KR101226484B1 - Multiple-heattreatment method of indium bearing 2090 alloy - Google Patents

Abstract

The present invention relates to a heat treatment method for improving the elongation of 2090 aluminum alloy used in aircraft, missiles, lightweight armor materials and various military supplies, heat treatment of 2090 aluminum alloy that can have a value higher than the elongation obtained by the existing heat treatment process Provide a method.
In the heat treatment method of the 2090 aluminum alloy according to the present invention for achieving the above object, by adding 0.04 to 0.08 wt% of indium to the 2090 aluminum alloy, two-stage aging after solution treatment (160 ~ 190 ℃, 9 to 30 hours + 130 ℃, 165 hours) or three stages of aging (160 to 190 ℃, 9 to 30 hours + 90 to 110 ℃, 3 to 5 hours + 145 to 150 ℃, 30 to 48 hours) relates to an aging heat treatment method Or, after the three-stage aging treatment, there is a markedly increased elongation of 7.9-13.1% with no decrease in strength compared to the elongation (0.5-6.5%) of the conventional heat treatment method.

Description

MULTIPLE-HEATTREATMENT METHOD OF INDIUM BEARING 2090 ALLOY}

The present invention adds indium to the 2090 aluminum alloy used for aircraft parts, missiles, lightweight armor materials and various military supplies to adequately control the change in precipitation occurring in the 2090 aluminum alloy, and the elongation is remarkably similar to that obtained in the existing heat treatment process. The present invention relates to a new heat treatment step to be raised, and more particularly, to a heat treatment method of a 2090 aluminum alloy capable of exhibiting an elongation of 7.9 to 13.1% higher than an elongation of 0.5 to 6.5% obtained by a conventional heat treatment process.

Lithium (symbol of element: Li) is about 3% per 1wt% Li added if the specific gravity of the addition of lithium because the specific gravity of aluminum, since only about 1/5 of 2.7g / cm ³ as 0.53g / cm ³ for Al As the weight of aluminum is reduced, the application of aluminum-lithium alloy to military parts such as aircraft, missiles and armored vehicles, which are required for lightweighting, contributes to the improvement of the performance of the weapon system and the reduction of fuel costs. In addition, the elastic modulus of about 6% per 1wt% of lithium is increased, which is very effective for problems such as fatigue and vibration, which are indispensable in aircraft structural materials.

However, aluminum-lithium alloys have the biggest problem of low toughness and ductility. The reason for this is that the plastic deformation of metastable phase δ '(Al ₃ Li) precipitated during aging, that is, the interfacial energy of the δ' precipitated phase with LI ₂ regular structure is low, so it is easily sheared by dislocations and also has a matching relationship with the mother phase. Since the slip plane coincides with the δ 'phase, which is a regular phase, as it is precipitated, cross slips because the dislocation moves as a superlattice dislocation when shearing and advancing the δ' phase, which has a regular potential during plastic deformation. ) Or dislocation rise (climb) is difficult to occur and the slip is concentrated on the same slip surface. This planar slip is increased to cause stress concentration at the grain boundary, and as a result, cracks occur at the intersection between the slip surface and the grain boundary, so that cracks propagate along the grain boundary or slip surface and fracture occurs.

Many efforts have been made to solve the problems of low ductility and low toughness. Among them, a representative method is to precipitate other precipitates other than the δ 'phase at the same time to directly change the precipitation behavior of the δ' phase or to make it stronger than the δ 'phase. Research is being conducted to uniformly disperse the strain by dispersing the two phases on a matrix. Representative alloying elements added for this purpose are magnesium (Mg) and copper (Cu). Since magnesium has a very high solubility in aluminum, it is known that the supersaturation degree is low and does not significantly affect the precipitation behavior of the δ 'phase. However, the presence of magnesium has been reported to affect the strengthening of precipitation by affecting the solubility of lithium. When copper is added, the reinforcing mechanism is greatly changed since the θ 'phase (Al ₂ Cu) and the T ₁ phase (Al ₂ CuLi), which is a ternary phase, are precipitated simultaneously in addition to the δ' phase.

