CN109825748B - Method for improving intergranular corrosion performance of Al-Cu-Mg series aluminum alloy - Google Patents
Method for improving intergranular corrosion performance of Al-Cu-Mg series aluminum alloy Download PDFInfo
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Abstract
The invention provides a method for improving intercrystalline corrosion performance of an Al-Cu-Mg series aluminum alloy, which comprises the following steps: (1) casting the Al-Cu-Mg series aluminum alloy ingot; (2) and carrying out homogenization heat treatment on the ingot. According to the technical scheme provided by the invention, the problem of dispersed phase precipitation is solved through homogenization heat treatment, and fine, uniform and dispersed AlCuMn phases can be precipitated in a matrix in a short homogenization time; through low-temperature short-time treatment, the dendritic crystal structure in the microstructure is eliminated, and simultaneously, a small amount of residual coarse phases in the microstructure are controlled, so that an aluminum matrix is in an undersaturation state during solid solution, the quenching sensitivity of the material is reduced, the precipitation of a nano-scale second phase at the grain boundary of the material after solid solution is inhibited, and the effects of improving the production efficiency and improving the intergranular corrosion resistance of the product are achieved. The technical scheme provided by the invention is suitable for industrial production of large ingots, has good operability, and can shorten the homogenization heat treatment time and save the heat treatment energy consumption.
Description
Technical Field
The invention relates to a homogenization heat treatment method of an alloy, in particular to a method for improving intercrystalline corrosion performance of an Al-Cu-Mg series aluminum alloy.
Background
With the design of aircraft manufacture from pure static strength emphasis to fatigue and modern damage tolerance, the requirements for structural materials are gradually evolving from strength only emphasis to toughness, fatigue resistance and corrosion resistance. The Al-Cu-Mg series alloy is an aluminum alloy with Cu as a main alloy element, and has the characteristics of high strength, excellent heat resistance and excellent processing performance, but the corrosion resistance is inferior to that of other aluminum alloys, and intergranular corrosion can be generated under certain conditions. Since the 70 s, a series of novel aluminum alloys with high purity, high toughness and corrosion resistance and processing states thereof, such as alloys of 2124, 7175, 7075 and 7475, and effective states of T851, T73, T76 and T74, are developed and applied through ways of alloying, improving purity, improving heat treatment and the like, and even a trend of sacrificing partial strength to replace toughness appears at one time.
The rapid development of the aerospace industry puts higher and higher requirements on the comprehensive performance of high-strength and high-toughness 2xxx series aluminum alloys, and not only is high strength required, but also stronger corrosion resistance is required. In the case of an airplane flying in a coastal region, intergranular corrosion, denudation and stress corrosion of aluminum alloy occur due to the action of humid air and industrial waste gas. Since intergranular corrosion occurs inside the metal, it is often not easily discovered and causes sudden damage to the structural member. The local corrosion is a main corrosion form of the high-strength aluminum alloy, which seriously affects the performance and the service life of the aluminum alloy aircraft structural member, especially the point corrosion, the intercrystalline corrosion, the spalling corrosion and the like with strong secrecy and uncertainty, so that the metal is suddenly damaged without aura, and a major disaster accident is caused. Therefore, the method has very important significance for improving the corrosion resistance of the high-strength aluminum alloy.
The homogenization treatment can eliminate nonequilibrium low melting point phase and dendritic crystal segregation, so that the alloy elements are uniformly distributed in the solid solution, and the content of coarse phases in the microstructure is reduced. Meanwhile, the addition of Mn element in the alloy can make the alloy precipitate and disperse with AlCuMn matrix in the homogenization process. The dispersion phase can effectively pin the grain boundary after the alloy is subjected to solid solution, prevent the migration of the grain boundary and the subboundary, retain the substructure and dislocation generated by rolling deformation, refine the grains and strengthen the matrix. Therefore, the homogenization heat treatment process is optimized to fully redissolve the coarse phase and the large phase, and the uniform precipitation of the dispersed phase is regulated and controlled, so that the method has important significance for improving the microstructure and the comprehensive performance of the alloy.
