CN1834277A - High Zn content, superstrength and supertoughness, high destroy limit type aluminium alloy material and prepn. method - Google Patents

Abstract

The invention discloses an ultra-high-strength, high-toughness and high damage-tolerance aluminum alloy material with (9-10)wt% Zn content and a preparation method thereof. The alloy composition is 9-10wt% Zn, Mg2. 0-2.5wt%, Cu 1.2-1.7wt%, Zr 0.2-0.5wt%, Fe<0.05wt%, Si<0.05wt%, and the rest is Al. The ingredients are distributed according to the alloy composition, the raw materials are melted, and cast into alloy prefabricated ingots. The alloy prefabricated ingot is melted at 780-800° C., and an inert gas is used as an atomizing gas to perform rapid solidification spray forming, and the atomizing pressure is 0.5-1.0 MPa. The high-strength and high-toughness aluminum alloy material with (9-10) wt% Zn content of the invention has uniform alloy composition, uniform microstructure, fine structure and no segregation. The material is deformed by hot extrusion or hot forging, and after reasonable heat treatment, the ultimate tensile strength of the material can reach more than 750MPa, and the elongation of the material remains at 8-11%. At the same time, its fracture toughness and fatigue performance are better than 7050T74 Material. The material can be applied to key structural components in aerospace, nuclear industry, military industry and other fields.

Description

High Zn content ultra-high strength, high toughness and high damage tolerance aluminum alloy material and preparation method

technical field

The invention relates to an aluminum alloy, especially a high-strength, high-toughness, high-damage-tolerance aluminum alloy material with a strength above 750 MPa and high fracture toughness and fatigue performance, and a preparation method thereof.

Background technique

As the most typical lightweight material among metal materials, aluminum alloy has the advantages of low specific gravity, easy processing, and low cost, and has always been a key dual-use material for military and civilian use. Aluminum alloy is the second largest metal structural material after steel, and high strength and high toughness are the eternal development direction of aluminum alloy. If the ultimate tensile strength of aluminum alloy reaches 800MPa, its specific strength value will reach 300MPa cm ³ / g (for the specific strength value of 300MPa.cm ³ /g, it means that the steel material requires a strength of 2350MPa, and the titanium alloy reaches 1450MPa), which will become one of the metal structural materials with the highest specific strength at present.

The 7000 series (AlZnMgCu series) high-strength aluminum alloy is a kind of aluminum alloy material developed and developed in the background of aerospace materials. It has been widely used in various aircraft fuselages, wing beams, cabin panels, nuclear industry and The manufacture of high-strength structural parts in rockets is an indispensable and important material in the aerospace industry of various countries in the world.

For a long time, in the process of developing and producing 7000 series ultra-high-strength alloys using traditional ingot metallurgical technology, it was found that with the increase of the total content of main alloying elements (Zn, Mg, Cu) and the improvement of alloying degree, the aging strengthening in the final alloy The phase volume fraction increases, and the performance of the material can be improved to a certain extent. However, when the total content of the main alloying elements (Zn, Mg, Cu) exceeds a certain limit, due to the limitation of the solidification cooling rate of the traditional billet making process (generally not exceeding 10K/s), a large number of coarse primary precipitates will be formed in the alloy. It is difficult for the precipitated phase to dissolve back into the matrix through subsequent solution treatment, which will not further increase the volume fraction of the aging-strengthened phase in the final alloy, but will deteriorate the properties of the material. Therefore, when using traditional ingot metallurgy and deformation processing techniques to produce 7000 series aluminum alloys, the total content of the main alloying elements (Zn, Mg, Cu) in the alloy is generally controlled to be no more than 12-13wt%. The ultimate tensile strength (σ _b ) of such alloys produced in the world has been hovering around 500-600MPa for a long time.

