Aluminum alloy capable of being quickly age-hardened and preparation method and application thereof

Abstract

The invention discloses an aluminum alloy capable of being subjected to age hardening quickly and a preparation method and application thereof, and the aluminum alloy comprises the following components in percentage by mass: 0.80-0.95% of Mg, 1.0-1.1% of Si, 0-0.15% of Cu, 0.55-0.65% of Mn, 0.2-0.25% of Cr, less than or equal to 0.03% of Ti, less than or equal to 0.15% of Fe, less than or equal to 0.015% of P, less than or equal to 0.015% of S and the balance of Al. The content of the aluminum alloy is 100% by adjusting the content of the Al; the content ratio of Mg to Si is 0.8-0.9, the total content of Mn and Cr is less than 0.9%, and the content ratio of Mn to Cr is 2.7-2.9; during preparation, an as-cast product is obtained through casting firstly, then homogenization treatment, extrusion treatment and aging treatment are conducted on the as-cast product, the aluminum alloy can achieve rapid aging hardening, meanwhile, the high strength and the excellent corrosion resistance are achieved, and the problem that in the prior art, the aluminum alloy cannot be used in order is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloy materials, and in particular to a high-strength, corrosion-resistant Al-Mg-Si alloy material capable of rapid aging hardening, and specifically to an aluminum alloy capable of rapid aging hardening, a preparation method thereof, and an application thereof. Background Art

[0002] With the comprehensive development of the shipbuilding industry at home and abroad, ship lightweighting has gradually attracted widespread attention. For ships with high weight requirements, the requirements for high toughness, corrosion resistance and weldability of materials have become increasingly stringent. Among them, aluminum alloys have the advantages of high specific strength, good processing performance, and strong energy absorption. They can be used in shipbuilding to significantly reduce weight, increase ship speed, and save fuel; improve the length-to-width ratio of the ship, increase stability, and make the ship easier to operate. Therefore, aluminum alloys have great application and development space in the shipbuilding industry.

[0003] For ships as a means of transportation, increasing speed is one of the main technical indicators for their improvement and development. The most effective way to increase its speed mainly includes two aspects: one is to reduce the weight of the ship, and the other is to reduce water resistance. On the other hand, the corrosion resistance requirements in the field of ship applications are relatively high, so the use of high-strength, lightweight, corrosion-resistant aluminum alloy materials is one of the main ways to achieve ship lightweighting. At present, the corrosion-resistant aluminum alloys widely used in the field of navigation and ships mainly include 5XXX series Al-Mg and 6XXX series Al-Mg-Si aluminum alloys. Although the 5XXX series aluminum alloys are very corrosion-resistant, their mechanical properties are poor; the 6XXX series alloys have high specific strength, excellent formability and good corrosion resistance, and excellent comprehensive performance, but the yield strength of the 6XXX series aluminum alloys used in ships is currently low, all below 300MPa. Therefore, it is of great significance to improve the strength of the 6XXX series aluminum alloys used in ships while ensuring good corrosion resistance.

[0004] For example, Chinese patent CN 106480343 A discloses a new type of Al-Mg-Si alloy material with high strength and seawater corrosion resistance and a preparation method thereof, Mg: 1.8-3.6wt.%; Si: 1.6-3.3wt.%; Mn: 0.45-0.65wt.%; Cr: 0.25-0.35wt.%; Zr: 0.15-0.3wt.%; Ti: 0.2-0.3wt.%; Ag: 0.2-0.5wt.%; other impurities are individually ≤0.03wt.%, and the total is ≤0.1wt.%, and the remainder is aluminum; however, more zirconium and silver elements are added in this patent, resulting in higher production costs;

[0005] Another example is Chinese patent CN 116005049 B, which discloses a corrosion-resistant aluminum alloy profile and a preparation method thereof, Cu 0.1-0.2%, Fe 0.05-0.15%, Mn 0.08-0.1%, Cr 0.14-0.16%, Mg 0.5-0.8%, Zn 0.1-0.2%, Si 0.3-0.8%, Zr 0.06-0.08%, Ni 0.01-0.02%, rare earth elements 0.1-0.3%, and the balance is Al; however, more Zn, Zr, Ni, rare earth elements, etc. are added in the patent, resulting in higher production costs;

[0006] In addition, there is also a technical solution to add Cu elements to 6XXX series aluminum alloys to improve strength, but Cu elements are prone to induce intergranular corrosion, which seriously affects the service life of equipment during actual service. Multi-stage aging process is often used to improve the corrosion resistance of 6XXX series aluminum alloys, which improves corrosion resistance by changing the morphology and distribution of the precipitated phase at the grain boundary, but this type of process is complex and has a long production cycle, and is not suitable for industrial production.

