength of the shift fork. This solves the problem of insufficient strength of the ZA27-2 shift fork causing gear shifting failure in AMTs under mountainous or extreme working conditions due to increased operating temperature, thereby improving the reliability and service life of the gearbox.

[0041] This invention develops a zinc alloy with excellent high-temperature strength and its application in heavy-duty truck AMT transmissions. By increasing the aluminum content and adding other alloying elements, combined with semi-solid extrusion remelting casting and modification treatment processes, the overall performance of the alloy can be improved. Compared with ZA27-2 zinc alloy, increasing the alloying elements, especially aluminum, and adding B-Ti composite salts are beneficial to improving strength. Compared with gravity casting, semi-solid extrusion remelting produces a finer and more uniform grain structure, significantly reducing casting defects such as porosity, improving the density of the microstructure, further increasing the strength of the zinc alloy, and producing a high-quality zinc alloy. The composition (by mass percentage) of the high-temperature strength zinc alloy of this invention is as follows: Al 39-41%, Cu 1.0-1.5%, Mg 0.03-0.06%, Mn 0.1-0.2%, Si 1.0-1.5%, Fe <0.1%, Sn <0.1%, balance Zn. The rare earth modifier is added at a rate of 0.1-0.3%, where the rare earth modifier refers to a composite of cerium and lanthanum metals, and the B-Ti composite salt is 0.8-1.2%.

[0042] Aluminum (Al): 39-41%; Aluminum is the most important element in zinc alloys, and has a decisive influence on the alloy's microstructure, mechanical properties, and casting characteristics. No intermetallic chemicals are formed between Zn and Al. Zn exhibits infinite solid solution in the liquid state and limited solid solution in the solid state, forming solid solutions, all with a face-centered cubic lattice. The Al content in ZA27-2 alloy is 22-33%, while this invention increases the aluminum content to 39-41%, forming an α phase (Zn-based solid solution containing Al) and a β phase (Zn... 11 Due to the increased α-solution phase, the melting point of zinc alloy is slightly increased. The solid solution of Al in Zn introduces lattice distortion, which hinders dislocation movement and thus improves strength and hardness. Due to the high Al content, the precipitation of the β-phase will further improve strength and hardness. At high temperatures, the α-phase hinders dislocation movement due to lattice distortion, slows down high-temperature softening, and can improve high-temperature hardness. However, the β-phase is prone to coarsening at high temperatures. Therefore, other elements and other treatments are used to stabilize the β-phase and prevent it from coarsening.

[0043] Copper (Cu): 1.0-1.5%; When copper is added to zinc alloy, it dissolves in zinc to form the main ε phase (CuZn4), and a small amount of aluminum is dissolved in it. It has high microhardness and is the hard and brittle phase in zinc alloy. It can improve high-temperature strength and wear resistance under high load conditions, and has a slight inhibitory effect on the high-temperature coarsening of β phase.

[0044] Silicon (Si): 1.0-1.5%; Silicon can improve the tensile strength, hardness, machinability and high-temperature strength of alloys, and help improve the stability of alloys at high temperatures. This is mainly because Si can form an Al-Si eutectic phase with Al, which inhibits the coarsening of the β phase and refines the β phase.

[0045] Magnesium (Mg): 0.03-0.06%; The addition of magnesium can not only improve the corrosion resistance of zinc alloys, but also form a reinforcing phase MgZn2 with the zinc matrix, partially replacing the β phase, reducing the volume fraction of the β phase, and increasing the recrystallization temperature of Zn, thus inhibiting high-temperature softening.

[0046] Manganese (Mn): 0.1-0.2%; Manganese can form a large number of hard-sheared and dispersed manganese-rich compound phases at the grain boundaries, which can prevent the recrystallization process, increase the recrystallization temperature, refine the recrystallized grains, thereby increasing the hardness and toughness of the alloy and improving its high-temperature strength.

[0047] Iron (Fe): <0.1%; Iron is a harmful impurity element. Controlling its content at a low level can prevent the formation of a hard and brittle phase, which affects the performance of the alloy.

[0048] Tin (Sn): <0.1%; Tin is also a harmful impurity element, and limiting its content helps to ensure the quality and performance of the alloy.

[0049] The balance is zinc (Zn), which is the matrix element of the alloy and provides the alloy with basic physical and chemical properties.

