Light, high-strength and heat-resistant aluminum-lithium alloy material and preparation method thereof

Abstract

The invention relates to a light, high-strength and heat-resistant aluminum-lithium alloy material and a preparation method thereof. The alloy material comprises the following chemical components in percentage by weight: 2.8-4.0% of Cu, 1.8-2.5% of Li, 0.40-0.80% of Zn, 0.10-0.25% of Zr, 0.10-0.50% of SC, less than or equal to 0.12% of impurity Si, less than or equal to 0.15% of impurity Fe, less than or equal to 0.05% of each of other impurities, less than or equal to 0.15% of the total amount of other impurities and the balance of Al. The preparation method comprises the following steps: burdening according to the components of the alloy material, melting the raw materials, refining in a furnace, fully standing, and pouring into an alloy ingot with the required specification. The alloy ingot obtains excellent comprehensive performance after being homogenized, and then the alloy ingot is processed into required parts.

Description

Technical Field

[0001] The invention discloses a light-weight, high-strength, heat-resistant aluminum-lithium alloy material and a preparation method thereof, and belongs to the field of metal material engineering. Background Art

[0002] Aluminum-lithium alloy has the advantages of low density, high elastic modulus, specific stiffness and specific strength, weldability, etc. Replacing traditional high-strength aluminum alloy with it can reduce the structural mass by 10% to 20% and increase the stiffness by 15% to 20%. It is considered to be one of the most promising lightweight and high-strength structural materials. The development focus of aluminum-lithium alloy in the past 30 years has been the third generation of aluminum-lithium alloy, Al-Cu-Li-X alloy, with Li content generally below 1.8wt%, Cu / Li ratio relatively high, and density of about 2.70 to 2.73g / cm 3 These alloys have a higher Cu content, which ensures higher strength, but the lower Li content makes the alloys denser and the weight reduction effect is lower. Summary of the invention

[0003] The present invention is designed to provide a lightweight, high-strength, heat-resistant aluminum-lithium alloy material and a preparation method thereof in response to the above-mentioned prior art conditions. The purpose is to make the alloy material have the characteristics of low density, high strength and excellent heat resistance. The specific index requirement is that the density ρ≤2.65g / cm 3 , the ultimate tensile strength at room temperature can reach more than 550MPa, and the yield strength can reach more than 500MPa; the tensile strength at 200°C can reach more than 430MPa, and the yield strength can reach more than 410MPa. Meeting the above requirements, the alloy material products described in the technical solution of the present invention can be used for structural components in the fields of aerospace, nuclear industry, transportation, sports goods, weapons, etc.

[0004] The objective of the present invention is achieved through the following technical solutions:

[0005] The light, high-strength, heat-resistant aluminum-lithium alloy material proposed in the technical solution of the present invention comprises the following chemical components and weight percentages: Cu 2.8% to 4.0%, Li 1.8% to 2.5%, Zn 0.40% to 0.80%, Zr 0.10% to 0.25%, S C 0.10%~0.50%, impurity Si≤0.12%, impurity Fe≤0.15%, other impurities each ≤0.05%, the total amount of other impurities ≤0.15%, the balance is Al.

[0006] In addition, the alloy material further comprises one or more of Mn, Mg and Ag, and the weight percentages of the above three alloy elements are: Mg 0.30% to 1.1%, Mn 0.20% to 0.60%, and Ag 0.20% to 0.60%.

[0007] The alloy material of the present invention is designed with a relatively high Li content, with the highest Li element weight percentage reaching 2.50%. The increase in the Li element content results in a lower alloy density and a higher elastic modulus, while also bringing about an improvement in the overall strength and toughness properties.

[0008] In addition, the alloy material of the present invention adds a maximum weight percentage content of 0.80% Zn element, which has solid solution strengthening and aging strengthening effects, can promote the precipitation of the δ′ phase and reduce its coarsening and growth rate; the Zn element can also promote the precipitation of the S′ and T1 phases, thereby improving the strength of the alloy; the Zn element can also enter the intergranular (A1CuFe) to form a complex low-melting point impurity phase during casting, which can reduce the number and size of micro-porosity and further improve the comprehensive performance of the alloy.

