Novel ultrahigh-strength 6-series aluminum alloy suitable for automobile cross beam and preparation method of novel ultrahigh-strength 6-series aluminum alloy

Abstract

The invention relates to the field of aluminum alloy material processing, in particular to an ultrahigh-strength novel 6-series aluminum alloy suitable for an automobile cross beam and a preparation method of the ultrahigh-strength novel 6-series aluminum alloy suitable for the automobile cross beam, and the ultrahigh-strength novel 6-series aluminum alloy suitable for the automobile cross beam comprises the following components in percentage by weight: 0.98-1.1% of Si; the content of Fe is 0.1 to 0.15 percent; the content of Cu is 0.9 to 0.95 percent; the content of Mg is 1.3 to 1.5 percent; the content of Mn is 0.5 to 0.6 percent; the content of Cr is 0.01 to 0.03 percent; the content of Ti is 0.02 to 0.03 percent; the content of Ni is 0.01 to 0.02 percent; the content of Zn is 0.5 to 0.6 percent; the content of Zr is 0.1 to 0.2 percent; the content of Ce is 0.11 to 0.14 percent; the single content of other impurity elements is less than or equal to 0.03%; the total content of other impurity elements is less than or equal to 0.15%; the yield strength of the aluminum alloy can reach 400 Mpa, the tensile strength of the aluminum alloy can reach 440 Mpa, and meanwhile a finished product has good formability and strength.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloy processes, and particularly relates to a new ultra-high strength 6-series aluminum alloy applicable to automotive crossbeams and a preparation method thereof. Background Art

[0002] 6-series aluminum alloy is an aluminum alloy with magnesium and silicon as the main alloying elements and Mg2Si as the main strengthening phase. The 6-series aluminum alloy has medium strength and belongs to heat-treatable aluminum alloy, so it is often used to make hot-extruded aluminum profiles. The 6-series aluminum alloy has the advantages of high corrosion resistance, no tendency to stress corrosion cracking, good welding performance, unchanged corrosion performance in the welding area, good formability and processing performance, etc.

[0003] With the rapid development of new energy vehicles, in order to provide the endurance of electric vehicles, automotive lightweighting has become one of the important directions for the development of automobiles. On the premise of meeting the vehicle performance requirements, the finished product weight can be effectively reduced through raw material selection, and finally automotive lightweighting can be achieved. Currently, the anti-collision beam aluminum alloy with a yield strength greater than 300 MPa is mainly 7-series aluminum alloy. However, in the anti-collision beam assembly system, the energy absorption box, energy absorption main beam, and baffle are all commonly made of 6-series aluminum alloy. Using different aluminum alloys will cause difficulties in classifying aluminum alloys during the recycling process, greatly increasing the application difficulty of recycled automotive aluminum. The 6-series aluminum alloy prepared by the prior art has great deficiencies in performance such as three-point bending and assembly collision.

[0004] Therefore, there is an urgent need to provide a 6-series aluminum alloy applicable to automotive crossbeams that combines strength, plastic toughness, and a yield strength greater than 400 MPa, as well as a preparation method thereof. Summary of the Invention

[0005] The present invention aims to solve the technical problem of how to provide a 6-series aluminum alloy applicable to automotive crossbeams that combines strength, plastic toughness, and a yield strength greater than 400 MPa.

[0006] To achieve the above object, in the first aspect of the present invention, a new ultra-high strength 6-series aluminum alloy applicable to automotive crossbeams is provided, wherein the components and their weight percentages in the aluminum alloy are as follows:

[0007] The Si content is 0.98 - 1.1%;

[0008] The Fe content is 0.1 - 0.15%;

[0009] The Cu content is 0.9 - 0.95%;

[0010] The Mg content is 1.3 - 1.5%;

[0011] The Mn content is 0.5 - 0.6%;

[0012] The Cr content is 0.01 - 0.03%;

[0013] The Ti content is 0.02 - 0.03%;

[0014] The Ni content is 0.01 - 0.02%;

[0015] The Zn content is 0.5 - 0.6%;

[0016] The Zr content is 0.1 - 0.2%;

[0017] The Ce content is 0.11 - 0.14%;

[0018] The single content of other impurity elements ≤ 0.03%;

[0019] The total content of other impurity elements ≤ 0.15%;

[0020] The balance is Al.