[0007] Based on this, finding an alloy component that can quickly achieve the purpose of improving strength and corrosion resistance is an effective way to achieve thin-walled aluminum alloy profiles and lightweight ships. Summary of the invention

[0008] The purpose of the present invention is to overcome one or more deficiencies in the prior art and to provide an improved high-strength, corrosion-resistant Al-Mg-Si aluminum alloy capable of rapid aging hardening, thereby solving the problem of the prior art of neglecting one thing while focusing on another.

[0009] The present invention also provides a method for preparing the aluminum alloy and application of the aluminum alloy in shipbuilding.

[0010] In order to achieve the above object, a technical solution adopted by the present invention is: an aluminum alloy, measured by mass percentage, the aluminum alloy comprises:

[0011] Mg: 0.80%-0.95%

[0012] Si: 1.0%-1.1%

[0013] Cu: 0-0.15%

[0014] Mn: 0.55%-0.65%

[0015] Cr: 0.2%-0.25%

[0016] Ti≤0.03%

[0017] Fe≤0.15%;

[0018] The aluminum alloy satisfies 100% by adjusting the content of Al;

[0019] Moreover, the content ratio of Mg to Si is 0.8-0.9, the total content of Mn and Cr is less than 0.9%, and the content ratio of Mn to Cr is 2.7-2.9.

[0020] According to the present invention, the content ratio of Mg to Si is 0.8, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.9, etc.

[0021] According to the present invention, the content ratio of Mn to Cr is 2.70, 2.71, 2.72, 2.73, 2.74, 2.75, 2.76, 2.77, 2.78, 2.79, 2.80, 2.81, 2.82, 2.83, 2.84, 2.85, 2.86, 2.87, 2.88, 2.89, 2.9, etc.

[0022] In some embodiments of the present invention, the content ratio of Mg to Si is 0.80-0.85.

[0023] In some embodiments of the present invention, the total content of Mn and Cr is 0.75%-0.88%.

[0024] In some embodiments of the present invention, in the aluminum alloy, Mg comprises 0.80%-0.90% by mass.

[0025] In some embodiments of the present invention, in the aluminum alloy, Ti comprises 0.01%-0.03% by mass.

[0026] According to some preferred aspects of the present invention, the aluminum alloy comprises a nano-scale α-AlFe(MnCr)Si dispersed phase and an Al6Mn dispersed phase.

[0027] Furthermore, the size of the nano-scale α-AlFe(MnCr)Si dispersed phase is 50-400nm.

[0028] According to some preferred and specific aspects of the present invention, the aluminum alloy comprises, in terms of mass percentage:

[0029] Mg: 0.82%-0.92%

[0030] Si: 1.02%-1.1%

[0031] Mn: 0.60%-0.65%

[0032] Cr: 0.2%-0.25%

[0033] Ti: 0.01%-0.03%

[0034] Fe≤0.15%;

[0035] The aluminum alloy satisfies 100% by adjusting the content of Al;

[0036] Moreover, the content ratio of Mg to Si is 0.8-0.86, the total content of Mn and Cr is 0.80%-0.88%, and the content ratio of Mn to Cr is 2.8-2.9.

[0037] According to some preferred and specific aspects of the present invention, the aluminum alloy comprises, in terms of mass percentage:

[0038] Mg: 0.80%-0.85%

[0039] Si: 1.0%-1.06%

[0040] Cu: 0.05%-0.15%

[0041] Mn: 0.55%-0.60%

[0042] Cr: 0.2%-0.25%

[0043] Ti: 0.01%-0.03%

[0044] Fe≤0.15%;

[0045] The aluminum alloy satisfies 100% by adjusting the content of Al;

[0046] Moreover, the content ratio of Mg to Si is 0.8-0.84, the total content of Mn and Cr is 0.75%-0.80%, and the content ratio of Mn to Cr is 2.7-2.8.

[0047] According to the present invention, the peak aging time of the aluminum alloy (referring to the time required to reach the highest strength and hardness state after aging treatment) is less than or equal to 4 hours.

[0048] According to the present invention, in some embodiments of the present invention, in the T5 state, the yield strength of the aluminum alloy at room temperature is greater than or equal to 330 MPa, the tensile strength is greater than or equal to 350 MPa, the elongation is greater than or equal to 10%, and the intergranular corrosion depth is less than 100 μm.

[0049] The T5 state is the state in which the extruded profile is directly aged without undergoing solid solution treatment. It is easier to achieve in industrial production and is usually the state.

[0050] According to some preferred aspects of the present invention, in the process of preparing the aluminum alloy, a cast product is first cast, and then the cast product is subjected to homogenization treatment, extrusion treatment and aging treatment; wherein the homogenization treatment includes: a first stage homogenization treatment at 250-330°C, a second stage homogenization treatment at 350-400°C, and a third stage homogenization treatment at 530-560°C.

[0051] Another technical solution provided by the present invention is a method for preparing the aluminum alloy described above, the method comprising:

[0052] The components except Ti are mixed, smelted, refined, and allowed to stand to form a first melt;

[0053] Then, adding Ti component to the first melt to prepare a second melt;

[0054] Casting the second melt to obtain a cast product;

[0055] The cast product is homogenized and then extruded to obtain an aluminum profile;

[0056] The aluminum profile is subjected to aging treatment to obtain the aluminum alloy.

