A high-strength Al-Zn-Mg-Cu-Mn alloy suitable for friction stir additive manufacturing and a forming process thereof

Abstract

The application discloses a high-strength Al-Zn-Mg-Cu-Mn alloy suitable for friction stir additive manufacturing and a forming process thereof, alloy elements including Zn: 9.0-11.0%, Mg: 1.8-2.2%, Mn: 1.5-2.0%, Cu: 2.1-2.5%, the balance of Al and inevitable impurities. The Al-Zn-Mg-Cu-Mn alloy is formed by combining friction stir additive manufacturing with a heat treatment process. The AlCuMn phase is formed by Mn and Cu elements, the grain boundary migration is inhibited, and the problem of abnormal grain growth in the solid solution treatment process after traditional high-strength aluminum alloy friction stir additive manufacturing is overcome. The MgZn2 precipitated phase of nanoscale is formed by Mg and Zn elements in cooperation with the heat treatment process of'solid solution + aging', and the strength is greatly improved. Finally, the Al-Zn-Mg-Cu-Mn alloy can be subjected to the'solid solution + aging' heat treatment after friction stir additive manufacturing, so that the strength of the friction stir additive manufacturing aluminum alloy component is greatly improved, and the application of the friction stir additive manufacturing technology in the manufacturing of large aerospace aluminum alloy components is laid a foundation.

Description

Technical Field

[0001] This invention belongs to the field of high-strength aluminum alloy technology, and particularly relates to a high-strength Al-Zn-Mg-Cu-Mn alloy suitable for friction stir additive manufacturing and its forming process. Background Technology

[0002] Aluminum alloy sheets have poor formability at room temperature and are prone to cracking. Therefore, the production of more complex parts often requires hot forming.

[0003] Currently, the main methods of aluminum alloy hot forming include aluminum alloy welding hot stamping and aluminum alloy hot forging. During the aluminum alloy hot forming process, the forming temperature gradually increases, second-phase particles dissolve, grain boundary pinning effect decreases, and a few grains continuously engulf fine recrystallized structures, forming abnormally large grains. This process is the phenomenon of abnormal grain growth in aluminum alloy hot forming. Abnormal grain growth during aluminum alloy hot forming reduces the fatigue strength and dimensional stability of aluminum alloy parts and causes twisting deformation.

[0004] Based on this, a high-strength Al-Zn-Mg-Cu-Mn alloy is designed. This aluminum alloy is suitable for friction stir additive manufacturing and can effectively suppress abnormal grain growth in the hot forming process, thus exhibiting excellent tensile strength and toughness. Summary of the Invention

[0005] Objective of the invention: The technical problem to be solved by the present invention is to provide a high-strength Al-Zn-Mg-Cu-Mn aluminum alloy, which can effectively suppress abnormal grain growth in the hot forming process, thereby exhibiting excellent tensile strength and toughness.

[0006] Technical solution: This invention is applicable to high-strength Al-Zn-Mg-Cu-Mn aluminum alloys manufactured by friction stir additive manufacturing, comprising the following components by mass fraction:

[0007] Zn: 9.0-11.0%;

[0008] Mg: 1.8-2.2%;

[0009] Mn: 1.5-2.0%;

[0010] Cu: 2.1-2.5%;

[0011] The balance is Al and unavoidable impurities; the Mn / Cu ratio is controlled between (0.60-0.95):1.

[0012] Furthermore, this high-strength Al-Zn-Mg-Cu-Mn alloy comprises the following components by mass fraction:

[0013] Zn: 10%;

[0014] Mg: 2.0%;

[0015] Mn: 1.5%;

[0016] Cu: 2.1%;

[0017] Balance Al and unavoidable impurities.

[0018] Furthermore, this high-strength Al-Zn-Mg-Cu-Mn alloy comprises the following components by mass fraction:

[0019] Zn: 10%;

[0020] Mg: 2.0%;

[0021] Mn: 2.0%;

[0022] Cu: 2.5%;

[0023] Balance Al and unavoidable impurities.

[0024] The forming process of the high-strength Al-Zn-Mg-Cu-Mn alloy of the present invention includes the following steps:

[0025] (1) The Al-Zn-Mg-Cu-Mn alloy rods or Al-Zn-Mg-Cu-Mn alloy wires obtained after melting and machining are subjected to friction stirring additive manufacturing to form Al-Zn-Mg-Cu-Mn alloy components;

[0026] (2) Heat the Al-Zn-Mg-Cu-Mn alloy component uniformly to 440-460 ℃, keep it at that temperature for 0.5-2 h, and then place it in a water bath to cool to room temperature; then heat it uniformly to 140-160 ℃, keep it at that temperature for 4-4.5 h, and then take it out and cool it to room temperature.