[0050] In addition, the following rare earth modifiers and additives were added:

[0051] Rare earth modifier: 0.1-0.3%, wherein the rare earth modifier refers to a composite of cerium and lanthanum metals (the mass ratio of cerium to lanthanum is 7:3). Compared with the 0.05-0.15% content in ZA27-2, the content of rare earth modifier in this invention is increased, which can significantly refine the grain size and increase the grain boundary area. The core mechanism of grain refinement is the dual effect of "heterogeneous nucleation + grain boundary pinning", of which the dominant mechanism is "heterogeneous nucleation". Rare earth elements in zinc alloy melt easily form high-melting-point, highly active compounds (such as La2O3, Ce2O3, LaZn5, etc.). These compounds have different crystal structures and low surface energy, thus providing a large number of low-energy-barrier nucleation sites. Zinc atoms tend to preferentially adsorb and arrange themselves in an orderly manner on these heterogeneous nuclei, thereby greatly increasing the nucleation rate, resulting in an increase in the number of grains and a decrease in size. Experiments show that the nucleation rate of zinc alloy can be increased by 10% after rare earth modification. 4 -10 6 Furthermore, rare earth elements have high chemical reactivity and easily adsorb onto the grain boundaries of zinc alloy grains, forming a "pinning effect" that prevents grain boundary migration and thus inhibits excessive grain growth. Simultaneously, the interaction between rare earth elements and the zinc matrix alters the energy state of the grain boundaries, making them more stable and further suppressing grain growth. Both cerium and lanthanum have grain-refining properties. Since this zinc alloy is in a high-aluminum state, lanthanum can form certain compounds with aluminum, affecting the microstructure and properties of the zinc alloy. Therefore, the proportion of lanthanum should be appropriately reduced. Moreover, given the relatively high price of lanthanum, reducing the proportion of lanthanum and increasing the proportion of cerium while meeting performance requirements also meets cost requirements. Therefore, the rare earth modifier in this patent consists of 70% cerium and 30% lanthanum.

[0052] B-Ti composite salt: 0.8–1.2% (B to Ti mass ratio 1:1). Both B and Ti can react with Al to form AlB2 particles and TiAl3 compounds, respectively. These substances can act as heterogeneous nucleation sites, effectively refining the grains. Due to the more refined grains, the strength and toughness of the alloy are further improved. The smaller grains increase the grain boundary area, making dislocation movement more difficult and requiring greater external force to induce plastic deformation, thus increasing the alloy's strength. Simultaneously, the uniform and fine grain distribution also helps improve the alloy's toughness, allowing it to absorb more energy before fracture. The refined and homogenized microstructure results in a more uniform surface hardness, reducing localized wear caused by microstructure inhomogeneity. Furthermore, the fine grains allow for the formation of a finer, more uniform wear layer on the alloy surface during friction, reducing the wear rate and improving wear resistance. Additionally, the uniform and refined grain structure reduces defects and impurity segregation at grain boundaries, decreasing the diffusion channels of corrosive media and thus improving corrosion resistance. The 1:1 ratio of B and Ti elements achieves the best synergistic effect in the "nucleation-grain boundary stabilization" process, maximizing the grain boundary refinement effect. The 1:1 ratio also makes it easier to weigh and mix raw materials, reducing proportioning errors and improving production efficiency. From the perspective of component compatibility, it avoids the precipitation of brittle phases or component segregation caused by excessive amounts of a certain element.

[0053] A method for machining the zinc alloy used for the shift fork lever block as described above includes the following steps:

[0054] 1) Raw material preparation: Select high-purity zinc ingots and alloying elements such as aluminum, copper, magnesium, and manganese as raw materials, and accurately calculate and weigh various raw materials according to the composition ratio.

[0055] 2) Smelting: Add zinc ingots to a smelting furnace and heat to 550℃-580℃ to melt them. After the zinc is completely melted, add alloying elements such as aluminum, copper, magnesium, and manganese in sequence. At this time, the temperature is controlled at 550℃-580℃ and stirred evenly. Keep it at this temperature for 30-45 minutes to ensure that the alloy components are fully mixed.

[0056] 3) Rare earth modification treatment: When the alloy melt reaches 550℃-580℃, add 0.1-0.3% rare earth modifier and 0.8-1.2% B-Ti composite salt, stir the melt thoroughly for 10-15 minutes to make the modifier evenly distributed, and then keep it at the temperature for 20-30 minutes to ensure the modification effect.