However, in the conventional solution treatment-aging heat treatment method, since the T ₁ phase is not finely and uniformly distributed in the matrix and copper and lithium are locally segregated and coarsened by the lamination defect mechanism on the 111 side of the matrix, In order to distribute uniformly and finely, aging treatment is usually performed after introduction of cold working after solution treatment. When cold working, dislocations are introduced to facilitate the precipitation of the T ₁ phase and the θ 'phase through the dislocations, thereby obtaining a fine T ₁ phase and the θ' phase after the final heat treatment. As another heat treatment method, the solution of 2090 aluminum alloy is subjected to room temperature aging and cold working, and then aged at 120 ° C. for 24 hours to precipitate the δ 'phase, and then to dissolve the δ' phase to re-use the precipitated δ 'phase. It is kept for a short time (1 minute) at about 270 degreeC or more which is more than temperature. Thereafter, in order to precipitate the fine δ 'phase and the T ₁ phase again, the aging heat treatment was performed at about 200 ° C. for a short time (20 minutes).

However, the introduction of cold working is often difficult in special cases, for example, in the case of complicated shapes of extruded products, forged products, and superplastic molded parts, and the method of reapplying the δ 'phase at a high temperature has a very short heat treatment time. It can be applied in the case of thin plate, but not in the case of thick plate. Therefore, in order to expand the application of the aluminum-lithium alloy, the T ₁ phase and the θ 'phase are finely precipitated without introducing cold processing after the solution treatment and without being held at high temperature for a short time in order to redistribute the δ' phase. Obtaining strength and elongation will extend the application of aluminum-lithium alloys.

The present invention has been proposed to solve the above-mentioned problems. The purpose of the present invention is to add an indium to 2090 aluminum alloy to change the precipitation behavior, thereby deriving an optimal aging heat treatment condition, which results in a higher elongation than the conventional 2090 aluminum alloy heat treatment method. To provide a greatly improved heat treatment method of 2090 aluminum alloy.

In the heat treatment method of the 2090 aluminum alloy according to the present invention, indium in a 2090 aluminum alloy composed of lithium: 1.9 to 2.6%, copper: 2.4 to 3.0%, zirconium: 0.08% to 0.15%, and the rest of aluminum and unavoidable impurities. An alloy to which 0.04 to 0.08 wt% is added is prepared and subjected to two-stage or three-stage aging treatment after the alloy is subjected to solution treatment.

According to a preferred embodiment of the present invention, the two-stage aging may be made of heat treatment of 160 ~ 190 ℃, 9 ~ 30 hours + 120 ~ 140 ℃, 100 ~ 165 hours.

According to a preferred embodiment of the present invention, the three stage aging may be made of heat treatment of 160 ~ 190 ℃, 9 ~ 30 hours + 90 ~ 110 ℃, 3 ~ 5 hours + 145 ~ 155 ℃, 30 ~ 48 hours.

According to the heat treatment method of the 2090 alloy to which indium is added according to the present invention, after the two-stage or three-stage aging treatment, there is a markedly increased elongation without decreasing the strength compared to the elongation of the conventional heat treatment method.

FIG. 1 shows the results of differential scanning thermal analysis of a 2090 alloy in which water is cooled and a 2090 alloy added with indium after solution treatment at 540 ° C. FIG.
FIG. 2 is a transmission electron microscope structure after 24 hours aging showing that the 2090 alloy is aged at 190 ° C. by the conventional method and exhibits the highest hardness. FIG.
3 is a transmission electron microscope structure after 9 hours of aging showing the highest hardness when the 2090 alloy added with 0.08wt% indium is aged at 190 ° C.
Figure 4 is a transmission electron microscope structure of the specimen by a three-stage aging treatment method (190 ℃, 9hr + 100 ℃, 3hr + 150 ℃, 48hr) 2020 alloy added 0.04wt% indium according to an embodiment of the present invention to be.

