CN112143988A - Method for improving mechanical property of Al-Cu-Li alloy through long-term low-temperature aging treatment - Google Patents
Method for improving mechanical property of Al-Cu-Li alloy through long-term low-temperature aging treatment Download PDFInfo
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- CN112143988A CN112143988A CN202011106136.2A CN202011106136A CN112143988A CN 112143988 A CN112143988 A CN 112143988A CN 202011106136 A CN202011106136 A CN 202011106136A CN 112143988 A CN112143988 A CN 112143988A
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
- C22F1/057—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with copper as the next major constituent
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C21/00—Alloys based on aluminium
- C22C21/12—Alloys based on aluminium with copper as the next major constituent
- C22C21/16—Alloys based on aluminium with copper as the next major constituent with magnesium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/002—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working by rapid cooling or quenching; cooling agents used therefor
Abstract
A method for improving the mechanical properties of Al-Cu-Li alloy by long-term low-temperature aging treatment is characterized in that the Al-Cu-Li alloy in a strain aging state (T8 state) is subjected to long-term low-temperature aging (50-5000 h) at a certain temperature of 60-120 ℃ to induce T1Further precipitation of solute elements between the laths provides additional strengthening and toughening effects to the alloy without inducing T in the T8 state alloy1The coarsening of the phase finally improves the comprehensive mechanical property of the Al-Cu-Li alloy. The tensile strength, yield strength and elongation after fracture of the T8-state Al-3.67Cu-1.12Li-0.26Mg-0.19Ag-0.11Zr alloy are respectively improved from 594.93 +/-7.39 MPa, 566.99 +/-8.34 MPa and 10.52 +/-0.53 percent to 599.89 +/-4.44 MPa, 573.18 +/-3.49 MPa and 12.93 +/-1.60 percent after heat preservation for 1500 hours at 85 ℃, and the tensile strength and elongation after fracture are respectively improved to 598.04 +/-2.51 MPa and 13.36 +/-0.46 percent after aging for 100 hours at 85 ℃. The preparation method is simple and has low energy consumptionLow cost, strong applicability and potential application in strengthening and toughening Al-Cu-Li alloy.
Description
The technical field is as follows:
the invention relates to a heat treatment method for strengthening and toughening an aluminum-lithium alloy for aerospace. Specifically, the method is to perform long-term aging at low temperature on the Al-Cu-Li alloy in the T8 state (solid solution + cold working + artificial aging state or strain aging state) so as to further improve the mechanical property of the Al-Cu-Li alloy.
Background
The aluminum-lithium alloy is a novel aluminum alloy with low density, high specific strength and specific stiffness, and good corrosion resistance and fatigue resistance, and has wide application prospects in the field of aerospace. Compared with carbon fiber composite materials, the aluminum lithium alloy has the advantages of convenience in forming and maintaining, low cost, obvious price advantage and performance advantage, and is considered to be one of the most competitive light high-strength structural materials in the aerospace industry in the 21 st century. [ document one: n.espara Prasad, a.a.gokhale, r.j.h.wanhill. aluminium-Lithium Alloys, Elsevier, Oxford, 2014; document two: the development and comprehensive performance evaluation of the plum blossom, the yao satellite and the aluminum lithium alloy material, and the progress of the aeronautical engineering 10(2019)12-20.]. The performance of the Al-Cu-Li alloy strongly depends on microstructure characteristics such as size, morphology, number, and distribution of precipitated phases, and the improvement of the comprehensive performance thereof greatly depends on the regulation and control of the microstructure of the precipitated phases [ document three: gumbmann, F.De Geuser, C.Sigli, A.Deschamps.Influence of Mg, Ag and Zn minor soluble additions on the precipitation kinetics and Strongth promotion of an Al-Cu-Li alloy, Acta Mater.133(2017)172-185.]. The precipitation sequence of Al-Cu-Li alloy is quite complex, such as different compositions, aging temperature or aging time result in different precipitation paths, and various types of metastable phases and stable phases are generated, wherein T is1(Al2CuLi) precipitation phase is the main strengthening phase of the Al-Cu-Li alloy and is formed on the base in a hexagonal plate strip shape (or a flake shape)Volume {111}AlOn the face, at a semi-coherent interface with the substrate, with an aspect ratio of up to 100 [ four: E.Gumbmann, F.De Geuser, A.Deschamps, W.Lefebvre, F.Robaut, C.Sigli.A combinatorial approach for interpreting the effect of Mg concentration on precipitation in an Al-Cu-Li alloy, script matrix.110 (2016)44-47.]。
