Homogenizing heat treatment process for Er, Yb and Sc composite microalloyed Al-Li alloy

Abstract

The invention discloses a homogenizing heat treatment process for Er, Yb and Sc composite microalloyed Al-Li alloy, and belongs to the field of metal material processing. The invention relates to a homogenization treatment process of an aluminum alloy ingot, which comprises the following alloy components in percentage by mass: 0.08 to 0.11 percent of Er, 0.07 to 0.11 percent of Yb, 0.07 to 0.16 percent of Sc, 1.2 to 1.7 percent of Li, less than or equal to 0.3 percent of inevitable impurities and the balance of aluminum alloy ingot casting. And the two-stage homogenization treatment process comprises the following steps: preserving heat at 580 DEG C for 24 hours, and then preserving heat at 630 DEG C for 48 hours. According to the method, the defects of an alloy as-cast structure can be eliminated, the uniformity and the hot working performance of the alloy structure can be improved, meanwhile, a primary precipitated phase in the alloy can be promoted to melt back into a matrix, precipitation and growth of a dispersed phase of the alloy in the hot working process can be improved, and growth of deformed grains is restrained.

Description

Technical Field

[0001] The invention belongs to the technical field of metal alloy materials, and in particular relates to a two-stage homogenization heat treatment process for Er, Yb, Sc composite microalloyed Al-Li alloy. Background Art

[0002] Al-Li aluminum alloys have the advantages of low density, high elastic modulus, and high specific strength, and have been widely used in the aerospace field. The addition of Li can reduce the density of the alloy and precipitate the metastable L12 structure Al3Li phase, which has a good second phase strengthening effect. However, the solid solubility of Li in Al is high, and the nucleation driving force of Al3Li is small, so it is difficult to precipitate in the current conventional Al-Li alloy. In order to promote the precipitation of Al3Li phase, the commonly used method is microalloying. Adding microalloying elements such as Er, Yb, and Sc to Al can also precipitate the L12 structure Al3M phase, and serve as heterogeneous nucleation points of Al3Li, which plays a role in promoting the precipitation of Al3Li phase. However, due to the problems of component segregation and primary phase precipitation in the solidification process of Er, Yb, and Sc composite microalloyed Al-Li alloys, the hot working properties of the alloy are seriously reduced. Therefore, in order to eliminate the segregation and primary phase problems in the ingot structure, so as not to affect the subsequent processing properties of the alloy, a reasonable homogenization heat treatment must be carried out before the hot deformation of the ingot.

[0003] Homogenization heat treatment is an extremely important process in alloy preparation and application. Reasonable homogenization heat treatment can achieve the following effects: 1. Eliminate the segregation of elements in alloy ingots, so that the elements are evenly distributed; 2. Eliminate the precipitation of primary phases in the alloy and improve the hot working properties of the alloy.

[0004] Therefore, for Er, Yb, Sc composite microalloyed Al-Li alloy, a suitable homogenization heat treatment process needs to eliminate the component segregation and primary phase of the alloy ingot. Based on the above technical background, the present invention designs a double-stage homogenization heat treatment process corresponding to the alloy. Summary of the invention

[0005] The purpose of the present invention is to provide a two-stage homogenization heat treatment process suitable for Er, Yb, Sc composite microalloyed Al-Li alloy. The provided treatment process can eliminate the segregation and primary phase problems existing in the ingot and improve the hot workability of the Er, Yb, Sc composite microalloyed Al-Li alloy.

[0006] The invention provides a two-stage homogenization heat treatment process suitable for Al-Li-Er-Yb-Sc alloy. The process is suitable for Er, Yb, Sc composite microalloyed Al-Li alloy in which the alloy components are (mass percentage) Er: 0.08-0.11wt.%, Yb: 0.07-0.11wt.%, Sc: 0.07-0.16wt.%, Li: 1.2-1.7wt.%, inevitable impurities are ≤0.3wt.%, and the balance is Al. The composition of the alloy is preferably: 0.09wt.% Er, 0.08wt.% Yb, 0.16wt.% Sc, 1.33wt.% Li, impurities are ≤0.3wt.%, and the balance is Al.

