Ultralow-temperature-warm composite forming method for aluminum alloy complex thin-wall component

Abstract

An ultralow-temperature-warm composite forming method for an aluminum alloy complex thin-wall component comprises the steps that after an aluminum alloy supersaturated solid solution subjected to solution treatment in advance is subjected to ultralow-temperature precooling treatment, ultralow-temperature preforming is carried out through a mold, then heating and heat preservation are carried out, then rapid transferring is carried out for warm forming, and finally an aluminum alloy thin-wall part is obtained through short-time artificial aging treatment. By means of the double-increasing effect that the elongation rate and the hardening capacity of the high-strength aluminum alloy at the ultralow temperature are improved at the same time, forming of most characteristics of the high-strength aluminum alloy complex thin-wall component is achieved through ultralow-temperature pre-forming. And compared with direct warm forming or hot forming, the wall thickness uniformity of the final part can be improved. Warm forming continues to be carried out after the high-strength aluminum alloy complex thin-wall component is subjected to ultralow-temperature pre-forming, the problem that ultralow-temperature forming is large in resilience can be solved, meanwhile, only a small amount of deformation of an extremely-difficult-to-form area exists in the warm forming process, and the problem that parts are excessively thinned in the warm forming process can be avoided. A large number of dislocations generated in high-strength aluminum alloy crystals after ultralow-temperature pre-forming are beneficial to the subsequent aging precipitation process, grain boundary precipitation phase distribution can be dispersed through multi-stage aging heat treatment of warm forming and short-time artificial aging, and finally the service performance requirements of part strength, corrosion resistance and the like are met.

Description

Technical Field

[0001] The present invention relates to a technology in the field of aluminum alloy forming, in particular to an ultra-low temperature-warm temperature composite forming method for complex thin-walled aluminum alloy components. Background Art

[0002] Existing thin-walled component forming technologies include room temperature forming, warm / hot forming, and ultra-low temperature forming. High-strength aluminum alloys have poor room temperature plasticity and are prone to cracking defects during room temperature forming. The forming limit of high-strength aluminum alloys can be improved to a certain extent by warm forming or hot forming. With the increase of temperature, microstructural evolutions such as dynamic recovery and dynamic recrystallization are prone to occur during the deformation of high-strength aluminum alloys, which enhances their thermal softening effect and increases the elongation of the material. However, severe local thinning occurs during warm forming or hot forming of complex thin-walled components of high-strength aluminum alloys, resulting in poor wall thickness uniformity of the final parts and difficulty in meeting the structural stiffness requirements. In recent years, studies have found that dynamic recovery and dynamic recrystallization of high-strength aluminum alloys are suppressed at ultra-low temperatures (≤-150°C), and multi-system slip of dislocations is promoted, which shows a double-increasing effect of simultaneously improving elongation and hardening ability on a macro scale, and can form parts with good wall thickness uniformity. However, at ultra-low temperatures, the strength of high-strength aluminum alloys increases, and the material's deformation resistance increases, which leads to increased springback of parts and dimensional accuracy problems. In addition, excessive dislocation accumulation within the crystal at ultra-low temperatures can also cause high-strength aluminum alloys to break. Therefore, at ultra-low temperatures, there is a limit to the improvement of the formability of high-strength aluminum alloys. In particular, when forming extremely complex structures (such as small fillet features) at ultra-low temperatures, there is still a serious problem of cracking. Summary of the invention

[0003] In view of the above-mentioned deficiencies in the prior art, the present invention proposes an ultra-low temperature-warm composite forming method for complex thin-walled components of aluminum alloys. First, the supersaturated solid solution of the aluminum alloy that has been solution treated in advance is subjected to ultra-low temperature pre-cooling treatment, and then ultra-low temperature pre-forming is performed through a mold, and then it is heated and kept warm and quickly transported for warm forming. Finally, the aluminum alloy thin-walled parts are obtained through a short-time artificial aging treatment. The present invention utilizes the double-increasing effect of the simultaneous improvement of the elongation and hardening ability of high-strength aluminum alloys at ultra-low temperatures, and realizes the forming of most of the features of complex thin-walled components of high-strength aluminum alloys through ultra-low temperature pre-forming. Compared with direct warm forming or hot forming, the wall thickness uniformity of the final parts can be improved. After ultra-low temperature pre-forming, the high-strength aluminum alloy complex thin-walled components continue to be warm-formed, which can solve the problem of large springback in ultra-low temperature forming. At the same time, only a small amount of deformation in the extremely difficult-to-form area occurs during the warm forming process, which can avoid the problem of excessive thinning during warm forming of parts. The large number of dislocations generated in the high-strength aluminum alloy crystals after ultra-low temperature pre-forming are beneficial to the subsequent aging precipitation process. The multi-stage aging heat treatment of warm forming and short-time artificial aging can disperse the grain boundary precipitation phase distribution, ultimately taking into account the service performance requirements such as part strength and corrosion resistance.