T1The phase microstructure can be regulated and controlled by a strain aging process, and the process involves multiple factors such as pre-deformation, aging temperature, aging time and the like [ document five: rodgers, P.B.Prangnell.the influence of Cu/Li ratio on precipitation in Al-Cu-Li-x alloys, Acta mater.108(2016) 55-67; document six: dorin, A.Deschamps, F.De Geuser, W.Lefebvre, C.Sigli.Quantitative description of the T.1 formation kinetics in an Al–Cu–Li alloy using differential scanning calorimetry,small-angle X-ray scattering and transmission electron microscopy,Phil.Mag.94(2014)1012–1030.]. First, the pre-deformation promotes T1The phases are dispersed and precipitated during artificial aging, the number of' phases is reduced, the formation of a grain boundary equilibrium phase is inhibited, the width of a grain boundary non-precipitation zone (PFZ) is reduced, the types and the distribution of the grain boundary and the intra-grain precipitated phases after artificial aging are effectively adjusted, the alloy strength is obviously improved, and the fracture toughness is improved. The aging temperature and the aging time are also T regulation and control in the strain aging process1Key parameters of phase microstructure. Lath T in Al-Cu-Li alloy during long-term heat preservation at typical aging temperature (about 155℃)1The thickness of the phase will remain at about 1.3nm due to T1Phase plate stripe coarsening (or nucleation of new cells in the thickness direction) requires overcoming higher energy barriers [ document six: dorin, A.Deschamps, F.De Geuser, W.Lefebvre, C.Sigli.Quantitative description of the T.1 formation kinetics in an Al–Cu–Li alloy using differential scanning calorimetry,small-angle X-ray scattering and transmission electron microscopy,Phil.Mag.94(2014)1012–1030.]。
T at typical ageing temperature1T is made by a special growth mechanism with increased strip length and stable thickness1Solute elements such as Cu, Li, Mg and the like remain among the laths,the solute over-saturation degree increases with the temperature reduction, and solute elements are likely to be further precipitated to form GP zones and equal phases when the temperature is kept below 120 ℃ for a long time, so that T is maintained1The premise of the phase characteristics provides an additional strengthening effect for the alloy. Therefore, the influence of long-term low-temperature aging on the mechanical property of the Al-Cu-Li alloy is explored, and a new method is provided for further excavating the strengthening and toughening potential of the alloy.
Disclosure of Invention
The invention aims to provide a method for promoting T in a strain aged state (solid solution + cold working + artificial aging, namely T8 state) Al-Cu-Li alloy by long-term low-temperature aging treatment1The solute elements are separated out among the battens, so that the comprehensive mechanical property of the alloy is further improved.
A method for improving mechanical properties of an Al-Cu-Li alloy through long-term low-temperature aging treatment is characterized in that the Al-Cu-Li alloy is a T8 state Al-Cu-Li alloy, and an oil bath furnace or a water bath furnace is utilized to perform low-temperature aging for 50-5000 hours on the strain aging state, namely the T8 state Al-Cu-Li alloy at a certain temperature of 60-120 ℃, so that on one hand, T cannot be caused1Coarsening of phase, keeping T in T8 state alloy1A characteristic of the phase; simultaneous induction of T1Solute elements among the strips are further separated out, an additional strengthening and toughening effect is provided for the alloy, and the comprehensive mechanical property of the Al-Cu-Li alloy is improved.
Further, the Al-Cu-Li alloy comprises 1.0-4.5 Cu, 0.5-2.5 Li, 0.2-1.0 Mg, 0.2-0.5 Ag, 0.08-0.15 Zr (wt%), and the balance Al, and specifically comprises the following steps:
(1) heating an oil bath furnace or a water bath furnace to a certain temperature T between 60 and 120 DEG C0；
(2) When the furnace temperature reaches T0Putting the T8 state Al-Cu-Li alloy into an oil bath furnace or a water bath furnace, and starting timing and heat preservation, wherein the heat preservation time is 50-5000 hours and is determined according to the performance requirement;
(3) and taking the Al-Cu-Li alloy out for water quenching after the heat preservation is finished, thereby obtaining the long-term low-temperature aging-state alloy.
