阅读说明：本技术 一种高强低镁Al-Mg铝合金材料及其制备方法 (High-strength low-magnesium Al-Mg aluminum alloy material and preparation method thereof ) 是由 刘满平 王晓芬 彭振 张振亚 孙少纯 赵国平 于 2021-06-07 设计创作，主要内容包括：本发明提供了一种高强低镁Al-Mg铝合金材料及其制备方法,属于金属及合金的制备技术领域。该方法先将铝合金进行铸造形成铸态坯料,再将铸态坯料车削成高压扭转圆盘后进行均匀化处理；随后将均匀化处理的圆盘在室温下进行高压扭转0.25～5圈。用本发明提供的方法制备的高强低镁Al-Mg铝合金材料,晶粒尺寸为265～86nm,抗拉强度高达490～670MPa,屈服强度可达390～505MPa。与通常中等强度5000系铝合金相比,本发明低镁Al-Mg铝合金材料的强度大幅度提高,可达到高强铝合金的水平,而且生产效率更高成本更低,扩大了5000系铝合金的应用范围。(The invention provides a high-strength low-magnesium Al-Mg aluminum alloy material and a preparation method thereof, belonging to the technical field of metal and alloy preparation. Casting aluminum alloy to form an as-cast blank, turning the as-cast blank into a high-pressure torsion disc, and then carrying out homogenization treatment; and then, carrying out high-pressure torsion on the homogenized disc for 0.25-5 circles at room temperature. The high-strength low-magnesium Al-Mg aluminum alloy material prepared by the method provided by the invention has the crystal grain size of 265-86 nm, the tensile strength of 490-670 MPa and the yield strength of 390-505 MPa. Compared with the common 5000 series aluminum alloy with medium strength, the low-magnesium Al-Mg aluminum alloy material has the advantages that the strength is greatly improved, the level of high-strength aluminum alloy can be reached, the production efficiency is higher, the cost is lower, and the application range of the 5000 series aluminum alloy is expanded.)

1. A high-strength low-magnesium Al-Mg aluminum alloy material is characterized in that: the Al-Mg aluminum alloy material comprises the following components in percentage by weight: 0.25-3.0% of Mg, and the balance of Al and impurity elements; the average grain size of the Al-Mg aluminum alloy material is less than 300nm, the tensile strength sigma b is 490-670 MPa, and the yield strength sigma 0.2 is 390-505 MPa.

2. The high-strength low-magnesium Al-Mg aluminum alloy material of claim 1, wherein: the impurity elements are: si is less than 0.06%, Fe is less than 0.08%, Ti is less than 0.05%.

3. The high-strength low-magnesium Al-Mg aluminum alloy material of claim 1, wherein: the average grain size d of the Al-Mg aluminum alloy material_TEM265-86 nm, 1038-1650 MPa of hardness HV, and sigma of tensile strength_b490-670 MPa, yield strength sigma_0.2Is 390 to 505 MPa.

4. The preparation method of the high-strength low-magnesium Al-Mg aluminum alloy material according to claim 1, which comprises the following specific steps:

the first step is as follows: preparation of as-cast blanks and high-pressure torsion discs

Adding alloy components according to an Al-Mg aluminum alloy component formula, heating to 720-750 ℃ for smelting, removing impurities and degassing, standing for 10-20 minutes, casting into a round as-cast blank with the diameter of 100mm to obtain an Al-Mg aluminum alloy as-cast blank, and turning the as-cast blank into a disc with the size phi 50 multiplied by 5mm for high-pressure torsion;

the second step is that: homogenization treatment

The high-pressure torsion disc is subjected to homogenization treatment, and the homogenization treatment process comprises the following steps: heating to 420-460 ℃ at a heating rate of 10-30 ℃/min, preserving heat for 1-6 hours, and cooling to room temperature at a cooling rate of 300 ℃/h to obtain a disk after homogenization treatment;

the third step: high pressure torsion

And (3) carrying out high-pressure torsion and large plastic deformation on the disk subjected to the homogenization treatment, wherein the high-pressure torsion process parameters are as follows: twisting for 0.25-5 circles under the process conditions of room temperature, pressure of 10GPa and rotating speed of 1r/min, wherein the process of high-pressure twisting comprises the following steps: the disc-shaped sample is placed in a die between an upper pressure head and a lower pressure head, the upper pressure head is fixed, the lower pressure head applies pressure up to 10GPa to the sample while twisting, and the friction force between the surface of the sample and the pressure heads enables the sample to generate extremely high shear strain, so that the torsional shear deformation of the sample is realized.

