CN103589977B - A kind of method improving Al-Cu-Mg alloy anti-fatigue performance - Google Patents

Abstract

A method for improving the fatigue resistance of Al-Cu-Mg alloys is that the homogenized aluminum alloy is subjected to high-temperature hot rolling, primary solution treatment, large deformation cold rolling, secondary solution treatment, and natural aging treatment . The present invention keeps the material at a higher temperature before hot rolling, so that the material undergoes dynamic recrystallization during the hot rolling process, thereby forming more recrystallization textures such as Goss and Cube, which is beneficial to improving the fatigue resistance of aluminum alloys; cold rolling Pre-solution treatment can greatly eliminate the coarse second phase particles except Fe and Si impurities, avoid the formation of high-energy regions, and thus avoid the formation of uneven recrystallization. Large-scale cold-rolling deformation greatly increases the dislocation density of the alloy, enables the alloy to obtain greater energy storage, increases the recrystallization nucleation rate during solution treatment, and forms extremely fine grains, further improving the alloy's strength. Anti-fatigue performance; the process method of the invention is simple, convenient to operate, cost saving, and suitable for industrial application.

Description

A Method for Improving the Fatigue Resistance of Al-Cu-Mg Alloy

technical field

The invention relates to a processing method of an Al-Cu-Mg alloy, in particular to a method for improving the anti-fatigue performance of the Al-Cu-Mg alloy; it belongs to the technical field of nonferrous metal processing.

technical background

Al-Cu-Mg series alloys are precipitation-hardening aluminum alloys widely used in aerospace because of their medium strength, good toughness and excellent fatigue resistance. They are especially often used as aircraft skin materials and are extremely important in the aviation field. status. However, the rapid development of composite materials in recent years has brought a greater impact on aluminum alloys, so it is of great significance to further improve the fatigue properties of aluminum alloys.

Studies have shown that in order to improve the fatigue resistance of this aluminum alloy, researches such as alloy impurity elements, atomic cluster size, pre-deformation, Cu-Mg composition ratio, excess phase, electric field effect, etc. have been mainly carried out, and major breakthroughs have been made. . Studies have shown that Al-Cu-Mg alloys with low Cu/Mg composition ratio have more excellent fatigue resistance. In the natural aging state of Al-Cu-Mg alloy with low Cu/Mg composition ratio, the aging precipitation of the alloy is in the precipitation stage of GPB region. The atomic segregation clusters precipitated by natural aging have been proved to be beneficial to the reciprocating slip of dislocations during cyclic loading, thereby reducing the fatigue damage of the alloy. In addition, the effects of excess phase, impurity, and temperature on the size of atomic clusters, the electric field effect of atomic segregation, and the influence of dislocations introduced by pre-deformation on slip under alternating stress have also been studied.

However, many of the above studies are only some aspects of improving the fatigue performance of aluminum alloys. The analysis shows that the fatigue performance of the alloy is directly related to the reciprocating slip of dislocations under alternating stress. The more hindered dislocation slippage is, the faster fatigue damage will accumulate and the higher the propagation rate will be. Studies have shown that dislocation slip is directly related to the special orientation of alloy grains, and the grains with Gaussian texture can increase the crack closure effect of the alloy, thereby reducing the crack growth rate. In contrast, deformation textures such as brass tend to cause cracks to propagate across grain boundaries, which is not conducive to improving the fatigue resistance of the alloy. Current studies have shown that high-density Gaussian textures can be obtained to a certain extent through intermediate annealing, high-temperature solid solution and other processes, and at the same time, the generation of deformation textures such as brass can be suppressed. The emergence of these processes can improve the fatigue resistance of this type of alloy to a certain extent, but the obtained Gaussian texture density is generally relatively low, and there is still a lot of room for improvement. In addition, these technical processes are relatively complicated, require more energy consumption, and are extremely inconvenient for industrial production.

