Al-Ni-Mn Die Casting Alloy with Mn-Regulated Thermal Conductivity after Brazing

Abstract

The present invention provides an Al-Ni-Mn series die-casting alloy based on Mn for regulating the thermal conductivity after brazing, which relates to the technical field of metal material preparation. The Al-Ni-Mn series die-casting alloy includes a high-thermal-conductivity Al-Ni-Mn series die-casting alloy and a low-thermal-conductivity Al-Ni-Mn series die-casting alloy; in the high-thermal-conductivity Al-Ni-Mn series die-casting alloy, the solid solution rate of Mn after brazing is <40%, and the thermal conductivity is 160-180 W / m·K; in the low-thermal-conductivity Al-Ni-Mn series die-casting alloy, the solid solution rate of Mn after brazing is >70%, and the thermal conductivity is 80-125 W / m·K. The Al-Ni-Mn series die-casting alloy provided by the present invention regulates the solid solution rate of Mn during the brazing cooling process, realizes applications in the fields of high thermal conductivity and low thermal conductivity, provides materials with thermal conductivity meeting the requirements for different fields, and expands the application fields and application effects of the Al-Ni-Mn series die-casting alloy.

Description

Technical Field

[0001] The present invention relates to the technical field of metal material preparation, and in particular to an Al-Ni-Mn series die-casting alloy for regulating the thermal conductivity after brazing based on Mn, and a preparation method and application thereof. Background Art

[0002] With the large-scale application of integrated structures in the thermal management system of new energy vehicles, the demand for complex-shaped aluminum alloy parts is increasing. For example, in the refrigerant valve island of a heat pump system, there are more than a dozen or even dozens of interfaces and flow channels distributed in one refrigerant valve island, and there are a large number of adjacent arrangements of cold-side and hot-side flow channels. Therefore, materials with low thermal conductivity are required to reduce the heat exchange between the hot-side flow channel and the cooling flow channel. For materials with low thermal conductivity requirements, the thermal conductivity generally needs to be controlled below 125 W / m·K. In addition, in the autonomous driving chip module and the inverter module, chip cooling management is required. Since high-power chips generate a large amount of heat during operation, it is necessary to transfer the heat to the circulating coolant in time through an aluminum alloy cooling plate to achieve chip cooling. In this case, aluminum alloy materials with high thermal conductivity are required. For materials with high thermal conductivity requirements, the thermal conductivity generally needs to be controlled above 160 W / m·K. Whether it is a chip cold plate or components such as refrigerant valve islands, there are requirements for withstanding the working medium pressure, and generally, the yield strength of the material is required to reach above 60 MPa.

[0003] The chip layout in the chip cold plate is extremely irregular, resulting in a very complex structure of the cooling plate for cooling the chips. On the other hand, as the integration degree of the heat pump system is getting higher and higher, the structures of components such as refrigerant valve islands are also becoming more and more complex. Currently, complex components are mainly manufactured by forging or casting. However, forging parts have a large machining allowance and high production costs, and the increasingly complex designs pose greater challenges to the forging process. In contrast, casting has high production efficiency, low production costs, and is particularly suitable for the production of complex components, with broad market prospects.

[0004] In the thermal management system of new energy vehicles, there are various cooling media inside the components, so there are requirements for the sealing performance of each component. After complex parts are cast, they need to be brazed with other parts at high temperature to form an integral whole before they can be used as a component. Therefore, the properties of the casting after brazing, such as thermal conductivity and yield strength, directly affect the performance and reliability of the casting product during actual operation. In addition, the brazing temperature of aluminum alloy high-temperature brazing is generally 590 - 620 °C. Therefore, for castings, the solidus temperature of the raw material needs to be higher than 620 °C, or even above 630 °C, otherwise local melting of the casting base material will occur during brazing.

[0005] Among existing aluminum alloy casting materials, the most widely used is the Al-Si series alloy. However, the solidus temperature of this series of alloys is generally relatively low, usually 510 - 577 °C, and it cannot be used for high-temperature brazing. The Al-Ni series alloy has been widely used in high-temperature components of new energy vehicles, such as rotors, etc., due to its advantages of high temperature resistance, corrosion resistance, excellent casting performance, and appropriate material strength and thermal conductivity. And the solidus temperature of this series of alloys is higher than 630, which is particularly suitable for die-casting materials that can be brazed at high temperatures.

[0006] Existing Al-Ni series alloys reduce the thermal conductivity through the solid solution of Cr. However, during melting and die-casting processes, a large amount of primary AlCrMnNi compounds containing Cr (respectively called ESCs (externally solidified crystals) and "Sludge") will be generated. This primary phase almost consumes all the added Cr, resulting in the inability to achieve the effect of reducing the thermal conductivity through Cr solid solution. In addition, the primary phase also causes a large amount of the scarce Ni element to be consumed, leading to poor fluidity of the material and deteriorating the castability.