After entering the 1980s, with the development of rapid solidification/powder metallurgy (RS/PM, Rapidly solidified technology/Powder metallurgy) technology, it became possible to develop a new generation of rapidly solidified 7XXX series ultra-high-strength aluminum alloys. After the rapid solidification process is adopted, even if the limit of the total content of the main alloy elements is 12-13wt%, the composition design of the new alloy is carried out, because the solidification speed in the billet making process is significantly accelerated (up to 10 ³ -10 ⁶ K/s or more), During the billet making process, the solid solubility of alloying elements increases, generally there will not be a large amount of coarse primary precipitates, and the structure can be significantly refined, so it is conducive to the formation of a higher volume fraction of aging strengthening phases and fine grains in the final alloy organization, the final performance of the material can be greatly improved. Applying rapid solidification technology to the preparation of high-strength aluminum alloy can greatly improve the performance of the material, and the ultimate tensile strength can be increased from 600MPa to more than 800MPa, making the performance of the material reach a new level.

In the mid-1990s, industrially developed countries represented by the United States and Germany have successfully developed and prepared 800MPa strength level rapid solidification ultra-high strength 7000 series aluminum alloys by using spray forming technology in the mid-1990s. The content is much higher than that of various 7000-series aluminum alloys produced by traditional processes, and can be mass-produced. The main performance indicators of its extruded materials can reach: yield strength above 750MPa, ultimate tensile strength above 800MPa, elongation 4-6%, the fracture toughness is not less than 21-22MPa*m1/2, and the elastic modulus is not less than 72GPa. Its main applications include various light-weight and high-strength parts in missiles and rockets, high-speed train hooks, and racing cars. key components, etc.

However, there are also obvious deficiencies in the development process of the above-mentioned rapid solidification ultra-high-strength 7000 series aluminum alloys, which are reflected in the relatively weak optimization design of alloy components. The current production of alloys has low elongation, poor fracture toughness and fatigue resistance, making it difficult to To meet the requirements of high damage tolerance, high reliability, high safety, and long life in the development of a large number of new-generation aerospace equipment, the application range of alloys is limited.

The patent application unit previously applied for an ultra-high-strength and high-toughness aluminum alloy material with a Zn content of (10-11) wt% and its preparation method. get practical application. However, as mentioned above, in some occasions that need to emphasize high fracture toughness, high fatigue performance, and high damage tolerance performance (for example, in the aerospace field), the application of such materials is greatly restricted. It is precisely based on the above knowledge and needs that the patent application unit has carried out targeted research and achieved good results, so this patent is applied for.

In addition, at present, industrially developed countries still adopt the form of KnowHow to protect the complete set of technology for preparing ultra-high-strength 7000-series aluminum alloy materials by spray forming, and no patent has been formed so far.

Contents of the invention

The object of the present invention is to provide an ultra-high-strength, high-toughness and high-damage-tolerance aluminum alloy material with an ultimate tensile strength of more than 750 MPa. The strength of the new alloy is more than 30% higher than that of traditional high-strength, high-toughness aluminum alloys.

Another object of the present invention is to provide a method for manufacturing an ultra-high-strength, high-toughness, and high damage-tolerant aluminum alloy material with an ultimate tensile strength above 750 MPa.

To achieve the above object, the present invention takes the following technical solutions:

The ultra-high-strength, high-toughness and high damage-tolerance aluminum alloy material of the present invention with an ultimate tensile strength above 750 MPa has an alloy composition of 9-10 wt% Zn, 2.0-2.5 wt% Mg, and 1.2-1.7 wt% Cu , Zr 0.2-0.5wt%, Fe<0.05wt%, Si<0.05wt%, and the rest is Al. The material has a uniform microstructure, fine grains, and no obvious micro and macro segregation. Through proper heat treatment, the main mechanical properties of the material can reach: σ _b ＝750～780Mpa, σ _0.2 ＝720～750MPa, δ ₅ ＝8～11%, K _IC (MPa*m ^1/2 )≥31, da/dN≤ 6×10 ⁻³ mm/cycle.