How to obtain a strong Gaussian texture or eliminate (or minimize) the deformation texture is the key to improving the fatigue resistance of this series of aluminum alloys. Therefore, it is necessary to develop a suitable aluminum alloy thermal processing process to eliminate or weaken the brass texture in the alloy and obtain a strong Gaussian texture, and at the same time eliminate the coarse phase in the alloy and reduce the probability of crack initiation. An effective way to resist fatigue performance. It will help to improve the application level of this series of aluminum alloys in the aerospace field, and has far-reaching practical significance.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for improving the fatigue resistance of Al-Cu-Mg alloys with simple process, convenient operation and cost saving; to further improve the fatigue resistance of existing aluminum alloy materials after heat treatment performance.

A method for improving the anti-fatigue performance of Al-Cu-Mg alloys in the present invention is to conduct homogenized Al-Cu-Mg alloys in sequence to high-temperature hot rolling, first solution treatment, large deformation cold rolling, and second solid solution treatment. Solvent treatment, natural aging treatment.

The invention discloses a method for improving fatigue resistance of Al-Cu-Mg alloy. The high-temperature hot rolling process is as follows: the hot rolling temperature is 430-490°C, the holding time is 20 minutes-4 hours, and the hot-rolling deformation is 30-60%.

The present invention is a method for improving the fatigue resistance of Al-Cu-Mg alloy. The first solution treatment and the second solution treatment process are: solution temperature 470-500°C, holding time 5 minutes-2 hours, water Quenching.

The invention discloses a method for improving the anti-fatigue performance of Al-Cu-Mg alloy. The large deformation cold rolling process is: the cold rolling deformation is 50%-90%.

The invention discloses a method for improving the anti-fatigue performance of Al-Cu-Mg alloy, wherein the secondary solid solution treatment adopts salt bath heating.

The invention discloses a method for improving the fatigue resistance of an Al-Cu-Mg alloy. The natural aging is placed at normal temperature for 50-200 hours.

The present invention is a method for improving the fatigue resistance of Al-Cu-Mg alloy. In the Al-Cu-Mg alloy, the mass percent content of each component is: Cu3.0-4.9%, Mg1.0-1.8%, Mn0. 3-1.0, the balance is Al.

Mechanism of the present invention and advantage are briefly described below:

The invention makes the dynamic recrystallization of the alloy occur through the high-temperature hot rolling process, so that the dynamic recrystallization of the alloy is fully completed during the rolling process, thereby forming more recrystallization textures with certain orientations such as Goss and Cube. The strength of textures such as Goss and Cube is directly related to the fatigue performance of materials. For alloys with strong Gaussian texture, more {111} planes in the grains are in or close to the direction of the maximum applied shear stress, which is conducive to the reciprocating slip of dislocations, making it easier for the alloy to generate resident slip bands, thus Enhance the plasticity-induced closure effect of fatigue cracks, reduce damage accumulation, and promote crack deflection, thereby reducing the fatigue crack growth rate of the alloy and effectively improving the fatigue resistance of the alloy.

Solution treatment before cold rolling will allow the coarse second phase particles except Fe and Si impurities to dissolve back, avoiding the formation of high-energy regions, thereby helping to eliminate the occurrence of uneven recrystallization and avoid the formation of uneven recrystallization; Because the formation of inhomogeneous recrystallization is conducive to the generation of deformation textures such as Brass, the existence of this texture will cause fatigue cracks to propagate across boundaries, which is not conducive to improving fatigue performance. Therefore, solution treatment before cold rolling can further improve the fatigue resistance of the material.

Subsequent cold rolling with a large amount of deformation is conducive to the generation of a large number of dislocations in the material, the interaction of dislocations is enhanced, and it is easy to form dislocation plugging and dislocation delivery, forming a large energy storage, which increases the recrystallization nucleation rate , forming fine grains. Fatigue cracks need to pass through more grain boundaries under fine grains, with large obstacles and low crack growth rate, which is conducive to the improvement of fatigue performance.

The final high-temperature short-term solution treatment in salt bath is conducive to the formation of recrystallization texture, and the stronger some orientations (such as Goss and Cube) are, the more conducive to the fatigue performance of the material.