[0057] 4) Semi-solid billet preparation: The modified alloy melt is rapidly cooled to 520-540℃, and the alloy is stirred electromagnetically for 15-25 minutes to form a semi-solid slurry. The semi-solid slurry is then poured into a specific mold. The pouring process should be as fast as possible and controlled within 5 minutes to produce a semi-solid billet.

[0058] 5) Semi-solid secondary remelting extrusion casting: The semi-solid billet is heated to 530-550℃ for secondary remelting to achieve a suitable semi-solid state. During extrusion casting, the mold temperature can be controlled at 350-400℃. The remelted semi-solid billet is then quickly transferred to the extrusion casting mold and extruded at 100-150MPa for 10-15 seconds to fill the mold cavity with the alloy, resulting in a complete zinc alloy part.

[0059] 6) Demolding and Cleaning: After the extrusion casting is completed, wait for the part to cool to a certain temperature, open the mold, and remove the part. Clean the part to remove burrs, flash, and other imperfections from the surface.

[0060] 7) Heat treatment aging: Place the cleaned zinc alloy parts into a heat treatment furnace for aging treatment. The process parameters for aging treatment are: hold at 160℃-180℃ for 4-6 hours, and control the temperature inside the furnace to ensure uniformity of the parts' performance.

[0061] Example 1:

[0062] The specific zinc alloy formula is as follows: Al: 40%, Cu: 1.25%, Mg: 0.045%, Mn: 0.15%, Si: 1.25%, Fe: <0.1%, Sn: <0.1%, rare earth modifier: 0.2% (cerium and lanthanum are compounded in a mass ratio of 7:3, i.e., Ce is 0.14% and La is 0.06%), B-Ti composite salt: 1.0% (boron and titanium are compounded in a mass ratio of 1:1, i.e., B is 0.5% and Ti is 0.5%), and the balance is Zn.

[0063] Specific preparation process:

[0064] 1. Smelting process

[0065] 1) Heat the zinc ingot to 560℃ to melt it, and add Al, Cu, Mg, Mn and Si in sequence (strictly control Fe and Sn < 0.1%). Maintain the temperature at 560±10℃ and hold for 35 minutes to allow the alloying elements to fully dissolve and form a uniform melt.

[0066] 2. Rare Earth Modification and Additive Treatment

[0067] 2) Add 0.2% rare earth modifier (mass ratio Ce:La = 7:3) and 1.0% B-Ti composite salt (mass ratio B:Ti = 1:1) to the melt, stir for 12 min and keep warm for 25 min.

[0068] Mechanism of action: Cerium and lanthanum form high-melting-point compounds (such as Ce₂O₃ and LaZn₅), providing heterogeneous nucleation sites and increasing the nucleation rate by 10%. 4 ~10 6B and Ti respectively form AlB2 and TiAl3, which enhance the grain refinement effect.

[0069] 3. Semi-solid billet preparation

[0070] 3) The melt is rapidly cooled to 530°C and electromagnetically stirred for 20 minutes to form a semi-solid slurry, which is then poured into the mold within 5 minutes.

[0071] Key controls: The solid content of the semi-solid slurry is controlled at 50%–60% to ensure fluidity and grain uniformity, and reduce casting porosity (e.g., Figure 1 As shown in b, the cross-section has no obvious holes.

[0072] 4. Semi-solid secondary remelting extrusion casting

[0073] 4) The billet is heated to 530-550℃ and remelted twice. It is then transferred to a mold at 350-400℃ and extruded under 120MPa pressure for 12s.

[0074] Process advantages: The melt filling under high pressure is more dense, and combined with the fine grain characteristics of the semi-solid structure, the tensile strength is increased by 64% compared with ZA27-2 (303MPa vs 185MPa at 160℃).

[0075] 5. Post-processing

[0076] 5) After the parts have cooled to room temperature, they are demolded and cleaned, and then aged at 170℃ for 5 hours to promote the precipitation of MgZn2 strengthening phase, stabilize the microstructure and further improve high-temperature toughness (elongation up to 9.5%).