A method for preparing an ultra-high-strength, high-toughness, and high damage-tolerant aluminum alloy material with an ultimate tensile strength of more than 750 MPa according to the present invention, the method comprising the following steps:

(1) According to the alloy composition, by weight percentage, the alloy composition is: Zn 9~10wt%, Mg2.0~2.5wt%, Cu 1.2~1.7wt%, Zr 0.2~0.5wt%, Fe<0.05wt% , Si < 0.05wt%, and the rest is Al, for batching and preparing prefabricated alloy ingots;

(2) After the alloy prefabricated ingot is melted by heating, inert gas is used to atomize through the atomizing nozzle. The atomizing nozzle scans at a high speed at a frequency of 1-5HZ. The atomizing gas is a high-purity inert gas, and the atomizing pressure is 0.5- 1.0Mpa;

(3) At the same time of aerosolization, the receiving device rotates at a high speed of 60-120rpm under the traction of the frequency conversion motor, and pulls down at an angle of 30-40° and at a speed of 20-40mm/min to make a round ingot ;

(4) Carry out hot extrusion or hot forging process molding, and process into required parts;

(5) The part is subjected to double-stage solid solution and double-stage aging, that is, an ultra-high-strength, high-toughness, and high-damage-tolerant aluminum alloy material with high Zn content is produced.

The Zn, Al, Cu, Mg, and Zr used in the present invention are selected from industrial pure Zn, industrial pure Al, electrolytic Cu, industrial pure Mg, and Al-Zr master alloy respectively.

In the step (1) of the method of the present invention, the process of preparing the prefabricated alloy ingot is to heat up to 850-900°C under the protection of an inert gas to melt the raw materials, mix them uniformly and then cast them into a prefabricated alloy ingot.

In step (2) of the method of the present invention, the process of melting the alloy prefabricated ingot is to put the prefabricated alloy ingot into the non-vacuum injection forming equipment, and to melt the alloy ingot by induction heating to 800-850°C under the protection of the covering agent , keep warm for 10 to 20 minutes to homogenize the alloy melt, and add slag remover and refining agent for degassing and slag refining. The covering agents used are conventional covering agents. The non-vacuum injection molding equipment used is open, that is, induction heating furnaces, induction heating or resistance heating tundishes and other equipment do not need to be sealed, they are open and do not require a vacuum system.

In the step (2) of the method of the present invention, the atomization process is to use an unrestricted airflow atomization nozzle for atomization.

In step (2) of the method of the present invention, the inert gas is argon or nitrogen.

In step (3) of the method of the present invention, the process of making a round ingot is carried out by controlling the scanning of the atomizing nozzle, the shape and the movement of the receiving system, and a round ingot with a typical rapid solidification tissue can be prepared. Ingot (Φ200～300X300～1000mm).

In the step (4) of the method of the present invention, the round ingot is peeled first, and the described process of peeling the round ingot is to use a peeling machine to process and peel off the skin, which can be prepared into a bar blank of a certain specification. And keep it warm at 360-420° C. for 2 hours, and then carry out the process of hot extrusion or hot forging.

In the step (5) of the method of the present invention, the process of heat treating the parts is to carry out two-stage solid solution treatment, so that the primary and secondary precipitated phases are fully redissolved, and then carry out two-stage aging treatment.

The key to this invention lies in the design of the alloy composition, which requires accurate content of each element, high degree of alloying, high content of main alloying elements, emphasizing the auxiliary strengthening of microalloying elements, through spray forming preparation, reasonable thermal deformation processing and heat treatment, to achieve Multi-strengthening phase coupling strengthening, no coarse second phase. At the same time, low Fe and Si impurity content is required to ensure high damage tolerance performance.

Another key factor of the invention is the spray forming preparation technology under the condition of this new alloy, the main technical details include the following:

In order to ensure the accuracy of the alloy composition, the melting temperature is selected as low as possible, and at the same time, a covering agent is added for protection during the melting process, and the gas and slag are removed before pouring.

In order to ensure the continuous progress of the preparation process, the present invention has studied a high-purity SiN ceramic guide tube material, which can withstand high temperatures above 1000 ° C, and has good anti-scourability and thermal shock resistance, which can ensure continuous industrialized production.

The receiving device is composed of a receiving plate, a support shaft, a rotating traction motor, a lifting traction motor, a transmission mechanism, and a dynamic sealing system. The receiving plate can realize high-speed rotation (0~120rpm) and stepless Variable speed drop (0 ~ 30mm/s). During the preparation process, the metal melt flow is broken into a large number of fine liquid droplets by the atomized gas flying at high speed, and is accelerated to fly forward under the action of gravity and atomized gas. When the atomized liquid droplets solidify but have not yet It is deposited on the receiving plate before it is completely solidified, and a round ingot with a certain diameter can be obtained by controlling the rotation speed and descending speed of the receiving plate.