To sum up, the process of the present invention is simple and reasonable. Through high-temperature hot rolling and solid solution before cold rolling, the alloy obtains a high-density Goss texture and a grain distribution that is conducive to dislocation reciprocating slippage and fatigue crack closure. . The Al-Cu-Mg alloy has higher fatigue resistance and is suitable for industrial applications.

Description of drawings

Accompanying drawing 1 is the fatigue expansion rate curve of embodiment 2,3,6,7 of the present invention

Accompanying drawing 2 is the metallographic structure of Example 2 of the present invention which adopts medium-temperature hot rolling + annealing after cold rolling + solution quenching and aging process.

Accompanying drawing 3 is the metallographic structure of Example 3 of the present invention treated by medium temperature hot rolling + solution + solution quenching and aging before cold rolling.

Accompanying drawing 4 is the metallographic structure of Example 6 of the present invention treated by high-temperature hot rolling + annealing after cold rolling + solution quenching and aging process.

Accompanying drawing 5 is the metallographic structure of Example 7 of the present invention treated by high temperature hot rolling + solution + solution quenching before cold rolling and aging process.

Accompanying drawing 6 is the orientation distribution function diagram of Example 2 of the present invention which adopts medium-temperature hot rolling + annealing after cold rolling + solution quenching and aging process.

Accompanying drawing 7 is the orientation distribution function diagram of Example 3 of the present invention treated by medium-temperature hot rolling + solution before cold rolling + solution quenching and aging process.

Accompanying drawing 8 is the orientation distribution function graph of embodiment 6 of the present invention treated by high temperature hot rolling + annealing after cold rolling + solution quenching and aging process.

Accompanying drawing 9 is the orientation distribution function diagram of Example 7 of the present invention treated by high temperature hot rolling + solution + solution quenching and aging before cold rolling.

In Figure 1:

Curve A is the fatigue growth rate curve of Example 2, and the treatment process is: medium temperature hot rolling+annealing after cold rolling+solution quenching and aging;

Curve B is the fatigue growth rate curve of Example 3, and the treatment process is: medium temperature hot rolling + solution before cold rolling + solution quenching aging;

Curve C is the fatigue growth rate curve of Example 6, and the treatment process is: high temperature hot rolling+annealing after cold rolling+solution quenching and aging;

Curve D is the fatigue growth rate curve of Example 7, and the treatment process is: high temperature hot rolling + solution before cold rolling + solution quenching and aging;

As can be seen from Fig. 1, the expansion rate of the alloy provided by the present invention through high-temperature hot rolling is obviously lower than that of the alloy treated by medium temperature hot rolling, and the fracture toughness and fatigue resistance of the alloy can be improved to a large extent, as shown in the examples 7 and embodiment 3 or embodiment 6 and embodiment 2;

The fatigue performance of the alloy subjected to solution treatment before cold rolling is also significantly higher than that of the alloy without solution treatment before cold rolling, such as Example 7 and Example 6 or Example 3 and Example 2.

It can be seen from Figure 2-5 that the metallographic structure of the alloy treated by high temperature hot rolling is relatively finer than that of alloy treated by medium temperature hot rolling, even about half of the grain size of other processes. To a certain extent, the finer the grain, the fatigue crack growth will be hindered, and the fatigue growth rate will be reduced. At the same time, the grain refinement will increase the strength of the alloy.

It can be seen from Figures 6-9 that the Goss texture density (3.72) of the alloy after high-temperature hot rolling is improved, while the rolling texture of brass and the like is reduced, and the fatigue performance is improved.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Table 1 shows the mechanical properties of the aluminum alloys treated in Examples 1-9 of the present invention.

Example 1

The alloy composition is: 3.8%Cu, 1.0%Mg, 0.3%Mn, and the balance is Al-Cu-Mg alloy homogenized. After the ingot is kept at 430°C for 1 hour, it is directly hot-rolled with 70% deformation. Then, it was subjected to air solution treatment at 470°C for 1 hour and water quenched, followed by cold rolling with 80% deformation, and then subjected to 470°C salt bath solution treatment for 20 minutes and then natural aging treatment after water quenching. The tensile strength is 456MPa, the yield strength is 327MPa, and the elongation is 23%. When the stress expansion factor ΔK=33MPa*m ^1/2 , the expansion rate of the alloy is 0.00595mm/cycle.

