Method of annealing an aluminum alloy

Abstract

This invention provides an annealing method for aluminum alloys, belonging to the field of alloy heat treatment. The annealing method for aluminum alloys provided by this invention includes: subjecting a cold-rolled aluminum alloy to a "flash annealing" treatment to obtain a flash-annealed aluminum alloy; the heating rate of the "flash annealing" treatment is 200–500 °C / s; the holding temperature of the "flash annealing" treatment is 400–450 °C; the holding time of the "flash annealing" treatment is 2–5 s; and the cooling rate of the "flash annealing" treatment is 40–100 °C / s. After performing the "flash annealing" treatment on the aluminum alloy using the annealing method provided by this invention, the grain size of the flash-annealed aluminum alloy is reduced by about half compared to the comparative aluminum alloy, the strength is 1.3–1.5 times that of the comparative aluminum alloy, the elongation is 0.7–0.9 times that of the comparative aluminum alloy, and the anisotropy is reduced by more than 50% compared to the comparative aluminum alloy, thus exhibiting high strength and ductility while reducing the anisotropy of the aluminum alloy.

Description

Technical Field

[0001] This invention relates to the field of alloy heat treatment technology, and more particularly to an annealing method for aluminum alloys. Background Technology

[0002] Due to continuous innovation in aerospace, automotive manufacturing, shipbuilding, and military industries, higher demands are being placed on aluminum alloys in terms of strength, ductility, and anisotropy. Currently, the strength and ductility of aluminum alloys are mainly improved by adding alloying elements and optimizing processing techniques. However, the introduction of alloying elements usually reduces ductility and corrosion resistance, and it is difficult to control anisotropy through the addition of alloying elements. Achieving both high strength and ductility while reducing anisotropy in aluminum alloys remains a challenge for aluminum alloy processing.

[0003] 3-series and 5-series aluminum alloys possess excellent plasticity; however, they cannot be stably deep-drawn, exhibiting common challenges such as high ear-making rate, tensile cracking, and large strength fluctuations. Therefore, the application of 3-series and 5-series aluminum alloys as thin sheet materials for deep-drawn parts of new energy vehicle battery casings requires both reducing anisotropy and ear-making rate, and improving strength and plasticity, making research of great significance.

[0004] Annealing can effectively control the recovery and recrystallization process of alloys after large plastic deformation, and has a significant impact on the strength, ductility and anisotropy of aluminum alloys. Annealing can be divided into conventional (below 10℃ / s), rapid (10~100℃ / s) and ultra-rapid (above 100℃ / s) according to the heating rate. Currently, the highest heating rate for aluminum alloy annealing is often no more than 100℃ / s. Compared with conventional rapid annealing, ultra-rapid annealing process usually consists of three parts: (1) rapid heating to the annealing temperature; (2) short-time holding; (3) rapid cooling. For ultra-rapid annealing, since the entire annealing process is very fast, it essentially affects the occurrence of the recovery, recrystallization and grain growth stages of the metal material. Furthermore, the degree of deformation of the material, the degree of grain refinement, whether there is a critical value of heating rate, the refinement mechanism, and whether high strength and ductility can be achieved while reducing the anisotropy of aluminum alloys are still controversial.

[0005] Therefore, providing an annealing method that can reduce the anisotropy of aluminum alloys while achieving high strength and ductility has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to provide an annealing method for aluminum alloys. The annealing method for aluminum alloys provided by this invention can achieve high strength and ductility while reducing the anisotropy of the aluminum alloy.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] This invention provides an annealing method for aluminum alloys, comprising: subjecting a cold-rolled aluminum alloy to a "flash annealing" process to obtain a flash annealed aluminum alloy;

[0009] The heating rate of the "flashback" process is 200-500℃ / s;

[0010] The heat preservation temperature for the "flashback" process is 400-450℃;

[0011] The heat preservation time for the "flashback" process is 2-5 seconds;

[0012] The cooling rate of the "flashback" process is 40-100℃ / s.

[0013] Preferably, the heating rate of the "flashback" process is 250-500℃ / s; the holding time of the "flashback" process is 2-3s; and the cooling rate of the "flashback" process is 40-60℃ / s.

[0014] Preferably, the method for preparing the cold-rolled aluminum alloy includes: pre-treating a commercial aluminum alloy and then performing cold rolling to obtain the cold-rolled aluminum alloy.

[0015] Preferably, the cold rolling process is a multi-pass cold rolling process.

[0016] Preferably, the number of passes in the multi-pass cold rolling is 8 to 20.