Generally, the homogenization heat treatment of the Al — Cu — Mg-based alloy can be classified into single-stage and two-stage homogenization processes. The invention patent of China, CN201510697239.3, discloses a heat treatment method for controlling the precipitation of dispersed phases of an Al-Cu-Mg-Mn alloy, wherein the heat treatment method comprises the steps of raising the temperature to 401-460 ℃ at a heating rate of 1-300 ℃/h from room temperature, preserving the heat for 0-30 h, then raising the temperature to 470-530 ℃ at a heating rate of 1-300 ℃/h, preserving the heat for 1-60 h, homogenizing and cooling. The soaking process is complicated and the time period is long. Most of the existing studies on the homogenization heat treatment process of Al-Cu-Mg alloy focus on how to reduce the content of coarse phases in a microstructure and regulate the precipitation distribution of dispersed phases, and the study on how to regulate the distribution of a grain boundary second phase after solid solution of a material and the influence rule on the intercrystalline corrosion performance of subsequent alloy is lacked.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides a method for improving the intercrystalline corrosion performance of Al-Cu-Mg series aluminum alloy, which greatly reduces the heat energy consumption, controls the dispersed phase to be uniformly precipitated, simultaneously enables a small amount of coarse phases to remain in the microstructure of the aluminum alloy, enables the aluminum matrix to be in an undersaturation state during solid solution, effectively inhibits the precipitation of nanoscale second phases at the grain boundary after the solid solution of the material, and finally greatly improves and improves the intercrystalline corrosion resistance of Al-Cu-Mg series aluminum alloy products.
In order to realize the purpose of the invention, the following technical scheme is adopted:
a method of improving the intercrystalline corrosion performance of an Al-Cu-Mg series aluminum alloy, the method comprising:
(1) casting the Al-Cu-Mg series aluminum alloy ingot;
(2) and carrying out homogenization heat treatment on the ingot.
Further, the Al-Cu-Mg series aluminum alloy is: cu3.6-4.5 wt.%, Mg1.3-1.8 wt.%, Mn0.3-0.8 wt.%, Ti <0.15 wt.%, Zn <0.25 wt.%, Fe < 0.3 wt.%, Si <0.2 wt.%, and Al in balance.
Further, the method comprises:
heating the Al-Cu-Mg aluminum alloy from room temperature to 460-495 ℃ at a heating rate of 5-100 ℃/h, preserving the heat for 3-20 h, and cooling in the air.
Further, the method comprises:
heating the Al-Cu-Mg series aluminum alloy from room temperature to 460-495 ℃ at a heating rate of 20-100 ℃/h, preserving the heat for 3-20 h, and cooling in the air.
Further, the method comprises: heating the Al-Cu-Mg aluminum alloy from room temperature to 460-485 ℃ at the heating rate of 20-100 ℃/h, preserving the heat for 3-15h, and cooling in the air.
Further, the method comprises: and sequentially carrying out hot rolling, cold rolling, intermediate annealing, solid solution and natural aging treatment on the cast ingot to prepare the plate.
Further, the hot rolling process includes:
preheating the cast ingot at 460 ℃ for 3 hours, and rolling the cast ingot into a hot rolled plate with the thickness of 6-7 mm by the pass reduction of 2-5 mm, wherein the hot rolling outlet temperature is more than or equal to 300 ℃.
Further, the cold rolling process includes:
and (3) after the hot rolled plate is subjected to heat preservation for 45min at the temperature of 410 ℃, cold rolling the hot rolled plate to a plate with the thickness of 2mm, preserving the heat for 60min at the temperature of 280 ℃, and then air cooling.
Further, the solution treatment includes: and (3) keeping the temperature of the plate at 496 ℃ for 30min, discharging the plate and performing water quenching.
Further, the natural aging treatment comprises the following steps: the plates were left standing at room temperature for 96 h.
Compared with the closest prior art, the technical scheme provided by the invention has the following beneficial effects:
(1) according to the technical scheme provided by the invention, the defect of dispersed phase precipitation is eliminated by controlling the temperature rise process, and fine, uniform and dispersed AlCuMn phases can be precipitated in the Al-Cu-Mg series aluminum alloy matrix in a short homogenization time.
(2) The low-temperature short-time process in the technical scheme provided by the invention can eliminate the dendritic crystal structure in the microstructure and obtain a small amount of residual coarse phases in the microstructure at the same time, so that an aluminum matrix is in an undersaturation state during solid solution, the quenching sensitivity of the material is reduced, the precipitation of a nanoscale second phase at a grain boundary after the solid solution of the material is inhibited, and the effects of improving the production efficiency and improving the intergranular corrosion resistance of the product are achieved.