Example 2

The alloy composition is: 4.4% Cu, 1.3% Mg, 0.45% Mn, and the Al-Cu-Mg alloy with the balance of Al is homogenized. After the ingot is kept at 440°C for 1 hour, it is directly hot-rolled with 70% deformation. After that, cold rolling with 80% deformation is carried out, followed by annealing treatment at 400°C for 1 hour, and then natural aging treatment after water quenching for 20 minutes in a salt bath at 490°C. The tensile strength is 476MPa, the yield strength is 334MPa, and the elongation is 23.2%. When the stress expansion factor ΔK=33MPa*m ^1/2 , the expansion rate of the alloy is 0.00335mm/cycle respectively.

Example 3

The alloy composition is: 4.9% Cu, 1.5% Mg, 0.8% Mn, and the Al-Cu-Mg alloy with the balance of Al is homogenized. After the ingot is heated at 440°C for 1 hour, it is directly hot-rolled with 70% deformation. Then air solution treatment at 490°C for 1 hour and water quenching followed by cold rolling with 80% deformation, followed by natural aging treatment at 490°C salt bath for 20 minutes after water quenching. The tensile strength is 475MPa, the yield strength is 331MPa, and the elongation is 22.3%. When the stress expansion factor ΔK=33MPa*m ^1/2 , the expansion rate of the alloy is 0.0043mm/cycle.

Example 4

The alloy composition is: 3.8%Cu, 1.8%Mg, 1.0%Mn, and the balance is Al-Cu-Mg alloy. After the ingot is homogenized, the ingot is kept at 450°C for 1 hour and then directly hot-rolled with 50% deformation. Then, it was subjected to air solution treatment at 480°C for 1 hour and water quenched, followed by cold rolling with 90% deformation, followed by natural aging treatment at 480°C salt bath for 20 minutes after water quenching. The tensile strength is 465MPa, the yield strength is 320MPa, and the elongation is 22%. When the stress expansion factor ΔK=33MPa*m ^1/2 , the expansion rate of the alloy is 0.0049mm/cycle.

Example 5

The alloy composition is: 3.8% Cu, 1.0% Mg, 0.3% Mn, and the Al-Cu-Mg alloy with the balance of Al is homogenized. After the ingot is kept at 460°C for 1 hour, it is directly hot-rolled with 50% deformation. Then, it was subjected to air solution treatment at 480°C for 1 hour and water quenched, followed by cold rolling with 90% deformation, followed by natural aging treatment at 480°C salt bath for 20 minutes after water quenching. The tensile strength is 477MPa, the yield strength is 330MPa, and the elongation is 22%. When the stress expansion factor ΔK=33MPa*m ^1/2 , the expansion rate of the alloy is 0.0055mm/cycle respectively.

Example 6

The alloy composition is: 3.8% Cu, 1.0Mg, 0.45% Mn, and the Al-Cu-Mg alloy with the balance of Al is homogenized. After the ingot is cast at 490 ° C, it is directly hot-rolled with 50% deformation, and then 90 % deformation of cold rolling, annealing at 400°C for 1 hour, and finally a solution in a salt bath at 490°C for 20 minutes and then natural aging treatment after water quenching. The tensile strength is 488.5MPa, the yield strength is 335MPa, and the elongation is 25.03%. When the stress expansion factor ΔK=33MPa*m ^1/2 , the expansion rate of the alloy is 0.0029mm/cycle respectively.