[0007] In the field with high thermal conductivity requirements, the existing technology uses another eutectic or near-eutectic system of Al-Ni alloy materials with a Ni content of 4.5 - 6%. The price of Ni element is very high, resulting in a high cost of this alloy. Therefore, the high-Ni Al-Ni alloy is not an ideal material.

[0008] In addition, currently, most Al-Ni series materials are developed for high-temperature applications. Since brazing involves the solid solution and precipitation of added elements, which will affect the properties such as the strength and thermal conductivity of the material, it is very difficult to directly apply this type of material to brazing, especially in the field of heat exchangers with high requirements for thermal conductivity.

[0009] Up to now, no relevant reports have been found on the regulation of thermal conductivity by controlling the solid solution and precipitation of Mn element in Al-Ni series alloys.

[0010] In view of this, the present invention is specifically proposed. Summary of the Invention

[0011] One of the purposes of the present invention is to provide an Al-Ni-Mn series die-casting alloy for regulating the thermal conductivity after brazing based on Mn to solve at least one of the above technical problems in the prior art.

[0012] Another purpose of the present invention is to provide a preparation method for the Al-Ni-Mn series die-casting alloy.

[0013] The third purpose of the present invention is to provide an application of the Al-Ni-Mn series die-casting alloy.

[0014] To achieve the above object of the present invention, the following technical solutions are specifically adopted:

[0015] In the first aspect of the present invention, an Al-Ni-Mn series die-casting alloy based on Mn-regulated thermal conductivity after brazing is provided, including a high-thermal-conductivity Al-Ni-Mn series die-casting alloy and a low-thermal-conductivity Al-Ni-Mn series die-casting alloy;

[0016] In the high-thermal-conductivity Al-Ni-Mn series die-casting alloy, the solid solution rate of Mn after brazing is < 40%, and the thermal conductivity is 160 - 180 W / m·K;

[0017] In the low-thermal-conductivity Al-Ni-Mn series die-casting alloy, the solid solution rate of Mn after brazing is > 70%, and the thermal conductivity is 80 - 125 W / m·K.

[0018] Further, in the high-thermal-conductivity Al-Ni-Mn series die-casting alloy, the Ni content is 2 - 6%, the Mn content is 0.5 - 1.5%, the solid solution rate of Mn after brazing is < 40%, the Er content is 0.1 - 0.3%, and the balance is Al and inevitable impurities.

[0019] Further, in the low-thermal-conductivity Al-Ni-Mn series die-casting alloy, the Ni content is 2 - 6%, the Mn content is 0.5 - 1.5%, the solid solution rate of Mn after brazing is > 70%, the Mo content is 0.1 - 0.3%, and the balance is Al and inevitable impurities.

[0020] Further, the thermal conductivity of the low-thermal-conductivity Al-Ni-Mn series die-casting alloy is 90 - 125 W / m·K.

[0021] Further, the low-thermal-conductivity Al-Ni-Mn series die-casting alloy further includes Zr and / or V.

[0022] Further, the content of Zr and / or V is 0.1 - 0.2%.

[0023] Further, the thermal conductivity of the low-thermal-conductivity Al-Ni-Mn series die-casting alloy is 80 - 110 W / m·K.

[0024] Further, in the Al-Ni-Mn die-casting alloy, for each impurity component: the Fe content < 0.8%, the Si content < 0.1%, the Cr content < 0.1%, and the contents of other various impurities are all < 0.1% and the total is < 0.2%.

[0025] The second aspect of the present invention provides a method for preparing the Al-Ni-Mn series die-casting alloy. The Al-Ni-Mn series castings, solder, and parts to be soldered are placed in a soldering furnace for high-temperature soldering at 590 - 620 °C. During the soldering cooling process, by controlling the solution and precipitation of Mn, a high-thermal-conductivity Al-Ni-Mn series die-casting alloy or a low-thermal-conductivity Al-Ni-Mn series die-casting alloy is obtained.

[0026] Furthermore, Mn in the Al-Ni-Mn series die-casting alloy is used to regulate the thermal conductivity of the die-casting alloy after soldering. Er in the die-casting alloy promotes the precipitation of Mn and reduces the solid solution of Mn during the soldering cooling process, obtaining the high-thermal-conductivity Al-Ni-Mn series die-casting alloy;

[0027] Or,

[0028] Mo in the Al-Ni-Mn series die-casting alloy inhibits the precipitation of Mn and promotes the solid solution of Mn during the soldering cooling process, obtaining the low-thermal-conductivity Al-Ni-Mn series die-casting alloy.