[0057] In some embodiments of the present invention, the temperature of the mixed smelting is 730-780°C. Further, the temperature of the mixed smelting is 740-750°C.

[0058] In some embodiments of the present invention, the refining temperature is 730-780°C. Further, the refining temperature is 740-750°C.

[0059] In some embodiments of the present invention, the refining time of the refining is 15-40 minutes. Further, the refining time of the refining is 20-30 minutes.

[0060] In some embodiments of the present invention, the static standing time is 30-60 min. Further, the static standing time is 40-50 min.

[0061] In some embodiments of the present invention, the temperature when the Ti component is added is 730-780° C. Further, the temperature when the Ti component is added is 730-740° C.

[0062] In some embodiments of the present invention, the Ti component is added in the form of Al-5Ti-B.

[0063] In some embodiments of the present invention, the casting adopts DC semi-continuous casting, and the melt temperature at the beginning of casting is 740-750°C.

[0064] In some embodiments of the present invention, the casting speed is 140-160 mm / min.

[0065] In some embodiments of the present invention, the temperature of the homogenization treatment is 250-560° C., and the holding time is 4-22 hours.

[0066] According to some preferred and specific aspects of the present invention, the homogenization treatment includes the following steps performed in sequence: a first-level homogenization treatment is performed at 250-330°C for 1-8 hours; a second-level homogenization treatment is performed at 350-400°C for 1-8 hours; and a third-level homogenization treatment is performed at 530-560°C for 4-14 hours.

[0067] In some embodiments of the present invention, during the homogenization process, the homogenization heating rate is 1-10°C / min, further 1.5-5°C / min, and further 2.5-3.5°C / min; during cooling, the temperature is reduced to below 120°C at a cooling rate of 90-900°C / h.

[0068] In some embodiments of the present invention, during the extrusion molding process, the preheating temperature of the homogenized product is 470-510°C, the mold preheating temperature is 460-500°C, the extrusion speed is 1-10 mm / s, the extrusion ratio is 25-50, and further 35-40, and the cooling method after extrusion is water mist cooling and / or water cooling.

[0069] In some embodiments of the present invention, the aging treatment temperature is 175-190° C., the treatment time is less than or equal to 24 hours, and the peak aging time is less than or equal to 4 hours.

[0070] Another technical solution provided by the present invention is: application of the above-mentioned aluminum alloy in shipbuilding.

[0071] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0072] Based on the fact that existing aluminum alloys are difficult to achieve rapid aging hardening, high strength, excellent corrosion resistance and other properties, the inventors of the present invention have innovatively provided a new low-cost alloy that can improve both strength and corrosion resistance without complicated processes during a large number of experimental studies, and at the same time, it can also achieve rapid aging hardening; it is beneficial to achieve thin-walled aluminum alloy profiles and lightweight hull structures; further, the present invention controls the content and proportion of each element, especially the ratio of Mg to Si elements, and the ratio of Mn to Cr elements, so that the alloy has a certain excess Si. Practice shows that this method can fully and quickly form Mg2Si strengthening phases in the crystal during the aging heat treatment stage, thereby accelerating the aging hardening process, and at the same time can also inhibit the formation and growth of Mg2Si phases at grain boundaries, thereby avoiding the generation of corrosion channels on the grain boundaries, while obtaining excellent mechanical properties. The invention can inhibit the tendency of intergranular corrosion at the same time, so that the alloy has good mechanical properties and excellent corrosion resistance, and can greatly shorten the process time and save production costs; at the same time, the content of Mn and Cr elements and the control of their mutual ratio are conducive to the formation of a large number of fine and uniformly distributed nano-scale dispersed phases, which can pin dislocations and subgrain boundaries during the processing process, thereby obtaining a large number of fine subgrains with small orientation differences, and inhibiting the occurrence of dynamic and static recrystallization, which can retain more small-angle grain boundaries and inhibit recrystallization, which is conducive to the formation of ultrafine substructures; in addition, the aluminum alloy of the present invention can accumulate dislocations near the grain boundaries during the processing process, provide nucleation positions for the precipitation phase, thereby reducing the grain boundary precipitation-free zone (PFZ), further improving the grain boundary strength, and inhibiting the galvanic corrosion between the grain boundary precipitation phase and the PFZ, thereby further improving the toughness and corrosion resistance of the alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 This is a metallographic morphology diagram of the as-cast structure after anodic coating in Example 1 of the present invention;

[0074] Figure 2 This is a dispersed phase distribution diagram of the product obtained after three-stage homogenization treatment during the processing of Example 1 of the present invention;

[0075] Figure 3 This is the aging hardening curve of the alloy obtained in Example 1 of the present invention;