[0007] The present invention provides a two-stage homogenization heat treatment process suitable for Al-Li-Er-Yb-Sc alloy, and the process comprises the following steps:

[0008] 1) Pure aluminum, Al-Yb, Al-Er, and Al-Sc master alloys are heated from room temperature to 800° C. within 80 minutes and kept at this temperature for 90 minutes to form aluminum alloy liquid;

[0009] 2) To prevent the Al-Li master alloy from burning when in contact with air, the Al-Li master alloy can be wrapped in multiple layers of aluminum foil and thrown into the aluminum alloy liquid, and kept warm for 20 minutes until it is completely melted;

[0010] 3) After the Al-Li alloy is completely melted, stir it evenly with a stainless steel stick, remove the slag, and keep it warm for 10 minutes; remove the slag again, cast it in a mold, and after 10 minutes, take it out and air cool it;

[0011] 4) Double-stage homogenization heat treatment: the first stage alloy ingot is heated to 580°C and then kept warm for 24 hours; the second stage is heated to 600°C-630°C and kept warm for 24-48 hours, preferably 630°C and kept warm for 24-48 hours (further preferably 48 hours); and then water quenched and cooled to room temperature.

[0012] The two-stage homogenization treatment process of the present invention can greatly eliminate the segregation of the ingot alloy, make the alloy components evenly distributed, eliminate the low melting point phase in the alloy, and improve the subsequent hot processing performance of the alloy.

[0013] The first stage of the two-stage homogenization process of the present invention is heated and kept at 580°C, which is conducive to the melting back of the precipitated phase containing the Li element in the alloy, and does not produce overburning. The second stage is heated and kept at 630°C for 24-48h to ensure the elimination of defects in the ingot alloy, and the higher temperature can make the primary phase containing Er, Yb, and Sc melt back into the matrix, which is beneficial to improving the thermal stability of the alloy.

[0014] The present invention has the following beneficial effects:

[0015] The two-stage homogenization heat treatment process provided by the present invention can not only eliminate the defects of the alloy cast structure and improve the heat processing performance of the alloy, but also dissolve the primary phase in the ingot structure, which is helpful to improve the performance of the alloy in the subsequent heat processing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of heat treatment process (the two-stage homogenization heat treatment system is to keep the temperature of the first stage at 580℃ for 24 hours and then increase the temperature to the second stage at 600℃-630℃ for 24-48 hours).

[0017] Figure 2 SEM photos of ingot samples

[0018] Figure 3 SEM photos of samples after heat treatment

[0019] a Scanning electron microscope photo of the sample subjected to homogenization heat treatment at 600℃ / 48h in the second stage

[0020] b1, b2 second level system is 620℃ / 24h / 48h homogenization heat treatment sample scanning electron microscope photos

[0021] SEM photos of samples of c1 and c2 at the second level of 630℃ / 24h and 48h homogenization heat treatment

[0022] Figure 4 Hardness variation curve of alloy double-stage homogenization treatment;

[0023] Figure 5 Conductivity change curve of alloy double-stage homogenization treatment;

[0024] Figure 6 The hardness of samples in different heat treatment states after aging heat treatment at the optimal system (120℃ / 120h). DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with the accompanying drawings and specific implementation methods, but the present invention is not limited to the following embodiments.

[0026] Embodiment 1:

[0027] 1) Pure aluminum, Al-10Yb, Al-6Er, and Al-2Sc master alloys were heated from room temperature to 800°C within 80 minutes and kept at this temperature for 90 minutes;

[0028] 2) To prevent the Al-20Li master alloy from burning when in contact with air, the AL-20Li master alloy can be wrapped in multiple layers of aluminum foil and thrown into the aluminum alloy liquid, and kept warm for 20 minutes until it is completely melted.