5. The preparation method of the high-strength low-magnesium Al-Mg aluminum alloy material according to claim 4, wherein in the second step, the technical scheme of homogenization treatment is as follows: 460 ℃ multiplied by 3 h.

6. The method for preparing the high-strength low-magnesium Al-Mg aluminum alloy material according to claim 4, wherein in the third step, the aluminum alloy material is twisted for 5 circles.

Technical Field

The invention belongs to the technical field of metal and alloy preparation, and relates to a high-strength low-magnesium Al-Mg aluminum alloy material and a preparation method thereof.

Background

As an important non-heat-treatable alloy, the 5000 series Al-Mg aluminum alloy has good corrosion resistance, formability, weldability and medium strength, is the most widely applied aluminum alloy material in the aspects of low-temperature storage tanks, aluminum wall plates, lighting products, memory magnetic disk substrates, marine engine parts, large-scale ship plates, military armored car outer plates, tank bottom plates, automobile body inner panels and the like so far, but with the rapid development of industry, the mechanical properties such as the strength of the 5000 series Al-Mg aluminum alloy in the prior art cannot meet the practical application, and the comprehensive mechanical properties of the alloy are urgently needed to be improved.

In order to improve the strength index of 5000 series Al-Mg aluminum alloys, it is one of the methods generally adopted to increase the content of Mg, the main alloying element. However, it has been found that, as early as the fifties of the last century, in Al-Mg aluminum alloys with Mg contents exceeding 3.5 wt.%, there is a magnesium-rich beta-phase (Mg) continuously precipitated at grain boundaries₂Al₃) Stress corrosion which easily causes serious disasters in the long-term service process, and the corrosion problem is more serious along with the increase of the Mg content. The invention patent with the domestic publication number of CN201510488048.6 discloses an Er/Sc/Zr composite micro-alloyed Al-6Mg-0.4Mn alloy stabilizing annealing process, which improves the Mg content to 6.0 wt%, controls the precipitation position and the morphology of a beta phase through composite micro-alloying and a special stabilizing process, improves the strength and the long-term intergranular corrosion resistance of the alloy, but the method needs to add precious rare earth Er and Sc, has complex process and is mostly suitable for high-end requirements of national defense and the like.

At present, on the premise of not increasing the content of Mg, the strength of 5000 series Al-Mg aluminum alloy is improved, so that the alloy becomes a hot spot for research and development at home and abroad; for example, U.S. patent publication No. US6695935B1, the tensile strength σ was obtained_bOver 403MPa, 5000 series aluminum alloy, however, the alloy contains noble alloy elements such as Ag and Sc, which makes the preparation of the alloy difficult and increases the cost, thereby limiting the productionThe application range of the alloy is widened; then, as the invention patent with the domestic publication number of CN104032192A, namely the rolling and heat treatment process for improving the fatigue damage resistance of the erbium-containing aluminum alloy plate, the tensile strength sigma is obtained_bThe aluminum alloy reaches 447MPa, but the method needs to add precious rare earth Er, so that the cost is increased, and the application range is limited.