[0004] The present invention is achieved through the following technical solutions:

[0005] The invention relates to an ultra-low temperature-warm composite forming method for a complex thin-walled aluminum alloy component. The method comprises the following steps: subjecting a supersaturated solid solution of an aluminum alloy that has been solution treated in advance to ultra-low temperature pre-cooling treatment, ultra-low temperature pre-forming through a mold, heating and heat preservation, and then rapidly transferring the pre-forming to warm forming. Finally, the aluminum alloy thin-walled component is subjected to a short-time artificial aging treatment.

[0006] The supersaturated solid solution is obtained by heating the aluminum alloy to a temperature above the solid solution temperature, keeping the temperature, and then rapidly cooling and quenching.

[0007] The pre-cooling treatment involves immersing the sheet material in a cooling medium, wherein the cooling medium used includes liquid nitrogen, liquid helium and / or liquid argon.

[0008] The mold is cooled overall and locally to cooperate with ultra-low temperature preforming, and its cooling method includes soaking and spraying with cooling medium and cooling with flow channels in the mold.

[0009] The ultra-low temperature preforming has a forming temperature of -100°C to -196°C.

[0010] The heating and heat preservation adopts but is not limited to induction heating, furnace heating or salt bath heating, and the temperature is 100°C to 250°C.

[0011] The warm forming has a forming temperature of 100°C to 250°C.

[0012] The short-time artificial aging treatment has a temperature of 80°C to 200°C and an aging treatment time of 5 minutes to 5 hours.

[0013] The aluminum alloy includes Al-Cu alloy, Al-Zn alloy and Al-Li alloy.

[0014] The aluminum alloy plate is preferably an aluminum alloy plate with a thickness of 1 mm to 3 mm. Technical Effects

[0015] The present invention realizes the characteristic forming of high-strength aluminum alloy complex thin-walled components except for the characteristic area of ​​small fillet (fillet radius is less than 5mm) by ultra-low temperature preforming and utilizing the double increase effect of high-strength aluminum alloy at ultra-low temperature; compared with direct warm forming or hot forming, the wall thickness uniformity of the final part can be improved. After ultra-low temperature preforming, the high-strength aluminum alloy complex thin-walled components continue to be warm-formed, which can solve the problem of large springback of ultra-low temperature forming. At the same time, only a small amount of deformation in the extremely difficult forming area occurs during the warm forming process, which can avoid the problem of excessive thinning during warm forming of the parts; a large number of dislocations are generated in the high-strength aluminum alloy crystals through ultra-low temperature preforming, which is beneficial to the subsequent aging precipitation process and improves the strength of the parts. Compared with the prior art, the present invention can obtain the final parts with good wall thickness uniformity and high dimensional accuracy through ultra-low temperature-warm composite forming, while the overall process aging time is short, which speeds up the overall beat of part forming; in addition, the multi-stage aging process of warm forming and aging heat treatment can disperse the grain boundary precipitation phase distribution and improve the corrosion and fatigue properties of the parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a temperature-time diagram of the forming method of Example 1;

[0017] Figure 2 Schematic diagram of the implementation process of the forming method of Example 1;

[0018] Figure 3 This is a microstructure evolution diagram of the forming method of Example 1;

[0019] Figure 4 This is a comparison chart of simulation results of different forming methods in Example 1. DETAILED DESCRIPTION

[0020] like Figure 1 and Figure 2 As shown, this embodiment relates to an ultra-low temperature-warm temperature composite forming method for a complex thin-walled aluminum alloy component, comprising:

[0021] Step 1: Solution heat treatment: The AA7075 aluminum alloy sheet is solution treated at a temperature of 475°C for 35 minutes, and then the sheet is taken out for water quenching to obtain a supersaturated solid solution.

[0022] Step 2: Ultra-low temperature pre-forming: Immediately pre-cool the solution treated sheet material, immerse it in liquid nitrogen for 15 minutes at a temperature of -196°C; then transfer it to the mold for ultra-low temperature pre-forming. The mold is cooled by a liquid nitrogen flow channel. The sheet material temperature is about -160°C during forming, and the overall rough shape is initially formed.

[0023] Step 3: Warm forming: Place the ultra-low temperature pre-formed component in a heating furnace and heat it at 200°C for 2 minutes; then quickly transfer it to the mold for warm forming. The warm forming temperature of the sheet metal is about 180°C to complete the forming of all features of the part, including the small fillet (fillet radius less than 5mm) area.

[0024] Step 4: Short-time artificial aging heat treatment: The formed aluminum alloy thin-walled component is subjected to aging treatment at a temperature of 180°C for 20 minutes to finally obtain the target part.