[0021] The second aspect of the present invention provides a preparation method of the 6 - series aluminum alloy applicable to automotive cross - beams as described above. Among them, the method includes:

[0022] Smelting and casting, homogenization, extrusion, solution aging;

[0023] The conditions of the smelting and casting include: using pure aluminum as raw material, adding Al - Si, Al - Cu, Al - Mn, Al - Zr and Al - Ce master alloys, using Al - 5%Ti - 1%B as grain refiner, not adding Fe during the smelting and casting process, the dosage of refining agent is 2 - 2.5 kg / T, the refining gas is argon, the refining temperature is 780 - 790 °C, the time is 10 - 15 min, and standing for 30 - 40 min after refining;

[0024] The conditions of homogenization include: the homogenization system is that the heating rate in the first stage is 10 - 15 °C / h to rise to 330 - 350 °C and hold for 5 - 6 h, and the heating rate in the second stage is 15 - 20 °C / h to rise to 540 - 560 °C and hold for 24 - 26 h to obtain aluminum ingots.

[0025] The beneficial effects of the present invention are:

[0026] The aluminum alloy provided by the present invention greatly improves the mechanical properties of 6 - series aluminum alloy profiles by controlling the smelting and casting process and adjusting the homogenization system of the cast rod. The yield strength can reach 400 Mpa, and the tensile strength can reach 440 Mpa. At the same time, the finished product has good formability and strength, meets the standard requirements of 6 - series aluminum alloy bars, improves the quality and quality of the finished product, controls the accuracy of extrusion process parameters, and can further improve the performance of aluminum alloy on the premise of ensuring the stability of profile dimensions. Brief Description of the Drawings

[0027] Figure 1 Cross-sectional view of the aluminum alloy of Example 1.

[0028] Figure 2 Front view and sectional view of the mold.

[0029] Figure 3 High-magnification metallographic structure diagram of Example 1.

[0030] Figure 4 High-magnification metallographic structure diagram of Example 2.

[0031] Figure 5 High-magnification metallographic structure diagram of Example 3. Detailed implementation manners

[0032] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0033] In the prior art, the performance of the aluminum alloy processed for automotive crossbeams cannot meet the requirements of the 6-series aluminum alloy for automotive crossbeams that combines strength with plastic toughness and has a yield strength greater than 400 MPa.

[0034] In the present invention, the inventors found that by controlling the alloy composition and adjusting the processing technology, the yield strength of the aluminum alloy for automotive crossbeams can reach 400 Mpa, the tensile strength can reach 440 Mpa, and at the same time, the finished product has good formability and strength.

[0035] To achieve this goal, the inventors tried to optimize the composition of each component of the aluminum alloy and the processing technology. The inventors found that through specific compositions of each component and melting, casting and homogenization processes, the above object can be achieved. Further, specific extrusion and solution aging processes make the performance of the aluminum alloy more excellent.

[0036] The first aspect of the present invention provides a 6-series aluminum alloy suitable for automotive crossbeams, wherein the components and their weight percentages in the aluminum alloy are as follows:

[0037] The Si content is 0.98 - 1.1%;

[0038] The Fe content is 0.1 - 0.15%;

[0039] The Cu content is 0.9 - 0.95%;

[0040] The Mg content is 1.3 - 1.5%;

[0041] The Mn content is 0.5 - 0.6%;

[0042] The Cr content is 0.01 - 0.03%;

[0043] The Ti content is 0.02 - 0.03%;

[0044] The Ni content is 0.01 - 0.02%;

[0045] The Zn content is 0.5 - 0.6%;

[0046] The Zr content is 0.1 - 0.2%;

[0047] The Ce content is 0.11 - 0.14%;

[0048] The single content of other impurity elements is ≤0.03%;

[0049] The total content of other impurity elements is ≤0.15%;

[0050] The balance is Al.

[0051] In the present invention, on the basis of the original 6-series aluminum alloy, the contents of Cu and Zn elements are increased and a certain amount of rare earth element cerium Ce is added. Cu, Zn, and Ce usually exist as trace addition elements. Cu can form strengthening phases such as Al2CuMg (S phase) or AlCu, improving the strength of the alloy, especially the strength at high temperatures. Zn can form a Mg-Zn strengthening phase (such as MgZn2) with magnesium. Under specific heat treatment conditions, such as T6 aging, the strength can be improved. Ce can refine the as-cast structure, improve the plasticity and toughness of the alloy, form high-melting-point compounds with impurity elements, such as Fe, and reduce harmful phases, such as β-AlFeSi, improving the processing performance.