[0029] The third aspect of the present invention provides the application of the described Al-Ni-Mn series die-casting alloy in the refrigerant valve island of a heat pump system or in an automotive thermal management system.

[0030] Compared with the prior art, the present invention has at least the following beneficial effects:

[0031] The Al-Ni-Mn series die-casting alloy provided by the present invention realizes applications in the fields of high thermal conductivity and low thermal conductivity by regulating the solid solution rate of Mn, provides materials with thermal conductivity meeting requirements for different fields, and expands the application fields and application effects of the Al-Ni-Mn series die-casting alloy.

[0032] The method for preparing the Al-Ni-Mn series die-casting alloy provided by the present invention realizes the interaction between the added alloying elements and the solid solution Mn during the soldering cooling process, promotes or inhibits the precipitation of Mn, realizes the adjustment of the solid solution rate of Mn, and thus achieves the regulation of the thermal conductivity. One way is to add the alloying element Er to promote the precipitation of the Al6Mn phase to meet the high thermal conductivity requirement; another way is to add the alloying element Mo to promote the solid solution of Mn and inhibit the precipitation of Al6Mn, thereby realizing the low thermal conductivity requirement of the Al-Ni-Mn series die-casting alloy.

[0033] The application provided by the present invention, due to the advantages of the above-mentioned Al-Ni-Mn series die-casting alloy, enables the above alloy materials to have better applications in the refrigerant valve island of a heat pump system or in the thermal management system of new energy vehicles, and expands the development of the downstream industry. Detailed Embodiments

[0034] The embodiments of the present invention will be described in detail below in conjunction with the embodiments and examples. However, those skilled in the art will understand that the following embodiments and examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0035] In the first aspect of the present invention, an Al-Ni-Mn series die-casting alloy is provided, including a high-thermal-conductivity Al-Ni-Mn series die-casting alloy and a low-thermal-conductivity Al-Ni-Mn series die-casting alloy;

[0036] In the high-thermal-conductivity Al-Ni-Mn series die-casting alloy, the solid solution rate of Mn after brazing is <40%, and the thermal conductivity is 160-180 W / m·K;

[0037] In the low-thermal-conductivity Al-Ni-Mn series die-casting alloy, the solid solution rate of Mn after brazing is >70%, and the thermal conductivity is 80-125 W / m·K.

[0038] The Al-Ni-Mn series die-casting alloy provided by the present invention realizes applications in the fields of high thermal conductivity and low thermal conductivity respectively by regulating the solid solution rate of Mn, provides materials with thermal conductivity meeting requirements for different fields, and expands the application fields and application effects of the Al-Ni-Mn series die-casting alloy.

[0039] The die-casting alloy described in the present invention can be high-pressure casting, squeeze casting, gravity casting, differential-pressure casting or low-pressure casting.

[0040] Brazing is a hot working process. The assembled parts are heated in a brazing furnace until the filler metal melts, wets and spreads on the base metal, and a brazed joint is formed after cooling. During the brazing process, while a series of physical changes occur to the filler metal, a series of changes also occur to the base metal. For aluminum alloys, the base metal will experience the solution of dispersed particles (if present in the base metal before brazing) during heating to form a solid solution. During cooling, depending on the types of alloying elements in the aluminum alloy and the cooling rate, some solid solutions will precipitate to form dispersed particles, and some solid solutions are not prone to precipitate dispersed particles, and the state of the solid solution remains until room temperature and exists stably. The solution and precipitation of alloying elements in aluminum alloys are the main factors affecting thermal conductivity, especially elements such as Li, Mn, Si, Cr, Ti, V, Zr, etc. Their solution can significantly reduce the thermal conductivity of aluminum alloys, while after their precipitation to form dispersed particles, the reduction in thermal conductivity is relatively small.

[0041] Brazing is carried out in a brazing furnace. Generally, the brazing furnace consists of three parts: a heating section, a brazing section, and a cooling section. The product to be brazed is heated to about 600 in the heating section and then enters the brazing section. It stays at 600 in the brazing section for about 3 minutes and then enters the cooling section. To prevent high-temperature oxidation of the aluminum alloy product during cooling, the cooling is carried out under a N2 protective atmosphere, and the injection port of N2 is located at the intersection of the brazing section and the cooling section. The temperature of the product coming out of the brazing section is as high as about 600. Under the direct impact of the introduced room-temperature N2, the product is rapidly cooled near the entrance of the cooling section, with a cooling rate of over 55 / min, and the temperature quickly drops from 600 to about 500. After the product leaves the N2 injection port in the cooling section, due to heat exchange, the temperature of N2 rises, the cooling effect on the product weakens, the cooling rate of the product drops to about 30 / min, and the product temperature drops below 300 and then leaves the furnace for cooling.