In the present invention for achieving the above object, in the aging heat treatment method of 2090 aluminum alloy, the material used is 2090 aluminum alloy which is applied to aircraft, missile, armored vehicle parts, etc. in weight% of lithium: 1.9-2.6%, copper: 2.4 -3.0%, zirconium: 0.08-0.15% and the remaining aluminum. Indium was added 0.04wt% to 0.08wt% to the 2090 aluminum alloy having this composition, followed by solution treatment at 540 ℃ (1 hour per 25mm thickness), followed by two-stage aging (160 ~ 190 ℃, 9 ~ 30 hours + 120 ~). 140 ℃, 100-165 hours) or three-stage aging (160-190 ℃, 9-30 hours + 90-110 ℃, 3-5 hours + 145-155 ℃, 30-48 hours) And a method for producing a 2090 aluminum alloy having an elongation of 7.9 to 13.1% without a decrease in strength compared to the elongation (0.5 to 6.5%) of the conventional method after the two-stage or three-stage aging heat treatment.

Table 1 shows the composition of the 2090 alloy used in the present invention.

Herein, the characteristics and effects of indium according to the temperature and time set during the two-stage and three-stage aging will be described as follows.

FIG. 1 shows the results of differential scanning thermal analysis of a 2090 alloy in which water is cooled and a 2090 alloy added with indium after solution treatment at 540 ° C. FIG. All three exothermic and three endothermic reactions occur. 2090 alloy is precipitated by the process of α (supersaturated solid) → GP zone → δ '→ θ' + T ₁ → T ₁ , and exothermic a is GP zone when compared with the differential scanning curve analysis in this experiment. , Exothermic c is believed to be due to the generation of the δ 'phase and exothermic e is due to the generation of the θ' phase and the T ₁ phase, and endotherms b, d and f are dissolved in the GP zone, δ 'phase and θ' + T ₁ , respectively. Judging by

As shown in Fig. 1, the addition of indium delays the precipitation of the GP zone and the δ 'phase, and the amount produced is also small. On the other hand, the formation of θ '+ T ₁ phase is shifted to a low temperature by the addition of indium, and formed in a narrow temperature range, it is inferred that the size of the precipitate is very fine. Thus, the θ 'phase and the T ₁ phase are finely precipitated by aging at 160 to 190 ° C for 9 to 30 hours, so that the lithium contributes to the formation of the T ₁ phase and the remaining lithium is produced as a fine δ' phase. It ages for 100 to 165 hours at 120-140 degreeC phosphorus. In three-stage aging, θ 'phase, which is a high temperature precipitated phase and T ₁ phase, is finely precipitated at 160 to 190 ° C for 9 to 30 hours of aging, and then aged at 3-5 ° C for 90 hours at a lower temperature, δ' Induction of phase nucleation and aging at 145-155 ° C. for 30-48 hours resulted in the same effect as two-stage aging and shortening of time.

If the weight ratio of indium is less than 0.04 wt%, the amount of insoluble solute atoms of indium in aluminum is small, which does not significantly affect the promotion of precipitation, and if it exceeds 0.08 wt, indium atoms larger than aluminum atoms are not dissolved and are in the grain boundary. Excessive presence promotes grain boundary breakdown, leading to a decrease in elongation.

[ Example  One]

Table 2 shows the results of comparing the mechanical properties of the test specimen to which the conventional aging treatment method and the aging treatment method proposed in the present invention are applied.

In the conventional method, the T6 treatment for aging after solution treatment and the cold treatment after solution treatment for 3 to 5% increase the nucleation position of the precipitated phase, and the T8 treatment for aging is mainly performed and the elongation is 0.5 to 6.5. % Level, even in complex processes such as the conventional heat treatment method (5) incorporating room temperature aging and cold working, the elongation is about 5 to 6%. There are disadvantages applicable.

In the heat treatment method of the present invention, the elongation is increased to 7.9 to 13.1% without deterioration of strength by adding indium and performing two-stage and three-stage heat treatment without cold working after the solution treatment.

[Example 2]

FIG. 1 shows the results of differential scanning sequence analysis after solution treatment of a 2090 alloy to which a 2090 alloy and indium are added by a conventional method and a method of the present invention. It can be inferred that, in the 2090 alloy (B) to which indium was added rather than the 2090 alloy (A), "e", which is a production peak of the θ 'phase and the T ₁ phase, exhibits a large heat generation in a narrow temperature range and is very finely generated and precipitated.