[0025] like Figure 3 As shown in the figure, the initial sheet material forms a supersaturated solid solution after solution quenching, and the sheet material in the solution quenching state is pre-formed at ultra-low temperature to obtain a large number of dislocation substructures, and then a part of the precipitation phase is pre-precipitated by warm forming, and finally a short-time artificial aging heat treatment is performed. On the one hand, a fine dispersed strengthening phase can be obtained in the crystal, and on the other hand, the precipitation phase distribution at the grain boundary can be dispersed. Through the above steps to regulate the microstructure, an aging state structure that takes into account both strength and corrosion resistance is obtained, which meets the service performance requirements of parts strength and corrosion resistance.

[0026] like Figure 4 As shown in the figure, taking the AA7075 aluminum alloy cabin door inner panel feature part as an example, the thinning rate of the part after hot forming, ultra-low temperature forming, and ultra-low temperature-warm composite forming is analyzed through simulation comparison. It can be found that the wall thickness uniformity of the cabin door inner panel feature part can be improved through ultra-low temperature-warm composite forming.

[0027] Compared with the prior art, the present invention can improve the wall thickness uniformity of parts by ultra-low temperature pre-forming and utilizing the double-increasing effect of simultaneously improving the elongation and hardening ability of high-strength aluminum alloy at ultra-low temperatures; continue to perform warm forming on a small number of extremely difficult-to-form areas (such as small fillet feature areas) after ultra-low temperature pre-forming, which can avoid the problem of excessive thinning compared to direct warm forming or hot forming; a large number of dislocations are generated in the high-strength aluminum alloy crystals through ultra-low temperature pre-forming, which is beneficial to the subsequent aging precipitation process, and the multi-stage aging heat treatment of warm forming and short-time artificial aging can disperse the grain boundary precipitation phase distribution, taking into account the service performance requirements such as part strength and corrosion resistance.

[0028] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principle and purpose of the present invention. The protection scope of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. Each implementation scheme within its scope shall be subject to the constraints of the present invention.

Claims

1. A method for ultra-low temperature-warm temperature composite forming of complex thin-walled aluminum alloy components, characterized in that: The supersaturated solid solution of aluminum alloy that has been solution treated in advance is subjected to ultra-low temperature pre-cooling treatment, and then ultra-low temperature pre-formed through a mold, and then heated and kept warm and quickly transferred for warm forming, and finally a short-term artificial aging treatment is performed to obtain aluminum alloy thin-walled parts.

2. The ultra-low temperature-warm temperature composite forming method of aluminum alloy complex thin-walled components according to claim 1 is characterized in that: The aluminum alloy is Al-Cu alloy, Al-Zn alloy and / or Al-Li alloy.

3. The ultra-low temperature-warm temperature composite forming method of aluminum alloy complex thin-walled components according to claim 1 is characterized in that: The supersaturated solid solution is obtained by heating the aluminum alloy to a temperature above the solid solution temperature, keeping the temperature, and then rapidly cooling and quenching.

4. The ultra-low temperature-warm temperature composite forming method of aluminum alloy complex thin-walled components according to claim 3 is characterized in that: The method is obtained by heating an aluminum alloy plate with a thickness of 1 mm to 3 mm to above the solid solution temperature, keeping the temperature, and then rapidly cooling and quenching the plate.

5. The ultra-low temperature-warm temperature composite forming method of aluminum alloy complex thin-walled components according to claim 1 is characterized in that: The short-time artificial aging treatment has a temperature of 80°C to 200°C and an aging treatment time of 5 minutes to 5 hours.

6. The ultra-low temperature-warm temperature composite forming method of aluminum alloy complex thin-walled components according to claim 1 is characterized in that: The pre-cooling treatment involves immersing the sheet material in a cooling medium, wherein the cooling medium used includes liquid nitrogen, liquid helium and / or liquid argon.

7. The ultra-low temperature-warm temperature composite forming method of aluminum alloy complex thin-walled components according to claim 1 is characterized in that: The mold adopts overall cooling and local cooling to cooperate with ultra-low temperature preforming, and its cooling method includes soaking and spraying of cooling medium and cooling of flow channels in the mold.

8. The ultra-low temperature-warm temperature composite forming method of aluminum alloy complex thin-walled components according to claim 1 or 7, characterized in that: The ultra-low temperature preforming has a forming temperature of -100°C to -196°C.

9. The ultra-low temperature-warm temperature composite forming method of aluminum alloy complex thin-walled components according to claim 1 is characterized in that: The heating and heat preservation adopts induction heating, furnace heating or salt bath heating, and the temperature is 100°C to 250°C.

10. The ultra-low temperature-warm temperature composite forming method of aluminum alloy complex thin-walled components according to claim 1, characterized in that: The warm forming has a forming temperature of 100°C to 250°C.

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