[0042] In the Al-Ni-Mn series die-casting alloy, the addition of the alloying element Mn mainly plays two roles. One is to strengthen α-Al by forming a solid solution through solid solution or precipitating to form dispersed particles. At the same time, it can increase the volume fraction of the strengthening phase in the eutectic structure, thereby achieving the strengthening of the material. The other is to replace Fe to solve the problem of die sticking of the casting. It can be seen that Mn is an essential additive element in the Al-Ni series die-casting alloy.

[0043] In addition, Mn also has a powerful thermal conductivity regulation effect. Because the maximum saturation solubility of Mn in the Al-Mn binary alloy is as high as 1.82%. During the die-casting process, due to the large cooling rate, the solubility of Mn is close to the saturation solubility, and the brazing process will cause the precipitation of Mn. The precipitation temperature range of Al6Mn in the aluminum alloy is 400 - 425°C. This temperature is exactly in the part with a slower cooling rate in the cooling section of the brazing furnace. In addition, the diffusion rate of Mn at 400°C is 6×10 -19 m 2 / s, which belongs to an element that is easy to diffuse among the alloying elements of the aluminum alloy. It can form Al6Mn dispersed particles, resulting in a large amount of precipitation of Mn dissolved in the aluminum alloy. After precipitation, the solid solution rate of Mn in the aluminum alloy is about 40% - 50%, and the thermal conductivity after brazing is about 130 - 150 W / m·K. At this time, the thermal conductivity can neither meet the requirements of high-thermal-conductivity aluminum alloys nor the requirements of low-thermal-conductivity aluminum alloys.

[0044] The inventors found that when 1% of Mn was added to the Al-3% Ni die-casting alloy, the solid solution rate of Mn after brazing was about 46%, and at this time the thermal conductivity was about 138 W / m·K. On this basis, when 0.1% of Er was added, the solid solution rate of Mn after brazing decreased to about 35%, and the thermal conductivity increased to about 163 W / m·K. In addition, on the basis of Al-3% Ni-1% Mn, when 0.1% of Mo was added, the solid solution rate of Mn after brazing increased to about 71%, and the thermal conductivity decreased to about 124 W / m·K.

[0045] Therefore, the solid solution and precipitation of Mn have a significant impact on the thermal conductivity of aluminum alloys. According to the influence of the solid solution and precipitation of Mn on the thermal conductivity, by adding elements that can promote or inhibit the solid solution of Mn, the thermal conductivity of die-casting alloys can be regulated, and its applications in the fields of low thermal conductivity and high thermal conductivity can be realized respectively.

[0046] For fields with high thermal conductivity requirements such as chip cold plates, it is necessary to ensure the precipitation of Mn as much as possible. In terms of promoting the precipitation of solid solution elements, rare earth element Er is a very ideal element. In the field of aluminum alloy materials, Er has been used to replace expensive Sc as the nucleation core of the precipitation phase. For the present invention, Er is more suitable than Sc, and its mechanism is as described below.

[0047] The limiting solid solubility of Er in aluminum alloy at 660 °C is only 0.23%, and the solid solubility is close to 0% at 400 °C. In addition, considering from the perspective of atomic radius, the atomic radius of Er is 23% larger than that of Al. Considering these two factors, it can be seen that Er has a large precipitation driving force in aluminum alloy. In addition, the diffusion rate of Er reaches 7×10 -18 m 2 / s at 300 °C. At 400 °C, the diffusion rate of Er in aluminum alloy is more than 10 times that of Mn. Therefore, for the die-casting alloy added with Er, it is very easy to precipitate during the brazing cooling process and complete precipitation before the precipitation of Mn. The precipitation phase is L12-type nano-particles Al3Er with a dispersed distribution. The nano-particles Al3Er can be used as the core for heterogeneous nucleation of Al6Mn dispersed particles, promoting the precipitation of Al6Mn dispersed particles. At this time, the solid solution rate of Mn in aluminum alloy is further reduced to 40%, or even below 30%. This can ensure that the die-casting alloy after brazing has a high thermal conductivity. The thermal conductivity after brazing is 160-180 W / m·K, and this die-casting alloy can be used in fields with high thermal conductivity requirements such as chip cold plates.

[0048] For fields with low thermal conductivity requirements such as refrigerant valve islands, it is necessary to ensure that most of the Mn in the die-casting alloy is solid-solved. However, through the brazing process, it is difficult to ensure the non-precipitation of Al6Mn. Therefore, alloying elements that interact with Mn need to be added to inhibit the precipitation of Al6Mn, thereby achieving a low thermal conductivity of the die-casting alloy.