(3) The technical scheme provided by the invention is suitable for industrial production of large ingots, has good operability, and can shorten the homogenization heat treatment time and save the heat treatment energy consumption and the production cost.
Drawings
FIG. 1 is a second phase morphology at grain boundaries for example 1(a) and comparative example 1 (b);
FIG. 2 shows the dispersed AlCuMn phase distribution precipitated in example 1;
FIG. 3 is the line scan analysis of the microstructure after the homogenization heat treatment of example 3: (a) SEM tissue morphology; (b) distribution of Mg element; (c) distribution of Cu element; (d) distribution of Mn element;
FIG. 4 is a metallographic structure of a cross section after intergranular corrosion in example 1 and comparative example 1: (a) example 1 tissue topography; (b) comparative example 1 tissue morphology.
Detailed Description
Example 1
The aluminum alloy comprises the following components in percentage by mass: cu4.0wt.%, Mg1.4wt.%, Mn0.5wt.%, Ti <0.1 wt.%, Fe <0.2 wt.%, Si <0.1 wt.%, and the balance of Al. And semi-continuously casting into a flat ingot with the thickness of 45 mm.
The process for homogenizing the aluminum alloy comprises: and (3) heating the aluminum alloy from room temperature to 465 ℃ at the heating rate of 50 ℃/h, keeping the temperature for 6h, and then cooling in the air. After the ingot is soaked uniformly, hot rolling, cold rolling, intermediate annealing, solid solution and natural aging treatment are carried out to prepare the plate. Preheating at a heating rate of 460 ℃/3h before ingot casting hot rolling, rolling a thick plate of 6-7 mm from the thickness of 40mm, wherein the pass reduction is 2-5 mm, and the hot rolling outlet temperature is controlled to be above 300 ℃. And (3) sequentially carrying out recrystallization annealing at 410 ℃/45min and cold rolling and thinning to 2mm, then carrying out stress relief annealing at 280 ℃/60min, carrying out recovery annealing and heat preservation on the plate, and then discharging the plate out of the furnace for air cooling. After the plate is subjected to 496 ℃/30min high-temperature solution treatment, the plate is directly taken out of the furnace and quenched by water, and is placed at room temperature for 96h, and then the performance is detected.
Example 2
The aluminum alloy comprises the following components in percentage by mass: cu4.0wt.%, Mg1.4wt.%, Mn0.5wt.%, Ti <0.1 wt.%, Fe <0.2 wt.%, Si <0.1 wt.%, and the balance of Al. And semi-continuously casting into a flat ingot with the thickness of 45 mm.
The alloy is homogenized by adopting the low-temperature short-time homogenization heat treatment system of the method, and the ingot is soaked uniformly and then is subjected to hot rolling, cold rolling, intermediate annealing, solid solution and natural aging treatment to prepare the plate. The specific process comprises the following steps: raising the temperature from room temperature to 475 ℃ at the average heating rate of 50 ℃/h, keeping the temperature for 6h, and then cooling in air. Preheating at 460 ℃/3h before ingot casting hot rolling, rolling a thick plate of 6-7 mm from the thickness of 40mm, the pass reduction is 2-5 mm, and the hot rolling outlet temperature is controlled to be above 300 ℃. The hot rolled plate was subjected to recrystallization annealing at 410 deg.C/45 min. And then carrying out cold rolling and thinning to 2mm, then carrying out stress relief annealing, and discharging from the furnace for air cooling after the heat preservation at 280 ℃/60min is finished. After the plate is subjected to high-temperature solid solution at 496 ℃/30min, the plate is directly taken out of a furnace and quenched by water, and then the plate is stood at room temperature for 96h for performance detection.
Example 3
The aluminum alloy comprises the following components in percentage by mass: cu4.0wt.%, Mg1.4wt.%, Mn0.5wt.%, Ti <0.1 wt.%, Fe <0.2 wt.%, Si <0.1 wt.%, and the balance of Al. And semi-continuously casting into a flat ingot with the thickness of 45 mm.