[0076] Figure 4 This is a schematic diagram of the intergranular corrosion cross-sectional structure of the alloy obtained in Example 1 of the present invention after being etched for 24 hours;

[0077] Figure 5 This is a schematic diagram of the intergranular corrosion cross-sectional structure of the alloy obtained in Example 2 of the present invention after being etched for 24 hours;

[0078] Figure 6 This is a schematic diagram of the intergranular corrosion cross-sectional structure of the alloy obtained in Example 3 of the present invention after being etched for 24 hours;

[0079] Figure 7 This is a schematic diagram of the intergranular corrosion cross-sectional structure of the alloy obtained in Comparative Example 1 of the present invention after being etched for 24 hours;

[0080] Figure 8 This is a schematic diagram of the intergranular corrosion cross-sectional structure of the alloy obtained in Comparative Example 2 of the present invention after being etched for 24 hours;

[0081] Fig. 9 This is a schematic diagram of the intergranular corrosion cross-sectional structure of the alloy obtained in Comparative Example 3 of the present invention after being etched for 24 hours;

[0082] Fig.10 This is a schematic diagram of the exfoliation corrosion morphology of the alloy obtained in Example 1 of the present invention after being etched for 48 hours;

[0083] Fig.11 This is a schematic diagram of the exfoliation corrosion morphology of the alloy obtained in Comparative Example 1 of the present invention after being etched for 48 hours. DETAILED DESCRIPTION

[0084] The present invention aims to at least provide an aluminum alloy that can be rapidly aged and hardened and has excellent strength and corrosion resistance, and a preparation method thereof.

[0085] Generally, in 6XXX series aluminum alloys, the mass ratio of Mg / Si when Mg and Si form the main strengthening phase Mg2Si is 1.73. In the formulation system of the present invention, a certain amount of excess Si is innovatively provided in the alloy, specifically, the Mg element content is controlled at 0.80%-0.95%, the Si element content is controlled at 1.0%-1.1%, and the Mg / Si is controlled at 0.8-0.9, which can accelerate the precipitation of the Mg2Si strengthening phase in the grain during the strong aging process, inhibit the formation and growth of the grain boundary precipitation phase, and avoid the generation of corrosion channels;

[0086] Fe can form AlFeSi ternary compound with excess Si, which helps to refine grains. However, excessive Fe forms coarse needle-like crystals at grain boundaries, which has a harmful effect on alloy properties. Therefore, the Fe content needs to be controlled to ≤ 0.15%, and further controlled to 0.01%-0.15%;

[0087] Adding Cu element to 6XXX series aluminum alloy can significantly enhance the precipitation kinetics of the alloy and thus improve the mechanical properties of the alloy. However, when the Cu content is too high, a Cu-rich film will be generated near the grain boundary. The Cu-rich film and the surrounding Cu-poor area constitute a corrosion microbattery, which will induce the occurrence of intergranular corrosion. In the formulation system of the present invention, the Cu content is controlled at 0-0.15%, which can ensure good mechanical properties while obtaining good corrosion resistance.

[0088] In the system of the present invention, adding a small amount of Mn element can improve the morphology of the Fe-rich phase, promote the transformation of the elongated β-AlFeSi phase to the spherical α-Fe phase, and reduce the number of β-AlFeSi phases; it can form a dispersed phase Al6Mn to refine the grains and improve the toughness and corrosion resistance of the alloy. Mn can also eliminate the adverse effects of excessive Si, generate Al-Fe-Mn-Si intermetallic compounds, and improve corrosion resistance. In the system of the present invention, adding an appropriate amount of Cr element not only helps to improve the wear resistance of the aluminum alloy, but also delays the natural aging process, improves the strength of the workpiece after artificial aging, and refines the grains at the same time, so that the grains after artificial aging are slender, thereby improving the corrosion resistance of the alloy. In the formula system of the present invention, by adding a certain proportion of Mn and Cr elements, it is beneficial to form a nano-scale dispersed phase in the later processing process, pin dislocations and subgrain boundaries, and thus improve the toughness of the alloy. However, excessive Mn and Cr will lead to the formation of more coarse hard and brittle phases (Al6Mn and Al7Cr phases) in the alloy. These coarse phases are poorly bonded to the matrix and cannot be completely removed in the subsequent homogenization process, which will have an adverse effect on the processability and mechanical properties of the material. In the formulation system of the present invention, practice shows that when the total amount of Mn+Cr is controlled to be less than 0.9% and Mn / Cr is controlled at 2.7-2.9, a dispersed phase with a high number density can be obtained.

[0089] In the system of the present invention, the addition of Ti element can increase the number of nucleation points in the α-Al matrix, achieve grain refinement, increase the grain boundary area, and then reduce the density of the second phase at the grain boundary, reduce the width of the eutectic structure, and hinder the corrosion from spreading along the grain boundary. The present invention controls the Ti content to 0.01% to 0.03%.