[0009] In addition, the alloy material of the present invention adds a maximum of 0.25% Zr element and 0.5% Sc by weight. When Zr and Sc are added simultaneously, the grains can be refined, recrystallization can be suppressed, and the size of the strengthening phase can be changed. Al3Zr and Al3Sc composite particles are precipitated, and a large amount of precipitation of the main strengthening phase T1 phase on the small-angle grain boundary is promoted, so that the T1 phase is further refined, the stability of the T1 phase under high temperature conditions is better, and the heat resistance of the alloy is improved.

[0010] Therefore, the alloy material of the present invention has the characteristics of high Li content, lower alloy density and better strength; the addition of Zn element can improve the alloy's strength, plasticity and metallurgical quality, and the addition of Zr and Sc elements can improve the alloy's strength, toughness and heat resistance.

[0011] In one embodiment, the alloy material comprises the following chemical components and weight percentages: Cu 2.8% to 3.8%, Li 2.05% to 2.35%, Zn 0.40% to 0.80%, Zr 0.1% to 0.2%, S C 0.20%~0.50%, impurity Si≤0.12%, impurity Fe≤0.15%, other impurities each ≤0.05%, the total amount of other impurities ≤0.15%, the balance is Al.

[0012] In one embodiment, the alloy material comprises the following chemical components and weight percentages: Cu 3.3% to 3.8%, Li 2.0% to 2.5%, Zn 0.40% to 0.80%, Zr 0.1% to 0.2%, S C 0.20%~0.50%, impurity Si≤0.12%, impurity Fe≤0.15%, other impurities each ≤0.05%, the total amount of other impurities ≤0.15%, the balance is Al.

[0013] In one embodiment, the alloy material comprises the following chemical components and weight percentages: Cu 2.8% to 3.4%, Li 1.8% to 2.4%, Zn 0.45% to 0.75%, Zr 0.1% to 0.2%, S C 0.10%~0.40%, Mg0.30%~1.1%, Mn 0.20%~0.60%, Ag 0.20%~0.60%, impurity Si≤0.12%, impurity Fe≤0.15%, other impurities each ≤0.05%, the total amount of other impurities ≤0.15%, the balance is Al.

[0014] The technical solution of the present invention also provides a method for preparing the above-mentioned lightweight, high-strength, heat-resistant aluminum-lithium alloy material, characterized in that the steps of the method are as follows:

[0015] Step 1: pre-batch the materials according to the composition ratio of the alloy materials, wherein the pre-batch does not contain metallic Li raw materials;

[0016] Step 2: Melting the pre-batch in a melting furnace at a melting temperature of 680°C to 780°C;

[0017] Step 3, refining the completely molten metal liquid, and maintaining the metal temperature in the range of 700°C to 760°C during refining;

[0018] Step 4: The refined molten metal is transferred to a vacuum standing furnace, and the metal Li raw material is added, and the molten metal is allowed to stand in a vacuum state, with a vacuum degree of 1000Pa to 1300Pa. The vacuum standing process is divided into the following four steps:

[0019] Step 1: Heat to 760°C and keep warm for at least 3 minutes;

[0020] Step 2: Heat to 790°C and keep warm for no less than 10 minutes;

[0021] Step 3: Cool down to 760℃ and keep warm for no less than 4 minutes;

[0022] Step 4: Cool down to 720℃ and keep warm for no less than 3 minutes;

[0023] Step 5: After the standing is completed, argon gas protection casting is started, the furnace mouth temperature is maintained in the range of 700℃~720℃, and the casting speed is 15~200mm / min;

[0024] Step 6: Perform a two-stage homogenization treatment on the alloy ingot in a heating furnace, wherein the first-stage homogenization temperature is 400°C to 420°C, the second-stage homogenization temperature is 480°C to 510°C, and the second-stage homogenization time is not less than 36 hours;

[0025] Step 7: After the homogenized ingot is peeled, high-temperature processing is performed. During the high-temperature processing, the billet should be kept in a temperature range of 380°C to 480°C. The high-temperature processing and forming methods include the following:

[0026] After the homogenized ingot is peeled, hot extrusion is performed. During the hot extrusion process, the billet should be kept in the temperature range of 380℃~440℃;

[0027] After the homogenized ingot is peeled, hot forging is performed. During the forging process, the billet should be kept in the temperature range of 380℃~470℃;

[0028] After the homogenized ingot is peeled, it is hot-ring rolled into a cylindrical piece. During the hot-ring rolling process, the billet should be kept in the temperature range of 380℃~470℃;

[0029] Step 8: heat-treat the formed blank to obtain excellent comprehensive properties, and then manufacture parts through drawing, bending, rolling and milling;

[0030] The heat treatment system is: 520°C solid solution, room temperature water quenching and cooling to room temperature, 1.5% to 7.0% permanent cold deformation pre-stretching, 140°C to 160°C / 20 to 48h aging treatment. DETAILED DESCRIPTION

[0031] The technical solution of the present invention will be further described in detail below in conjunction with embodiments:

[0032] The chemical composition and weight percentage of the alloy material selected in this embodiment are shown in Table 1.