In the step (4) of the method of the present invention, in the process of hot extrusion, the extrusion temperature is 380°C to 420°C, the temperature is kept for 2h, and the extrusion speed is 1 to 5m/min. The ratio can reach up to 40:1.

In step (5) of the method of the present invention, the heat treatment of the parts includes solution treatment and aging treatment. The precipitated phase was fully redissolved. The solid solution treatment in the present invention is two-stage solid solution, and the specific system is: (440-450)°C/1h+(475-490)°C/1.5h.

Then carry out two-stage aging treatment, the specific system is: (110-120) ℃/(16-24) h+(150-160) ℃/(6-10) h. After aging treatment, the ultimate tensile strength of the material can reach more than 750MPa, and it also has high plasticity and damage tolerance properties.

The advantages of the present invention are:

After precise control of alloy composition, deformation processing and heat treatment, the ultimate tensile strength of the material can reach more than 750MPa, while maintaining high plasticity and damage tolerance performance.

Description of drawings

Fig. 1 is the structural representation of the non-vacuum spray forming equipment of the present invention

Fig. 2 is a structural schematic diagram of the receiving device of the present invention

Fig. 3 is the microstructure photo of the alloy bulk material of the present invention

Fig. 4 is the round ingot photo prepared by the present invention

Detailed ways

The present invention can adopt the following non-vacuum injection forming equipment to cooperate with the method of the present invention to prepare alloy powder. As shown in Figure 1, the non-vacuum injection molding equipment adopts a receiving tank body 2, and the top of the receiving tank body 2 is sequentially provided with an induction heating furnace (not shown), an induction heating or resistance heating tundish 4. The inlet of the induction heating tundish 4 is connected to the outlet of the induction heating smelting furnace, while the outlet of the induction heating or resistance heating tundish 4 is connected to the guide pipe 5 , and the outlet of the guide pipe 5 leads into the receiving tank 2 . An induction heating system (not shown) is provided around the tube wall of the draft tube 5, and an unrestricted airflow atomizing nozzle 7 is provided at the outlet of the draft tube 5, and the outlet section of the draft tube 5 is located at an unrestricted In the middle of the air-flow atomizing nozzle, and between the draft tube 5 and the non-restricted air-flow atomizing nozzle 7, a separation and matching method is adopted. Due to the high atomization temperature of the alloy, a completely unrestricted gas atomization nozzle is selected in the gas atomization process, and the separation and cooperation method is adopted between the guide tube and the nozzle during the working process. The nozzle is used to prepare the gas-atomized alloy powder, which avoids various problems caused when the high-melting-point alloy is atomized to the restricted nozzle. During atomization, the atomized gas will continuously flow in from the atomized nozzle (the flow rate is determined by the nozzle parameters and the atomized pressure), so a port for an exhaust system is provided at the bottom of the receiving tank 2 to discharge the atomized gas. The tank body 2 is received, and the air flow of the exhaust system is required to be greater than the flow of the atomizing gas.

A receiving device for preparing a round ingot is installed in the receiving tank body 2, and the receiving device is a known device. As shown in Figure 3, the receiving device includes two parts, namely the rotating part 21 and the lifting part 22. connection, the support shaft 26 is provided with a receiving tray 27; the lifting part 22 is provided with a lifting traction motor 28 on the base, and the lifting motor is connected with the screw 30 through a transmission mechanism 29, and is provided with a connecting rod on the base. Lead screw 30 is parallel to feed rod 31, and lead screw 30 and feed rod 31 form 30～35 angles with the vertical line of horizontal plane, and receiving seat 23 is fixedly connected stroke piece 32, and stroke piece 32 is provided with nut and casing head, and nut and wire The rod 30 is screwed, and the casing head is socketed with the light rod 31. During the preparation process, the rotating traction motor 24 is started, the receiving plate 23 is rotated at high speed, and the lifting traction motor 28 is started, so that the lead screw 30 rotates, and the nut also moves accordingly. , and slide on the light rod 31 with the light rod 31 as a track, pull down the receiving plate 27 at a certain angle and speed, so that the atomized liquid droplets are directly deposited on the receiving plate 27, and a round ingot with a certain diameter is obtained.