[0017] Preferably, the deformation per pass of the multi-pass cold rolling is 4-5%.

[0018] Preferably, the total deformation of the cold rolling process is 40-80%.

[0019] Preferably, the pretreatment is as follows: after the commercial aluminum alloy undergoes initial annealing, it is then polished and cleaned in sequence.

[0020] Preferably, the holding temperature for the initial annealing treatment is 350–390°C, and the holding time for the initial annealing treatment is 60–120 min.

[0021] Preferably, the aluminum alloy is a 3-series aluminum alloy or a 5-series aluminum alloy.

[0022] This invention provides an annealing method for aluminum alloys, comprising: subjecting a cold-rolled aluminum alloy to a "flash annealing" treatment to obtain a flash-annealed aluminum alloy; wherein the heating rate of the "flash annealing" treatment is 200–500 °C / s; the holding temperature of the "flash annealing" treatment is 400–450 °C; the holding time of the "flash annealing" treatment is 2–5 s; and the cooling rate of the "flash annealing" treatment is 40–100 °C / s. This invention employs a "flash annealing" treatment, and by adjusting the heating rate and holding time of the "flash annealing" treatment, achieves a reasonable match between soft and hard microstructures and the coupling of multi-component texture types. Under non-equilibrium recrystallization conditions, the cubic texture is weakened, the multi-component transition texture is enhanced, the grains are refined, and high and low dislocation density grains appear, endowing the flash-annealed aluminum alloy with excellent strength and plasticity. Moreover, compared with traditional annealing, it reduces the anisotropy of the aluminum alloy. The results of the examples show that after the aluminum alloy is subjected to "flash annealing" treatment using the annealing method of the present invention, the grain size of the flash annealed aluminum alloy is reduced by about half compared with the comparative aluminum alloy, the strength is 1.3 to 1.5 times that of the comparative aluminum alloy, the elongation is 0.7 to 0.9 times that of the comparative aluminum alloy, and the anisotropy is reduced by more than 50% compared with the comparative aluminum alloy. While reducing the anisotropy of the aluminum alloy, it also has high strength and plasticity. Attached Figure Description

[0023] Figure 1 This is a microstructure diagram of the flash-out aluminum alloy in Embodiment 1 of the present invention;

[0024] Figure 2 This is a microstructure diagram of the flash-out aluminum alloy in Embodiment 2 of the present invention;

[0025] Figure 3 This is a microstructure diagram of the flash-out aluminum alloy in Embodiment 3 of the present invention;

[0026] Figure 4 This is a microstructure diagram of the flash-out aluminum alloy in Example 4 of the present invention;

[0027] Figure 5 This is a microstructure diagram of the pretreated aluminum alloy in Comparative Example 1 of the present invention;

[0028] Figure 6 This is a texture distribution diagram of the aluminum alloy that flashes during processing in Example 1;

[0029] Figure 7 This is a texture distribution diagram of the aluminum alloy that flashes during processing in Example 2;

[0030] Figure 8 This is a texture distribution diagram of the aluminum alloy that flashes off in Example 3;

[0031] Figure 9 This is a texture distribution diagram of the aluminum alloy that flashes off in Example 4;

[0032] Figure 10 The texture distribution diagram is shown for the pretreated aluminum alloy in Comparative Example 1.

[0033] Figure 11 This is a statistical chart of the grain size of the aluminum alloy that flashed out in Example 1;

[0034] Figure 12 This is a statistical chart of the grain size of the aluminum alloy that flashed out in Example 2;

[0035] Figure 13 This is a statistical chart of the grain size of the aluminum alloy that flashed out in Example 3;

[0036] Figure 14 This is a statistical chart of the grain size of the aluminum alloy that flashed out in Example 4;

[0037] Figure 15 This is a statistical chart of the grain size of the pretreated aluminum alloy in Comparative Example 1.

[0038] Figure 16 This is a texture composition diagram of the aluminum alloy that flashed out in Example 1;

[0039] Figure 17 This is a texture composition diagram of the aluminum alloy that flashed out in Example 2;

[0040] Figure 18 The texture composition diagram of the pretreated aluminum alloy in Comparative Example 1 is shown.

[0041] Figure 19 A diagram showing the specifications of the tensile test specimens and the sampling locations;

[0042] Figure 20 The stress-strain curves of the flash-out aluminum alloy at room temperature in the rolling direction, 45° direction and transverse direction are shown in Example 1.

[0043] Figure 21 The stress-strain curves of the flash-out aluminum alloy at room temperature in the rolling direction, 45° direction, and transverse direction are shown in Example 2.