[0052] According to the present invention, the yield strength of the aluminum alloy is greater than 400 MPa, and the tensile strength is greater than 440 MPa.

[0053] The second aspect of the present invention provides a preparation method of the above-mentioned 6-series aluminum alloy applicable to automobile crossbeams. Among them, the method includes:

[0054] Melting and casting, homogenization, extrusion, solution aging;

[0055] The conditions of the melting and casting include: using pure aluminum as the raw material, adding Al-Si, Al-Cu, Al-Mn, Al-Zr, and Al-Ce master alloys, using Al-5%Ti-1%B as the grain refiner, not adding Fe during the melting and casting process, the dosage of the refining agent is 2 - 2.5 kg / T, the refining gas is argon, the refining temperature is 780 - 790 °C, the time is 10 - 15 min, and standing for 30 - 40 min after refining;

[0056] The conditions for homogenization include: the homogenization system is that in the first stage, the heating rate is 10 - 15 °C / h to rise to 330 - 350 °C and keep warm for 5 - 6 h, and in the second stage, the heating rate is 15 - 20 °C / h to rise to 540 - 560 °C and keep warm for 24 - 26 h to obtain aluminum ingots.

[0057] In the present invention, the content of Fe impurities is strictly controlled. Excessive Fe elements will form the second phases of α - AlFeSi and β - AlFeSi as hard particles. When they aggregate, they will form insoluble second phases, which will have an adverse effect on the toughness and plasticity of the material.

[0058] In the present invention, the main reason for adopting gradient heating in the homogenization system is to optimize the tissue uniformity, avoid defects, and improve the performance of the final product, which can eliminate the internal stress of the ingot, promote the dissolution of non - equilibrium solidification phases in the ingot, and make strengthening phases such as MgZn2 uniformly, finely and dispersedly distributed.

[0059] According to the present invention, the conditions for extrusion include: 4 flow - dividing holes are arranged at the contact position between the ingot and the die, and the 4 flow - dividing holes are symmetrically distributed at the four corners of the working belt. The depth of the diversion pit is 15 - 20 mm, the included angle between the slope angle of the diversion pit and the contact surface of the aluminum ingot is 20° - 25°, the width of the working belt is 4 - 4.5 mm, the shape of the flow - dividing bridge is raindrop - shaped, the chamfer at the head end of the raindrop - shaped structure is R8 mm - R15 mm, and the chamfer at the tail end extending to the welding chamber is R1 mm - R2 mm.

[0060] In the present invention, R of the chamfer at the head end of the raindrop - shaped structure and the chamfer at the tail end extending to the welding chamber is the radius.

[0061] In the present invention, when the number of flow - dividing holes is less than 4, the flow - dividing pressure will increase when the ingot contacts the die, resulting in die blockage, and the equipment will be blocked by pressure and unable to break through the die resistance. When the number of flow - dividing holes is greater than 4, the die strength will be reduced, resulting in the die being damaged or cracked under the impact of high temperature and high pressure of cemented carbide. The 4 flow - dividing holes are symmetrically distributed at the four corners of the working belt, which can reduce the extrusion pressure, help the metal to be evenly filled in the die cavity, avoid local turbulence or uneven flow, and reduce the defects such as tearing, scratching, and scuffing on the product surface caused by unbalanced flow and inability to be extruded into shape.

[0062] In the present invention, if the chamfer at the head end is beyond the required range, the effect of reducing the extrusion pressure, improving the metal fluidity, and improving the metal formability cannot be achieved. If the chamfer at the tail end is beyond the required range, the area of the welding chamber will be reduced, and the welding quality of the profile product cannot be guaranteed, and it is easy to crack under external force. Because the streamline structure of the raindrop shape can guide the metal liquid to smoothly bypass the flow - dividing bridge, avoiding sharp turns or eddies, thereby further reducing the extrusion pressure and improving the product formability. And the flow - dividing bridge is the area directly impacted by the metal. The round - head design of the raindrop shape increases the heat - receiving area, makes the heat distribution more uniform, prevents the bridge body from being damaged due to local overheating, and improves the overall service life of the die.