[0027] Furthermore, in step (1) of forming the high-strength Al-Zn-Mg-Cu-Mn alloy of the present invention, the rotation speed of the friction stir additive manufacturing is 300-1200 r / min and the forward speed is 60-300 mm / min.

[0028] Furthermore, in step (1) of the present invention, the Al-Zn-Mg-Cu-Mn alloy bar or Al-Zn-Mg-Cu-Mn alloy wire is obtained by the following steps: the raw materials are prepared according to the alloy elements and placed in a melting furnace. After isothermal refining at 690-710 ℃ for 25-35 min, the bar or wire is obtained by casting and machining.

[0029] Beneficial effects: Compared with the prior art, the significant advantages of this invention are as follows: Based on the Al-Zn-Mg-Cu-Mn alloy, this high-strength Al-Zn-Mg-Cu alloy, on the one hand, forms nanoscale MgZn2 precipitates through Mg and Zn elements combined with a "solution + aging" heat treatment process, which greatly improves the strength; on the other hand, by increasing the content of Mn element (reaching 1.5-2%), and at the same time increasing the Cu content to control the Mn / Cu ratio at (0.60-0.95):1, the AlCuMn phase is formed through Mn and Cu elements, instead of Al6Mn. The AlCuMn phase inhibits grain boundary migration and overcomes the problem of abnormal grain growth during the solution treatment process after traditional high-strength aluminum alloy friction stir additive manufacturing. Ultimately, this enables Al-Zn-Mg-Cu-Mn alloys to undergo "solution + aging" heat treatment after friction stir additive manufacturing, thereby significantly improving the strength of friction stir additive manufacturing aluminum alloy components and laying the foundation for the application of friction stir additive manufacturing technology in the manufacturing of large aerospace aluminum alloy components. Attached Figure Description

[0030] Figure 1 The phase diagrams of the Al-Zn-Mg-Cu-Mn aluminum alloy at different hot forming temperatures in Example 1 of this invention are shown below.

[0031] Figure 2 The image shows the microstructure of the Al-Zn-Mg-Cu-Mn aluminum alloy from Example 1 of this invention.

[0032] Figure 3 This is an image showing the microstructure (EBSD orientation imaging) of the Al-Zn-Mg-Cu-Mn aluminum alloy of Example 1 of the present invention;

[0033] Figure 4 This is a phase element distribution diagram of the Al-Zn-Mg-Cu-Mn aluminum alloy in the additive manufacturing state according to Example 1 of the present invention; wherein, a is the alloy phase distribution diagram; b is the Mn element distribution diagram; and c is the Cu element distribution diagram.

[0034] Figure 5 This is a phase diagram of the Al-Zn-Mg-Cu aluminum alloy at different hot forming temperatures in Comparative Example 1 of this invention;

[0035] Figure 6 This is a microstructure diagram of the Al-Zn-Mg-Cu aluminum alloy of Comparative Example 1 of the present invention;

[0036] Figure 7 The phase diagrams of the Al-Zn-Mg-Cu-Mn aluminum alloy at different hot forming temperatures in Example 2 of this invention are shown below.

[0037] Figure 8The phase diagrams of the Al-Zn-Mg-Cu-Mn aluminum alloy at different hot forming temperatures in Example 3 of this invention are shown below.

[0038] Figure 9 The stress-strain curves of Embodiment 1 and Comparative Example 1 of the present invention are shown below;

[0039] Figure 10 for Figure 9 A magnified view of the elastic phase. Detailed Implementation

[0040] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0041] The raw materials used in the following embodiments of the present invention are: pure aluminum (purity greater than or equal to 99.9 wt.%), Al-Mg master alloy (Mg content greater than or equal to 10 wt.%), Al-Mn master alloy (Mg content greater than or equal to 10 wt.%), Al-Cu master alloy (Cu content greater than or equal to 10 wt.%), and pure Zn (purity greater than or equal to 99.9 wt.%), wherein the Mg content is fed at a mass fraction of 1.1 to cope with the loss of Mg element by burning.

[0042] The "machining" mentioned in the following embodiments and comparative examples of the present invention refers to purely mechanical processing to produce the required components.

[0043] Example 1: Al-10.0Zn-2.0Mg-2.1Cu-1.5Mn alloy (wt%).

[0044] The forming process of the high-strength Al-Zn-Mg-Cu-Mn aluminum alloy in Example 1 is suitable for friction stir additive manufacturing + heat treatment (solution + aging), and specifically includes the following steps:

[0045] (1) Melting: The alloying elements are added to the vacuum induction melting furnace in proportion, and after isothermal refining at 700 °C for 30 min, the bars are obtained by casting and machining.

[0046] (2) Using a friction stir additive manufacturing equipment, the bar is placed in the feeding mechanism of the equipment. The rotation speed is 600 r / min, the forward speed is 120 mm / min, the single-layer additive manufacturing thickness is 2 mm, and the component is formed according to the geometric dimensions of the construction.