[0033] The specific steps of the alloy material preparation process are as follows:

[0034] Step 1: pre-batch the materials according to the composition ratio of the alloy materials, wherein the pre-batch does not contain metallic Li raw materials;

[0035] Step 2: Melting the pre-batch in a melting furnace at a melting temperature of 680°C to 780°C;

[0036] Step 3, refining the completely molten metal liquid, and maintaining the metal temperature in the range of 700°C to 760°C during refining;

[0037] Step 4: The refined molten metal is transferred to a vacuum standing furnace, and the metal Li raw material is added, and the molten metal is allowed to stand in a vacuum state, with a vacuum degree of 1000Pa to 1300Pa. The vacuum standing process is divided into the following four steps:

[0038] Step 1: Heat to 760°C and keep warm for at least 3 minutes;

[0039] Step 2: Heat to 790°C and keep warm for no less than 10 minutes;

[0040] Step 3: Cool down to 760℃ and keep warm for no less than 4 minutes;

[0041] Step 4: Cool down to 720℃ and keep warm for no less than 3 minutes;

[0042] Step 5: After the standing is completed, argon gas protection casting is started, the furnace temperature is maintained in the range of 700°C to 720°C, the casting speed is 15 to 200 mm / min, and a 200×600 mm square ingot is cast;

[0043] Step 6: Perform a two-stage homogenization treatment on the alloy ingot in a heating furnace, wherein the first-stage homogenization temperature is 400°C to 420°C, the second-stage homogenization temperature is 480°C to 510°C, and the second-stage homogenization time is not less than 36 hours;

[0044] Step 7: After the homogenized ingot is peeled, it is hot-ring rolled into a cylindrical piece. During the hot ring rolling process, the billet should be kept in the temperature range of 380°C to 470°C, and a plate with a size of 60mm thickness × 600mm width × 2000mm length is rolled out;

[0045] Step 8: heat-treat the formed blank to obtain excellent comprehensive properties, and then manufacture parts through drawing, bending, rolling and milling;

[0046] The heat treatment system is: 520°C solid solution, room temperature water quenching and cooling to room temperature, 1.5% to 7.0% permanent cold deformation pre-stretching, 140°C to 160°C / 20 to 48h aging treatment.

[0047] The properties of the thick plate finally obtained are shown in Table 2. It can be seen that the density of the alloy material prepared by the present invention is ρ≤2.65g / cm 3 The tensile strength can reach more than 550MPa and the yield strength can reach more than 500MPa at room temperature; the tensile strength can reach more than 430MPa and the yield strength can reach more than 410MPa at 200℃. This material product can be used for structural parts in the fields of aviation, aerospace, nuclear industry, transportation, sports goods, weapons, etc.

[0048] Table 1 Alloy composition

[0049]

[0050]

[0051] Table 2 Thick plate properties

[0052]

Claims

1. A lightweight, high-strength, heat-resistant aluminum-lithium alloy material, characterized by: The alloy material comprises the following chemical components and weight percentages: Cu 2.8% to 4.0%, Li 1.8% to 2.5%, Zn 0.40% to 0.80%, Zr 0.10% to 0.25%, S C 0.10%~0.50%, impurity Si≤0.12%, impurity Fe≤0.15%, other impurities each ≤0.05%, the total amount of other impurities ≤0.15%, the balance is Al.

2. The lightweight, high-strength, heat-resistant aluminum-lithium alloy material according to claim 1, characterized in that: The alloy material further comprises one or more of Mn, Mg and Ag, wherein the weight percentages of the three alloy elements are as follows: Mg 0.30% to 1.1%, Mn 0.20% to 0.60%, and Ag 0.20% to 0.60%.