The strength of the 5000 series Al-Mg aluminum alloy can be improved by large plastic deformation (SPD), such as High Pressure Torsion (HPT), Equal Channel Angular Pressing (ECAP), surface mechanical grinding (SMAT), Dynamic Plastic Deformation (DPD) and the like (Phys. Met. Metal.106 (2008) 90-96); the large plastic deformation methods can obviously refine the grain size of the alloy, thereby improving the strength of the alloy, wherein the high-pressure torsion method has the strongest capability of refining the grains, and can prepare nanocrystalline metal materials with the grain size less than 100nm, such as 5083 aluminum alloy (Russian 1570 aluminum alloy) prepared by high-pressure torsion methods such as Valiev and the like, the average grain size of the 5083 aluminum alloy is 45nm, and the strength sigma of the 5083 aluminum alloy is sigma_bThe alloy is as high as 950MPa (Phys. Met. Metal.106 (2008)90-96), but the alloy also contains valuable alloy element Sc, so the cost is higher and the application range is limited; and then as the invention patent with the domestic publication number of CN105543587B, namely 'an ultra-high strength nanocrystalline Al-Mg aluminum alloy material and a preparation method thereof', the tensile strength sigma is obtained by a high-pressure torsion method_bAluminum alloy of 5000 series reaching 855MPa, but this method adds Mg of more than 6.0 wt.%, because easy to appear serious stress corrosion during use, the application range is limited.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, and provides a preparation method of a high-strength low-magnesium Al-Mg aluminum alloy material aiming at the problem of low strength of the existing 5000 series Al-Mg aluminum alloy on the premise of not increasing the Mg content, wherein the crystal grains of the Al-Mg aluminum alloy are refined to be less than 300nm through the combination of proper component design and high-pressure torsion, high-density dislocation is obtained in the alloy, the strength of the alloy is greatly improved by utilizing strengthening mechanisms such as strong fine grain strengthening, dislocation strengthening and the like, the application range of the 5000 series Al-Mg aluminum alloy is expanded, and the preparation method is simple and has lower manufacturing cost compared with the existing preparation method.

In order to achieve the purpose, the invention adopts the following technical scheme.

The formula of the components of the invention is (weight percentage wt.%): 0.25-3.0% of Mg, and the balance of Al and impurity elements, wherein the impurity elements are as follows: si is less than 0.06%, Fe is less than 0.08%, Ti is less than 0.05%.

The preparation method of the high-strength low-magnesium Al-Mg aluminum alloy material comprises the following steps:

the first step is as follows: preparation of as-cast blanks and high-pressure torsion discs

Adding alloy components according to the designed Al-Mg aluminum alloy component formula, heating to 720-750 ℃, smelting, removing impurities and degassing, standing for 10-20 minutes, casting into a round cast blank with the diameter of 100mm to obtain an Al-Mg aluminum alloy cast blank, and turning the cast blank into a disc with the size phi 50 multiplied by 5mm for high-pressure torsion.

The second step is that: homogenization treatment

The high-pressure torsion disc is subjected to homogenization treatment, and the homogenization treatment process comprises the following steps: heating to 420-460 ℃ at a heating rate of 10-30 ℃/min, preserving heat for 1-6 hours, and cooling to room temperature at a cooling rate of 300 ℃/h to obtain the disk after homogenization treatment.

The third step: high pressure torsion

And (3) carrying out high-pressure torsion and large plastic deformation on the disk subjected to the homogenization treatment, wherein the high-pressure torsion process parameters are as follows: twisting for 0.25-5 circles under the process conditions of room temperature, pressure of 10GPa and rotating speed of 1r/min, wherein the process of high-pressure twisting comprises the following steps: the disc-shaped sample is placed in a die between an upper pressure head and a lower pressure head, the upper pressure head is fixed, the lower pressure head applies pressure up to 10GPa to the sample while twisting, and the friction force between the surface of the sample and the pressure heads enables the sample to generate extremely high shear strain, so that the torsional shear deformation of the sample is realized.

The invention relates to a high-strength low-magnesium Al-Mg aluminum alloy material and a preparation method thereof, wherein a casting-state blank is formed by adopting a direct water-cooling semi-continuous casting (DC casting) process on an alloy melt.

According to the high-strength low-magnesium Al-Mg aluminum alloy material and the preparation method thereof, the corresponding sample edge equivalent strain can reach 30-300 after 0.25-5 circles of high-pressure torsion.

According to the high-strength low-magnesium Al-Mg aluminum alloy material and the preparation method thereof, the average grain size of the prepared alloy is less than 300 nm.