Example 7

The alloy composition is: 3.8%Cu, 1.3%Mg, 0.45%Mn, and the balance is Al-Cu-Mg alloy. After the ingot is homogenized, the ingot is kept at 490°C for 1 hour and then directly hot-rolled with 50% deformation. Then, it was subjected to air solution treatment at 490°C for 1 hour and then water quenched, followed by cold rolling with a deformation of 90%, followed by natural aging treatment after 490°C salt bath solution treatment for 20 minutes and water quenching. The tensile strength is 493.6MPa, the yield strength is 338MPa, and the elongation is 24.33%. When the stress expansion factor ΔK=33MPa*m ^1/2 , the expansion rate of the alloy is 0.00187mm/cycle respectively.

Example 8

The alloy composition is: 4.5% Cu, 1.8Mg, 0.9% Mn, and the Al-Cu-Mg alloy with the balance of Al is homogenized. After the ingot is kept at 480°C for 1 hour, it is directly hot-rolled with 50% deformation, and then Air solution treatment at 470°C for 1 hour and water quenching followed by cold rolling with 90% deformation, followed by natural aging treatment at 470°C salt bath for 20 minutes after water quenching. The tensile strength is 480MPa, the yield strength is 332MPa, and the elongation is 25%. When the stress expansion factor ΔK=33MPa*m ^1/2 , the expansion rate of the alloy is 0.0069mm/cycle respectively.

Example 9

The alloy composition is: 4.9% Cu, 1.8% Mg, 1.0% Mn, and the Al-Cu-Mg alloy with the balance of Al is homogenized. After the ingot is kept at 490°C for 1 hour, it is directly hot-rolled with 50% deformation. Then, it was subjected to air solution treatment at 490°C for 1 hour and then water quenched, followed by cold rolling with a deformation of 90%, followed by natural aging treatment after 490°C salt bath solution treatment for 20 minutes and water quenching. The tensile strength is 470MPa, the yield strength is 330MPa, and the elongation is 23%. When the stress expansion factor ΔK=33MPa*m ^1/2 , the expansion rate of the alloy is 0.0070mm/cycle respectively.

The mechanical property contrast of table 1 alloy of the present invention

Example σ _b /MPa σ _0.2 /MPa δ/%da/dN (mm/cycle) Example 1 456.0 327.0 23.0(△K=33MPa*m ^1/2 )0.00595 Example 2 475.0 331.0 22.3(△K=33MPa*m ^1/2 )0.00335 Example 3 476.0 334.0 23.2(△K=33MPa*m ^1/2 )0.00432 Example 4 465.0 320.0 22.0(△K=33MPa*m ^1/2 )0.0049 Example 5 477.0 333.0 22.0(△K=33MPa*m ^1/2 )0.0055 Example 6 488.5 335.0 25.3(△K=33MPa*m ^1/2 )0.0029 Example 7 493.6 338.0 24.3(△K=33MPa*m ^1/2 )0.00187 Example 8 480.0 332.0 25.0(△K=33MPa*m ^1/2 )0.0069 Example 9 470.0 330.0 23(△K=33MPa*m ^1/2 )0.0070

It can be seen from Table 1 that the heat treatment process provided by the present invention not only improves the strength of the alloy, but also significantly improves the fracture toughness and fatigue resistance of the alloy, broadening its application range.

Claims (2)

1. A method for improving the fatigue resistance of Al-Cu-Mg alloys is to carry out high-temperature hot rolling successively to the Al-Cu-Mg alloy after the homogenization treatment, once solution treatment, large deformation cold rolling, and secondary solidification Solvent treatment, natural aging treatment; The high-temperature hot-rolling process is: hot-rolling temperature 440-490°C, holding time 20 minutes-4 hours, hot-rolling deformation 30-60%; The primary solid solution treatment and secondary solid solution treatment processes are: solution temperature 470-500°C, holding time 5 minutes-2 hours, water quenching; The large deformation amount cold rolling process is: cold rolling deformation amount 50%-90%; The natural aging is placed at room temperature for 50-200 hours; In the Al-Cu-Mg alloy, the mass percentage content of each component is: Cu3.0-4.9%, Mg1.0-1.8%, Mn0.3-1.0%, and the balance is Al. 2. A method for improving the fatigue resistance of Al-Cu-Mg alloy according to claim 1, characterized in that: said secondary solution treatment adopts salt bath heating.