[0090] In some embodiments, the aluminum alloy or aluminum alloy cast product described in the present invention may have the element composition shown in Table 1.

[0091] Table 1

[0092]

[0093]

[0094] The preparation method of the aluminum alloy of the present invention comprises:

[0095] After mixing the components except Ti, the components are mixed and smelted at 730-780°C, and after being fully melted, they are refined in a furnace, and after being allowed to stand for 15-40 minutes, a first melt is obtained;

[0096] Then, adding Ti component to the first melt to prepare a second melt;

[0097] When the melt temperature is 740-750° C., the second melt is cast by DC semi-continuous casting at a casting speed of 140-160 mm / min to obtain a cast product;

[0098] The as-cast product is homogenized by a three-stage homogenization system, wherein the first stage homogenization is performed at 250-330° C. for 1-8 hours; the second stage homogenization is performed at 350-400° C. for 1-8 hours; and the third stage homogenization is performed at 530-560° C. for 4-14 hours.

[0099] Before extrusion, the homogenized cast rod is preheated at a temperature of 470-510°C and a mold preheating temperature of 460-500°C; the extrusion speed is 1-10 mm / s, the extrusion ratio is 25-50, the profile outlet temperature is 510-530°C, and water mist cooling and / or water-penetrating cooling are used for online quenching to obtain aluminum profiles;

[0100] The aluminum profile is subjected to aging treatment at a temperature of 175-190° C. for a treatment time of less than or equal to 24 hours, and then cooled to room temperature to obtain the aluminum alloy.

[0101] The above scheme is further described below in conjunction with specific embodiments; it should be understood that these embodiments are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following embodiments; the implementation conditions adopted in the embodiments can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions in conventional experiments.

[0102] Unless otherwise specified in the following examples, all raw materials are commercially available or prepared by conventional methods in the art.

[0103] Embodiment 1:

[0104] This example provides an aluminum alloy and a preparation method thereof, wherein the aluminum alloy consists of the following components in mass percentage: Mg: 0.85%, Si: 1.05%, Mn: 0.63%, Cr: 0.22%, Ti: 0.03%, Fe: 0.08%; the remainder is Al and unavoidable impurities, Mg / Si (the content ratio of Mg to Si, the same below) = 0.81, Mn+Cr (the total content of Mn and Cr, the same below) = 0.85%, Mn / Cr (the content ratio of Mn to Cr, the same below) = 2.86.

[0105] The preparation method of the aluminum alloy comprises:

[0106] (1) After mixing the components except Ti, smelt at 745±5℃, fully melt, refine in the furnace, let stand for 40min after refining, add Al-5Ti-B rod, stir until melted. DC casting starts when the melt temperature is in the range of 745±5℃, with a casting speed of 150±10mm / min, and obtain an aluminum alloy round bar with a diameter of 90mm.

[0107] (2) A three-stage homogenization system is used to homogenize the cast rods to eliminate segregation and dissolve the low-melting-point second phase: the first-stage homogenization temperature is 275°C and the time is 6 h; the second-stage homogenization temperature is 375°C and the time is 6 h; the third-stage homogenization temperature is 550°C and the time is 10 h.

[0108] (3) The homogenized cast rod was preheated before extrusion at a temperature of 480°C and a mold preheating temperature of 480°C; the extrusion speed was 4 mm / s, the extrusion ratio was 35, the profile outlet temperature was 520±10°C, and online quenching was performed by water cooling to obtain an extruded profile.

[0109] (4) The extruded profile was kept at 180°C for 3 h for aging treatment and then air-cooled to room temperature to obtain an aluminum alloy.

[0110] Embodiment 2:

[0111] This example provides an aluminum alloy and a preparation method thereof, wherein the aluminum alloy is composed of the following components in percentage by mass: Mg: 0.89%, Si: 1.08%, Mn: 0.65%, Cr: 0.23%, Ti: 0.02%, Fe: 0.09%; the remainder is Al and unavoidable impurities, Mg / Si=0.82, Mn+Cr=0.88%, Mn / Cr=2.83.

[0112] The preparation method of the aluminum alloy comprises:

[0113] (1) After mixing the components except Ti, smelt at 745±5℃, fully melt, refine in the furnace, let stand for 40min after refining, add Al-5Ti-B rod, stir until melted. DC casting starts when the melt temperature is in the range of 745±5℃, with a casting speed of 150±10mm / min, and obtain an aluminum alloy round bar with a diameter of 90mm.

[0114] (2) A three-stage homogenization system is used to homogenize the cast rods to eliminate segregation and dissolve the low-melting-point second phase: the first-stage homogenization temperature is 275°C and the time is 6 h; the second-stage homogenization temperature is 400°C and the time is 4 h; the third-stage homogenization temperature is 550°C and the time is 10 h.