The alloy is homogenized by adopting the low-temperature short-time homogenization heat treatment system of the method, and the ingot is soaked uniformly and then is subjected to hot rolling, cold rolling, intermediate annealing, solid solution and natural aging treatment to prepare the plate. The specific process comprises the following steps: raising the temperature from room temperature to 485 ℃ at the average heating rate of 50 ℃/h, keeping the temperature for 6h, and then cooling in air. Preheating at 460 ℃/3h before ingot casting hot rolling, rolling a thick plate of 6-7 mm from the thickness of 40mm, the pass reduction is 2-5 mm, and the hot rolling outlet temperature is controlled to be above 300 ℃. The hot rolled plate was subjected to recrystallization annealing at 410 deg.C/45 min. And then carrying out cold rolling and thinning to 2mm, then carrying out stress relief annealing, and discharging from the furnace for air cooling after the heat preservation at 280 ℃/60min is finished. After the plate is subjected to solid solution at 496 ℃/30min, the plate is directly taken out of the furnace and quenched by water, and then the plate is stood at room temperature for 96h for performance detection.
Example 4
The aluminum alloy comprises the following components in percentage by mass: cu4.0wt.%, Mg1.4wt.%, Mn0.5wt.%, Ti <0.1 wt.%, Fe <0.2 wt.%, Si <0.1 wt.%, and the balance of Al. And semi-continuously casting into a flat ingot with the thickness of 45 mm.
The alloy is homogenized by adopting the low-temperature short-time homogenization heat treatment system of the method, and the ingot is soaked uniformly and then is subjected to hot rolling, cold rolling, intermediate annealing, solid solution and natural aging treatment to prepare the plate. The specific process comprises the following steps: raising the temperature from room temperature to 465 ℃ at the average heating rate of 50 ℃/h, keeping the temperature for 6h, and then cooling in air. Preheating at 460 ℃/3h before ingot casting hot rolling, rolling a thick plate of 6-7 mm from the thickness of 40mm, the pass reduction is 2-5 mm, and the hot rolling outlet temperature is controlled to be above 300 ℃. The hot rolled plate was subjected to recrystallization annealing at 410 deg.C/45 min. And then carrying out cold rolling and thinning to 2mm, then carrying out stress relief annealing, and discharging from the furnace for air cooling after the heat preservation at 280 ℃/60min is finished. After the plate is subjected to solid solution at 496 ℃/30min, the plate is directly taken out of the furnace and quenched by water, and then the plate is stood at room temperature for 96h for performance detection.
Example 5
The aluminum alloy comprises the following components in percentage by mass: cu4.1wt.%, Mg1.24wt.%, Mn0.7 wt.%, Ti <0.1 wt.%, Fe <0.2 wt.%, Si <0.1 wt.%, Zn <0.2 wt.%, and Al in balance. And semi-continuously casting into a flat ingot with the thickness of 45 mm.
The alloy is homogenized by adopting the low-temperature short-time homogenization heat treatment system of the method, and the ingot is soaked uniformly and then is subjected to hot rolling, cold rolling, intermediate annealing, solid solution and natural aging treatment to prepare the plate. The specific process comprises the following steps: raising the temperature from room temperature to 475 ℃ at the average heating rate of 50 ℃/h, keeping the temperature for 6h, and then cooling in air. Preheating at 460 ℃/3h before ingot casting hot rolling, rolling a thick plate of 6-7 mm from the thickness of 40mm, the pass reduction is 2-5 mm, and the hot rolling outlet temperature is controlled to be above 300 ℃. The hot rolled plate was subjected to recrystallization annealing at 410 deg.C/45 min. And then carrying out cold rolling and thinning to 2mm, then carrying out stress relief annealing, and discharging from the furnace for air cooling after the heat preservation at 280 ℃/60min is finished. After the plate is subjected to solid solution at 496 ℃/30min, the plate is directly taken out of the furnace and quenched by water, and then the plate is stood at room temperature for 96h for performance detection.
Example 6
The aluminum alloy comprises the following components in percentage by mass: cu4.1wt.%, Mg1.24wt.%, Mn0.7 wt.%, Ti <0.1 wt.%, Fe <0.2 wt.%, Si <0.1 wt.%, Zn <0.2 wt.%, and Al in balance. And semi-continuously casting into a flat ingot with the thickness of 45 mm.