[0063] In the present invention, the attached drawings of the specification Figure 2 are the front view and sectional view of the die. If the depth of the diversion pit is less than 15 mm or the slope angle of the diversion pit is less than 20°, there will be too much metal in the dead zone of the ingot, and the extruded products are prone to the defect of through-root tailing, resulting in a low yield. If the depth of the diversion pit is greater than 20 mm or the slope angle of the diversion pit is greater than 25°, the contact area between the aluminum metal and the die increases, resulting in an increase in friction force, so the extrusion force is likely to be too large and cause die blockage and inability to form. The shape of the distribution bridge extends to the welding chamber in a raindrop shape, which can effectively increase the area of the welding chamber, increase the welding pressure at the weld of the profile product, and achieve the purpose of improving the weld quality.

[0064] In the present invention, if the working belt is less than 4 mm, the working belt will be damaged under high temperature and high pressure, resulting in out-of-tolerance wall thickness of the product. If the working belt is greater than 4.5 mm, after continuous extrusion for a period of time, defects such as scratching and peeling will appear on the product surface, and some hard particles will adhere to the surface of the working belt, thus affecting the surface quality of the product.

[0065] According to the present invention, the conditions for extrusion include: the length of the ingot is 200 - 500 mm, the breakthrough pressure is 15 - 17 MPa, the die temperature is 480 - 500 °C, the extrusion ingot temperature is 460 - 480 °C, the profile outlet temperature is 390 - 430 °C, the extrusion rod speed is 1.7 - 2.2 m / min, and the quenching is off-line quenching.

[0066] In the present invention, if the length of the ingot is less than 200 mm, the length of the extruded product is too short to achieve continuous extrusion, and subsequent stretching and straightening cannot be carried out, resulting in out-of-tolerance product dimensions. If the length of the ingot exceeds 500 mm, the contact area of the ingot in the extrusion cylinder of the forward extruder is too large, and the friction force will further increase, which is not conducive to product forming.

[0067] In the present invention, using the above specific breakthrough pressure can protect the die and stabilize the dimensional accuracy at the same time. The quenching method is off-line quenching, which can take into account both ultra-high standard dimensional requirements and meet high-precision mechanical property standards at the same time.

[0068] According to the present invention, the conditions for solution aging include: the solution aging system is 550 - 570 °C × 1 - 3 h + 150 - 170 °C × 11 - 13 h.

[0069] In the present invention, the above specific solution aging can improve the tissue uniformity and obtain better comprehensive properties.

[0070] The mechanical property testing equipment is an AG-X 100KN electronic universal testing machine. The testing method is GB / T16865-2013 Test Specimens and Methods for Tensile Testing of Wrought Aluminum, Magnesium and Their Alloys.

[0071] Bending performance test Test equipment: AG-X 100KN electronic universal testing machine. Test standard: VDA238-100 Test specification for sheet bending test of metallic materials.

[0072] High magnification structure test equipment: AXIO universal research grade inverted material microscope. Test standard: GB / T6892-2015 Extruded profiles of aluminium and aluminium alloys for general engineering purposes. Test method: GB / T3246.1-2012 Test methods for structures of wrought aluminium and aluminium alloy products - Part 1: Test methods for microscopic structures.

[0073] Macroscopic test Test equipment: Alkaline etching solution. Test standard: GB / T6892-2015 Extruded profiles of aluminium and aluminium alloys for general engineering purposes. Test method: GB / T3246.2-2012 Test methods for structures of wrought aluminium and aluminium alloy products - Part 2: Test methods for macroscopic structures.

[0074] The technical solutions of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. Obviously, the embodiments described herein are only partial embodiments of the present invention and are not used to limit the present invention. All other embodiments implemented by those of ordinary skill in the art based on the embodiments of the present invention without making creative improvements fall within the protection scope of the present invention.

[0075] Embodiment 1

[0076] The alloy selected has the following chemical composition: Si content is 1%; Fe content is 0.12%; Cu content is 0.93%; Mg content is 1.4%; Mn content is 0.56%; Cr content is 0.02%; Ti content is 0.028%; Ni content is 0.015%; Zn content is 0.55%; Zr content is 0.015%; Ce content is 0.12%; the content of each other impurity element is ≤0.03%; the total content of other impurity elements is ≤0.15%; the balance is Al.

[0077] Melting and casting: Using pure aluminium as raw material, adding Al-Si, Al-Cu, Al-Mn, Al-Zr and Al-Ce master alloys, using Al-5%Ti-1%B as grain refiner, not adding Fe during the melting and casting process, using powder spraying method for refining in the melting and casting process, the dosage of refining agent is 2.25kg / T, the refining gas is argon, the refining temperature is 785°C, the time is 12min, and standing for 35min after refining.