[0049] In the high-temperature resistant aluminum alloy die-casting material, Mn and Mo are added simultaneously to improve the high-temperature resistance of the material. The advantage that the diffusion rate of Mo is slow at high temperatures and the dispersed particles of Al6(MnMo) are not easily coarsened is utilized. This mechanism can also be applied to control the precipitation of Mn. The specific mechanism is as follows:

[0050] With the addition of Mo, the precipitation phase is transformed from Al6Mn to Al6(MnMo). Al6(MnMo) is a stable phase and the only Mn-containing precipitation phase. The diffusion coefficient of Mo in the aluminum alloy at 400 °C is 5.5×10 -23 m 2 / s, which is 1 / 10000 of the diffusion coefficient of Mn under the same conditions. This makes it difficult for Al6(MnMo) to precipitate at 400 °C, thereby raising the precipitation temperature of Al6(MnMo) to approximately 540 °C. And due to the extremely slow diffusion rate of Mo, the precipitation driving force of Al6(MnMo) is much smaller than that of Al6Mn. At the same time, the precipitation temperature of 540 °C happens to be in the rapid cooling region of the cooling section, and the rapid cooling further restricts the precipitation of Al6(MnMo), ensuring the solid solution of Mn, and thus realizing the low thermal conductivity performance of the die-casting alloy.

[0051] In the specific implementation process of the present invention, when obtaining the high-thermal conductivity Al-Ni-Mn series die-casting alloy, the thermal conductivity is typically but not limited to 160 W / m·K, 170 W / m·K, or 180 W / m·K.

[0052] Furthermore, in the high-thermal conductivity Al-Ni-Mn series die-casting alloy, the Ni content is 2-6%, the Mn content is 0.5-1.5%, the solid solution rate of Mn after brazing < 40%, the Er content is 0.1-0.3%, and the balance is Al and unavoidable impurities.

[0053] In the Al-Ni-Mn series die-casting alloy of the present invention, the fluidity and volume shrinkage rate of the material during die-casting are mainly ensured by the Ni element. When the Ni content exceeds 2%, the Al-Ni alloy itself has a low hot crack sensitivity. Whether it is used in the field with high thermal conductivity requirements or the field with low thermal conductivity requirements, the present invention controls the Ni content at 2-6%, and the optimal is 3-4%.

[0054] Whether it is used in the field with high thermal conductivity requirements or the field with low thermal conductivity requirements, the present invention controls the Mn content at 0.5%-1.5%. When the Mn content < 0.5%, there are problems with difficult demolding of the casting. When the Ni content is near the lower limit, it is necessary to increase the Mn content to make up for the insufficient material strength caused by the decrease in the Ni content. When the Mn content exceeds 1.5%, coarse primary AlMnNi phases are likely to be generated, affecting the fluidity and strength of the die-casting material.

[0055] In the specific implementation process, the Ni content is typically but not limited to 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5% or 6%; the Mn content is typically but not limited to 0.5%, 0.7%, 0.9%, 1.1%, 1.3% or 1.5%. In the specific implementation process of the present invention, the Er content is typically but not limited to 0.1%, 0.15%, 0.2%, 0.25% or 0.3%.

[0056] In the specific implementation process of the present invention, when obtaining a low-thermal-conductivity Al-Ni-Mn series die-casting alloy, the thermal conductivity is typically but not limited to 90 W / m·K, 100 W / m·K, 110 W / m·K, 120 W / m·K or 125 W / m·K.

[0057] Furthermore, in the low-thermal-conductivity Al-Ni-Mn series die-casting alloy, the Ni content is 2-6%, the Mn content is 0.5-1.5%, the solid solution rate of Mn after brazing > 70%, the Mo content is 0.1-0.3%, and the balance is Al and inevitable impurities.

[0058] When the content of the Mn element is 0.5%-1.5% and 0.1-0.3% of the Mo element is added, when most of the Mn and Mo are solid-solved under the brazing cooling condition, a thermal conductivity value as low as 90-125 W / m·K can be achieved. At the same time, the solid solution of Mn and Mo can improve the yield strength of the aluminum alloy.

[0059] The Mo content is controlled at 0.1-0.3%. When the Mo content is less than 0.1%, the strengthening effect on the material and the regulation effect on the thermal conductivity are not obvious, while when the Mo content exceeds 0.3%, it is easy to appear Al 12 Mo primary phase.

[0060] In the specific implementation process of the present invention, the Mo content is typically but not limited to 0.1%, 0.15%, 0.2%, 0.25% or 0.3%; the Mn content is typically but not limited to 0.5%, 0.7%, 0.9%, 1.1%, 1.3% or 1.5%.

[0061] Furthermore, in the low-thermal-conductivity Al-Ni-Mn series die-casting alloy, it also includes Zr and / or V.