Furthermore, the Al-Cu-Li alloy comprises Al-3.67Cu-1.12Li-0.26Mg-0.19Ag-0.11Zr (wt%), the tensile strength, yield strength and elongation after fracture of the alloy are respectively improved from 594.93 +/-7.39 MPa, 566.99 +/-8.34 MPa and 10.52 +/-0.53% to 599.89 +/-4.44 MPa, 573.18 +/-3.49 MPa and 12.93 +/-1.60% after heat preservation for 1500h at 85 ℃, and the tensile strength and elongation after fracture are respectively improved to 598.04 +/-2.51 MPa and 13.36 +/-0.46% after long-term low-temperature aging for 100h at 85 ℃.
The invention has the beneficial effects that:
1. without affecting the main strengthening phase (i.e. T)1) Induce additional nanoscalation, resulting in a simultaneous increase in strength and plasticity. Lath T in Al-Cu-Li alloy when keeping temperature for long time at typical aging temperature1The thickness of the phase will remain constant, so that T1Solute elements such as Cu, Li, Mg and the like remain among the strips (see the area I in figure 1); but at higher temperatures T1The phase thickness will be destabilized. The invention adopts long-time heat preservation at a certain temperature of 60-120 ℃ for the T8 state Al-Cu-Li alloy, so that T cannot be caused1Coarsening of the phases and T1Solute elements between the strips are further precipitated after long-term aging at low temperature, so that T is maintained1The premise of the phase characteristics provides an additional strengthening and toughening effect for the alloy. For example, the tensile strength, yield strength and elongation after fracture of the T8 Al-3.67Cu-1.12Li-0.26Mg-0.19Ag-0.11Zr (wt%) alloy are respectively improved from 594.93 +/-7.39 MPa, 566.99 +/-8.34 MPa and 10.52 +/-0.53% to 599.89 +/-4.44 MPa, 573.18 +/-3.49 MPa and 12.93 +/-1.60% after heat preservation at 85 ℃ for 1500 h.
2. The preparation method is simple, low in energy consumption, low in cost and strong in applicability. By adopting the method of the invention, the T can be realized by directly utilizing the low-temperature treatment of the oil bath furnace or the water bath furnace1Further precipitation of solute elements among the strips and the corresponding strengthening and toughening effect have application potential in the strengthening and toughening aspect of the Al-Cu-Li alloy.
Drawings
Other features, details and advantages of the present invention will become more fully apparent from the following detailed description of the specific embodiments of the invention when taken in conjunction with the accompanying drawings.
Lath shaped T in Al-Cu-Li alloy in state T8 in FIG. 11Phase characteristics, white dotted frame tableRegion I is shown as a supersaturated zone of residual solute elements.
FIG. 2 is a comparison of the engineering stress strain curves of Al-Cu-Li alloys in the T8 temper and in the long term low temperature aged temper (85 ℃ C. for 1500 h).
The specific implementation mode is as follows:
the invention is described in detail below by means of exemplary embodiments. It is pointed out that the person skilled in the art will readily understand that the following examples are given by way of illustration only and are not intended to limit the invention in any way.
Example 1:
taking a T8 Al-Cu-Li alloy as an example (the components are shown in Table 1), the evolution of the normal temperature mechanical properties of the alloy after aging at 85 ℃ for different times is studied. Heating the DV-20 digital display constant-temperature oil bath pan to 85 ℃, putting the T8-state Al-Cu-Li alloy into the oil bath pan, starting timing and heat preservation, respectively preserving heat for 100, 500, 1000 and 1500 hours, taking out the alloy and performing water quenching to obtain the long-term low-temperature aging-state Al-Cu-Li alloy with different heat preservation times. A tensile test sample is taken from the alloy in a long-term low-temperature aging state, the surface of the tensile sample is pre-ground and polished, the tensile test is completed on a German FPZ100 universal material testing machine, 4 samples are obtained, and the measured mechanical properties are shown in Table 2. The tensile strength and the elongation after fracture are both improved at the same time after long-term low-temperature ageing for 100 hours at 85 ℃, particularly the latter is improved more obviously, which is probably due to T1After precipitation of solute elements between laths, T1Lath vicinity and T1Differential strain hardening (i.e. T) in the inter-strip region1High degree of strain hardening in the vicinity of the phase T1Low strain hardening in the inter-strip region, resulting in poor strain hardening in both regions) and enhanced co-ordinated deformability, T1The generation tendency of the phase-matrix interface cracks is reduced. When long-term low-temperature aging reaches 1000 h and 1500h at 85 ℃, solute elements are fully separated out, effective strengthening and toughening effects are generated, and the tensile strength, the yield strength and the elongation after fracture are all simultaneously improved (see table 2 and figure 2).