The above-mentioned preparation device is to cooperate with the process method of the present invention, but the method for completing the present invention is not limited to the preparation device, and other types of preparation devices can also be used to carry out the process method of the present invention.

Example 1:

The alloy composition is Zn 10wt%, Mg 2.5wt%, Cu 1.7%, Zr 0.5%, Fe<0.05wt%, Si<0.05wt%, and the rest is Al. After the alloy prefabricated ingot is prepared, it is loaded into the melting furnace and heated to 800°C, heat preservation for 30min, deslag and degassing, spray forming preparation, using high-purity argon, atomization pressure 1.0Mpa. As shown in Figure 2, turn on the rotating motor 24 and the lifting motor 28, and rotate the receiving tray at a high speed at a speed of 60 to 120rpm with a rotating speed. min, the receiving tray 27 is pulled down so that the atomized liquid droplets are directly deposited on the receiving tray 27. Continuous atomization of 150 kg of the new alloy at one time produced a new type of high-strength and high-toughness aluminum alloy round ingot weighing 100Kg. The photo of the prepared round ingot is shown in Figure 4. Process the deposited billet into a billet of a certain specification, keep it warm at 410°C for 2 hours, and perform hot extrusion processing with an extrusion ratio of 24:1 to extrude a φ30mm round bar, 440°C/1h+480°C/1.5 h solid solution treatment, the aging system adopts double-stage aging 120℃/24h+160℃/8h. The ultimate tensile strength is 780MPa, while the elongation is 11%, K _IC =36MPa*m ^1/2 , the fatigue limit of the alloy is 0.1, the stress concentration factor is 1, and the specified life is 10 ⁷ cycles. It can reach more than 410MPa, and when the stress concentration factor increases to 3, the fatigue limit is higher than 130MPa; da/dN≤6×10 ^-3 mm/cycle. As shown in Figure 3, the material has a fine microstructure without obvious defects and macrosegregation.

And be composed of Zn 10wt%, Mg 2.7wt%, Cu 1.7%, Zr 0.1%, Ni 0.1% (application number is the composition of embodiment 1 in the patent application of 03119605.5), adopts exactly the same preparation and processing technology, only Solution treatment and aging system are different, adopt 435～440℃/1h+485～490℃/1.5h solution treatment, aging system can adopt single-stage aging 120℃/24h, ultimate tensile strength is 810MPa, and elongation is 10%, K _IC ＝19MPa*m ^1/2 , the fatigue limit of this alloy is 380MPa when the stress ratio is 0.1, the stress concentration factor is 1, and the specified life is 10 ⁷ cycles. When the stress concentration factor is increased to 3 , the fatigue limit is 100MPa, da/dN≤6×10 ^-3 mm/cycle.

The damage tolerance performance of the material of Example 1 of the present invention is better than that of Example 1 in the patent application with application number 03119605.5.

Example 2:

Zn 9wt%, Mg 2.0wt%, Cu 1.3%, Zr 0.2%, Fe<0.05wt%, Si<0.05wt%, and the rest is Al. After the alloy prefabricated ingot is prepared, put it into the melting furnace, raise the temperature to 800 ° C, and keep it for 10 minutes , deslagging and degassing, spray forming preparation, using high-purity argon, atomization pressure 0.8MPa, and adopting the same rotating speed of the receiving tray, the angle of the receiving tray, and the speed of pulling down as in Example 1, one-time continuous Atomize 100 kg of new alloy to prepare a new high-strength and high-toughness aluminum alloy round ingot weighing 70Kg. Process the deposited billet into a billet of a certain specification, heat it at 390°C for 2 hours, and heat it with an extrusion ratio of 24:1. Extrusion processing, extruding a Φ25mm round rod, 450°C/1h+485°C/1.5h solution treatment, and the aging system adopts 115°C/16h+150°C/8h. , the ultimate tensile strength is 750MPa, and the elongation is 12%, K _IC (MPa*m ^1/2 )=34, da/dN≤6×10 ^-3 mm/cycle.