[0062] If lower thermal conductivity requirements are needed, based on the Al-Ni-Mn-Mo alloy system, the content of Zr and V added alone or in combination can be 0.1-0.2%, which means adding 0.1-0.2% of Zr or V alone in the Al-Ni-Mn-Mo alloy system, or adding 0.1-0.2% of Zr and V simultaneously, to achieve the stable solid solution of Zr and / or V in the aluminum alloy, further reducing the thermal conductivity while improving the strength of the alloy.

[0063] In some embodiments of the present invention, when the content of Zr and / or V is 0.1-0.2%, typically but not limitedly, the amount of Zr added alone can be 0.1%, 0.12%, 0.14%, 0.16%, 0.18% or 0.2%; the amount of V added alone can be 0.1%, 0.12%, 0.14%, 0.16%, 0.18% or 0.2%; the amount of Zr and V added simultaneously can be 0.1%, 0.12%, 0.14%, 0.16%, 0.18% or 0.2%. When adding Zr and V simultaneously, the ratio of Zr and V is not specifically limited.

[0064] Furthermore, after the low thermal conductivity Al-Ni-Mn series die-casting alloy includes Zr and / or V, the thermal conductivity is 80-110 W / m·K.

[0065] Furthermore, in the Al-Ni-Mn series die-casting alloy, for each impurity component: the Fe content < 0.8%, the Si content < 0.1%, the Cr content < 0.1%, and the content of each of the remaining various impurities is < 0.1% and the total is < 0.2%. Here, the remaining various impurities refer to impurity elements other than Fe, Si, and Cr.

[0066] Controlling the Si content to be less than 0.1% can ensure excellent resistance to thermal crack sensitivity. If the Si content is greater than 0.1%, local Si segregation is likely to occur, and then the low-melting-point Al-Si eutectic will appear, resulting in thermal crack defects.

[0067] If there is impurity Cr in the die-casting alloy, it is easy to form the AlCrMnNi primary phase during melting or die-casting. On the one hand, it consumes the Ni content in the die-casting alloy, and on the other hand, the appearance of the primary phase affects the fluidity of the die-casting alloy. Therefore, the Cr content is controlled within 0.1%.

[0068] Regarding the problem of sticking to the mold during die-casting, currently in the Al-Si series alloy, adding Fe element to the die-casting material can solve the problem of sticking to the mold, but the addition of Fe will generate the brittle AlFeSi phase, affecting the toughness of the casting. In the Al-Ni series alloy, when the Fe content ≥ 0.8%, the Al9FeNi primary phase is likely to appear, not only consuming the Ni content but also affecting the mechanical properties of the material.

[0069] The second aspect of the present invention provides a method for preparing the Al-Ni-Mn series die-casting alloy. The Al-Ni-Mn series castings, solder, and parts to be soldered are placed in a soldering furnace for high-temperature soldering at 590 - 620 °C. During the cooling process of soldering, by controlling the solution and precipitation of Mn, a high-thermal-conductivity Al-Ni-Mn series die-casting alloy or a low-thermal-conductivity Al-Ni-Mn series die-casting alloy is obtained.

[0070] The method for preparing the Al-Ni-Mn series die-casting alloy provided by the present invention realizes the interaction between the added alloying elements and the dissolved Mn during the cooling process of soldering, promotes or inhibits the precipitation of Mn, realizes the adjustment of the solution rate of Mn, and thus achieves the regulation of the thermal conductivity. One way is to add the alloying element Er to promote the precipitation of the Al6Mn phase to meet the high-thermal-conductivity requirement; another way is to add the alloying element Mo to promote the solution of Mn and inhibit the precipitation of Al6Mn, thereby realizing the low-thermal-conductivity requirement of the Al-Ni-Mn series die-casting alloy.

[0071] Furthermore, Er in the Al-Ni-Mn series die-casting alloy promotes the precipitation of Mn during the cooling process of soldering, reduces the solution of Mn, and obtains the high-thermal-conductivity Al-Ni-Mn series die-casting alloy;

[0072] Or,

[0073] Mo in the Al-Ni-Mn series die-casting alloy inhibits the precipitation of Mn during the cooling process of soldering, promotes the solution of Mn, and obtains the low-thermal-conductivity Al-Ni-Mn series die-casting alloy.

[0074] In the specific implementation process of the present invention, the temperature of high-temperature soldering is typically but not limited to 590 °C, 600 °C, 610 °C, or 620 °C.

[0075] Furthermore, the material of the solder is an Al-Si series alloy.

[0076] The third aspect of the present invention provides the application of the Al-Ni-Mn series die-casting alloy in the refrigerant valve island of a heat pump system or an automotive thermal management system.