[0078] Homogenization treatment: The homogenization system is that the heating rate in the first stage is 12°C / h to 340°C and keep warm for 5.5h, and the heating rate in the second stage is 18°C / h to 550°C and keep warm for 25h to obtain aluminium ingots.

[0079] Extrusion: There are 4 distribution holes at the contact position between the ingot and the die. The 4 distribution holes are symmetrically distributed at the four corners of the working belt. The depth of the diversion pit is 18 mm, the included angle between the slope angle of the diversion pit and the contact surface of the aluminum ingot is 22°, the width of the working belt is 4 mm, the shape of the distribution bridge is raindrop-shaped, the chamfer at the head end of the raindrop-shaped structure is R12 mm, and the chamfer at the tail end extending to the welding chamber is R1.5 mm. The length of the ingot is 300 mm, the breakthrough pressure is 16 MPa, the die temperature is 485 °C, the extrusion ingot temperature is 490 °C, the profile outlet temperature is 420 °C, the extrusion rod speed is 2 m / min, and the quenching is off-line quenching.

[0080] Solution aging: The solution aging system is 560 °C × 2 h + 160 °C × 12 h.

[0081] Aluminum alloy A1 is obtained.

[0082] Example 2

[0083] Prepare the aluminum alloy according to the processing method of Example 1. The difference is that the Si content in the aluminum alloy components is 0.98%; the Fe content is 0.1%; the Cu content is 0.9%; the Mg content is 1.3%; the Mn content is 0.5%; the Cr content is 0.01%; the Ti content is 0.02%; the Ni content is 0.01%; the Zn content is 0.5%; the Zr content is 0.1%; the Ce content is 0.11%.

[0084] Aluminum alloy A2 is obtained.

[0085] Example 3

[0086] Prepare the aluminum alloy according to the processing method of Example 1. The difference is that the aluminum alloy components are Si content of 1.1%; Fe content of 0.15%; Cu content of 0.95%; Mg content of 1.5%; Mn content of 0.6%; Cr content of 0.03%; Ti content of 0.03%; Ni content of 0.02%; Zn content of 0.6%; Zr content of 0.2%; Ce content of 0.14%.

[0087] Aluminum alloy A3 is obtained.

[0088] Example 4

[0089] Prepare the aluminum alloy according to the processing method of Example 1. The difference is that the homogenization system is that the heating rate in the first stage is 10 °C / h to 330 °C and kept warm for 5 h, and the heating rate in the second stage is 15 °C / h to 540 °C and kept warm for 24 h.

[0090] Aluminum alloy A4 is obtained.

[0091] Example 5

[0092] Prepare aluminum alloy according to the processing method of Example 1, except that the homogenization system is that the heating rate in the first stage is increased to 350 °C at a rate of 15 °C / h and held for 6 h, and the heating rate in the second stage is increased to 560 °C at a rate of 20 °C / h and held for 26 h.

[0093] Obtain aluminum alloy A5.

[0094] Example 6

[0095] Prepare aluminum alloy according to the processing method of Example 1, except that the depth of the diversion pit is 15 mm, the included angle between the slope angle of the diversion pit and the contact surface of the aluminum ingot is 20°, the width of the working belt is 4 mm, the chamfer at the head end of the raindrop-shaped structure is R8 mm, and the chamfer at the tail end extending to the welding chamber is R1 mm.

[0096] Obtain aluminum alloy A6.

[0097] Example 7

[0098] Prepare aluminum alloy according to the processing method of Example 1, except that the depth of the diversion pit is 20 mm, the included angle between the slope angle of the diversion pit and the contact surface of the aluminum ingot is 25°, the width of the working belt is 4.5 mm, the chamfer at the head end of the raindrop-shaped structure is R15 mm, and the chamfer at the tail end extending to the welding chamber is R2 mm.

[0099] Obtain aluminum alloy A7.

[0100] Example 8

[0101] Prepare aluminum alloy according to the processing method of Example 1, except that the length of the ingot is 200 mm, the breakthrough pressure is 15 MPa, the die temperature is 480 °C, the extrusion ingot temperature is 460 °C, the profile outlet temperature is 390 °C, the extrusion rod speed is 1.7 m / min, the quenching is off-line quenching, and the die heating temperature is 480 °C.

[0102] Obtain aluminum alloy A8.

