A high-strength corrosion-resistant formable 7xxx-series aluminum alloy and method of making

Abstract

The application discloses a high-strength corrosion-resistant formable 7xxx series aluminum alloy, and a preparation method thereof. The high-strength corrosion-resistant formable 7xxx series aluminum alloy has a chemical composition and mass percentage of Zn: 3.5-5.8%, Mg: 0.5-2.5%, Cu: 0.3-1.6%, Zr: 0.01-0.15%, Y: 0.01-0.30%, Fe: 0.01-0.5%, Si: 0.01-0.5%, In: 0.01-0.5% and / or Sn: 0.01-0.5%, and the balance of Al. The 7xxx series aluminum alloy provided by the application has high plasticity and good processing performance, and has high parking stability and corrosion resistance.

Description

Technical Field

[0001] This invention relates to the field of 7xxx series aluminum alloys and their processing and preparation, specifically to a high-strength, corrosion-resistant, formable 7xxx series aluminum alloy and its preparation method. Background Technology

[0002] The rapid development of the modern economy has placed increasingly stringent demands on the lightweighting of high-end transportation equipment. Using aluminum alloys instead of steel and titanium alloys to process parts can reduce manufacturing costs and save energy while achieving lightweighting. 7xxx series aluminum alloys are heat-treatable alloys used to manufacture profiles, plates, and wire rods. Their excellent room-temperature tensile, shear, and fatigue properties, as well as good pressure processing and machining performance, make them the preferred material for lightweight design. Processing methods include casting, homogenization, extrusion, hot rolling, cold rolling, annealing, cold drawing, solution treatment, and aging. Currently, 7xxx series aluminum alloy bars that have undergone annealing and cold drawing typically undergo a period of transportation or storage before being formed and processed when needed. During this process, alloying elements dissolved in the aluminum alloy matrix continuously decompose and precipitate, generating fine, dispersed strengthening phases. This leads to a natural aging strengthening effect in the material during storage and transportation, resulting in a continuous increase in strength and a decrease in plasticity. Furthermore, the grain boundaries of the material become channels for corrosion to occur and develop, making them highly susceptible to intergranular corrosion in complex processing and service environments. This severely affects the material's processing performance, forming performance, and overall product quality. Summary of the Invention

[0003] This invention designs and develops a high-strength, corrosion-resistant, formable 7xxx series aluminum alloy. The purpose of this invention is to solve the problems of increased natural aging strength, poor formability, and intergranular corrosion that occur in 7xxx series aluminum alloy products after intermediate annealing and cold deformation by adding Sn or In elements.

[0004] This invention also designed and developed a method for preparing high-strength, corrosion-resistant, and formable 7xxx series aluminum alloys. One of the objectives of this invention is to solve the problems of increased natural aging strength, poor formability, and intergranular corrosion in 7xxx series aluminum alloy products after intermediate annealing and cold deformation by adding Sn or In elements to the raw materials during the preparation process.

[0005] The second objective of this invention is to improve intergranular corrosion performance by regulating the effects of annealing and slow cooling on grain boundary elements and precipitated phases, thereby increasing industrial production efficiency, reducing production costs, and improving the quality of material products.

[0006] The technical solution provided by this invention is as follows:

[0007] A high-strength, corrosion-resistant, formable 7xxx series aluminum alloy comprises the following chemical composition and mass percentages: Zn: 3.5-5.0%, Mg: 0.5-1.8%, Cu: 0.3-1.2%, Zr: 0.01-0.05%, Y: 0.01-0.05%, Fe: 0.05-0.35%, Si: 0.05-0.35%.

[0008] In: 0.01-0.5% and / or Sn: 0.01-0.5%; and

[0009] The balance is Al.

[0010] Preferably, the chemical composition and mass percentage of the high-strength, corrosion-resistant, formable 7xxx series aluminum alloy are as follows: Zn: 3.5-5.0%, Mg: 0.5-1.8%, Cu: 0.3-1.2%, Zr: 0.01-0.05%, Y: 0.01-0.05%, Fe: 0.05-0.35%, Si: 0.05-0.35%.

[0011] In: 0.15-0.3% and / or Sn: 0.15-0.3%; and

[0012] The balance is Al.

[0013] Preferably, the chemical composition and mass percentage of the high-strength, corrosion-resistant, formable 7xxx series aluminum alloy are as follows: Zn: 3.5-5.0%, Mg: 0.5-1.8%, Cu: 0.3-1.2%, Zr: 0.01-0.05%, Y: 0.01-0.05%, Fe: 0.05-0.35%, Si: 0.05-0.35%, In+Sn≥0.15%, with the balance being Al.

[0014] A method for preparing a high-strength, corrosion-resistant, formable 7xxx series aluminum alloy includes the following steps:

[0015] Step 1: After melting and casting the raw material of the 7xxx series aluminum alloy into an ingot, it is homogenized, then machined to remove the oxide scale, and then extruded to obtain aluminum alloy rods.

[0016] Step 2: Perform intermediate annealing and cold rolling on the aluminum alloy bar to obtain cold-rolled bar;

[0017] Step 3: Perform intermediate annealing and cold drawing on the cold-rolled bar to obtain the 7xxx series aluminum alloy;

[0018] In step one, the chemical composition and mass percentage of the raw materials for the 7xxx series aluminum alloy are as follows: Zn: 3.5-5.0%, Mg: 0.5-1.8%, Cu: 0.3-1.2%, Zr: 0.01-0.05%, Y: 0.01-0.05%, Fe: 0.05-0.35%, Si: 0.05-0.35%.

[0019] In: 0.01-0.5% and / or Sn: 0.01-0.5%; and

[0020] The balance is Al.