[0115] (3) The homogenized cast rod was preheated before extrusion at a temperature of 490°C and a mold preheating temperature of 490°C; the extrusion speed was 3.5 mm / s, the extrusion ratio was 35, the profile outlet temperature was 520±10°C, and online quenching was performed by water cooling to obtain an extruded profile.

[0116] (4) The extruded profile was kept at 180°C for 3 h for aging treatment and then air-cooled to room temperature to obtain an aluminum alloy.

[0117] Embodiment 3:

[0118] This example provides an aluminum alloy and a preparation method thereof, wherein the aluminum alloy is composed of the following components in mass percentage: Mg: 0.82%, Si: 1.02%, Cu: 0.15%, Mn: 0.55%, Cr: 0.2%, Ti: 0.02%, Fe: 0.08%; the remainder is Al and unavoidable impurities, Mg / Si=0.8, Mn+Cr=0.75%, Mn / Cr=2.75.

[0119] The preparation method of the aluminum alloy comprises:

[0120] (1) After mixing the components except Ti, smelt at 745±5℃, fully melt, refine in the furnace, let stand for 40min after refining, add Al-5Ti-B rod, stir until melted. DC casting starts when the melt temperature is in the range of 745±5℃, with a casting speed of 150±10mm / min, and obtain an aluminum alloy round bar with a diameter of 90mm.

[0121] (2) A three-stage homogenization system is used to homogenize the cast rods to eliminate segregation and dissolve the low-melting-point second phase: the first-stage homogenization temperature is 275°C and the time is 6 h; the second-stage homogenization temperature is 350°C and the time is 6 h; the third-stage homogenization temperature is 540°C and the time is 10 h.

[0122] (3) The homogenized cast rod was preheated before extrusion at a temperature of 500°C and a die preheating temperature of 490°C. The extrusion speed was 3 mm / s, the extrusion ratio was 35, the profile outlet temperature was 520±10°C, and online quenching was performed by water cooling to obtain an extruded profile.

[0123] (4) The extruded profile was kept at 180°C for 3 h for aging treatment and then air-cooled to room temperature to obtain an aluminum alloy.

[0124] Comparative Example 1:

[0125] This example provides an aluminum alloy and a preparation method thereof, wherein the aluminum alloy is composed of the following components in mass percentage: Mg: 0.73%, Si: 1.12%, Cu: 0.09%, Mn: 0.69%, Cr: 0.21%, Ti: 0.02%, Fe: 0.09%, Zn: 0.06%; the remainder is Al and unavoidable impurities, Mg / Si=0.65, Mn+Cr=0.9%, Mn / Cr=3.3.

[0126] The preparation method of the aluminum alloy comprises:

[0127] (1) After mixing the components except Ti, smelt at 745±5℃, fully melt, refine in the furnace, let stand for 40min after refining, add Al-5Ti-B rod, stir until melted. DC casting starts when the melt temperature is in the range of 745±5℃, with a casting speed of 150±10mm / min, and obtain an aluminum alloy round bar with a diameter of 90mm.

[0128] (2) A two-stage homogenization system is used to homogenize the cast rods: the first stage homogenization temperature is 300°C and the time is 8 h; the second stage homogenization temperature is 550°C and the time is 10 h.

[0129] (3) The homogenized cast rod was preheated before extrusion at a temperature of 500°C and a die preheating temperature of 490°C. The extrusion speed was 3 mm / s, the extrusion ratio was 35, the profile outlet temperature was 520±10°C, and online quenching was performed by water cooling to obtain an extruded profile.

[0130] (4) The extruded profile was kept at 180°C for 6 h for aging treatment and then air-cooled to room temperature to obtain an aluminum alloy.

[0131] Comparative Example 2:

[0132] This example provides an aluminum alloy and a preparation method thereof, wherein the aluminum alloy is composed of the following components in percentage by mass: Mg: 0.81%, Si: 0.84%, Cu: 0.16%, Mn: 0.50%, Cr: 0.15%, Ti: 0.03%, Fe: 0.08%; the remainder is Al and unavoidable impurities, Mg / Si=0.96, Mn+Cr=0.65%, Mn / Cr=3.3.

[0133] The preparation method of the aluminum alloy comprises:

[0134] (1) After mixing the components except Ti, smelt at 745±5℃, fully melt, refine in the furnace, let stand for 40min after refining, add Al-5Ti-B rod, stir until melted. DC casting starts when the melt temperature is in the range of 745±5℃, with a casting speed of 150±10mm / min, and obtain an aluminum alloy round bar with a diameter of 90mm.

[0135] (2) A two-stage homogenization system is used to homogenize the cast rods: the first stage homogenization temperature is 300°C and the time is 8 h; the second stage homogenization temperature is 550°C and the time is 10 h.

[0136] (3) The homogenized cast rod was preheated before extrusion at a temperature of 500°C and a die preheating temperature of 490°C. The extrusion speed was 4 mm / s, the extrusion ratio was 28.5, the profile outlet temperature was 505±5°C, and online quenching was performed by water cooling to obtain an extruded profile.