[0077] The application provided by the present invention, due to the advantages of the above-mentioned Al-Ni-Mn series die-casting alloy, enables the above alloy material to have better applications in the refrigerant valve island of a heat pump system or the thermal management system of a new energy vehicle, and expands the development of the downstream industry.

[0078] The present invention will be further described below through specific examples and comparative examples. However, it should be understood that these examples are only for more detailed description and should not be construed as limiting the present invention in any way. For the raw materials used in the examples and comparative examples of the present invention, those without specific conditions are carried out according to conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained by purchasing in the market.

[0079] Examples and Comparative Examples

[0080] The examples and comparative examples respectively provide an Al-Ni-Mn series die-casting alloy, and the alloy component ratios of each example and comparative example are shown in Table 1.

[0081] Table 1

[0082]

[0083] The manufacturing methods of the Al-Ni-Mn series die-casting alloys in the examples and comparative examples are as follows:

[0084] (1) Preparation

[0085] According to Table 1, the elemental composition ratios of the die-casting alloy are carried out.

[0086] (2) Melting

[0087] Heat the raw material of Al to melt it into an aluminum melt, add the raw materials of other elements into the aluminum melt, and after all the raw materials are melted, stir evenly to obtain an alloy melt. Among them, during the whole melting process, the temperature is controlled at 740 - 780 °C.

[0088] (3) Refining

[0089] Add a refining agent to the alloy melt for refining treatment.

[0090] (4) Post-treatment

[0091] For the refined aluminum alloy melt, after degassing, then skim the slag, and then stand still at 730 - 760 °C for 15 - 25 min to precipitate or float the impurities in the aluminum alloy melt and remove the impurities.

[0092] (5) Die-casting

[0093] During die-casting, the temperature of the aluminum liquid is 720 °C, the mold temperature is 240 °C, the injection pressure is 70 MPa, and the injection time is 8 s. After cooling, a casting is obtained.

[0094] (6) Brazing

[0095] Place the casting, brazing filler metal, and parts to be brazed in a brazing furnace at 600 °C for high-temperature brazing, keep warm for 3 min and then cool to obtain the die-casting alloy.

[0096] Test Example 1

[0097] Perform thermal crack sensitivity analysis, demolding effect analysis, and analysis of primary phases inside the Al-Ni-Mn series castings after die casting and before brazing.

[0098] The thermal crack sensitivity analysis is determined by CT analysis. If there are more than 5 cracks inside the casting, the thermal crack sensitivity is judged as "high"; if there are 1 - 4 cracks, the thermal crack sensitivity is judged as "medium"; if there are no cracks inside the casting, the thermal crack sensitivity is judged as "low".

[0099] The demolding effect is judged according to the appearance quality of the casting after die casting. If there is a sticking mold phenomenon on the casting surface, the demolding effect is judged as "poor"; if the casting surface is smooth and there is no sticking mold phenomenon, the demolding effect is judged as "good".

[0100] The primary phases inside the casting are judged by metallographic analysis. Select any cross-section of the casting. In the range of 10mm * 10mm, if the number of primary compound phases ≥ 5, it is judged as "yes"; if the number of primary compound phases < 5, it is judged as "no".

[0101] The results obtained are shown in Table 2.

[0102] Table 2

[0103]

[0104]

[0105] Test Example 2

[0106] Measure the Mn solid solution rate, thermal conductivity, and yield strength of the brazed Al-Ni-Mn series die-casting alloy, and conduct brazability analysis of the die-casting alloy.

[0107] The test method for the Mn solid solution rate is as follows: Divide the die-casting alloy into granular form, add it to boiling phenol for dissolution, put the solution into a polytetrafluoroethylene filter membrane with a pore size less than 0.1um for filtration. The dispersed particles and other compound phases in the die-casting alloy remain on the filter membrane, and the dissolved elements and Al ions pass through the filter membrane. Conduct ICP-OES composition testing on the filtered solution. The measured Mn content is the solid solution Mn content dissolved in the die-casting alloy. Then divide this content by the Mn content added during the batching of the die-casting alloy, which is the Mn solid solution rate.

[0108] That is, Mn solid solution rate = solid solution Mn content / Mn content added in raw materials.

[0109] The method for measuring the thermal conductivity is as follows: The die-cast alloy sample block is processed into a cylinder with a diameter of 3 mm and a height of 2 mm, and then placed in a laser thermal conductivity meter to measure the thermal diffusivity α of the sample block, and the thermal conductivity is obtained according to the following formula.

[0110] λ = αρc

[0111] Among them, λ is the thermal conductivity, with the unit of W / (m·K);

[0112] ρ is the density, with the unit of Kg / m 3 ;

[0113] c is the specific heat capacity, with the unit of J / (Kg·K).

[0114] The yield strength is carried out according to the provisions in GB / T228.1-2021 "Metallic materials - Tensile testing - Part 1: Method of test at room temperature".