[Example 3]

2 is a transmission electron microscope structure taken at 50,000 times after 24 hours aging showing the highest hardness when the 2090 alloy is aged at 190 ° C. by a conventional method. (A) of Figure 2 [100] dark field image, (b) on the shaft of the constant δ in (zone axis) 'a and θ' is the [100] T ₁ is implied on the field image in the forward shaft of. The δ 'phase is spherical and the T ₁ , θ' phase is plate-shaped. Number per unit area on the T ₁ and θ 'are each 31 / ㎛ ^2, 22 gae / ㎛ ² Considering only the precipitated phase generated by the one of the specific surface (variant).

Example 4

3 is a transmission electron microscope structure taken at 100,000 times after 9 hours aging showing the highest hardness when the 2090 alloy added with 0.08wt% indium is aged at 190 ° C. (A) is a dark field image of (theta) 'phase in a [100] azimuth axis, (b) is a dark field image of the T ₁ phase in a [100] axial axis. In this case, considering only the precipitated phase generated from one specific surface, the number of T ₁ and θ 'phases per unit area is 350 pieces / μm ² and 700 pieces / μm ² , respectively. It can be seen that due to the addition, the T ₁ phase and the θ 'phase are finely and uniformly distributed. In addition, when indium is not added, the δ 'phase exists as in FIG. 2, but when the indium is added, the δ' phase is not observed.

[Example 5]

FIG. 4 is a transmission electron image taken at 100,000 times of a specimen subjected to three stages of aging (190 ° C, 9hr + 100 ° C, 3hr + 150 ° C, 48hr) after solution treatment of a 2090 alloy containing 0.04wt% indium by the method of the present invention. Microscopic tissue. (a) is the θ 'phase and the δ' phase in the [100] axle axis, and (b) is the T ₁ phase in the [100] axle axis. Compared with the case where the indium of FIG. 2 is not added, the δ 'phase and the θ' phase are very small and fine, and the T ₁ phase tends to be the same. Here, the θ 'phase and the T ₁ phase are produced at the first stage (190 ℃, 9hr) aging, and the fine δ' phase is nucleated at the second stage (100 ℃, 3hr) aging and grown at the third stage (150 ℃, 48hr) aging. It seems to be. Although the δ 'phase was not observed in FIG. 3, which is a T6 treated tissue when indium was added, a very fine δ' phase is observed in the three-stage aging of FIG.

As mentioned above, although preferred embodiment of this invention was described, the scope of the present invention is not limited only to this embodiment, It can be variously modified without departing from the essential and essential structure of this invention. Accordingly, the foregoing embodiments in the present invention are merely exemplary and should not be construed as having a limiting meaning, the scope of the present invention including matters set forth in the appended claims and all modifications that may be understood therefrom. It should be understood that.

Claims (4)

By weight, in a 2090 aluminum alloy composed of lithium: 1.9 to 2.6%, copper: 2.4 to 3.0%, zirconium: 0.08% to 0.15%, and the remaining aluminum and unavoidable impurities, inhibits the formation of the δ 'phase during the first stage of aging treatment. To prepare an alloy in which 0.04 to 0.08 wt% of indium was added so as to be solvated, a two-stage aging treatment was performed after solution treatment.
The two-stage aging heat treatment,
The heat treatment method of 2090 aluminum alloy comprising the heat treatment at 160 to 190 ℃ for 9 to 30 hours as the first step, and 100 to 165 hours at 120 to 140 ℃ as a second step. delete In terms of weight percent, an alloy containing indium was added in an amount of 0.04 to 0.08 wt% to a 2090 aluminum alloy composed of lithium: 1.9 to 2.6%, copper: 2.4 to 3.0%, zirconium: 0.08% to 0.15%, and the remaining aluminum and inevitable impurities. After the solution treatment, three-stage aging treatment,
The three-stage aging heat treatment,
9 to 30 hours of heat treatment at 160 to 190 ° C as the first step, 3 to 5 hours of heat treatment at 90 to 110 ° C as the second step, and 30 to 48 hours at 145 to 155 ° C as the third step Heat treatment method of a 2090 aluminum alloy comprising a. A 2090 aluminum alloy produced according to the method of claim 1.

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