The alloy is homogenized by adopting the low-temperature short-time homogenization heat treatment system of the method, and the ingot is soaked uniformly and then is subjected to hot rolling, cold rolling, intermediate annealing, solid solution and natural aging treatment to prepare the plate. The specific process comprises the following steps: raising the temperature from room temperature to 485 ℃ at the average heating rate of 50 ℃/h, keeping the temperature for 6h, and then cooling in air. Preheating at 460 ℃/3h before ingot casting hot rolling, rolling a thick plate of 6-7 mm from the thickness of 40mm, the pass reduction is 2-5 mm, and the hot rolling outlet temperature is controlled to be above 300 ℃. The hot rolled plate was subjected to recrystallization annealing at 410 deg.C/45 min. And then carrying out cold rolling and thinning to 2mm, then carrying out stress relief annealing, and discharging from the furnace for air cooling after the heat preservation at 280 ℃/60min is finished. After the plate is subjected to solid solution at 496 ℃/30min, the plate is directly taken out of the furnace and quenched by water, and then the plate is stood at room temperature for 96h for performance detection.
Example 7
The aluminum alloy comprises the following components in percentage by mass: cu4.5wt.%, Mg1.6 wt.%, Mn0.7 wt.%, Ti <0.1 wt.%, Fe <0.2 wt.%, Si <0.1 wt.%, Zn <0.2 wt.%, and the balance Al. And semi-continuously casting into a flat ingot with the thickness of 45 mm.
The alloy is homogenized by adopting the low-temperature short-time homogenization heat treatment system of the method, and the ingot is soaked uniformly and then is subjected to hot rolling, cold rolling, intermediate annealing, solid solution and natural aging treatment to prepare the plate. The specific process comprises the following steps: raising the temperature from room temperature to 475 ℃ at the average heating rate of 50 ℃/h, keeping the temperature for 6h, and then cooling in air. Preheating at 460 ℃/3h before ingot casting hot rolling, rolling a thick plate of 6-7 mm from the thickness of 40mm, the pass reduction is 2-5 mm, and the hot rolling outlet temperature is controlled to be above 300 ℃. The hot rolled plate was subjected to recrystallization annealing at 410 deg.C/45 min. And then carrying out cold rolling and thinning to 2mm, then carrying out stress relief annealing, and discharging from the furnace for air cooling after the heat preservation at 280 ℃/60min is finished. After the plate is subjected to solid solution at 496 ℃/30min, the plate is directly taken out of the furnace and quenched by water, and then the plate is stood at room temperature for 96h for performance detection.
Example 8
The aluminum alloy comprises the following components in percentage by mass: cu4.0 wt.%, Mg1.8 wt.%, Mn0.3 wt.%, Ti <0.1 wt.%, Fe <0.2 wt.%, Si <0.1 wt.%, Zn <0.2 wt.%, and Al in balance. And semi-continuously casting into a flat ingot with the thickness of 45 mm.
The alloy is homogenized by adopting the low-temperature short-time homogenization heat treatment system of the method, and the ingot is soaked uniformly and then is subjected to hot rolling, cold rolling, intermediate annealing, solid solution and natural aging treatment to prepare the plate. The specific process comprises the following steps: raising the temperature from room temperature to 475 ℃ at the average heating rate of 50 ℃/h, keeping the temperature for 6h, and then cooling in air. Preheating at 460 ℃/3h before ingot casting hot rolling, rolling a thick plate of 6-7 mm from the thickness of 40mm, the pass reduction is 2-5 mm, and the hot rolling outlet temperature is controlled to be above 300 ℃. The hot rolled plate was subjected to recrystallization annealing at 410 deg.C/45 min. And then carrying out cold rolling and thinning to 2mm, then carrying out stress relief annealing, and discharging from the furnace for air cooling after the heat preservation at 280 ℃/60min is finished. After the plate is subjected to solid solution at 496 ℃/30min, the plate is directly taken out of the furnace and quenched by water, and then the plate is stood at room temperature for 96h for performance detection.
Example 9
The aluminum alloy comprises the following components in percentage by mass: cu3.6 wt.%, Mg1.3 wt.%, Mn0.8 wt.%, Ti <0.1 wt.%, Fe <0.2 wt.%, Si <0.1 wt.%, Zn <0.2 wt.%, and Al in balance. And semi-continuously casting into a flat ingot with the thickness of 45 mm.