[0047] (3) Heat the component as a whole in a heat treatment furnace to 450±10 ℃, keep it at that temperature for 1 h, and then cool it to room temperature in a water bath; then heat it again in the heat treatment furnace to 150±10 ℃, keep it at that temperature for 4 h, and then take it out and cool it to room temperature.

[0048] Based on the elemental composition of the aluminum alloy in Example 1 and the heat deformation temperature, the phase composition of the generated phase was theoretically analyzed, and the results are as follows. Figure 1 As shown. Simultaneously, the aluminum alloy component prepared in Example 1 was structurally characterized, and the results are as follows. Figures 2 to 4 As shown. Combined with Figure 1 and Figure 4 It is known that by using the lower limit of Mn content and controlling the Mn / Cu ratio between 0.60 and 0.96 (0.71) in this invention, the formation of the AlCuMn phase can be fully promoted, with no Al6Mn phase and a ratio reaching 6.1 mol.%. Simultaneously, combined with... Figure 2 and Figure 3 It can be seen that the aluminum alloy maintains fine grain characteristics and has no abnormally large grains.

[0049] Comparative Example 1: Al-10.0Zn-2.0Mg-2.1Cu alloy (wt%).

[0050] The forming process of the Al-Zn-Mg-Cu aluminum alloy in Comparative Example 1 adopts friction stir additive manufacturing + heat treatment (solution + aging), specifically including the following steps:

[0051] (1) Melting: The alloying elements are added to the vacuum induction melting furnace in proportion, and after isothermal refining at 700 °C for 30 min, the bars are obtained by casting and machining.

[0052] (2) Using a friction stir additive manufacturing equipment, the bar is placed in the feeding mechanism of the equipment. The rotation speed is 600 r / min, the forward speed is 120 mm / min, the single-layer additive manufacturing thickness is 2 mm, and the component is formed according to the geometric dimensions of the construction.

[0053] (3) Heat the component as a whole in a heat treatment furnace to 450±10 ℃, keep it at that temperature for 1 h, and then cool it to room temperature in a water bath; heat it in a heat treatment furnace to 150±10 ℃, keep it at that temperature for 4 h, and then take it out and cool it to room temperature.

[0054] Based on the elemental composition of the aluminum alloy in Comparative Example 1 and the heat deformation temperature, the phase composition of the generated phase was theoretically analyzed, and the results obtained are as follows. Figure 5 As shown, the alloy did not form the AlCuMn phase; the main phase was MgZn2. Simultaneously, the aluminum alloy component prepared in Comparative Example 1 was structurally characterized, and the results are as follows. Figure 6 As shown. Combined with Figure 6 It can be seen that the aluminum alloy has coarse grains, that is, abnormally large grains.

[0055] Example 2 Al-10.0Zn-2.0Mg-2.5Cu-2.0Mn alloy (wt%).

[0056] The forming process of the high-strength Al-Zn-Mg-Cu-Mn aluminum alloy in Example 2 is suitable for friction stir additive manufacturing + heat treatment (solution + aging), and specifically includes the following steps:

[0057] (1) Melting: The alloying elements are added to the vacuum induction melting furnace in proportion, and after isothermal refining at 700 °C for 30 min, the bars are obtained by casting and machining.

[0058] (2) Using a friction stir additive manufacturing equipment, the bar is placed in the feeding mechanism of the equipment. The rotation speed is 600 r / min, the forward speed is 120 mm / min, the single-layer additive manufacturing thickness is 2 mm, and the component is formed according to the geometric dimensions of the construction.

[0059] (3) Heat the component as a whole in a heat treatment furnace to 450±10 ℃, keep it at that temperature for 1 h, and then cool it to room temperature in a water bath; heat it in a heat treatment furnace to 150±10 ℃, keep it at that temperature for 4 h, and then take it out and cool it to room temperature.

[0060] Based on the elemental composition of the aluminum alloy in Example 2 and the heat deformation temperature, the phase composition of the generated phase was theoretically analyzed, and the results are as follows. Figure 7 As shown. The present invention uses the upper limit of Mn content and controls the Mn / Cu ratio between 0.60 and 0.96 (0.8), which can fully promote the formation of AlCuMn phase, without Al6Mn phase, and the ratio reaches 8.3 mol.%.

[0061] Example 3 Al-9Zn-1.8Mg-2.3Cu-1.8Mn alloy (wt%).

[0062] The forming process of the high-strength Al-Zn-Mg-Cu-Mn aluminum alloy in Example 3 is suitable for friction stir additive manufacturing + heat treatment (solution + aging), and specifically includes the following steps:

[0063] (1) Melting: The alloying elements are added to the vacuum induction melting furnace in proportion, and after isothermal refining at 700 °C for 30 min, the bars are obtained by casting and machining.