[0021] Preferably, in step three, the annealing process involves a heating rate of 10-100℃ / h, a holding temperature of 350-450℃, a holding time of 0.5-15h, followed by cooling to room temperature at a cooling rate of 1-30℃ / h.

[0022] Preferably, in step one, the chemical composition and mass percentage of the raw material for the 7xxx series aluminum alloy are as follows: Zn: 3.5-5.0%, Mg: 0.5-1.8%, Cu: 0.3-1.2%, Zr: 0.01-0.05%, Y: 0.01-0.05%, Fe: 0.05-0.35%, Si: 0.05-0.35%.

[0023] In: 0.15-0.3% and / or Sn: 0.15-0.3%; and

[0024] The balance is Al.

[0025] Preferably, in step one, the chemical composition and mass percentage of the raw material of the 7xxx series aluminum alloy are as follows: Zn: 3.5-5.0%, Mg: 0.5-1.8%, Cu: 0.3-1.2%, Zr: 0.01-0.05%, Y: 0.01-0.05%, Fe: 0.05-0.35%, Si: 0.05-0.35%, In+Sn≥0.15%, with the balance being Al.

[0026] Preferably, in step one, the homogenization treatment is performed at a temperature of 450-475℃ for 3-72 hours; and

[0027] The extrusion temperature is 380-420℃, and the extrusion ratio is 45-70:1.

[0028] Preferably, in step two, the annealing temperature is 380-450℃, and the holding time is 0.5-15 hours; and

[0029] The cooling methods are water cooling, furnace cooling, and / or air cooling.

[0030] Preferably, in step three, the annealing and cold drawing process is: one annealing and one cold drawing; or

[0031] The annealing and cold drawing process is as follows: one cold drawing, one intermediate annealing, and one cold drawing.

[0032] Of which, the cold drawing amount is 20%-40%.

[0033] The beneficial effects of this invention are as follows:

[0034] 1. The high-strength, corrosion-resistant, formable 7xxx series aluminum alloy provided by the present invention, by adding one or more of In and Sn elements, utilizes their binding advantage to vacancies to mitigate or eliminate the adverse effects of natural aging strengthening on plasticity and formability.

[0035] 2. The high-strength, corrosion-resistant, formable 7xxx series aluminum alloy provided by this invention captures vacancies during the annealing and resting process by adding In and Sn elements, reducing the vacancy concentration during the cooling process, delaying or inhibiting the precipitation of MgZn2 strengthening phase during natural resting, so that the mechanical properties of the material are in a stable state, maintaining high plasticity and good processing performance.

[0036] 3. The preparation method of high-strength corrosion-resistant formable 7xxx series aluminum alloy provided by the present invention adopts a single-stage annealing method of high temperature + slow cooling. The high temperature annealing process eliminates the work hardening of the material and improves the plasticity of the material; the slow cooling adjusts the morphology and elemental composition of the precipitated phases at the grain boundaries, reduces the potential difference between the grain boundaries and the grain interior, avoids the rapid development of intergranular corrosion along the grain boundaries, and comprehensively improves the material's formability, storage stability and corrosion resistance.

[0037] 4. The preparation method of high-strength corrosion-resistant formable 7xxx series aluminum alloy provided by the present invention achieves the elimination of work hardening effect through a single-stage high-temperature annealing process during cold drawing and annealing, which is beneficial to subsequent cold forming. During the slow cooling process, discontinuous precipitates are formed at the grain boundaries, which prevents intergranular corrosion from continuously occurring along the grain boundary precipitates during the material's storage after annealing, thereby improving the alloy's storage stability and corrosion resistance.

[0038] 5. The preparation method of high-strength, corrosion-resistant, and formable 7xxx series aluminum alloys provided by this invention has strong operational feasibility, high controllability in industrial-scale production, and good results, and can keep the corrosion resistance and formability of 7xxx series aluminum alloys stable. Attached Figure Description

[0039] Figure 1a This is a diagram of the intergranular corrosion morphology of Example 1 of the present invention.

[0040] Figure 1b This is a diagram of the intergranular corrosion morphology of Comparative Example 1 of the present invention.

[0041] Figure 2 This is a schematic diagram illustrating the parking stability of Embodiment 1 and Comparative Example 1 of the present invention.

[0042] Figure 3a This is a second phase morphology diagram of Embodiment 1 of the present invention.

[0043] Figure 3b This is a second phase morphology diagram of Comparative Example 1 of the present invention. Detailed Implementation

[0044] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0045] This invention provides a high-strength, corrosion-resistant, formable 7xxx series aluminum alloy, characterized in that it comprises: the chemical composition and mass percentage of the high-strength, corrosion-resistant, formable 7xxx series aluminum alloy are as follows: Zn: 3.5-5.0%, Mg: 0.5-1.8%, Cu: 0.3-1.2%, Zr: 0.01-0.05%, Y: 0.01-0.05%, Fe: 0.05-0.35%, Si: 0.05-0.35%; In: 0.01-0.5% and / or Sn: 0.01-0.5%; the balance being Al.

[0046] In another embodiment, the chemical composition and mass percentage of the high-strength, corrosion-resistant, formable 7xxx series aluminum alloy are as follows: Zn: 3.5-5.0%, Mg: 0.5-1.8%, Cu: 0.3-1.2%, Zr: 0.01-0.05%, Y: 0.01-0.05%, Fe: 0.05-0.35%, Si: 0.05-0.35%, In: 0.01-0.5%, with the balance being Al.

[0047] In another embodiment, the chemical composition and mass percentage of the high-strength, corrosion-resistant, formable 7xxx series aluminum alloy are as follows: Zn: 3.5-5.0%, Mg: 0.5-1.8%, Cu: 0.3-1.2%, Zr: 0.01-0.05%, Y: 0.01-0.05%, Fe: 0.05-0.35%, Si: 0.05-0.35%, Sn: 0.01-0.5%; the balance is Al.