The alloy is homogenized by adopting the low-temperature short-time homogenization heat treatment system of the method, and the ingot is soaked uniformly and then is subjected to hot rolling, cold rolling, intermediate annealing, solid solution and natural aging treatment to prepare the plate. The specific process comprises the following steps: raising the temperature from room temperature to 475 ℃ at the average heating rate of 50 ℃/h, keeping the temperature for 6h, and then cooling in air. Preheating at 460 ℃/3h before ingot casting hot rolling, rolling a thick plate of 6-7 mm from the thickness of 40mm, the pass reduction is 2-5 mm, and the hot rolling outlet temperature is controlled to be above 300 ℃. The hot rolled plate was subjected to recrystallization annealing at 410 deg.C/45 min. And then carrying out cold rolling and thinning to 2mm, then carrying out stress relief annealing, and discharging from the furnace for air cooling after the heat preservation at 280 ℃/60min is finished. After the plate is subjected to solid solution at 496 ℃/30min, the plate is directly taken out of the furnace and quenched by water, and then the plate is stood at room temperature for 96h for performance detection.
Example 10
The aluminum alloy comprises the following components in percentage by mass: cu4.5wt.%, Mg1.3wt.%, Mn0.5wt.%, Ti <0.1 wt.%, Fe <0.2 wt.%, Si <0.1 wt.%, Zn <0.2 wt.%, and the balance Al. And semi-continuously casting into a flat ingot with the thickness of 45 mm.
The alloy is homogenized by adopting the low-temperature short-time homogenization heat treatment system of the method, and the ingot is soaked uniformly and then is subjected to hot rolling, cold rolling, intermediate annealing, solid solution and natural aging treatment to prepare the plate. The specific process comprises the following steps: raising the temperature from room temperature to 475 ℃ at the average heating rate of 50 ℃/h, keeping the temperature for 6h, and then cooling in air. Preheating at 460 ℃/3h before ingot casting hot rolling, rolling a thick plate of 6-7 mm from the thickness of 40mm, the pass reduction is 2-5 mm, and the hot rolling outlet temperature is controlled to be above 300 ℃. The hot rolled plate was subjected to recrystallization annealing at 410 deg.C/45 min. And then carrying out cold rolling and thinning to 2mm, then carrying out stress relief annealing, and discharging from the furnace for air cooling after the heat preservation at 280 ℃/60min is finished. After the plate is subjected to solid solution at 496 ℃/30min, the plate is directly taken out of the furnace and quenched by water, and then the plate is stood at room temperature for 96h for performance detection.
Comparative example 1
The aluminum alloy comprises the following components in percentage by mass: cu4.0wt.%, Mg1.4wt.%, Mn0.5wt.%, Ti <0.1 wt.%, Fe <0.2 wt.%, Si <0.1 wt.%, and the balance of Al. And semi-continuously casting into a flat ingot with the thickness of 45 mm.
The alloy is homogenized by adopting the low-temperature short-time homogenization heat treatment system of the method, and the ingot is soaked uniformly and then is subjected to hot rolling, cold rolling, intermediate annealing, solid solution and natural aging treatment to prepare the plate. The specific process comprises the following steps: heating the mixture from room temperature to 495 ℃ for 30 hours, and then cooling the mixture in air. Preheating at 460 ℃/3h before ingot casting hot rolling, rolling a thick plate of 6-7 mm from the thickness of 40mm, the pass reduction is 2-5 mm, and the hot rolling outlet temperature is controlled to be above 300 ℃. The hot rolled plate was subjected to recrystallization annealing at 410 deg.C/45 min. And then carrying out cold rolling and thinning to 2mm, then carrying out stress relief annealing, and discharging from the furnace for air cooling after the heat preservation at 280 ℃/60min is finished. After the plate is subjected to solid solution at 496 ℃/30min, the plate is directly taken out of the furnace and quenched by water, and then the plate is stood at room temperature for 96h for performance detection.
Comparative example 2
The aluminum alloy comprises the following components in percentage by mass: cu4.1wt.%, Mg1.24wt.%, Mn0.7 wt.%, Ti <0.1 wt.%, Fe <0.2 wt.%, Si <0.1 wt.%, Zn <0.2 wt.%, and Al in balance. And semi-continuously casting into a flat ingot with the thickness of 45 mm.