Example 3:

Zn 9.5wt%, Mg 2.3wt%, Cu 1.5%, Zr 0.4%, Fe<0.05wt%, Si<0.05wt%, and the rest is Al. After preparing the alloy prefabricated ingot, put it into the melting furnace, raise the temperature to 780°C, and keep it warm. 20min, deslagging and degassing, spray forming preparation, using high-purity nitrogen, atomization pressure 0.8MPa, and adopting the same rotating speed of the receiving tray, angle of receiving tray, and speed of pulling down as in Example 1, one-time continuous Atomize 100 kg of new alloy to prepare a new type of high-strength and high-toughness aluminum alloy round ingot weighing 70Kg, process the deposited billet into a billet of a certain specification, heat it at 400°C for 2 hours, and heat it with an extrusion ratio of 24:1. Extrusion processing, extruding a Φ25mm round rod, 440°C/1h+485°C/1.5h solution treatment, and the aging system adopts 120°C/20h+160°C/10h. , the ultimate tensile strength is 760MPa, while the elongation is 11%, K _IC (MPa*m ^1/2 )=34, da/dN≤6×10 ^-3 mm/cycle.

Claims (6)

1, a kind of superstrength and supertoughness, high destroy limit type aluminium alloy material of high Zn content, it is characterized in that: by weight percentage, this alloying constituent is Zn 9～10wt%, Mg 2.0～2.5wt%, Cu1.2～1.7wt%, Zr 0.2～0.5wt%, Fe＜0.05wt%, Si＜0.05wt%, all the other are Al, wherein, Fe and Si are impurity element.

2, a kind of method for preparing the superstrength and supertoughness, high destroy limit type aluminium alloy material of high Zn content, it is characterized in that: this method comprises the steps:

(1) by alloying constituent, by weight percentage, this alloying constituent is Zn 9～10wt%, Mg2.0～2.5wt%, Cu 1.2～1.7wt%, Zr 0.2～0.5wt%, Fe＜0.05wt%, Si＜0.05wt%, all the other are Al, prepare burden preparation prealloy ingot;

(2) heat up after the prefabricated ingot fusing of alloy, adopt rare gas element and atomize by atomizing nozzle, atomizing nozzle is with the frequency high-speed sweep of 1～5HZ, and atomizing gas is a rare gas element, and atomizing pressure is 0.5～1.0MPa;

(3) in aerosolization, with the speed high speed rotating of 60～120rpm, and the velocity pull-down of and 20～40mm/min drop-down with 30～40 ° angle is made billet to receiving trap under the traction of variable-frequency motor;

(4) carry out hot extrusion or the moulding of forge hot compression technology, be processed into required parts;

(5) parts are carried out twin-stage solution treatment and two-stage time effect and handle, promptly make the superstrength and supertoughness, high destroy limit type aluminium alloy material of high Zn content.

3, the method for the superstrength and supertoughness, high destroy limit type aluminium alloy material of preparation high Zn content according to claim 2, it is characterized in that: in described step (4), be earlier billet to be stripped off the skin, spray formed material is incubated 2 hours down at 380～420 ℃, carries out hot extrusion or the moulding of forge hot compression technology again.

4, the method for the superstrength and supertoughness, high destroy limit type aluminium alloy material of preparation high Zn content according to claim 3, it is characterized in that: in described step (5), the concrete system of twin-stage solution treatment is: (440～450) ℃/1h+ (475～490) ℃/1.5h.

5, according to the method for the superstrength and supertoughness, high destroy limit type aluminium alloy material of claim 3 or 4 described preparation high Zn contents, it is characterized in that: in described step (5), the concrete system that two-stage time effect is handled is: (110～120) ℃/(16～24) h+ (150～160) ℃/(6～10) h.

6, the method for the superstrength and supertoughness, high destroy limit type aluminium alloy material of preparation high Zn content according to claim 1 is characterized in that: the rare gas element that is adopted in step (2) is argon gas or nitrogen.

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