[0064] (2) Using a friction stir additive manufacturing equipment, the bar is placed in the feeding mechanism of the equipment. The rotation speed is 600 r / min, the forward speed is 120 mm / min, the single-layer additive manufacturing thickness is 2 mm, and the component is formed according to the geometric dimensions of the construction.

[0065] (3) Heat the component as a whole in a heat treatment furnace to 450±10 ℃, keep it at that temperature for 1 h, and then cool it to room temperature in a water bath; heat it in a heat treatment furnace to 150±10 ℃, keep it at that temperature for 4 h, and then take it out and cool it to room temperature.

[0066] Based on the elemental composition of the aluminum alloy in Example 3 and the heat deformation temperature, the phase composition of the generated phase was theoretically analyzed, and the results are as follows. Figure 8 As shown. This invention increases the Mn content to 1.8% and controls the Mn / Cu ratio between 0.60 and 0.96 (0.78), which can still fully promote the formation of the AlCuMn phase, with no Al6Mn phase, and the ratio reaches 7.4 mol.%.

[0067] Performance testing -- Mechanical performance testing.

[0068] The aluminum alloys prepared in Example 1 and Comparative Example 1 of this invention were subjected to mechanical property testing, and the results are as follows: Figure 9 , Figure 10 As shown in the figure. Meanwhile, the mechanical properties of Example 1, Example 2, and Comparative Example 1 were characterized, and the results are shown in Table 1 below.

[0069] Table 1. Mechanical property data of aluminum alloys in Examples 1, 2 and Comparative Example 1.

[0070]

[0071] Through Table 1 and in conjunction with Figures 1 to 10 As can be seen from Comparative Example 1 and Comparative Example 1, the present invention forms an AlCuMn phase through Mn and Cu elements, which suppresses abnormal grain growth during the solid solution process, that is, maintains a fine grain state, forms fine grain strengthening, and simultaneously improves strength and plasticity. Ultimately, the Al-Zn-Mg-Cu-Mn alloy can undergo "solution + aging" heat treatment after friction stir additive manufacturing, thereby significantly improving the strength of aluminum alloy components manufactured by friction stir additive manufacturing. Compared with Comparative Example 1, the tensile strength of the present invention can reach more than 600 MPa, and the elongation of heat treatment can reach more than 10%.

[0072] In addition to the above embodiments, it should be noted that the alloys and processes of the present invention can achieve the technical effects claimed by the present invention, and therefore no further testing and verification are required.

Claims

1. A high-strength Al-Zn-Mg-Cu-Mn alloy suitable for friction stir additive manufacturing, characterized in that, The following elements are included by mass fraction: Zn: 9.0-11.0%; Mg: 1.8-2.2%; Mn: 1.5-2.0%; Cu: 2.1-2.5%; The balance is Al and unavoidable impurities; the Mn / Cu ratio is controlled between (0.60-0.95):1; The forming process of this high-strength Al-Zn-Mg-Cu-Mn alloy includes the following steps: (1) The Al-Zn-Mg-Cu-Mn alloy rods or Al-Zn-Mg-Cu-Mn alloy wires obtained after melting and machining are subjected to friction stirring additive manufacturing to form Al-Zn-Mg-Cu-Mn alloy components; (2) Heat the Al-Zn-Mg-Cu-Mn alloy component uniformly to 440-460 ℃, keep it at that temperature for 0.5-2 h, and then place it in a water bath to cool to room temperature; then heat it uniformly to 140-160 ℃, keep it at that temperature for 4-4.5 h, and then take it out and cool it to room temperature.

2. The high-strength Al-Zn-Mg-Cu-Mn alloy according to claim 1, characterized in that, The following elements are included by mass fraction: Zn: 10%; Mg: 2.0%; Mn: 1.5%; Cu: 2.1%; Balance Al and unavoidable impurities.

3. The high-strength Al-Zn-Mg-Cu-Mn alloy according to claim 1, characterized in that, The following elements are included by mass fraction: Zn: 10%; Mg: 2.0%; Mn: 2.0%; Cu: 2.5%; Balance Al and unavoidable impurities.

4. The high-strength Al-Zn-Mg-Cu-Mn alloy according to claim 1, characterized in that, In step (1), the rotational speed of the friction stir additive manufacturing is 300-1200 r / min and the forward speed is 60-300 mm / min.

5. The high-strength Al-Zn-Mg-Cu-Mn alloy according to claim 1, characterized in that, In step (1), the Al-Zn-Mg-Cu-Mn alloy bar or Al-Zn-Mg-Cu-Mn alloy wire is obtained by the following steps: the raw materials are prepared according to the alloy elements and placed in a melting furnace. After isothermal refining at 690-710 ℃ for 25-35 min, the bar or wire is obtained by casting and machining.

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