[0048] In another embodiment, the chemical composition and mass percentage of the high-strength, corrosion-resistant, formable 7xxx series aluminum alloy are as follows: Zn: 3.5-5.0%, Mg: 0.5-1.8%, Cu: 0.3-1.2%, Zr: 0.01-0.05%, Y: 0.01-0.05%, Fe: 0.05-0.35%, Si: 0.05-0.35%, In: 0.01-0.5%, Sn: 0.01-0.5%; the balance is Al.

[0049] In another embodiment, the chemical composition and mass percentage of the high-strength, corrosion-resistant, formable 7xxx series aluminum alloy are as follows: Zn: 3.5-5.0%, Mg: 0.5-1.8%, Cu: 0.3-1.2%, Zr: 0.01-0.05%, Y: 0.01-0.05%, Fe: 0.05-0.35%, Si: 0.05-0.35%; In: 0.15-0.3% and / or Sn: 0.15-0.3%; balance Al.

[0050] In another embodiment, the chemical composition and mass percentage of the high-strength, corrosion-resistant, formable 7xxx series aluminum alloy are as follows: Zn: 3.5-5.0%, Mg: 0.5-1.8%, Cu: 0.3-1.2%, Zr: 0.01-0.05%, Y: 0.01-0.05%, Fe: 0.05-0.35%, Si: 0.05-0.35%, In: 0.15-0.3%; the balance is Al.

[0051] In another embodiment, the chemical composition and mass percentage of the high-strength, corrosion-resistant, formable 7xxx series aluminum alloy are as follows: Zn: 3.5-5.0%, Mg: 0.5-1.8%, Cu: 0.3-1.2%, Zr: 0.01-0.05%, Y: 0.01-0.05%, Fe: 0.05-0.35%, Si: 0.05-0.35%, Sn: 0.15-0.3%; the balance is Al.

[0052] In another embodiment, the chemical composition and mass percentage of the high-strength, corrosion-resistant, formable 7xxx series aluminum alloy are as follows: Zn: 3.5-5.0%, Mg: 0.5-1.8%, Cu: 0.3-1.2%, Zr: 0.01-0.05%, Y: 0.01-0.05%, Fe: 0.05-0.35%, Si: 0.05-0.35%, In: 0.15-0.3%, Sn: 0.15-0.3%; the balance is Al.

[0053] In another embodiment, the chemical composition and mass percentage of the high-strength, corrosion-resistant, formable 7xxx series aluminum alloy are as follows: Zn: 3.5-5.0%, Mg: 0.5-1.8%, Cu: 0.3-1.2%, Zr: 0.01-0.05%, Y: 0.01-0.05%, Fe: 0.05-0.35%, Si: 0.05-0.35%, In+Sn≥0.15%, with the balance being Al.

[0054] This invention also provides a method for preparing a high-strength, corrosion-resistant, formable 7xxx series aluminum alloy, specifically including the following steps:

[0055] Step 1: After melting and casting the raw material of 7xxx series aluminum alloy into ingots, homogenize it, then machine it to remove the oxide scale, and finally extrude it to obtain aluminum alloy rods.

[0056] Step 2: Perform intermediate annealing and cold rolling on the aluminum alloy bars to obtain cold-rolled bars;

[0057] Step 3: Perform intermediate annealing and cold drawing on the cold-rolled bar to obtain 7xxx series aluminum alloy;

[0058] In step one, the chemical composition and mass percentage of the raw materials for the 7xxx series aluminum alloy are as follows: Zn: 3.5-5.0%, Mg: 0.5-1.8%, Cu: 0.3-1.2%, Zr: 0.01-0.05%, Y: 0.01-0.05%, Fe: 0.05-0.35%, Si: 0.05-0.35%; In: 0.01-0.5% and / or Sn: 0.01-0.5%; the balance is Al.

[0059] In another embodiment, in step one, the chemical composition and mass percentage of the raw material of the 7xxx series aluminum alloy are as follows: Zn: 3.5-5.0%, Mg: 0.5-1.8%, Cu: 0.3-1.2%, Zr: 0.01-0.05%, Y: 0.01-0.05%, Fe: 0.05-0.35%, Si: 0.05-0.35%, In: 0.01-0.5%, with the balance being Al.

[0060] In another embodiment, in step one, the chemical composition and mass percentage of the raw material of the 7xxx series aluminum alloy are as follows: Zn: 3.5-5.0%, Mg: 0.5-1.8%, Cu: 0.3-1.2%, Zr: 0.01-0.05%, Y: 0.01-0.05%, Fe: 0.05-0.35%, Si: 0.05-0.35%, Sn: 0.01-0.5%; the balance is Al.

[0061] In another embodiment, in step one, the chemical composition and mass percentage of the raw material of the 7xxx series aluminum alloy are as follows: Zn: 3.5-5.0%, Mg: 0.5-1.8%, Cu: 0.3-1.2%, Zr: 0.01-0.05%, Y: 0.01-0.05%, Fe: 0.05-0.35%, Si: 0.05-0.35%, In: 0.01-0.5%, Sn: 0.01-0.5%; the balance is Al.

[0062] In another embodiment, in step one, the chemical composition and mass percentage of the raw material of the 7xxx series aluminum alloy are as follows: Zn: 3.5-5.0%, Mg: 0.5-1.8%, Cu: 0.3-1.2%, Zr: 0.01-0.05%, Y: 0.01-0.05%, Fe: 0.05-0.35%, Si: 0.05-0.35%; In: 0.15-0.3% and / or Sn: 0.15-0.3%; the balance is Al.