The alloy is homogenized by adopting the low-temperature short-time homogenization heat treatment system of the method, and the ingot is soaked uniformly and then is subjected to hot rolling, cold rolling, intermediate annealing, solid solution and natural aging treatment to prepare the plate. The specific process comprises the following steps: heating the mixture from room temperature to 495 ℃ for 30 hours, and then cooling the mixture in air. Preheating at 460 ℃/3h before ingot casting hot rolling, rolling a thick plate of 6-7 mm from the thickness of 40mm, the pass reduction is 2-5 mm, and the hot rolling outlet temperature is controlled to be above 300 ℃. The hot rolled plate was subjected to recrystallization annealing at 410 deg.C/45 min. And then carrying out cold rolling and thinning to 2mm, then carrying out stress relief annealing, and discharging from the furnace for air cooling after the heat preservation at 280 ℃/60min is finished. After the plate is subjected to solid solution at 496 ℃/30min, the plate is directly taken out of a furnace and quenched by water, then natural aging treatment is carried out, and the plate is stood at room temperature for 96h and then performance detection is carried out.
After the high-temperature homogenization at 495 ℃ and long-time soaking for 30 hours, the coarse phase in the microstructure is basically redissolved. In this state, no residual coarse phase which is not redissolved exists in the aluminum matrix in the solid solution process in the later stage of the plate which is subjected to hot rolling and cold rolling, so that the solid solubility of the supersaturated solid solution is high after the solid solution heat preservation. FIG. 1 shows high-magnification TEM second phase morphology at grain boundaries of example 1(a) and comparative example 1 (b). It can be seen that after the high-temperature homogenization is carried out at 495 ℃ and the heat preservation is carried out for a long time of 30h, fine and continuous Al with the size of about 20nm can be precipitated at the crystal boundary in the later solid solution quenching process2The Cu phase precipitated as shown in FIG. 1 (b). After low-temperature short-time uniform treatment, the grain boundary in the solid solution quenching microstructure is relatively straight and clean, and only a small amount of 100-plus 200nm AlCuMn dispersoid phase is reserved at the grain boundary for precipitation. The AlCuMn dispersed phase is a second phase precipitated in the soaking process, and remains at a recrystallization grain boundary due to pinning the grain boundary when the material is recrystallized in the later period. And because the temperature rising rate is controlled by soaking treatment, a dispersed and fine nanoscale disperse AlCuMn phase is uniformly precipitated in the soaking process, as shown in figure 2. FIG. 3 is a graph of the microstructure morphology quenched after the 485 deg.C/6 h homogenization heat preservation and the corresponding line scanning spectrogram, and it can be seen that the dendritic structure formed by casting is eliminated after the low-temperature short-time homogenization heat treatment heat preservation for 6 h. The enrichment of Cu and Mn elements occurs at local positions of grain boundaries, which is mainly due to the fact that line scanning is just to scan coarse phase Al at the grain boundaries2Cu phase grains, as shown in FIG. 3 (a). Low-temperature short-time homogenizing annealing heat treatment process for retaining a certain degree of coarse phase Al2When the Cu phase is in the aluminum matrix, the supersaturated solid solubility of the deformed plate in the aluminum matrix is reduced in the solid solution heat preservation process,therefore, the quenching sensitivity of the matrix is effectively reduced, and fine and continuous nano-scale second phase Al is not easy to precipitate on the crystal boundary after the solid solution heat preservation and rapid quenching2The Cu phase is shown in FIG. 1 (a). As a result of investigation, it has been found that, in the natural aging (T4 temper) of 2xxx type aluminum alloys, Cu-rich Al is continuously precipitated in the grain boundaries2Cu phase, grain boundary producing copper-poor zone, Al2The Cu and the area with poor copper of grain boundary form a corrosion cell, which causes intercrystalline corrosion.
TABLE 1 results of texture analysis under different homogenization heat treatment processes in examples and comparative examples
Table 1 shows the results of intercrystalline corrosion depth test of the examples and comparative examples of the present invention under different homogenization heat treatment processes and the corresponding coarse phase Al on DSC temperature rise curve2Endothermic peak area of Cu phase. Generally, the endothermic peak area on the DSC corresponds to the content of coarse phase, and the larger the content of coarse phase in the matrix, the larger the corresponding endothermic peak area. And the content of coarse phases under different heat treatment processes is reflected by testing DSC temperature rise curves of samples subjected to different homogenization heat treatments. As can be seen from the table, coarse phase Al in the microstructure after the high-temperature homogenization heat treatment for a long period of time in the comparative example2The Cu phase has substantially redissolved, and the area of the corresponding endothermic peak on the DSC curve obtained in this test is 0J. The coarse phase Al obtained by DSC test after the process homogenization heat treatment of the invention2The endothermic peak area of the Cu phase is obviously increased relative to the soaking process at 495 ℃ for 30h, which shows that the coarse phase Al which is not redissolved in the matrix2The Cu phase area fraction increases. It can be seen that in examples 1-3, the endothermic peak area of the material increases with decreasing soaking temperature of the homogenizing annealing, which indicates that the residual coarse phase content in the microstructure increases and the intergranular corrosion depth of the corresponding plate after natural aging of solution quenching decreases. And it is noted that by varying the homogenization annealing process regime, the intercrystalline corrosion depth of the example alloy is significantly reduced relative to the comparative example, as shown in fig. 4 and table 1. Meanwhile, compared with the comparative example, the heat treatment time of the process is reduced by about 25 hours, the reduction amplitude is 62 percent, and the heat efficiency is greatly improved.