[0044] Figure 22 The stress-strain curves of the pretreated aluminum alloy in Comparative Example 1 at room temperature are shown in the rolling direction, 45° direction and transverse direction.

[0045] Figure 23 Line graphs showing the anisotropy (r-value) of the flash-out aluminum alloys in Examples 1 and 2 and the pretreated aluminum alloys in Comparative Example 1 at room temperature in the rolling direction, 45° direction and transverse direction;

[0046] Figure 24 This is a stress-strain curve of the aluminum alloy that flashed out in Example 3;

[0047] Figure 25 This is the stress-strain curve of the flash-out aluminum alloy in Example 4. Detailed Implementation

[0048] This invention provides an annealing method for aluminum alloys, comprising: performing a "flash annealing" treatment on a cold-rolled aluminum alloy to obtain a flash annealed aluminum alloy.

[0049] In this invention, the "flash annealing" process is a type of annealing process; the "flash annealing" process refers to an annealing process with a heating rate ≥200℃ / s, a holding time ≤5s, and a cooling rate ≥40℃ / s.

[0050] In this invention, the preferred method for preparing the cold-rolled aluminum alloy includes: pre-treating a commercial aluminum alloy and then performing cold rolling to obtain the cold-rolled aluminum alloy.

[0051] In this invention, the aluminum alloy is preferably a 3-series or 5-series aluminum alloy, more preferably a grade of 5052, 5A06, 5083, 3003, or 3105. Limiting the type of aluminum alloy to the above range ensures that annealing treatment achieves better performance improvement for the aluminum alloy.

[0052] In this invention, the pretreatment is preferably performed by first annealing the commercial aluminum alloy, followed by polishing and cleaning.

[0053] In embodiments of the present invention, the aluminum alloy is preferably cut into aluminum strips of 100mm × 60mm × 5mm before use. Limiting the aluminum alloy to these dimensions facilitates subsequent cold rolling.

[0054] In this invention, the holding temperature for the initial annealing treatment is preferably 350–390°C, more preferably 360–380°C; the holding time for the initial annealing treatment is preferably 60–120 min, more preferably 80–100 min; the heating rate for the initial annealing treatment is preferably 5–20°C / s; and the cooling rate for the initial annealing treatment is preferably 5–20°C / s. Limiting the parameters of the initial annealing treatment to the above ranges ensures that the aluminum alloy transforms into the O state, facilitating subsequent cold rolling.

[0055] In this invention, the polishing is preferably performed mechanically using SiC sandpaper with a grit of 500-1200 grit. This invention removes the oxide layer from the aluminum alloy surface through polishing, preventing the introduction of impurities.

[0056] In this invention, the cleaning is preferably ultrasonic cleaning. This invention does not impose any special limitations on the solvent used for cleaning or the ultrasonic operation; conventional methods used by those skilled in the art to clean the polished aluminum alloy surface are sufficient.

[0057] In this invention, the cold rolling process is preferably multi-pass cold rolling; the number of passes in the multi-pass cold rolling is preferably 8 to 20, more preferably 10 to 18; the deformation per pass in the multi-pass cold rolling is preferably 4 to 5%, more preferably 4.5%; the total deformation of the cold rolling process is preferably 40 to 80%, more preferably 60 to 80%; the initial cold rolling temperature is preferably room temperature; the cold rolling process is preferably carried out in a four-high rolling mill with a rolling force of 2000 kN and a worktable width of 300 mm. By limiting the cold rolling parameters to the above range, this invention can reduce the grain size of the aluminum alloy and improve its strength and plasticity.

[0058] In this invention, the heating rate of the "flash-out" treatment is 200–500 °C / s, preferably 250–500 °C / s, more preferably 400–500 °C / s; the holding temperature of the "flash-out" treatment is 400–450 °C, preferably 420–430 °C; the holding time of the "flash-out" treatment is 2–5 s, preferably 2–3 s; and the cooling rate of the "flash-out" treatment is 40–100 °C / s, preferably 40–60 °C / s, more preferably 45–55 °C / s. By setting the parameters of the "flash-out" treatment within the above ranges, this invention achieves a reasonable match between soft and hard microstructures and the coupling of multi-component texture types. Under non-equilibrium recrystallization conditions, the cubic texture is weakened, the multi-component transition texture is enhanced, the grains are refined, and high and low dislocation density grains appear, endowing the flash-out aluminum alloy with excellent strength and plasticity and reducing the anisotropy of the aluminum alloy.