[0063] In another embodiment, in step one, the chemical composition and mass percentage of the raw material of the 7xxx series aluminum alloy are as follows: Zn: 3.5-5.0%, Mg: 0.5-1.8%, Cu: 0.3-1.2%, Zr: 0.01-0.05%, Y: 0.01-0.05%, Fe: 0.05-0.35%, Si: 0.05-0.35%, In: 0.15-0.3%; the balance is Al.

[0064] In another embodiment, in step one, the chemical composition and mass percentage of the raw material of the 7xxx series aluminum alloy are as follows: Zn: 3.5-5.0%, Mg: 0.5-1.8%, Cu: 0.3-1.2%, Zr: 0.01-0.05%, Y: 0.01-0.05%, Fe: 0.05-0.35%, Si: 0.05-0.35%, Sn: 0.15-0.3%; the balance is Al.

[0065] In another embodiment, in step one, the chemical composition and mass percentage of the raw material of the 7xxx series aluminum alloy are as follows: Zn: 3.5-5.0%, Mg: 0.5-1.8%, Cu: 0.3-1.2%, Zr: 0.01-0.05%, Y: 0.01-0.05%, Fe: 0.05-0.35%, Si: 0.05-0.35%, In: 0.15-0.3%, Sn: 0.15-0.3%; the balance is Al.

[0066] In another embodiment, in step one, the chemical composition and mass percentage of the raw material of the 7xxx series aluminum alloy are as follows: Zn: 3.5-5.0%, Mg: 0.5-1.8%, Cu: 0.3-1.2%, Zr: 0.01-0.05%, Y: 0.01-0.05%, Fe: 0.05-0.35%, Si: 0.05-0.35%, In+Sn≥0.15%, with the balance being Al.

[0067] In another embodiment, in step one, the homogenization treatment is carried out at a temperature of 450-475°C for 3-72 hours.

[0068] In another embodiment, in step one, the extrusion temperature of the extrusion operation is 380-420°C, and the extrusion ratio is 45-70:1.

[0069] In another embodiment, in step two, the annealing temperature is 380-450℃, the holding time is 0.5-15h, and the cooling method is water cooling, furnace cooling, or air cooling.

[0070] In another embodiment, in step three, the annealing process is heated at a rate of 10-100°C / h, held at 350-450°C for 0.5-15h, and then cooled to room temperature at a rate of 1-30°C / h.

[0071] In another embodiment, in step three, the annealing and cold drawing process is: one annealing and one cold drawing; wherein the cold drawing amount is 20%-40%.

[0072] In another embodiment, in step three, the annealing and cold drawing process is as follows: one cold drawing, one intermediate annealing, and one cold drawing; wherein the cold drawing amount is 20%-40%.

[0073] Example 1

[0074] The method for preparing high-strength, corrosion-resistant, formable 7xxx series aluminum alloys provided in this embodiment specifically includes the following steps:

[0075] Step 1: Melt and cast the aluminum alloy raw material into an ingot; wherein the chemical composition and mass percentage of the aluminum alloy raw material are: Zn: 5.0%, Mg: 1.8%, Cu: 1.2%, Zr: 0.05%, Y: 0.05%, Si: 0.05%, Fe: 0.05%, In: 0.15%, Sn: 0.15%, with the balance being Al;

[0076] Step 2, Homogenization treatment: The homogenization temperature for the ingot is 475℃, and the holding time is 3h.

[0077] Step 3, Extrusion: The homogenized heat-treated ingot is heated to 420℃, and the extrusion ratio is 45:1;

[0078] Step 4, Cold rolling: The annealing temperature of the extruded bar is 380℃, the holding time is 15h, and then it is cold rolled after water cooling.

[0079] Step 5, Cold drawing: The cold-rolled bar is subjected to intermediate annealing at a heating rate of 70℃ / h, a holding temperature of 350℃, a holding time of 5h, and a cooling rate of 10℃ / h to room temperature. Then, cold drawing is performed with a cold drawing amount of 40%.

[0080] Example 2

[0081] The method for preparing high-strength, corrosion-resistant, formable 7xxx series aluminum alloys provided in this embodiment specifically includes the following steps:

[0082] Step 1: Melt and cast the aluminum alloy raw material into an ingot; wherein the chemical composition and mass percentage of the aluminum alloy raw material are: Zn: 3.5%, Mg: 0.5%, Cu: 0.3%, Zr: 0.05%, Y: 0.05%, Si: 0.35%, Fe: 0.35%, In: 0.3%, with the balance being Al;

[0083] Step 2, Homogenization treatment: The homogenization temperature for the ingot is 450℃, and the holding time is 72h.

[0084] Step 3, Extrusion: Heat the homogenized heat-treated ingot to 380℃ and extrude it at a ratio of 70:1.

[0085] Step 4, Cold rolling: The annealing temperature of the extruded bar is 400℃, the holding time is 0.5h, and then it is cold rolled after water cooling;

[0086] Step 5, Cold drawing: The cold-rolled bar is subjected to intermediate annealing with a heating rate of 100℃ / h, a holding temperature of 450℃, a holding time of 15h, and a cooling rate of 30℃ / h to room temperature. Then, cold drawing is performed with a cold drawing amount of 30%.

[0087] Example 3

[0088] The method for preparing high-strength, corrosion-resistant, formable 7xxx series aluminum alloys provided in this embodiment specifically includes the following steps:

[0089] Step 1: Melt and cast the aluminum alloy raw material into an ingot; wherein the chemical composition and mass percentage of the aluminum alloy raw material are: Zn: 4.5%, Mg: 1.2%, Cu: 0.9%, Zr: 0.01%, Y: 0.01%, Si: 0.1%, Fe: 0.1%, Sn: 0.3%, with the balance being Al;

[0090] Step 2, Homogenization treatment: The homogenization temperature for the ingot is 465℃, and the holding time is 24h.

[0091] Step 3, Extrusion: Heat the homogenized heat-treated ingot to 400℃ and extrude it at a ratio of 60:1.

