Method for regulating and controlling thickness of aluminum alloy precipitate

Abstract

The invention discloses a method for regulating and controlling the thickness of an aluminum alloy precipitate, and belongs to the field of nonferrous metal material testing. According to the method, a cylindrical sample with the diameter-height ratio larger than or equal to 2 is cut from an aluminum alloy plate, and the diameter of the cylindrical sample is smaller than the section radius of a rod; the impact equipment is sequentially composed of a high-strength metal bullet with the tensile strength larger than or equal to 1800 MPa, an incidence rod and an absorption rod, and an infrared heating furnace is arranged for a sample. Before an impact experiment, a cylindrical sample with strain gauges attached to the side faces is clamped by special tweezers and placed between an incident rod and an absorption rod, the temperature is set, the preheating time is waited for 6-11 minutes, then the strain rate is set, and then a bullet loading button is started for the impact experiment; and recovering the impacted sample, carrying out ion thinning according to requirements to prepare a metal film, observing precipitates by using a transmission electron microscope, and testing the thickness of the precipitates. The method provided by the invention is relatively high in test precision, has strong guidance on heat treatment processes such as solid solution and aging of the aluminum alloy, and is beneficial to improving the mechanical property and the processing property of the aluminum alloy.

Description

Technical Field

[0001] The present invention discloses a method for regulating the thickness of precipitates in aluminum alloy, belonging to the field of non-ferrous metal materials. Background Art

[0002] The regulation of the morphology and microstructure of precipitates in aluminum alloy is a complex process, involving changes in the physical state, microstructure, and properties of the material. Generally, the changes in the morphology and microstructure of precipitates in aluminum alloy mainly occur during processes such as solution treatment, precipitation, and aging. For plate-like precipitates, thickening will inevitably lead to a decrease in strength. However, while the strength of the aluminum alloy decreases, the plasticity has a significant increase, and the changes in the microstructure have both advantages and disadvantages.

[0003] The driving force is a key factor in the process of the change in the morphology of precipitates in aluminum alloy. Simply put, under sufficient driving force conditions, the morphology and microstructure of precipitates in aluminum alloy will change. For aluminum alloy with plate-like precipitates, temperature and impact force are the key factors leading to its thickening. Studying the thickening of precipitates can better understand and regulate the precipitation strengthening effect of aluminum alloy, thereby optimizing the performance indicators of aluminum alloy. How to regulate the thickness of precipitates in aluminum alloy is a key technical problem restricting its further development.

[0004] The present invention discloses a method for regulating the thickness of precipitates in aluminum alloy, mainly by the synergistic action of high temperature and impact force loading to regulate the thickness of precipitates in aluminum alloy. The method for regulating the thickness of precipitates in aluminum alloy provided by the present invention has a relatively high test accuracy, strong guidance for heat treatment processes such as solution treatment and aging of aluminum alloy, and is beneficial to improving its mechanical properties and process performance. Summary of the Invention

[0005] The present invention provides a method for regulating the thickness of precipitates in aluminum alloy, including the following steps:

[0006] (1) Specimen preparation: Cut cylindrical specimens from aluminum alloy sheet materials, with the diameter-height ratio of the cylindrical specimens ≥ 2. Under the condition of ensuring that the upper and lower surfaces are always parallel and perpendicular to the axis, polish them smoothly with 400# sandpaper;

[0007] (2) Specimen preheating: The impact device consists of a bullet, an incident bar, and an absorption bar made of high-strength metal material with a tensile strength ≥ 1800 MPa in sequence; in addition, an infrared heating furnace is specifically equipped for regulating the temperature of the specimen, and the diameter of the specimen is smaller than the radius of the cross-section of the bar; before the impact experiment, use special tweezers to clamp a cylindrical specimen with a strain gauge attached to one side and place it between the incident bar and the absorption bar, ensure that the axis of the specimen coincides with the axis of the bar, set the temperature and wait for the preheating time of 6 - 11 min, and after the data on the display screen is stable, confirm that the impact device is ready;

[0008] (3) Driving force loading: Set the strain rate, repeatedly check whether the equipment is in good preparation, then turn on the switch of the ejection gun, and start the impact experiment by pressing the button to load the bullet;

[0009] (4) Precipitate thickness measurement: Recover the impacted specimen, cut a sheet specimen with a thickness of 1 mm, polish it on sandpaper, and grind it step by step according to the order from low to high sandpaper models to a thickness of 40 - 50 μm, then prepare a metal thin film by ion thinning according to the requirements. After the thin film meets the conditions, observe the disc-shaped precipitates with a transmission electron microscope and measure their thickness. Description of the Drawings

[0010] Figure 1 is the impact equipment, where 1 is the bullet, 2 is the incident rod, 3 is the cylindrical specimen, 4 is the absorber rod, 5 is the infrared heating furnace, 6 is the strain gauge, and 7 is the direction of impact force loading.

[0011] Figure 2 is the transmission electron microscope microstructure of the precipitates in the aged aluminum alloy without impact.

[0012] Figure 3 is the transmission electron microscope microstructure of the precipitates in the aged aluminum alloy after impact in Example 1.

[0013] Figure 4 is the transmission electron microscope microstructure of the precipitates in the aged aluminum alloy after impact in Example 2. Detailed Embodiments

[0014] The present invention will be further described below in conjunction with embodiments.