[0029] 3) After the Al-20Li alloy is completely melted, stir it thoroughly with a stainless steel stick, remove the slag, and keep it warm for 10 minutes; remove the slag again and cast it in a mold. After 10 minutes, take it out and air cool it.

[0030] 4) The composition of the ingot was tested, and the ingot composition was 0.09wt% Er, 1.33wt% Li, 0.16wt% Sc, 0.08wt% Yb, impurities <0.3wt%, and the balance was Al.

[0031] 5) Double-stage homogenization heat treatment: the first stage alloy ingot is heated to 580℃ and kept at this temperature for 24h, the second stage is heated to 630℃ and kept at this temperature for 48h, and then cooled to room temperature by water quenching.

[0032] Comparative Example 1:

[0033] 1) Pure aluminum, Al-10Yb, Al-6Er, and Al-2Sc master alloys were heated from room temperature to 800°C within 80 minutes and kept at this temperature for 90 minutes;

[0034] 2) To prevent the Al-20Li master alloy from burning when in contact with air, the AL-20Li master alloy can be wrapped in multiple layers of aluminum foil and thrown into the aluminum alloy liquid, and kept warm for 20 minutes until it is completely melted.

[0035] 3) After the Al-20Li alloy is completely melted, stir it thoroughly with a stainless steel stick, remove the slag, and keep it warm for 10 minutes; remove the slag again and cast it in a mold. After 10 minutes, take it out and air cool it.

[0036] 4) The composition of the ingot was tested, and the ingot composition was 0.09wt% Er, 1.33wt% Li, 0.16wt% Sc, 0.08wt% Yb, impurities <0.3wt%, and the balance was Al.

[0037] 5) The double-stage homogenization heat treatment is as follows: the first stage alloy ingot is heated to 580℃ and then kept at this temperature for 24h, and the second stage is heated to 600℃ and kept at this temperature for 48h. Then it is water quenched and cooled to room temperature.

[0038] Comparative Example 2:

[0039] 1) Pure aluminum, Al-10Yb, Al-6Er, and Al-2Sc master alloys were heated from room temperature to 800°C within 80 minutes and kept at this temperature for 90 minutes;

[0040] 2) To prevent the Al-20Li master alloy from burning when in contact with air, the AL-20Li master alloy can be wrapped in multiple layers of aluminum foil and thrown into the aluminum alloy liquid, and kept warm for 20 minutes until it is completely melted.

[0041] 3) After the Al-20Li alloy is completely melted, stir it thoroughly with a stainless steel stick, remove the slag, and keep it warm for 10 minutes; remove the slag again and cast it in a mold. After 10 minutes, take it out and air cool it.

[0042] 4) The composition of the ingot was tested, and the ingot composition was 0.09wt% Er, 1.33wt% Li, 0.16wt% Sc, 0.08wt% Yb, impurities <0.3wt%, and the balance was Al.

[0043] 5) Double-stage homogenization heat treatment: the first stage alloy ingot is heated to 580℃ and kept at this temperature for 24h, the second stage is heated to 620℃ and kept at this temperature for 24h, and then cooled to room temperature by water quenching.

[0044] Comparative Example 3:

[0045] 1) Pure aluminum, Al-10Yb, Al-6Er, and Al-2Sc master alloys were heated from room temperature to 800°C within 80 minutes and kept at this temperature for 90 minutes;

[0046] 2) To prevent the Al-20Li master alloy from burning when in contact with air, the AL-20Li master alloy can be wrapped in multiple layers of aluminum foil and thrown into the aluminum alloy liquid, and kept warm for 20 minutes until it is completely melted.

[0047] 3) After the Al-20Li alloy is completely melted, stir it thoroughly with a stainless steel stick, remove the slag, and keep it warm for 10 minutes; remove the slag again and cast it in a mold. After 10 minutes, take it out and air cool it.