[0092] Step 4, Cold rolling: The annealing temperature of the extruded bar is 400℃, the holding time is 5h, and it is then cold rolled after water cooling.

[0093] Step 5, Cold Drawing: The cold-rolled bar undergoes two intermediate annealing processes followed by cold drawing. The first intermediate annealing involves a heating rate of 10℃ / h, a holding temperature of 400℃, a holding time of 0.5h, and a cooling rate of 30℃ / h to room temperature. This is followed by the first cold drawing, with a cold drawing amount of 20%. The second intermediate annealing is then performed, with a heating rate of 10℃ / h, a holding temperature of 400℃, a holding time of 0.5h, and a cooling rate of 1℃ / h to room temperature. This is followed by the second cold drawing, with a cold drawing amount of 40%.

[0094] Example 4

[0095] The method for preparing high-strength, corrosion-resistant, formable 7xxx series aluminum alloys provided in this embodiment specifically includes the following steps:

[0096] Step 1: Melt and cast the aluminum alloy raw material into an ingot; wherein the chemical composition and mass percentage of the aluminum alloy raw material are: Zn: 5.0%, Mg: 1.8%, Cu: 1.2%, Zr: 0.05%, Y: 0.05%, Si: 0.05%, Fe: 0.05%, In: 0.1%, Sn: 0.1%, with the balance being Al;

[0097] Step 2, Homogenization treatment: The homogenization temperature for the ingot is 475℃, and the holding time is 3h.

[0098] Step 3, Extrusion: The homogenized heat-treated ingot is heated to 420℃, and the extrusion ratio is 45:1;

[0099] Step 4, Cold rolling: The annealing temperature of the extruded bar is 380℃, the holding time is 15h, and then it is cold rolled after water cooling.

[0100] Step 5, Cold drawing: The cold-rolled bar is subjected to intermediate annealing at a heating rate of 70℃ / h, a holding temperature of 350℃, a holding time of 5h, and a cooling rate of 10℃ / h to room temperature. Then, cold drawing is performed with a cold drawing amount of 40%.

[0101] Example 5

[0102] The method for preparing high-strength, corrosion-resistant, formable 7xxx series aluminum alloys provided in this embodiment specifically includes the following steps:

[0103] Step 1: Melt and cast the aluminum alloy raw material into an ingot; wherein the chemical composition and mass percentage of the aluminum alloy raw material are: Zn: 5.0%, Mg: 1.8%, Cu: 1.2%, Zr: 0.05%, Y: 0.05%, Si: 0.05%, Fe: 0.05%, In: 0.12%, Sn: 0.03%, with the balance being Al;

[0104] Step 2, Homogenization treatment: The homogenization temperature for the ingot is 475℃, and the holding time is 3h.

[0105] Step 3, Extrusion: The homogenized heat-treated ingot is heated to 420℃, and the extrusion ratio is 45:1;

[0106] Step 4, Cold rolling: The annealing temperature of the extruded bar is 380℃, the holding time is 15h, and then it is cold rolled after water cooling.

[0107] Step 5, Cold drawing: The cold-rolled bar is subjected to intermediate annealing at a heating rate of 70℃ / h, a holding temperature of 350℃, a holding time of 5h, and a cooling rate of 10℃ / h to room temperature. Then, cold drawing is performed with a cold drawing amount of 40%.

[0108] Example 6

[0109] The method for preparing high-strength, corrosion-resistant, formable 7xxx series aluminum alloys provided in this embodiment specifically includes the following steps:

[0110] Step 1: Melt and cast the aluminum alloy raw material into an ingot; wherein the chemical composition and mass percentage of the aluminum alloy raw material are: Zn: 5.0%, Mg: 1.8%, Cu: 1.2%, Zr: 0.05%, Y: 0.05%, Si: 0.05%, Fe: 0.05%, In: 0.01%, Sn: 0.10%, with the balance being Al;

[0111] Step 2, Homogenization treatment: The homogenization temperature for the ingot is 475℃, and the holding time is 3h.

[0112] Step 3, Extrusion: The homogenized heat-treated ingot is heated to 420℃, and the extrusion ratio is 45:1;

[0113] Step 4, Cold rolling: The annealing temperature of the extruded bar is 380℃, the holding time is 15h, and then it is cold rolled after water cooling.

[0114] Step 5, Cold drawing: The cold-rolled bar is subjected to intermediate annealing at a heating rate of 70℃ / h, a holding temperature of 350℃, a holding time of 5h, and a cooling rate of 10℃ / h to room temperature. Then, cold drawing is performed with a cold drawing amount of 40%.

[0115] Example 7

[0116] The method for preparing high-strength, corrosion-resistant, formable 7xxx series aluminum alloys provided in this embodiment specifically includes the following steps:

[0117] Step 1: Melt and cast the aluminum alloy raw material into an ingot; wherein the chemical composition and mass percentage of the aluminum alloy raw material are: Zn: 5.0%, Mg: 1.8%, Cu: 1.2%, Zr: 0.05%, Y: 0.05%, Si: 0.05%, Fe: 0.05%, In: 0.5%, with the balance being Al;

[0118] Step 2, Homogenization treatment: The homogenization temperature for the ingot is 475℃, and the holding time is 3h.

[0119] Step 3, Extrusion: The homogenized heat-treated ingot is heated to 420℃, and the extrusion ratio is 45:1;

[0120] Step 4, Cold rolling: The annealing temperature of the extruded bar is 380℃, the holding time is 15h, and then it is cold rolled after water cooling.

[0121] Step 5, Cold drawing: The cold-rolled bar is subjected to intermediate annealing at a heating rate of 70℃ / h, a holding temperature of 350℃, a holding time of 5h, and a cooling rate of 10℃ / h to room temperature. Then, cold drawing is performed with a cold drawing amount of 40%.