[0137] (4) The extruded profile was kept at 180°C for 6 h for aging treatment and then air-cooled to room temperature to obtain an aluminum alloy.

[0138] Comparative Example 3:

[0139] This example provides an aluminum alloy and a preparation method thereof. The formula content is the same as that in Example 1, and the only difference is that the preparation method is different. This comparative example adopts a two-stage homogenization system to homogenize the cast rods: the first stage homogenization temperature is 300°C and the time is 8h; the second stage homogenization temperature is 550°C and the time is 10h. The rest is the same as in Example 1.

[0140] Performance Testing

[0141] (1) The metallographic structure of the anode film after the cast condition in Example 1 at 200X is as follows Figure 1 As shown. According to statistics, the average grain size of the cast alloy is about 96μm, which is relatively small. This shows that in the system of the present invention, there are more nucleation points in the α-Al matrix, which has the effect of refining the grains.

[0142] (2) The dispersed phase distribution of the product obtained after three-stage homogenization treatment during the processing of Example 1 is as follows Figure 2As shown. It can be seen that after the three-stage homogenization treatment, the α dispersed phase with uniform dispersion, small size and high number density is distributed in the crystal. The three-stage homogenization of the present invention makes the alloy fully precipitate the metastable Mg2Si phase with uniform distribution and high number density in the first stage. In the subsequent heating process, the Mg atoms in the metastable Mg2Si phase gradually dissolve back into the matrix, leaving the Si-rich region, which can be used as the heterogeneous nucleation point of α-dispersion. The purpose of the second-stage homogenization is to increase the stage of single nucleation of the dispersed phase and increase the number density of the dispersed phase in the alloy. The third stage is to continue to promote the precipitation of more dispersed phases, and at the same time dissolve the low melting point second phase generated by non-equilibrium solidification in the alloy, such as coarse Mg2Si. In addition, the β-Fe phase can be transformed into the α-Fe phase which is more conducive to the performance of the alloy. The overburning temperature of Al-Mg-Si alloy is generally 560-580℃. In order to avoid overburning and dissolve the melting point second phase as much as possible, the temperature of the third stage is set at ≤550℃. The dispersed phase can pin dislocations and grain boundaries, retain more small-angle grain boundaries and inhibit recrystallization, which is beneficial to the formation of ultrafine substructures, thereby improving the comprehensive properties of the alloy.

[0143] (3) The aging hardening curves of the aluminum alloy (Al-Mg-Si alloy) obtained in Example 1 at 180°C for different holding times are shown in FIG. Figure 3 It can be seen that the alloy can reach a peak hardness of 109.3HV in 2 hours. As the holding time increases, the hardness of the alloy decreases slightly, but it can still reach 108HV in 6 hours, indicating that the alloy of the invention can achieve a rapid aging hardening effect and has a large process window.

[0144] (4) Using the aluminum alloy (Al-Mg-Si alloy) profiles obtained in the above embodiment and comparative example, three standard tensile specimens, intergranular corrosion specimens and exfoliation corrosion specimens were prepared respectively;

[0145] According to ASTM E8 / E8M-22 standard, the tensile test specimens of Examples 1-3 and Comparative Examples 1-3 were subjected to room temperature tensile tests, and the tensile performance results are shown in Table 2;

[0146] According to ASTM G110-92 (2022) e2 standard, 24h immersion corrosion test was carried out on Examples 1-3 and Comparative Examples 1-3. The intergranular corrosion depth results are shown in Table 2. The intergranular corrosion results of the longitudinal section are shown in Table 2. Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Fig. 9 As shown;

[0147] According to GB / T22639-2022 standard, the examples 1-3 and comparative examples 1-3 were subjected to a 48h exfoliation corrosion test. The exfoliation corrosion results are shown in Table 2. The exfoliation corrosion morphology of the sample in Example 1 is shown in Fig.10 As shown, no obvious corrosion phenomenon was observed; the exfoliation corrosion morphology of the sample in comparative example 1 is as follows Fig.11 As shown, compared with Example 1, the corrosion is relatively obvious, and more obvious corrosion points can be seen.

[0148] Table 2 Mechanical and corrosion properties of aluminum alloys obtained in various embodiments and comparative examples

[0149]

[0150] It can be seen from Table 2 that the yield strength of the embodiment alloy in T5 state is ≥330MPa, the tensile strength is ≥350MPa, the elongation is ≥10%, the intergranular corrosion depth is <100μm, and the exfoliation corrosion reaches PB level; compared with Example 1, the corrosion resistance of Comparative Example 1 is the worst, Comparative Example 2 not only has poor corrosion resistance, but also relatively poor strength, and the corrosion resistance of Comparative Example 3 is relatively poor. At the same time, the aging hardening time of Comparative Examples 1-2 in the aging hardening process is relatively long, which is not conducive to improving production efficiency.