The invention relates to a high-strength low-magnesium Al-Mg aluminum alloy material and a preparation method thereof, and the prepared alloy has tensile strength sigma_b490-670 MPa, yield strength sigma_0.2Is 390 to 505 MPa.

The preferred embodiment of the present invention is as follows (other embodiments are the same as above).

The preferable technical scheme of the homogenization treatment is as follows: 460 ℃ multiplied by 3 h.

The preferred technical scheme of high-pressure torsion is as follows: and 5 turns are twisted.

According to the high-strength low-magnesium Al-Mg aluminum alloy material and the preparation method thereof, the average grain size of the alloy prepared under the preferable scheme is 265-86 nm, and the tensile strength sigma is_b490-670 MPa, yield strength sigma_0.2Is 390 to 505 MPa.

The invention is further explained and illustrated below:

the principle of the invention is as follows:

the high-strength low-magnesium Al-Mg aluminum alloy material and the preparation method thereof provided by the invention have a strengthening mechanism which is greatly different from that of the traditional method.

The strengthening mechanism of 5000 series aluminum alloy prepared by the traditional method is mainly solid solution strengthening and deformation strengthening.

The method (figure 1) of the invention has the solid solution strengthening and deformation strengthening of the traditional method, and also has strong strengthening mechanisms such as fine crystal strengthening and dislocation strengthening; through the combination of proper component design and high-pressure torsion, the grains of the Al-Mg aluminum alloy are refined to be less than 300nm, so that the strength of the alloy is obviously improved through fine grain strengthening (attached figures 3 and 4); meanwhile, after high-pressure torsion, the alloy generates great plastic deformation, the equivalent strain can reach 30-300, the dislocation density is obviously increased, and the average dislocation density is as high as 10¹⁴m^-2(table 2), the strength of the alloy is further improved by dislocation strengthening; moreover, the high-pressure torsion large deformation can lead the harmful phase such as beta phase in the alloy to be crushed and dissolved back into the matrix, thereby not only improving the traditional solid solution strengthening effect, but also completely avoiding the precipitation of the beta phase which is harmful to the corrosion performance.

Compared with the prior art, the invention has the advantages that:

1. the high-strength low-magnesium Al-Mg aluminum alloy material and the preparation method thereof do not need to add noble rare earth elements such as Sc and Er, have simple preparation process and stable quality, and are beneficial to reducing the cost and saving resources.

2. The high-strength low-magnesium Al-Mg aluminum alloy material has the magnesium content far lower than 3.5 wt.% of commercial 5000-series aluminum alloy, and is not easy to continuously precipitate a beta phase in a crystal boundary, so that the long-term intergranular corrosion resistance of the alloy can be greatly improved.

2. Compared with the traditional 5000 series aluminum alloy preparation method, the high-pressure torsion process in the preparation method only needs dozens of seconds to dozens of seconds, the time is very short, the energy consumption is favorably reduced, and the cost is saved.

3. The high-pressure torsion method in the preparation method can realize large plastic deformation under the condition that the shape of the product is not changed, and can obtain the Al-Mg aluminum alloy with the average grain size of less than 300 nm.

4. The strength of the aluminum alloy processed and manufactured by the preparation technology provided by the invention can be greatly improved, the strength is far higher than that of the traditional 5000 series aluminum alloy, the level of high-strength aluminum alloy is reached, and the application range of the low-cost 5000 series aluminum alloy is widened.

Drawings

Fig. 1 is a schematic diagram of a high pressure twisting process according to the present invention.

FIG. 2 is a schematic representation of a high pressure torsion specimen and its tensile specimen (in mm).

FIG. 3 is a Transmission Electron Microscope (TEM) photograph of the Al-0.5Mg aluminum alloy of example 1 after high-pressure twisting for 5 turns, wherein FIG. 3(a) is a TEM morphology (the lower left corner is the selected area electron diffraction pattern), and FIG. 3(b) is a crystal grain size distribution histogram measured by a TEM dark field image, and the average crystal grain size is 265 nm.