3. The lightweight, high-strength, heat-resistant aluminum-lithium alloy material according to claim 1, characterized in that: The alloy material comprises the following chemical components and weight percentages: Cu 2.8% to 3.8%, Li 2.05% to 2.35%, Zn 0.40% to 0.80%, Zr 0.1% to 0.2%, S C 0.20%~0.50%, impurity Si≤0.12%, impurity Fe≤0.15%, other impurities each ≤0.05%, the total amount of other impurities ≤0.15%, the balance is Al.

4. The lightweight, high-strength, heat-resistant aluminum-lithium alloy material according to claim 1, characterized in that: The alloy material comprises the following chemical components and weight percentages: Cu 3.3% to 3.8%, Li 2.0% to 2.5%, Zn 0.40% to 0.80%, Zr 0.1% to 0.2%, S C 0.20%~0.50%, impurity Si≤0.12%, impurity Fe≤0.15%, other impurities each ≤0.05%, the total amount of other impurities ≤0.15%, the balance is Al.

5. The lightweight, high-strength, heat-resistant aluminum-lithium alloy material according to claim 1 or 2, characterized in that: The alloy material comprises the following chemical components and weight percentages: Cu 2.8% to 3.4%, Li 1.8% to 2.4%, Zn 0.45% to 0.75%, Zr 0.1% to 0.2%, S C 0.10%~0.40%, Mg 0.30%~1.1%, Mn 0.20%~0.60%, Ag 0.20%~0.60%, impurity Si≤0.12%, impurity Fe≤0.15%, other impurities each ≤0.05%, the total amount of other impurities ≤0.15%, the balance is Al.

6. A method for preparing the lightweight, high-strength, heat-resistant aluminum-lithium alloy material according to claim 1, characterized in that: The steps of this method are as follows: Step 1: pre-batch the materials according to the composition ratio of the alloy materials, wherein the pre-batch does not contain metallic Li raw materials; Step 2: Melting the pre-batch in a melting furnace at a melting temperature of 680°C to 780°C; Step 3, refining the completely molten metal liquid, and maintaining the metal temperature in the range of 700°C to 760°C during refining; Step 4: The refined molten metal is transferred to a vacuum standing furnace, and the metal Li raw material is added, and the molten metal is allowed to stand in a vacuum state, with a vacuum degree of 1000Pa to 1300Pa. The vacuum standing process is divided into the following four steps: Step 1: Heat to 760°C and keep warm for at least 3 minutes; Step 2: Heat to 790℃ and keep warm for not less than 10 minutes; Step 3: Cool down to 760℃ and keep warm for no less than 4 minutes; Step 4: Cool down to 720℃ and keep warm for no less than 3 minutes; Step 5: After the standing is completed, argon gas protection casting is started, the furnace mouth temperature is maintained in the range of 700℃~720℃, and the casting speed is 15~200mm / min; Step 6: Perform a two-stage homogenization treatment on the alloy ingot in a heating furnace, wherein the first-stage homogenization temperature is 400°C to 420°C, the second-stage homogenization temperature is 480°C to 510°C, and the second-stage homogenization time is not less than 36 hours; Step 7: After the homogenized ingot is peeled, high-temperature processing is performed to form the ingot. During the high-temperature processing, the temperature of the ingot should be kept within the range of 380°C to 480°C; Step 8: heat-treat the formed blank to obtain excellent comprehensive properties, and then manufacture parts through drawing, bending, rolling and milling; The heat treatment system is: 520°C solid solution, room temperature water quenching and cooling to room temperature, 1.5% to 7.0% permanent cold deformation pre-stretching, 140°C to 160°C / 20 to 48h aging treatment.

7. The method for preparing a lightweight, high-strength, heat-resistant aluminum-lithium alloy material according to claim 6, characterized in that: In the step 7, the homogenized ingot is peeled and then hot extruded. During the hot extrusion process, the billet should be kept in a temperature range of 380° C. to 440° C.

8. The method for preparing a lightweight, high-strength, heat-resistant aluminum-lithium alloy material according to claim 6, characterized in that: In the step 7, the homogenized ingot is peeled and then hot forged. During the forging process, the billet should be kept in a temperature range of 380° C. to 470° C.

9. The method for preparing a lightweight, high-strength, heat-resistant aluminum-lithium alloy material according to claim 6, wherein The feature is that: in the step 7, the homogenized ingot is peeled and then hot-ring rolled into a cylindrical piece. During the hot ring rolling process, the billet should be kept in the temperature range of 380℃~470℃.

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