[0103] Example 9

[0104] Prepare aluminum alloy according to the processing method of Example 1, except that the length of the ingot is 500 mm, the breakthrough pressure is 17 MPa, the die temperature is 500 °C, the extrusion ingot temperature is 480 °C, the profile outlet temperature is 430 °C, the extrusion rod speed is 2.2 m / min, the quenching is off-line quenching, and the die heating temperature is 500 °C.

[0105] Obtain aluminum alloy A9.

[0106] Example 10

[0107] Prepare aluminum alloy according to the processing method of Example 1, except that the solution aging system is 550 °C × 1 h + 150 °C × 11 h.

[0108] Aluminum alloy A10 was obtained.

[0109] Example 11

[0110] An aluminum alloy was prepared according to the processing method of Example 1, except that the solution aging regime was 570 °C × 3 h + 170 °C × 13 h.

[0111] Aluminum alloy A11 was obtained.

[0112] Comparative Example 1

[0113] An aluminum alloy was prepared according to the processing method of Example 1, except that the aluminum alloy components were: Si content 0.95%; Fe content 0.08%; Cu content 0.85%; Mg content 1.2%; Mn content 0.45%; Cr content 0.008%; Ti content 0.01%; Ni content 0.005%; Zn content 0.45%; Zr content 0.05%; Ce content 0.1%.

[0114] Aluminum alloy DA1 was obtained.

[0115] Comparative Example 2

[0116] An aluminum alloy was prepared according to the processing method of Example 1, except that the aluminum alloy components were: Si content 1.12%; Fe content 0.2%; Cu content 1%; Mg content 1.6%; Mn content 0.65%; Cr content 0.04%; Ti content 0.05%; Ni content 0.03%; Zn content 0.7%; Zr content 0.3%; Ce content 0.15%.

[0117] Aluminum alloy DA2 was obtained.

[0118] Comparative Example 3

[0119] An aluminum alloy was prepared according to the processing method of Example 1, except that the homogenization regime was: in the first stage, the heating rate was 8 °C / h to 320 °C and held for 4 h, and in the second stage, the heating rate was 14 °C / h to 530 °C and held for 23 h.

[0120] Aluminum alloy DA3 was obtained.

[0121] Comparative Example 4

[0122] An aluminum alloy was prepared according to the processing method of Example 1, except that the homogenization regime was: in the first stage, the heating rate was 16 °C / h to 360 °C and held for 8 h, and in the second stage, the heating rate was 22 °C / h to 570 °C and held for 27 h.

[0123] Aluminum alloy DA4 was obtained.

[0124] Comparative Example 5

[0125] Prepare an aluminum alloy according to the processing method of Example 1, except that the depth of the diversion pit is 14 mm, the included angle between the slope angle of the diversion pit and the contact surface of the aluminum ingot is 18, the width of the working belt is 3.8 mm, the chamfer at the head end of the raindrop-shaped structure is R7 mm, and the chamfer at the tail end extending to the welding chamber is R0.5 mm.

[0126] Obtain aluminum alloy DA5.

[0127] Comparative Example 6

[0128] Prepare an aluminum alloy according to the processing method of Example 1, except that the depth of the diversion pit is 21 mm, the included angle between the slope angle of the diversion pit and the contact surface of the aluminum ingot is 27, the width of the working belt is 4.7 mm, the chamfer at the head end of the raindrop-shaped structure is R16 mm, and the chamfer at the tail end extending to the welding chamber is R2.5 mm.

[0129] Obtain aluminum alloy DA6.

[0130] Comparative Example 7

[0131] Prepare an aluminum alloy according to the processing method of Example 1, except that the length of the ingot is 180 mm, the breakthrough pressure is 13 MPa, the die temperature is 460 °C, the extrusion ingot temperature is 450 °C, the profile exit temperature is 380 °C, the extrusion rod speed is 1.5 m / min, and the quenching is off-line quenching.

[0132] Obtain aluminum alloy DA7.

[0133] Comparative Example 8

[0134] Prepare an aluminum alloy according to the processing method of Example 1, except that the length of the ingot is 600 mm, the breakthrough pressure is 20 MPa, the die temperature is 520 °C, the extrusion ingot temperature is 500 °C, the profile exit temperature is 450 °C, the extrusion rod speed is 2.5 m / min, and the quenching is off-line quenching.

[0135] Obtain aluminum alloy DA8.

[0136] Comparative Example 9

[0137] Prepare an aluminum alloy according to the processing method of Example 1, except that the solution aging system is 540 °C × 0.8 h + 140 °C × 10 h.