[0122] Example 8

[0123] The method for preparing high-strength, corrosion-resistant, formable 7xxx series aluminum alloys provided in this embodiment specifically includes the following steps:

[0124] Step 1: Melt and cast the aluminum alloy raw material into an ingot; wherein the chemical composition and mass percentage of the aluminum alloy raw material are: Zn: 5.0%, Mg: 1.8%, Cu: 1.2%, Zr: 0.05%, Y: 0.05%, Si: 0.05%, Fe: 0.05%, In: 0.10%, Sn: 0.01%, with the balance being Al;

[0125] Step 2, Homogenization treatment: The homogenization temperature for the ingot is 475℃, and the holding time is 3h.

[0126] Step 3, Extrusion: The homogenized heat-treated ingot is heated to 420℃, and the extrusion ratio is 45:1;

[0127] Step 4, Cold rolling: The annealing temperature of the extruded bar is 380℃, the holding time is 15h, and then it is cold rolled after water cooling.

[0128] Step 5, Cold drawing: The cold-rolled bar is subjected to intermediate annealing at a heating rate of 70℃ / h, a holding temperature of 350℃, a holding time of 5h, and a cooling rate of 10℃ / h to room temperature. Then, cold drawing is performed with a cold drawing amount of 40%.

[0129] Example 9

[0130] The method for preparing high-strength, corrosion-resistant, formable 7xxx series aluminum alloys provided in this embodiment specifically includes the following steps:

[0131] Step 1: Melt and cast the aluminum alloy raw material into an ingot; wherein the chemical composition and mass percentage of the aluminum alloy raw material are: Zn: 5.0%, Mg: 1.8%, Cu: 1.2%, Zr: 0.05%, Y: 0.05%, Si: 0.05%, Fe: 0.05%, Sn: 0.5%, with the balance being Al;

[0132] Step 2, Homogenization treatment: The homogenization temperature for the ingot is 475℃, and the holding time is 3h.

[0133] Step 3, Extrusion: The homogenized heat-treated ingot is heated to 420℃, and the extrusion ratio is 45:1;

[0134] Step 4, Cold rolling: The annealing temperature of the extruded bar is 380℃, the holding time is 15h, and then it is cold rolled after water cooling.

[0135] Step 5, Cold drawing: The cold-rolled bar is subjected to intermediate annealing at a heating rate of 70℃ / h, a holding temperature of 350℃, a holding time of 5h, and a cooling rate of 10℃ / h to room temperature. Then, cold drawing is performed with a cold drawing amount of 40%.

[0136] Comparative Example 1

[0137] The preparation method of the 7xxx series aluminum alloy provided in this comparative example specifically includes the following steps:

[0138] Step 1: Melt and cast the aluminum alloy raw material into an ingot; wherein the chemical composition and mass percentage of the aluminum alloy raw material are: Zn: 5.0%, Mg: 1.8%, Cu: 1.2%, Zr: 0.05%, Y: 0.05%, Si: 0.05%, Fe: 0.05%, with the balance being Al;

[0139] Step 2, Homogenization treatment: The homogenization temperature for the ingot is 475℃, and the holding time is 3h.

[0140] Step 3, Extrusion: The homogenized heat-treated ingot is heated to 420℃, and the extrusion ratio is 45:1;

[0141] Step 4, Cold rolling: The annealing temperature of the extruded bar is 380℃, the holding time is 15h, and then it is cold rolled after water cooling.

[0142] Step 5, Cold drawing: The cold-rolled bar is subjected to intermediate annealing at a heating rate of 70℃ / h, a holding temperature of 350℃, a holding time of 5h, and water cooling. Then, cold drawing is performed with a cold drawing amount of 40%.

[0143] Comparative Example 2

[0144] The preparation method of the 7xxx series aluminum alloy provided in this comparative example specifically includes the following steps:

[0145] Step 1: Melt and cast the aluminum alloy raw material into an ingot; wherein the chemical composition and mass percentage of the aluminum alloy raw material are: Zn: 5.0%, Mg: 1.8%, Cu: 1.2%, Zr: 0.05%, Y: 0.05%, Si: 0.05%, Fe: 0.05%, Sn: 0.005%, with the balance being Al;

[0146] Step 2, Homogenization treatment: The homogenization temperature for the ingot is 475℃, and the holding time is 3h.

[0147] Step 3, Extrusion: The homogenized heat-treated ingot is heated to 420℃, and the extrusion ratio is 45:1;

[0148] Step 4, Cold rolling: The annealing temperature of the extruded bar is 380℃, the holding time is 15h, and then it is cold rolled after water cooling.

[0149] Step 5, Cold drawing: The cold-rolled bar is subjected to intermediate annealing at a heating rate of 70℃ / h, a holding temperature of 350℃, a holding time of 5h, and water cooling. Then, cold drawing is performed with a cold drawing amount of 40%.

[0150] Comparative Example 3

[0151] The preparation method of the 7xxx series aluminum alloy provided in this comparative example specifically includes the following steps:

[0152] Step 1: Melt and cast the aluminum alloy raw material into an ingot; wherein the chemical composition and mass percentage of the aluminum alloy raw material are: Zn: 3.5%, Mg: 0.5%, Cu: 0.3%, Zr: 0.05%, Y: 0.05%, Si: 0.35%, Fe: 0.35%, In: 0.005%, with the balance being Al;

[0153] Step 2, Homogenization treatment: The homogenization temperature for the ingot is 450℃, and the holding time is 72h.

[0154] Step 3, Extrusion: Heat the homogenized heat-treated ingot to 380℃ and extrude it at a ratio of 70:1.