TABLE 1 chemical composition (wt%) of Al-Cu-Li experimental alloys
TABLE 2 evolution of the mechanical properties at room temperature of Al-Cu-Li experimental alloys in T8 state and long-term low-temperature aging state at 85 deg.C
Claims (3)
1. A method for improving mechanical properties of an Al-Cu-Li alloy through long-term low-temperature aging treatment is characterized in that the Al-Cu-Li alloy is a T8 state Al-Cu-Li alloy, and when an oil bath furnace or a water bath furnace is used for carrying out low temperature treatment on the strain aging state, namely the T8 state Al-Cu-Li alloy for 50-5000 hours at a certain temperature of 60-120 ℃), on one hand, T cannot be caused1Coarsening of phase, keeping T in T8 state alloy1A characteristic of the phase; simultaneous induction of T1Solute elements among the strips are further separated out, an additional strengthening and toughening effect is provided for the alloy, and the comprehensive mechanical property of the Al-Cu-Li alloy is improved.
2. The method for improving the mechanical properties of the Al-Cu-Li alloy in a long-term low-temperature aged state according to claim 1, wherein the Al-Cu-Li alloy comprises the following components in the range of 1.0-4.5 Cu, 0.5-2.5 Li, 0.2-1.0 Mg, 0.2-0.5 Ag, 0.08-0.15 Zr (wt%), and the balance Al, and comprises the following steps:
(1) heating an oil bath furnace or a water bath furnace to a certain temperature T between 60 and 120 DEG C0；
(2) When the furnace temperature reaches T0Putting the T8 state Al-Cu-Li alloy into an oil bath furnace or a water bath furnace, and starting timing and heat preservation, wherein the heat preservation time is 50-5000 hours and is determined according to the performance requirement;
(3) and taking the Al-Cu-Li alloy out for water quenching after the heat preservation is finished, thereby obtaining the long-term low-temperature aging-state alloy.
3. The method of claim 2, wherein the Al-Cu-Li alloy has Al-3.67Cu-1.12Li-0.26Mg-0.19Ag-0.11Zr (wt%), the tensile strength, yield strength and elongation after fracture of the alloy are respectively increased from 594.93 + -7.39 MPa, 566.99 + -8.34 MPa and 10.52 + -0.53% to 599.89 + -4.44 MPa, 573.18 + -3.49 MPa and 12.93 + -1.60% after being kept at 85 ℃ for 1500h, and the tensile strength and elongation after fracture are respectively increased to 598.04 + -2.51 MPa and 13.36 + -0.46% after being kept at 85 ℃ for 100 h.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2974118A1 (en) * | 2011-04-15 | 2012-10-19 | Alcan Rhenalu | HIGH TEMPERATURE PERFORMANCE ALUMINUM COPPER MAGNESIUM ALLOYS |
| CN106834830A (en) * | 2017-03-14 | 2017-06-13 | 北京工业大学 | A kind of Si microalloyings Al Mg Cu alloys |
| CN111676431A (en) * | 2020-04-30 | 2020-09-18 | 中南大学 | Two-stage continuous aging treatment method for aluminum-lithium alloy |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2974118A1 (en) * | 2011-04-15 | 2012-10-19 | Alcan Rhenalu | HIGH TEMPERATURE PERFORMANCE ALUMINUM COPPER MAGNESIUM ALLOYS |
| CN106834830A (en) * | 2017-03-14 | 2017-06-13 | 北京工业大学 | A kind of Si microalloyings Al Mg Cu alloys |
| CN111676431A (en) * | 2020-04-30 | 2020-09-18 | 中南大学 | Two-stage continuous aging treatment method for aluminum-lithium alloy |
Non-Patent Citations (2)
| Title |
|---|
| [印]N.伊斯瓦拉•普拉萨德等编，戴圣龙等译: "《铝锂合金：工艺、性能和应用》", 30 November 2016, 航空工业出版社 * |
| A. DESCHAMPS等: ""Influence of Mg and Li content on the microstructure evolution of Al-Cu-Li alloys during long-term ageing"", 《ACTA MATERIALIA》 * |
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