Therefore, the quenching sensitivity of the processed plate structure can be effectively reduced by implementing the low-temperature short-time homogenization heat treatment process, so that the continuous precipitation of Cu-rich Al at the grain boundary in the quenching process is inhibited2And the Cu phase finally improves the intergranular corrosion resistance of the material. And the AlCuMn phase particles in the sample are distributed more uniformly and finely after the sample is subjected to homogenization heat treatment under the condition of slow temperature rise. More precipitated number density and more fine precipitated size dispersoids are beneficial to inhibiting recrystallization and grain growth in the thermal processing process.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.
Claims (2)
1. A method for improving intergranular corrosion performance of Al-Cu-Mg series aluminum alloy, which is characterized by comprising the following steps:
(1) casting the Al-Cu-Mg series aluminum alloy ingot;
(2) carrying out homogenization heat treatment on the cast ingot;
carrying out homogenization heat treatment on the cast ingot, and then sequentially carrying out hot rolling, cold rolling, intermediate annealing, solid solution and natural aging treatment to prepare a plate;
the hot rolling treatment comprises:
preheating the cast ingot at 460 ℃ for 3 hours, and rolling the cast ingot into a hot rolled plate with the thickness of 6-7 mm by the pass reduction of 2-5 mm, wherein the hot rolling outlet temperature is more than or equal to 300 ℃;
the cold rolling treatment comprises the following steps:
keeping the temperature of the hot rolled plate at 410 ℃ for 45min, then cold-rolling the hot rolled plate to a plate with the thickness of 2mm, keeping the temperature at 280 ℃ for 60min, and then air-cooling;
the solution treatment comprises: keeping the temperature of the plate at 496 ℃ for 30min, discharging and quenching in water;
the natural aging treatment comprises the following steps: standing the plate for 96h at room temperature;
the homogenizing heat treatment comprises:
heating the Al-Cu-Mg aluminum alloy from room temperature to 460-485 ℃ at the heating rate of 20-100 ℃/h, preserving the heat for 3-15h, and cooling in the air.
2. The method for improving the intergranular corrosion performance of the Al-Cu-Mg aluminum alloy according to claim 1, wherein the Al-Cu-Mg aluminum alloy is: cu3.6-4.5 wt.%, Mg1.3-1.8 wt.%, Mn0.3-0.8 wt.%, Ti <0.15 wt.%, Zn <0.25 wt.%, Fe < 0.3 wt.%, Si <0.2 wt.%, and Al in balance.
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| CN111647831A (en) * | 2020-05-21 | 2020-09-11 | 范语楠 | Device and method for preparing Al-Cu-Mg alloy nanocrystalline grain structure |
| CN112553512B (en) * | 2020-12-02 | 2022-07-26 | 中铝材料应用研究院有限公司 | Aluminum-magnesium alloy sheet material with high thermal stability, weldability and corrosion resistance and use thereof |
| CN114134376A (en) * | 2021-12-08 | 2022-03-04 | 无锡市世达精密焊管制造有限公司 | Mg-Cu aluminum alloy and preparation method thereof |
| CN114293116A (en) * | 2021-12-30 | 2022-04-08 | 西南铝业（集团）有限责任公司 | Method for improving intergranular corrosion of aluminum alloy sheet |
| CN114737144B (en) * | 2022-03-23 | 2023-07-14 | 天津忠旺铝业有限公司 | Homogenization heat treatment method of 2324 aluminum alloy |
| CN116043146A (en) * | 2023-01-05 | 2023-05-02 | 国网浙江省电力有限公司电力科学研究院 | Method for improving intergranular corrosion resistance of aluminum alloy and aluminum alloy prepared by method |
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