[0059] This invention employs a "flash annealing" process. By adjusting the heating rate and holding time of the flash annealing process, a reasonable match between soft and hard microstructures and the coupling of multi-component texture types are achieved. Under non-equilibrium recrystallization conditions, the cubic texture is weakened, the multi-component transition texture is enhanced, the grains are refined, and high and low dislocation density grains appear. This microstructure endows the flash annealed aluminum alloy with excellent strength and plasticity, and compared with traditional annealing, it reduces the anisotropy of the aluminum alloy.

[0060] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0061] Example 1

[0062] An annealing heat treatment method for aluminum alloys, comprising the following steps:

[0063] 5052 aluminum alloy was cut into 100mm×60mm×5mm aluminum strips and placed in a muffle furnace. The temperature was raised to 350℃ at a heating rate of 10℃ / s for initial annealing for 120 minutes. Then, the temperature was cooled to room temperature at a cooling rate of 10℃ / s to transform the 5052 aluminum alloy into the O state. The surface of the O state 5052 aluminum alloy was then mechanically polished with SiC sandpaper with a grit of 500-1200 grit. The polished aluminum alloy surface was then cleaned with ultrasonic waves to obtain the pretreated 5052 aluminum alloy.

[0064] The pretreated 5052 aluminum alloy was subjected to multi-pass cold rolling, with 20 passes and a single-pass deformation of 5%, resulting in a total deformation of 80%. The cold rolling was carried out in a four-high rolling mill with a rolling force of 2000 kN and a worktable width of 300 mm. The initial cold rolling temperature was room temperature, resulting in a cold-rolled 5052 aluminum alloy. The cold-rolled 5052 aluminum alloy was then subjected to a "flash-out" treatment to obtain a flash-out aluminum alloy. The heating rate of the flash-out treatment was 250 °C / s; the holding temperature of the flash-out treatment was 450 °C; the holding time of the flash-out treatment was 3 s; and the cooling rate of the flash-out treatment was 40 °C / s.

[0065] The alloy composition of the 5052 aluminum alloy in Example 1 is shown in Table 1.

[0066] Example 2

[0067] The only difference between Example 2 and Example 1 is that the heating rate to the temperature of the "flashback" treatment is 500℃ / s, and everything else is the same as Example 1.

[0068] Example 3

[0069] The only difference between Example 3 and Example 2 is that the aluminum alloy is 5083 aluminum alloy and the "flashback" heat preservation time is 3 seconds. Everything else is the same as Example 2.

[0070] The alloy composition of the 5083 aluminum alloy in Example 3 is shown in Table 1.

[0071] Example 4

[0072] The only difference between Example 4 and Example 3 is that the aluminum alloy is 3003 aluminum alloy; otherwise, they are the same as in Example 3.

[0073] The alloy composition of the 3003 aluminum alloy in Example 4 is shown in Table 1.

[0074] Comparative Example 1

[0075] Comparative Example 1 is the 5052 aluminum alloy pretreated in Example 1.

[0076] Table 1 Alloy composition of aluminum alloys in Examples 1, 3 and 4 / wt.%

[0077]

[0078]

[0079] Test case

[0080] Electron backscatter diffraction (EBSD) data were acquired for Examples 1-4 and Comparative Example 1, and analyzed using OIM Analysis. TM The software analyzes the data;

[0081] According to GB / T 228.1-2010 standard, uniaxial tensile tests were conducted at room temperature on the flash-out aluminum alloys in Examples 1 and 2, and the pretreated aluminum alloy in Comparative Example 1, in the rolling direction, 45° direction, and transverse direction using an INSTRON universal testing machine (UK). The tensile rate was 1.0 mm / min. The tensile specimen specifications and sampling locations are as follows. Figure 19 As shown;

[0082] According to GB / T 228.1-2010 standard, the tensile strength of Examples 3 and 4 was tested using the British INSTRON universal testing machine;

[0083] Microstructure images of the flash-out aluminum alloys in Examples 1-4 and the pretreated aluminum alloy in Comparative Example 1 are shown below. Figures 1-5 As shown; the texture distribution diagrams of the flash-out aluminum alloys in Examples 1-4 and the pretreated aluminum alloy in Comparative Example 1 are as follows. Figures 6-10 As shown in the figure; the grain size statistics of the flash-exit aluminum alloys in Examples 1-4 and the pretreated aluminum alloy in Comparative Example 1 are shown in the figure. Figures 11-15 As shown; the texture composition diagrams of the flash-out aluminum alloys in Examples 1 and 2 and the pretreated aluminum alloy in Comparative Example 1 are as follows. Figures 16-18 As shown; the stress-strain curves of the flash-knock aluminum alloys in Examples 1 and 2 and the pretreated aluminum alloys in Comparative Example 1 at room temperature in the rolling direction, 45° direction and transverse direction are shown in the figure. Figures 20-22 As shown; the line graphs of anisotropy (r-value) in the rolling direction, 45° direction and transverse direction of the flash-out aluminum alloys in Examples 1 and 2 and the pretreated aluminum alloy in Comparative Example 1 at room temperature are shown. Figure 23 As shown; the stress-strain curves of the flash-out aluminum alloys in Examples 3 and 4 are shown in the figure. Figure 24 and 25 As shown.