[0155] Step 4, Cold rolling: The annealing temperature of the extruded bar is 400℃, the holding time is 0.5h, and then it is cold rolled after water cooling;

[0156] Step 5, Cold drawing: The cold-rolled bar is subjected to intermediate annealing at a heating rate of 100℃ / h, a holding temperature of 450℃, a holding time of 15h, and a cooling rate of 50℃ / h to room temperature. Then, cold drawing is performed with a cold drawing amount of 30%.

[0157] Comparative Example 4

[0158] The preparation method of the 7xxx series aluminum alloy provided in this comparative example specifically includes the following steps:

[0159] Step 1: Melt and cast the aluminum alloy raw material into an ingot; wherein the chemical composition and mass percentage of the aluminum alloy raw material are: Zn: 5.0%, Mg: 1.8%, Cu: 1.2%, Zr: 0.05%, Y: 0.05%, Si: 0.05%, Fe: 0.05%, In: 0.005%, Sn: 0.005%, with the balance being Al;

[0160] Step 2, Homogenization treatment: The homogenization temperature for the ingot is 475℃, and the holding time is 3h.

[0161] Step 3, Extrusion: The homogenized heat-treated ingot is heated to 420℃, and the extrusion ratio is 45:1;

[0162] Step 4, Cold rolling: The annealing temperature of the extruded bar is 380℃, the holding time is 15h, and then it is cold rolled after water cooling.

[0163] Step 5, Cold drawing: The cold-rolled bar is subjected to intermediate annealing at a heating rate of 70℃ / h, a holding temperature of 350℃, a holding time of 5h, and a cooling rate of 100℃ / h to room temperature. Then, cold drawing is performed with a cold drawing amount of 40%.

[0164] Comparative Example 5

[0165] The preparation method of the 7xxx series aluminum alloy provided in this comparative example specifically includes the following steps:

[0166] Step 1: Melt and cast the aluminum alloy raw material into an ingot; wherein the chemical composition and mass percentage of the aluminum alloy raw material are: Zn: 5.0%, Mg: 1.8%, Cu: 1.2%, Zr: 0.05%, Y: 0.05%, Si: 0.05%, Fe: 0.05%, In: 1.0%, Sn: 1.0%, with the balance being Al;

[0167] Step 2, Homogenization treatment: The homogenization temperature for the ingot is 475℃, and the holding time is 3h.

[0168] Step 3, Extrusion: The homogenized heat-treated ingot is heated to 420℃, and the extrusion ratio is 45:1;

[0169] Step 4, Cold rolling: The annealing temperature of the extruded bar is 380℃, the holding time is 15h, and then it is cold rolled after water cooling.

[0170] Step 5, Cold drawing: The cold-rolled bar is subjected to intermediate annealing at a heating rate of 70℃ / h, a holding temperature of 350℃, a holding time of 5h, and a cooling rate of 100℃ / h to room temperature. Then, cold drawing is performed with a cold drawing amount of 40%.

[0171] Comparative Example 6

[0172] The preparation method of the 7xxx series aluminum alloy provided in this comparative example specifically includes the following steps:

[0173] Step 1: Melt and cast the aluminum alloy raw material into an ingot; wherein the chemical composition and mass percentage of the aluminum alloy raw material are: Zn: 5.0%, Mg: 1.8%, Cu: 1.2%, Zr: 0.05%, Y: 0.05%, Si: 0.05%, Fe: 0.05%, In: 0.15%, Sn: 0.15%, with the balance being Al;

[0174] Step 2, Homogenization treatment: The homogenization temperature for the ingot is 475℃, and the holding time is 3h.

[0175] Step 3, Extrusion: The homogenized heat-treated ingot is heated to 420℃, and the extrusion ratio is 45:1;

[0176] Step 4, Cold rolling: The annealing temperature of the extruded bar is 380℃, the holding time is 15h, and then it is cold rolled after water cooling.

[0177] Step 5, Cold drawing: The cold-rolled bar is subjected to intermediate annealing at a heating rate of 70℃ / h, a holding temperature of 350℃, a holding time of 5h, and a cooling rate of 100℃ / h to room temperature. Then, cold drawing is performed with a cold drawing amount of 40%.

[0178] Comparative Example 7

[0179] The preparation method of the 7xxx series aluminum alloy provided in this comparative example specifically includes the following steps:

[0180] Step 1: Melt and cast the aluminum alloy raw material into an ingot; wherein the chemical composition and mass percentage of the aluminum alloy raw material are: Zn: 5.0%, Mg: 1.8%, Cu: 1.2%, Zr: 0.05%, Y: 0.05%, Si: 0.05%, Fe: 0.05%, with the balance being Al;

[0181] Step 2, Homogenization treatment: The homogenization temperature for the ingot is 475℃, and the holding time is 3h.

[0182] Step 3, Extrusion: The homogenized heat-treated ingot is heated to 420℃, and the extrusion ratio is 45:1;

[0183] Step 4, Cold rolling: The annealing temperature of the extruded bar is 380℃, the holding time is 15h, and then it is cold rolled after water cooling.

[0184] Step 5, Cold drawing: The cold-rolled bar is subjected to intermediate annealing at a heating rate of 70℃ / h, a holding temperature of 350℃, a holding time of 5h, and a cooling rate of 10℃ / h to room temperature. Then, cold drawing is performed with a cold drawing amount of 40%.

[0185] Test case

[0186] In this invention, by adjusting the amount of Sn or In added, and combining this with slow cooling control during annealing, high-strength, corrosion-resistant, formable 7xxx series aluminum alloys can be obtained. Test examples are as follows:

[0187] Tensile strength: The test was conducted using a Shimadzu AG-X Plus-100kN electronic tensile testing machine, and the test method was in accordance with GB / T228.1-2021.

[0188] Intergranular corrosion depth: A constant temperature water bath was used, and the test method was in accordance with GB / T 7998-2005.