[0138] Obtain aluminum alloy DA9.

[0139] Comparative Example 10

[0140] Prepare an aluminum alloy according to the processing method of Example 1, except that the solution aging system is 580 °C × 3.2 h + 180 °C × 14 h.

[0141] The aluminum alloy DA10 was obtained.

[0142] The performance tests were carried out on A1 - A11 and DA1 - DA10, as shown in Table 1.

[0143] Table 1

[0144]

[0145]

[0146] Through the comparison between the examples and the comparative examples, it can be seen that the aluminum alloy provided by the present invention finely tunes the alloy composition, improves the mechanical properties of the profiles while ensuring the surface quality of the profiles, improves the filling ability. After adjusting the homogenization system of the casting rods, it ensures that the metal flow rate is uniform at all positions of the profiles and strictly monitors its breakthrough pressure to ensure that the pressure value is between 15 - 17 mpa, then ultra - high strength cross - beam products with a yield strength > 400 Mpa and a tensile strength > 440 Mpa can be extruded. Further, the specific extrusion process and solution aging system can further improve the performance of the aluminum alloy.

[0147] The above - mentioned is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A new ultra-high-strength 6-series aluminum alloy applicable to automotive crossbeams, characterized in that, The components and their weight percentages in the aluminum alloy are as follows: The Si content is 0.98 - 1.1%; The Fe content is 0.1 - 0.15%; The Cu content is 0.9 - 0.95%; The Mg content is 1.3 - 1.5%; The Mn content is 0.5 - 0.6%; The Cr content is 0.01 - 0.03%; The Ti content is 0.02 - 0.03%; The Ni content is 0.01 - 0.02%; The Zn content is 0.5 - 0.6%; The Zr content is 0.1 - 0.2%; The Ce content is 0.11 - 0.14%; The individual content of other impurity elements is ≤ 0.03%; The total content of other impurity elements is ≤ 0.15%; The balance is Al.

2. The aluminum alloy according to claim 1, wherein, The yield strength of the aluminum alloy is greater than 400 MPa, and the tensile strength is greater than 440 MPa.

3. A preparation method of the 6-series aluminum alloy applicable to automotive crossbeams according to claim 1 or 2, characterized in that, The method includes: Melting and casting, homogenization, extrusion, solution aging; The conditions for melting and casting include: using pure aluminum as the raw material, adding Al - Si, Al - Cu, Al - Mn, Al - Zr, and Al - Ce master alloys, using Al - 5%Ti - 1%B as the grain refiner, not adding Fe during the melting and casting process, the dosage of the refining agent is 2 - 2.5 kg / T, the refining gas is argon, the refining temperature is 780 - 790 °C, the time is 10 - 15 min, and after refining, it is statically placed for 30 - 40 min; The conditions for homogenization include: the homogenization system is that the heating rate in the first stage is 10 - 15 °C / h to rise to 330 - 350 °C and hold for 5 - 6 h, and the heating rate in the second stage is 15 - 20 °C / h to rise to 540 - 560 °C and hold for 24 - 26 h.

4. The method according to claim 3, wherein The conditions for extrusion include: 4 shunt holes are set at the position where the ingot contacts the die, the 4 shunt holes are symmetrically distributed at the four corners of the working belt, the depth of the diversion pit is 15 - 20 mm, the included angle between the slope angle of the diversion pit and the contact surface of the aluminum ingot is 20° - 25°, the width of the working belt is 4 - 4.5 mm, the shape of the shunt bridge is raindrop - like, the chamfer at the head end of the raindrop - like structure is R8 mm - R15 mm, and the chamfer at the tail end extending to the welding chamber is R1 mm - R2 mm.

5. The method according to claim 3, wherein The conditions for extrusion include: the length of the ingot is 200 - 500 mm, the breakthrough pressure is 15 - 17 MPa, the die temperature is 480 - 500 °C, the extrusion ingot temperature is 460 - 480 °C, the profile outlet temperature is 390 - 430 °C, the extrusion rod speed is 1.7 - 2.2 m / min, the quenching is off - line quenching, the extrusion cylinder temperature is 420 - 440 °C, and the die heating temperature is 480 - 500 °C.

6. The method according to claim 3, characterized in that, The conditions for solution aging include: the solution aging system is 550 - 570 °C × 1 - 3 h + 150 - 170 °C × 11 - 13 h.

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