[0084] from Figure 1 , 2 and Figure 5 It can be seen that the grain size of the aluminum alloys in Examples 1 and 2 is about half that of the pretreated aluminum alloy; from Figures 6-7As can be seen from 10–12 and 15–18, the grain size exhibits a bimodal distribution, and with the increase of texture components, the strength weakens. The grain size of the flash-extruded aluminum alloy is mainly concentrated in the ranges of 1.2–2.9 μm and 3.1–27.2 μm, accounting for 22% and 78% respectively. The recrystallized Cube texture strength decreases from 11.6 to 1.6, and Twin-copper and R-Cube textures appear. ND Texture components with an intensity lower than 3, such as Goss / Brass and Brass;

[0085] from Figures 20-22 It can be seen that the tensile strengths of the pretreated aluminum alloy in Comparative Example 1 in the rolling direction, 45° direction, and transverse direction are 180.1 MPa, 167.3 MPa, and 157.5 MPa, respectively, and the elongations are 13.4%, 16.8%, and 14.2%, respectively. The tensile strengths of the flash-treated aluminum alloy in Example 2 in the rolling direction, 45° direction, and transverse direction are 247.1 MPa, 242.3 MPa, and 237.5 MPa, respectively, and the elongations are 12.1%, 11.7%, and 12.7%, respectively. The tensile strength and elongation are 1.3 to 1.5 times and 0.7 to 0.9 times that of Comparative Example 1, respectively. The anisotropy (r-values) of the sample after flash treatment in Example 2 in the rolling direction, 45° direction, and transverse direction are 0.92, 0.8, and 1.08, respectively, with a standard deviation of 0.14, which is 58.8% lower than the standard deviation of 0.34 for the r-value of the pretreated aluminum alloy in Comparative Example 1.

[0086] After the aluminum alloy is subjected to "flash annealing" treatment using the annealing method provided by this invention, the grain size of the flash annealed aluminum alloy is reduced by about half compared with the comparative aluminum alloy, the strength is 1.3 to 1.5 times that of the comparative aluminum alloy, the elongation is 0.7 to 0.9 times that of the comparative aluminum alloy, and the anisotropy is reduced by more than 50% compared with the comparative aluminum alloy. While reducing the anisotropy of the aluminum alloy, it also has high strength and plasticity.

[0087] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An annealing method for aluminum alloys, comprising: Cold-rolled aluminum alloys are subjected to a "flash-knock" process to obtain flash-knock aluminum alloys; The heating rate of the "flashback" process is 200~500℃ / s; The heat preservation temperature for the "flashback" process is 400~450℃; The heat preservation time for the "flashback" process is 2-5 seconds; The cooling rate of the "flashback" process is 40~100℃ / s; The aluminum alloy is a 3-series or 5-series aluminum alloy; The method for preparing the cold-rolled aluminum alloy includes: pre-treating commercial aluminum alloy by cutting it into 100mm×60mm×5mm aluminum strips before use, and then cold-rolling it to obtain the cold-rolled aluminum alloy. The total deformation of the cold rolling process is 40-80%.

2. The annealing method according to claim 1, characterized in that, The heating rate of the "flashback" process is 250~500℃ / s; the holding time of the "flashback" process is 2~3s; and the cooling rate of the "flashback" process is 40~60℃ / s.

3. The annealing method according to claim 1, characterized in that, The cold rolling process is a multi-pass cold rolling process.

4. The annealing method according to claim 3, characterized in that, The number of passes in the multi-pass cold rolling is 8 to 20.

5. The annealing method according to claim 3, characterized in that, The deformation per pass in the multi-pass cold rolling is 4-5%.

6. The annealing method according to claim 1, characterized in that, The pretreatment involves first annealing the commercial aluminum alloy, followed by polishing and cleaning.

7. The annealing method according to claim 6, characterized in that, The holding temperature for the initial annealing treatment is 350~390℃, and the holding time for the initial annealing treatment is 60~120min.

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