FIG. 4 is a Transmission Electron Microscope (TEM) photograph of the Al-2.5Mg aluminum alloy of example 3 after high-pressure twisting for 5 turns, wherein FIG. 4(a) is a TEM morphology (the lower left corner is the selected area electron diffraction pattern), and FIG. 4(b) is a crystal grain size distribution histogram measured by a TEM dark field image, and the average crystal grain size is 86 nm.

Fig. 5 is a tensile stress strain curve for example 1 and comparative example 1.

Fig. 6 is a tensile stress strain curve for example 2 and comparative example 1.

Fig. 7 is a tensile stress strain curve for example 3 and comparative example 1.

Detailed Description

The room temperature of the invention is generally between 0 and 30 ℃.

Alloy hardness characterization adopts a Micromet-5101 micrometer indentator: hardness test specimens of phi 3 × 2mm were polished with 1000-mesh sandpaper, an applied load of 250mN, a duration of 15s, hardness test of each specimen not less than 5 times, and finally the average value was taken.

The tensile test was carried out on a laser extensometer using a tensile rate of 10^-4s^-1The whole experiment process is controlled by a computer, and a tension-displacement curve is automatically recorded. The tensile specimen was sampled in a manner such that the length of the tensile specimen scale was 2mm, the width was 1mm, and the thickness was 0.4mm, as shown in FIG. 2.

The average grain size of the alloy is determined by transmission electron microscopy dark field imaging technique (TEM-DF), and is randomly averaged over at least 100 grain sizes.

The average grain dislocation density of the alloy is measured by an X-ray diffractometer of D8ADVANCE type, and the measurement parameters are as follows: the experimental current was 30mA, voltage was 40kV, Cu target Ka line, experimental data were processed using MDIJade 6.5 software.

The preparation process of the present invention is further illustrated and described below with reference to examples, but the present invention is not limited to these examples.

For comparison, the Al-Mg aluminum alloys used in the examples were Al-0.5Mg, Al-1.0Mg and Al-2.5Mg, respectively. The comparative examples all used commercial 5000 series aluminum alloy AA5182 in a state just before casting and homogenization treatment, i.e., high-pressure twisting. Chemical compositions of commercial AA5182 aluminum alloy of comparative example and aluminum alloy of three examples are shown in Table 1

Table 1 compositions (wt.%) of Al-Mg aluminum alloys of examples and comparative examples

Kind of alloy	Mg	Fe	Si	Ti	Mn	Al
							AA5182	4.1	0.32	0.13	-	0.35	Balance of
Al-0.5Mg	0.493	0.0679	0.0562	0.0046	-	Balance of
							Al-1.0Mg	0.971	0.0722	0.0482	0.0048	-	Balance of
Al-2.5Mg	2.488	0.0685	0.0490	0.0045	-	Balance of

Comparative example 1

The commercial AA5182 aluminum alloy was cast into a round blank having a diameter of 100mm, turned into a disc having a size of Φ 50 × 5mm, subjected to homogenization treatment at 460 ℃ for 3 hours in a circulating air resistance furnace, and then subjected to the hardness measurement and tensile test.

The results of the hardness and tensile tests of the AA5182 aluminum alloy after homogenization treatment are shown in Table 2 and FIG. 5, wherein the hardness HV is 656MPa, and the tensile strength σ is_b255MPa, yield strength sigma_0.2Is 115 MPa.

Example 1

Pouring the Al-0.5Mg aluminum alloy into a circular blank with the diameter of 100mm, turning and processing the blank into a disc with the size of phi 50 multiplied by 5mm, carrying out homogenization treatment on the disc at 460 ℃ for 3h in a circulating air resistance furnace, and then carrying out high-pressure torsion on the disc after the homogenization treatment, wherein the process of the high-pressure torsion is as follows: and twisting for 5 circles under the process conditions of room temperature, pressure of 10GPa and rotating speed of 1 r/min. The room temperature high pressure twisted aluminum alloy was then subjected to the average grain size determination, average dislocation density determination, hardness determination, and tensile test.