[0077] Friction and wear tests were conducted at different operating temperatures according to GB / T 12444-2006 "Metallic Materials Wear Test Methods - Test Ring-Block Sliding Friction and Wear Test". The test conditions were: load: 1000 N, rotation speed: 160 rpm, linear velocity: 0.2 m / s, and time: 180 minutes. Test 1# was conducted at an operating temperature of 90℃, and test 2# at an operating temperature of 160℃. The test results are shown in Table 1. It can be seen that at a test temperature of 90℃, the wear amount and wear rate of the zinc alloy of this invention are comparable to those of ZA27-2. However, at a test temperature of 160℃, the zinc alloy of this invention has a significant advantage, with both its wear amount and wear rate being less than those of ZA27-2. This indicates that the zinc alloy of this invention has superior wear resistance under high-temperature conditions. At a working temperature of 90℃, the average friction coefficients of the zinc alloy of this invention and the ZA27-2 zinc alloy are 0.075 and 0.08, respectively, with little difference. As the working temperature increases, at 160℃, the average friction coefficients of both the zinc alloy of this invention and the ZA27-2 zinc alloy increase. This is mainly because the hardness of the zinc alloy material decreases after the temperature increases, and the surface is more prone to plastic deformation, resulting in an increase in the friction contact area, which in turn increases the friction coefficient. However, because the alloy of this invention has better high-temperature performance, its average friction coefficient increases only slightly, at 0.078.

[0078] The zinc alloy of this invention is designed to have higher high-temperature strength than ZA27-2 zinc alloy. Mechanical property tests were conducted at different operating temperatures according to GB / T228.2-2015 "Metallic Materials; Tensile Testing Part 2: High-Temperature Test Method". The experimental results are shown in Table 2. At a working temperature of 90℃, the tensile strength of the zinc alloy of this invention is 352 MPa, higher than that of ZA27-2 zinc alloy, while the elongation is comparable. At a working temperature of 160℃, the tensile strength of the zinc alloy of this invention decreases, but the decrease is much smaller than that of ZA27-2 zinc alloy, whose tensile strength is only 185 MPa. Therefore, the zinc alloy of this invention exhibits a significant advantage in high-temperature strength.

[0079] The microporousness of the zinc alloy of this invention is far superior to that of the ZA27-2 zinc alloy, such as... Figure 1 As shown, the ZA27-2 zinc alloy exhibits micro-porosity, with numerous randomly distributed micro-porosities and pores on its cross-section, measuring approximately 0.01mm-0.1mm in size. This can affect the overall strength and impact resistance of the parts. In contrast, the zinc alloy of this invention has a dense and compact cross-section, without any obvious casting defects such as pores or micro-porosity.

[0080] Table 1: Wear Rate

[0081]

[0082]

[0083] Table 2: Mechanical Properties

[0084]

[0085] The AMT synchronizer life test was conducted using a front-drive fixed input speed and integrated test software to control clutch engagement. The total lifespan across high and low gears was required to reach 2.8 million cycles, and the target value was achieved. No abnormal noise was observed during the transmission test. The zinc alloy shift fork rocker block of this invention remained intact after disassembly, while the ZA27-2 zinc alloy shift fork rocker block broke. Figure 2 As shown.

[0086] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A zinc alloy with excellent high-temperature strength, characterized in that, The zinc alloy has the following mass percentage content: Al 39%–41%, Cu 1.0%–1.5%, Mg 0.03%–0.06%, Mn 0.1%–0.2%, Si 1.0%–1.5%, Fe <0.1%, Sn <0.1%, with the balance being Zn; Rare earth modifiers and additives are also added; The rare earth modifier is added at a rate of 0.1% to 0.3% of the total mass of the zinc alloy, and the rare earth modifier is cerium and lanthanum, with a mass ratio of cerium to lanthanum of 7:

3. The amount of the additive is 0.8 to 1.2% of the total mass of the zinc alloy, and the additive is boron and titanium, with a mass ratio of boron to titanium of 1:

1.

2. The zinc alloy with excellent high-temperature strength according to claim 1, characterized in that, The zinc alloy has the following mass percentage content: Al: 40%, Cu: 1.25%, Mg: 0.045%, Mn: 0.15%, Si: 1.25%, Fe: <0.1%, Sn: <0.1%, rare earth modifier: 0.2%, B-Ti composite salt: 1.0%, and the balance is Zn.