[0115] The brazability of the die-cast alloy is analyzed by metallography. Three parts are randomly selected from the casting for cross-section metallographic analysis, and the diffusion depth of the filler metal in the casting adjacent to the brazing seam is measured. If the diffusion depth of the filler metal is less than 0.2 mm, it is judged as "good"; if the diffusion depth of the filler metal is ≥0.2 mm, it is judged as "poor".

[0116] The results obtained are shown in Table 3 below.

[0117] Table 3

[0118]

[0119] In Examples 1-3, due to the addition of Er element, the precipitation of a large number of Al6Mn dispersed particles is promoted, and the solid solution Mn content is greatly reduced, so they have a relatively high thermal conductivity.

[0120] In Examples 4-6, the addition of Mo element promotes the solid solution of Mn during brazing cooling, inhibits the precipitation of Mn, and greatly reduces the thermal conductivity.

[0121] In Examples 7-9, on the basis of adding Mo element, 0.1-0.2% of Zr and V are added respectively, or 0.1-0.2% of Zr and V are added simultaneously, further reducing the thermal conductivity.

[0122] For Comparative Examples 1-5, they are Al-Ni-Mn ternary alloys, which can neither meet the requirements of high thermal conductivity die-cast alloys with a thermal conductivity higher than 160 W / m·K nor meet the requirements of low thermal conductivity die-cast alloys with a thermal conductivity lower than 125 W / m·K.

[0123] In Comparative Example 1, the Ni content is relatively low, the sensitivity of the die-cast alloy to hot cracking is relatively high, and the yield strength of the die-cast alloy is also very low.

[0124] The Mn content of the components in Comparative Example 2 is relatively low, resulting in difficulty in demolding the castings after die-casting.

[0125] In Comparative Example 3, since the Ni content is on the lower limit and the Mn content is not high either, the yield strength of the die-casting alloy cannot meet the requirements.

[0126] In Comparative Example 4, due to the increase in Ni content, even if the Mn content is relatively low, the yield strength can still meet the requirements.

[0127] In Comparative Example 5 and Comparative Example 6, primary phases of AlMnNi and Al 12 Mo appeared respectively.

[0128] Finally, it should be noted that the above embodiments are only used to illustrate the technical embodiments of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical embodiments described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical embodiments to deviate from the scope of the technical embodiments of the present invention.

Claims

1. An Al-Ni-Mn die-casting alloy based on Mn to regulate thermal conductivity after brazing, characterized in that: Including high thermal conductivity Al-Ni-Mn die-casting alloy and low thermal conductivity Al-Ni-Mn die-casting alloy; The high thermal conductivity Al-Ni-Mn die-casting alloy has a Ni content of 2-6%, a Mn content of 0.5-1.5%, a Mn solid solution rate of <40% after brazing, an Er content of 0.1-0.3%, and the balance of Al and unavoidable impurities, and a thermal conductivity of 160-180 W / m·K; The low thermal conductivity Al-Ni-Mn die-casting alloy has a Ni content of 2-6%, a Mn content of 0.5-1.5%, a Mn solid solution rate of more than 70% after brazing, a Mo content of 0.1-0.3%, and the remainder is Al and unavoidable impurities, and a thermal conductivity of 80-125 W / m·K.

2. The Al-Ni-Mn die-casting alloy according to claim 1, characterized in that: Thermal conductivity is 90-125 W / m·K.

3. The Al-Ni-Mn die-casting alloy according to claim 1, characterized in that: Zr and / or V are also included.

4. The Al-Ni-Mn die-casting alloy according to claim 3, characterized in that: The content of Zr and / or V is 0.1-0.2%.

5. The Al-Ni-Mn based die casting alloy according to claim 4, characterized in that: Thermal conductivity is 80-110 W / m·K.

6. The Al-Ni-Mn die-casting alloy according to any one of claims 1 to 5, characterized in that: Impurity components: Fe content <0.8%, Si content <0.1%, Cr content <0.1%, and the contents of other impurities are all <0.1% and the total is <0.2%.

7. The method for preparing the Al-Ni-Mn die-casting alloy according to any one of claims 1 to 6, characterized in that: The Al-Ni-Mn castings, brazing materials and parts to be brazed are placed in a brazing furnace at 590-620°C for high-temperature brazing. During the brazing cooling process, the solid solution and precipitation of Mn are controlled to obtain a high thermal conductivity Al-Ni-Mn die-casting alloy or a low thermal conductivity Al-Ni-Mn die-casting alloy.

8. Use of the Al-Ni-Mn die-casting alloy according to any one of claims 1 to 6 in a refrigerant valve island of a heat pump system or an automobile thermal management system.

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