[0151] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

[0152] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

Claims

1. An aluminum alloy, characterized in that: Measured in percentage by mass, the aluminum alloy comprises: Mg: 0.80%-0.95% Si: 1.0%-1.1% Cu: 0-0.15% Mn: 0.55%-0.65% Cr：0.2％-0.25％ Ti≤0.03% Fe≤0.15%; The aluminum alloy satisfies 100% by adjusting the content of Al; Moreover, the content ratio of Mg to Si is 0.8-0.9, the total content of Mn and Cr is less than 0.9%, and the content ratio of Mn to Cr is 2.7-2.

9.

2. The aluminum alloy according to claim 1, characterized in that The content ratio of Mg to Si is 0.80-0.85; and / or the total content of Mn and Cr is 0.75%-0.88%.

3. The aluminum alloy according to claim 1, characterized in that In terms of mass percentage, the aluminum alloy contains 0.80%-0.90% Mg; and / or in terms of mass percentage, the aluminum alloy contains 0.01%-0.03% Ti.

4. The aluminum alloy according to claim 1, characterized in that The aluminum alloy comprises a nano-scale α-AlFe(MnCr)Si dispersed phase and an Al6Mn dispersed phase.

5. The aluminum alloy according to claim 1, characterized in that Measured in percentage by mass, the aluminum alloy comprises: Mg: 0.82%-0.92% Si: 1.02%-1.1% Mn: 0.60%-0.65% Cr：0.2％-0.25％ Ti: 0.01%-0.03% Fe≤0.15%; The aluminum alloy satisfies 100% by adjusting the content of Al; Moreover, the content ratio of Mg to Si is 0.8-0.86, the total content of Mn and Cr is 0.80%-0.88%, and the content ratio of Mn to Cr is 2.8-2.

9.

6. The aluminum alloy according to claim 1, characterized in that Measured in percentage by mass, the aluminum alloy comprises: Mg: 0.80%-0.85% Si: 1.0%-1.06% Cu: 0.05%-0.15% Mn: 0.55%-0.60% Cr：0.2％-0.25％ Ti: 0.01%-0.03% Fe≤0.15%; The aluminum alloy satisfies 100% by adjusting the content of Al; Moreover, the content ratio of Mg to Si is 0.8-0.84, the total content of Mn and Cr is 0.75%-0.80%, and the content ratio of Mn to Cr is 2.7-2.

8.

7. The aluminum alloy according to claim 1, characterized in that The peak aging time of the aluminum alloy is less than or equal to 4h; and / or, in the T5 state, the yield strength of the aluminum alloy at room temperature is greater than or equal to 330MPa, the tensile strength is greater than or equal to 350MPa, the elongation is greater than or equal to 10%, and the intergranular corrosion depth is less than 100μm.

8. The aluminum alloy according to claim 1, characterized in that In the process of preparing the aluminum alloy, a cast product is first cast, and then the cast product is subjected to homogenization treatment, extrusion treatment and aging treatment; wherein the homogenization treatment includes: a first-level homogenization treatment at 250-330°C, a second-level homogenization treatment at 350-400°C, and a third-level homogenization treatment at 530-560°C.

9. A method for preparing the aluminum alloy according to any one of claims 1 to 8, characterized in that: The preparation method comprises: The components except Ti are mixed, smelted, refined, and allowed to stand to form a first melt; Then, adding Ti component to the first melt to prepare a second melt; Casting the second melt to obtain a cast product; The cast product is homogenized and then extruded to obtain an aluminum profile; The aluminum profile is subjected to aging treatment to obtain the aluminum alloy.

10. The method for preparing the aluminum alloy according to claim 9, characterized in that: The mixed smelting temperature is 730-780°C; and / or, the refining temperature is 730-780°C; and / or, the temperature when the Ti component is added is 730-780°C; and / or, the Ti component is added in the form of Al-5Ti-B.

11. The method for preparing an aluminum alloy according to claim 9, characterized in that: The casting adopts DC semi-continuous casting, and the melt temperature at the beginning of casting is 740-750° C.; and / or, the casting speed of the casting is 140-160 mm / min.

12. The method for preparing an aluminum alloy according to claim 9, characterized in that: The homogenization treatment includes the following steps in sequence: a first-stage homogenization treatment at 250-330°C for 1-8 hours; a second-stage homogenization treatment at 350-400°C for 1-8 hours; a third-stage homogenization treatment at 530-560°C for 4-14 hours; and / or, During the extrusion molding process, the preheating temperature of the homogenized product is 470-510°C, the preheating temperature of the mold is 460-500°C, the extrusion speed is 1-10 mm / s, the extrusion ratio is 25-50, and the cooling method after extrusion is water mist cooling and / or water cooling; and / or, The aging treatment temperature is 175-190° C., the treatment time is less than or equal to 24 hours, and the peak aging time is less than or equal to 4 hours.

13. Use of the aluminum alloy according to any one of claims 1 to 8 in shipbuilding.

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