3. The method for preparing the zinc alloy with excellent high-temperature strength according to claim 1 or 2, characterized in that, include: 1) Smelting: After melting the zinc ingots at 550-580℃, aluminum, copper, magnesium, manganese, silicon, iron and tin alloying elements are added in sequence. At this time, the temperature is controlled at 550-580℃ and held for 30-45 minutes to obtain the alloy melt. 2) Add rare earth modifiers and additives: Add rare earth modifiers and additives to the alloy melt, stir the melt thoroughly for 10-15 minutes, and then keep it at the temperature for 20-30 minutes. 3) Semi-solid billet preparation: The alloy melt treated in step 2) is rapidly cooled to 520-540℃ and stirred for 15-25 minutes to form a semi-solid slurry. The semi-solid slurry is then poured into a mold, and the pouring time is controlled within 5 minutes to make a semi-solid billet. 4) Semi-solid secondary remelting extrusion casting: The semi-solid billet is heated to 530-550℃ for secondary remelting and then extruded; during extrusion casting, the temperature of the extrusion casting mold is 350-400℃, the semi-solid billet after secondary remelting is quickly transferred to the extrusion casting mold, and extrusion casting is carried out at 100-150MPa for holding pressure for 10-15S.

4. The method for preparing the zinc alloy with excellent high-temperature strength according to claim 3, characterized in that, include: 1) Smelting: Heat the zinc ingot to 560℃ to melt it, and add Al, Cu, Mg, Mn, Si, Fe and Sn in sequence. Maintain the temperature at 560±10℃ and hold for 35 minutes to allow the alloying elements to fully dissolve and form a homogeneous melt.

5. The method for preparing a zinc alloy with excellent high-temperature strength according to claim 3, characterized in that, 2) Add rare earth modifiers and additives: Add rare earth modifiers and additives to the alloy melt, stir the melt thoroughly for 12 minutes, and then keep it at the temperature for 25 minutes.

6. The method for preparing a zinc alloy with excellent high-temperature strength according to claim 3, characterized in that, 3) Semi-solid billet preparation: The alloy melt treated in step 2) is rapidly cooled to 530°C and stirred for 20 minutes to form a semi-solid slurry. The semi-solid slurry is then poured into a mold, and the pouring time is controlled within 5 minutes to make a semi-solid billet. 4) Semi-solid secondary remelting extrusion casting: The semi-solid billet is heated to 530-550℃ for secondary remelting and then extruded; during extrusion casting, the temperature of the extrusion casting mold is 350-400℃, the semi-solid billet after secondary remelting is quickly transferred to the extrusion casting mold, and extrusion casting is carried out at 120MPa for 12S.

7. The application of the zinc alloy with excellent high-temperature strength as described in claim 1 or 2 in the manufacture of shift fork lever blocks.

8. The application according to claim 7, characterized in that, The machining method of the shift fork rocker block includes the following steps: 1) Smelting: After melting the zinc ingots at 550-580℃, aluminum, copper, magnesium, manganese, silicon, iron and tin alloying elements are added in sequence. At this time, the temperature is controlled at 550-580℃ and held for 30-45 minutes to obtain the alloy melt. 2) Add rare earth modifiers and additives: Add rare earth modifiers and additives to the alloy melt, stir the melt thoroughly for 10-15 minutes, and then keep it at the temperature for 20-30 minutes. 3) Semi-solid billet preparation: The alloy melt treated in step 2) is rapidly cooled to 520-540℃ and stirred for 15-25 minutes to form a semi-solid slurry. The semi-solid slurry is then poured into a mold, and the pouring time is controlled within 5 minutes to make a semi-solid billet. 4) Semi-solid secondary remelting extrusion casting: The semi-solid billet is heated to 530-550℃ for secondary remelting and then extruded; during extrusion casting, the temperature of the extrusion casting mold is 350-400℃, the semi-solid billet after secondary remelting is quickly transferred to the extrusion casting mold, and extrusion casting is carried out at 100-150MPa for holding pressure for 10-15S.

9. The application according to claim 8, characterized in that, Also includes: 5) Demolding and cleaning: After the extrusion casting is completed, wait for the parts to cool to a certain temperature, open the mold and remove the parts; Clean the parts; 6) Heat treatment aging: Place the cleaned zinc alloy parts into a heat treatment furnace for aging treatment. The process parameters for aging treatment are: hold at 160-180℃ for 4-6 hours.

10. The application according to claim 9, characterized in that, 6) Heat treatment aging: Place the cleaned zinc alloy parts into a heat treatment furnace for aging treatment. The process parameters for aging treatment are: hold at 170℃ for 5 hours.

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