[0015] Example 1

[0016] A method for regulating the thickness of aluminum alloy precipitates includes the following steps:

[0017] (1) Specimen preparation: Cut a Φ6×3 mm cylindrical specimen from an aged 2XXX series aluminum alloy sheet. The diameter-height ratio of the cylindrical specimen is 2. Under the condition of ensuring that the upper and lower surfaces are always parallel and perpendicular to the axis, polish it smooth with 400# sandpaper;

[0018] (2) Specimen preheating: The impact equipment consists of a bullet, an incident rod, an absorber rod, and a heating furnace in sequence. The schematic diagram is as Figure 1As shown in the figure; the impact device consists of a bullet, an incident rod, and an absorption rod made of 30CrMnMoA high-strength round steel in sequence; in addition, an infrared heating furnace is equipped specifically for controlling the temperature of the specimen; the diameters of the bullet and the rod are 16 mm, and the diameter of the specimen is smaller than the radius of the rod cross-section; before the impact experiment, use special tweezers to pick up a cylindrical specimen with a strain gauge attached to one side and place it between the incident rod and the absorption rod, ensure that the axis of the specimen coincides with the axis of the rod, set the waiting preheating time at 450 °C for 6 min, and after the data on the display screen is stable, confirm that the impact device is ready;

[0019] (3) Driving force loading: Set the strain rate to 2360 s -1 , repeatedly check whether the equipment is in good preparation, and then turn on the switch of the ejection gun and start the button to load the bullet to conduct the impact experiment;

[0020] (4) Precipitate thickness measurement: Recover the specimen after impact, cut a sheet specimen with a thickness of 1 mm, polish it on sandpaper, and grind it step by step to 45 μm in ascending order of sandpaper model, and then prepare a metal thin film by ion thinning according to the requirements. After the thin film meets the conditions, use a transmission electron microscope to observe the disc-shaped precipitates and measure their thickness; Figure 3 is the transmission electron microscope microstructure of the precipitates of the aluminum alloy specimen, compared with Figure 2 the precipitate thickness, and the average value of the measured precipitate thickness increases from 2 nm to 5.5 nm, showing a significant increase.

[0021] Example 2

[0022] A method for controlling the thickness of precipitates in aluminum alloy, comprising the following steps:

[0023] (1) Specimen preparation: Cut a Φ6×3 mm cylindrical specimen from the 2XXX series aluminum alloy sheet in the aged state. The diameter-height ratio of the cylindrical specimen is 2. Under the condition of ensuring that the upper and lower surfaces are always parallel and perpendicular to the axis, polish it smooth with 400# sandpaper;

[0024] (2) Specimen preheating: The impact device consists of a bullet, an incident rod, an absorption rod and a heating furnace in sequence, and the schematic diagram is as Figure 1 shown in the figure; the impact device consists of a bullet, an incident rod, and an absorption rod made of 30CrMnMoA high-strength round steel in sequence; in addition, an infrared heating furnace is equipped specifically for controlling the temperature of the specimen; the diameters of the bullet and the rod are 16 mm, and the diameter of the specimen is smaller than the radius of the rod cross-section; before the impact experiment, use special tweezers to pick up a cylindrical specimen with a strain gauge attached to one side and place it between the incident rod and the absorption rod, ensure that the axis of the specimen coincides with the axis of the rod, set the waiting preheating time at 450 °C for 7 min, and after the data on the display screen is stable, confirm that the impact device is ready;

[0025] (3) Driving force loading: Set the strain rate to 4100 s-1 , repeatedly check whether the equipment is in good condition, then turn on the switch of the ejection gun and start the loading bullet button to conduct the impact experiment;

[0026] (4) Precipitate thickness test: Recover the specimens after impact, cut out sheet specimens with a thickness of 1 mm, polish them on sandpaper, and grind them step by step to 43 μm in ascending order of sandpaper model. Then, prepare a metal thin film by ion thinning according to the requirements. After the thin film meets the conditions, observe the disc-shaped precipitates by transmission electron microscopy and measure their thickness; Figure 4 is the transmission electron microscopy microstructure of the precipitates in the aluminum alloy specimen, compared with Figure 2 the precipitate thickness. The average value of the measured precipitate thickness increases from 2 nm to 11 nm, showing an obvious thickening.

Claims

1. A method for regulating the thickness of aluminum alloy precipitates, characterized in that The impact loading driving force is applied, and the impact equipment is composed of a bullet of equal diameter, an incident rod, and an absorption rod made of high-strength metal with a tensile strength ≥1800MPa. The length of the bullet is 0.2m, and the lengths of the incident rod and the absorption rod are 1m.

2. A method for regulating the thickness of aluminum alloy precipitates according to claim 1, characterized in that The aluminum alloy specimen is cylindrical, the diameter-to-height ratio of the cylindrical specimen is ≥2, and the diameter of the cylindrical specimen is smaller than the radius of the rod cross section.

3. A method for regulating the thickness of aluminum alloy precipitates according to claim 1, characterized in that A cylindrical aluminum alloy specimen with a strain gauge attached to the side is placed between the incident rod and the absorbing rod, ensuring that the axis of the specimen coincides with the axis of the rod, and the temperature is set and the preheating time is 6 to 11 minutes.

4. The method for controlling the thickness of aluminum alloy precipitates according to claim 1, characterized in that The impact equipment is equipped with an infrared heating furnace, and the sample preheating temperature is ≥300℃.

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