[0189] The tensile strength at 0 days, the tensile strength after 270 days of storage, and the intergranular corrosion depth of the aluminum alloy materials prepared in the above examples and comparative examples are shown in Table 1.

[0190] The test results are as follows:

[0191] In Example 1 and Comparative Example 1, as shown in Figures 1 to 3, the intergranular corrosion morphology of Example 1 is shown below. Figure 1a The intergranular corrosion morphology of Comparative Example 1 is shown in the figure. Figure 1b As can be seen, Comparative Example 1 showed obvious intergranular corrosion with a corrosion depth of 142 μm, indicating poor resistance to intergranular corrosion. In Example 1, the intergranular corrosion depth was significantly reduced to only 12 μm, and the resistance to intergranular corrosion was greatly improved.

[0192] The tensile strength and storage stability of Example 1 and Comparative Example 1 after 270 days of storage are shown in the figure. Figure 2 As can be seen, the strength of Comparative Example 1 increased by 34 MPa after 270 days of storage, while the tensile strength of Example 1 of the present invention only increased by 1 MPa after 270 days of storage, showing better storage stability.

[0193] Example 1, second phase morphology is shown Figure 3a Comparative Example 1 shows the second phase morphology. Figure 3b As can be seen in Comparative Example 1, only spherical Al3Zr dispersed phase is visible in the tissue, indicating that trace elements are all dissolved in the aggregate and there are few overall precipitates, which provides a basis for the natural aging enhancement of cluster precipitation during the subsequent storage process. In Example 1, spherical Al3Zr and a large number of submicron-sized black blocky precipitates are visible in the tissue. On the one hand, the desolvation of trace elements is relatively sufficient, and on the other hand, the trapping effect of In and / or Sn elements on free vacancies provides a basis for inhibiting natural aging and improving corrosion resistance.

[0194] As shown in Table 1, the embodiments and comparative examples show that Comparative Examples 1-5, which are outside the process range of this invention, exhibited a >30 MPa increase in stability and >100 μm in intergranular corrosion depth after 270 days of storage, but both their storage stability and intergranular corrosion performance were poor. Comparative Example 6, which only added In and Sn within the scope of this invention, showed some improvement in storage stability, but its intergranular corrosion performance remained poor. Comparative Example 7, which only used slow cooling annealing, showed some improvement in intergranular corrosion, but its storage stability was still unsatisfactory. By adopting the preparation process parameters of this invention, adding Sn and / or In elements, and combining them with a slow annealing cooling process, the embodiments controlled the precipitation behavior of grain boundary phases and strengthening phases, thereby delaying natural aging and improving intergranular corrosion performance. After 270 days of natural storage, the strength increase of each embodiment was <5 MPa, and the intergranular corrosion depth was <15 μm, indicating better performance.

[0195] Table 1 Performance indicators of the alloys in the examples and the comparative alloys

[0196]

[0197] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for preparing a high-strength, corrosion-resistant, formable 7xxx series aluminum alloy, characterized in that, Includes the following steps: Step 1: After melting and casting the raw material of the 7xxx series aluminum alloy into an ingot, it is homogenized, then machined to remove the oxide scale, and then extruded to obtain aluminum alloy rods. Step 2: Perform intermediate annealing and cold rolling on the aluminum alloy bar to obtain cold-rolled bar; Step 3: Perform intermediate annealing and cold drawing on the cold-rolled bar to obtain the 7xxx series aluminum alloy; In step one, the chemical composition and mass percentage of the raw materials for the 7xxx series aluminum alloy are as follows: Zn: 3.5-5.0%, Mg: 0.5-1.8%, Cu: 0.3-1.2%, Zr: 0.01-0.05%, Y: 0.01-0.05%, Fe: 0.05-0.35%, Si: 0.05-0.35%. In: 0.01-0.5% and / or Sn: 0.01-0.5%; and The balance is Al; In step two, the annealing temperature is 380-450℃, the holding time is 0.5-15h, and the cooling method is water cooling; In step three, the heating rate of the annealing process is 10-100℃ / h, the holding temperature is 350-450℃, the holding time is 0.5-15h, and then the temperature is cooled to room temperature at a rate of 1-30℃ / h. In step three, the annealing and cold drawing process is: one annealing and one cold drawing; or the annealing and cold drawing process is: one cold drawing, one intermediate annealing, and one cold drawing; wherein the cold drawing amount is 20%-40%.

2. The method for preparing high-strength, corrosion-resistant, formable 7xxx series aluminum alloy as described in claim 1, characterized in that, In step one, the chemical composition and mass percentage of the raw materials for the 7xxx series aluminum alloy are as follows: Zn: 3.5-5.0%, Mg: 0.5-1.8%, Cu: 0.3-1.2%, Zr: 0.01-0.05%, Y: 0.01-0.05%, Fe: 0.05-0.35%, Si: 0.05-0.35%; In: 0.15-0.3% and / or Sn: 0.15-0.3%; and The balance is Al.

3. The method for preparing high-strength, corrosion-resistant, formable 7xxx series aluminum alloy as described in claim 1, characterized in that, In step one, the chemical composition and mass percentage of the raw material of the 7xxx series aluminum alloy are as follows: Zn: 3.5-5.0%, Mg: 0.5-1.8%, Cu: 0.3-1.2%, Zr: 0.01-0.05%, Y: 0.01-0.05%, Fe: 0.05-0.35%, Si: 0.05-0.35%, In+Sn≥0.15%, with the balance being Al.

4. The method for preparing high-strength, corrosion-resistant, formable 7xxx series aluminum alloy as described in claim 2 or 3, characterized in that, In step one, the homogenization treatment is carried out at a temperature of 450-475℃ for 3-72 hours; and The extrusion temperature is 380-420℃, and the extrusion ratio is 45-70:1.

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