The detection results of the Al-0.5Mg aluminum alloy after being twisted for 5 circles at room temperature and high pressure are shown in Table 2 and FIG. 5, and the average grain size of the prepared alloy is d_TEM265nm and an average dislocation density of 1.39X 10¹⁴m^-2Hardness HV 1038MPa and tensile strength σ_b490MPa, yield strength sigma_0.2Is 390 MPa.

Example 2

Pouring the Al-1.0Mg aluminum alloy into a circular blank with the diameter of 100mm, turning and processing the blank into a disc with the size of phi 50 multiplied by 5mm, carrying out homogenization treatment on the disc at 460 ℃ for 3h in a circulating air resistance furnace, and then carrying out high-pressure torsion on the disc after the homogenization treatment, wherein the process of the high-pressure torsion is as follows: and twisting for 5 circles under the process conditions of room temperature, pressure of 10GPa and rotating speed of 1 r/min. The room temperature high pressure twisted aluminum alloy was then subjected to the average grain size determination, average dislocation density determination, hardness determination, and tensile test.

The detection results of the Al-1.0Mg aluminum alloy after being twisted for 5 circles at room temperature and high pressure are shown in Table 2 and FIG. 6, and the average grain size of the prepared alloy is d_TEM152nm and an average dislocation density of 1.87X 10¹⁴m^-2Hardness HV 1263MPa and tensile strength sigma_b560MPa, yield strength sigma_0.2Is 430 MPa.

Example 3

Pouring the Al-2.5Mg aluminum alloy into a circular blank with the diameter of 100mm, turning and processing the blank into a disc with the size of phi 50 multiplied by 5mm, carrying out homogenization treatment on the disc at 460 ℃ for 3h in a circulating air resistance furnace, and then carrying out high-pressure torsion on the disc after the homogenization treatment, wherein the process of the high-pressure torsion comprises the following steps: and twisting for 5 circles under the process conditions of room temperature, pressure of 10GPa and rotating speed of 1 r/min. The room temperature high pressure twisted aluminum alloy was then subjected to the average grain size determination, average dislocation density determination, hardness determination, and tensile test.

The detection results of the Al-2.5Mg aluminum alloy after being twisted for 5 circles at room temperature and high pressure are shown in Table 2 and FIG. 7, and the average crystal grains of the prepared alloyDimension d_TEM86nm and an average dislocation density of 2.58X 10¹⁴m^-2Hardness HV 1650MPa and tensile strength sigma_b670MPa, yield strength sigma_0.2Is 505 MPa.

Table 2 average grain size, dislocation density and mechanical properties test results of comparative examples and examples

Note: d_TEMIs the average grain size (nm) determined by randomly taking at least 100 grains from a transmission electron microscope dark field image, and rho is the average dislocation density (multiplied by 10)¹⁴m^-2) HV is hardness value (MPa), σ_bIs tensile strength (MPa), σ_0.2Is the yield strength (MPa). FIGS. 5-7 show corresponding tensile stress-strain curves.

As can be seen from Table 2 and attached figures 5-7, the mechanical property of the Al-Mg aluminum alloy after being twisted for 5 circles at room temperature and high pressure is obviously improved, the yield strength is more than 3.3 times that of the corresponding commercial AA5182 aluminum alloy subjected to homogenization treatment, and the highest tensile strength sigma of the Al-Mg aluminum alloy is higher than that of the commercial AA5182 aluminum alloy subjected to corresponding homogenization treatment_bAnd yield strength σ_0.2670MPa and 505MPa respectively. For example, after the Al-2.5Mg aluminum alloy is twisted for 5 turns at room temperature and high pressure (example 3), the average grain size of the alloy is 86nm, the hardness HV is 1650MPa, and the tensile strength σ is_b670MPa, yield strength sigma_0.2Is 505 MPa; compared with the performance of the commercial AA5182 aluminum alloy after homogenization treatment (comparative example 1), the hardness, the tensile strength and the yield strength after high-pressure torsion are respectively improved by 994MPa, 415MPa and 390MPa, and the yield strength after high-pressure torsion is more than 4.3 times of the yield strength corresponding to the homogenization treatment.