[0048] 4) The composition of the ingot was tested, and the ingot composition was 0.09wt% Er, 1.33wt% Li, 0.16wt% Sc, 0.08wt% Yb, impurities <0.3wt%, and the balance was Al.

[0049] 5) Double-stage homogenization heat treatment: the first stage alloy ingot is heated to 580℃ and kept at this temperature for 24h, the second stage is heated to 620℃ and kept at this temperature for 48h, and then cooled to room temperature by water quenching.

[0050] Comparative Example 4:

[0051] 1) Pure aluminum, Al-10Yb, Al-6Er, and Al-2Sc master alloys were heated from room temperature to 800°C within 80 minutes and kept at this temperature for 90 minutes;

[0052] 2) To prevent the Al-20Li master alloy from burning when in contact with air, the AL-20Li master alloy can be wrapped in multiple layers of aluminum foil and thrown into the aluminum alloy liquid, and kept warm for 20 minutes until it is completely melted.

[0053] 3) After the Al-20Li alloy is completely melted, stir it thoroughly with a stainless steel stick, remove the slag, and keep it warm for 10 minutes; remove the slag again and cast it in a mold. After 10 minutes, take it out and air cool it.

[0054] 4) The composition of the ingot was tested, and the ingot composition was 0.09wt% Er, 1.33wt% Li, 0.16wt% Sc, 0.08wt% Yb, impurities <0.3wt%, and the balance was Al.

[0055] 5) Double-stage homogenization heat treatment: the first stage alloy ingot is heated to 580℃ and kept at this temperature for 24h, the second stage is heated to 630℃ and kept at this temperature for 24h, and then cooled to room temperature by water quenching.

[0056] The samples in the embodiments and comparative examples that were subjected to multi-stage homogenization treatment in different states were observed by scanning electron microscopy to compare the primary phases in each sample. Figure 2 Casting scan to observe the melting condition of the primary phase. Figure 3 As shown in the figure, at the same temperature, the area fraction of the primary phase in the sample decreases with the increase of the holding time, and then remains basically stable. The overall results show that the second-level homogenization system is 630℃ / 48h. After the homogenization treatment, the primary phase in the sample reaches the lowest value and the remelting is complete.

[0057] The Vickers hardness and corresponding conductivity of samples in different heat treatment states of the embodiments and comparative examples were tested. The test results are shown in Figure 4 , Figure 5 As shown. At the same temperature, the average hardness of the sample decreases with the increase of the holding time and then remains constant, while the corresponding conductivity decreases with the increase of the holding time and then remains stable; the hardness of the sample after the double-stage homogenization treatment at 580℃ / 24h+630℃ / 48h reaches the lowest, and the corresponding conductivity is the lowest, which is 37.9HV and 18.1653mΩ*mm.

[0058] Finally, samples of the embodiments and comparative examples in different heat treatment states were subjected to aging heat treatment at the optimal system (120°C / 120h). The test results are as follows: Figure 6 As shown, the sample after double-stage homogenization treatment at 580℃ / 24h+630℃ / 48h has the highest hardness of 115.6HV after aging treatment.

Claims

1. A homogenization heat treatment process for Er, Yb, Sc composite microalloyed Al-Li alloy, characterized in that: The components of the alloy are (mass percentage) Er: 0.08~0.11wt.%, Yb: 0.07~0.11wt.%, Sc: 0.07~0.16wt.%, Li: 1.2~1.7wt.%, unavoidable impurities ≤0.3wt.%, the balance is Al; The following steps are involved: 1) Pure aluminum, Al-Yb, Al-Er, and Al-Sc master alloys are heated from room temperature to 800° C. within 80 minutes and kept at this temperature for 90 minutes to form aluminum alloy liquid; 2) To prevent the Al-Li master alloy from burning when in contact with air, the Al-Li master alloy can be wrapped in multiple layers of aluminum foil and thrown into the aluminum alloy liquid, and kept warm for 20 minutes until it is completely melted; 3) After the Al-Li alloy is completely melted, stir it evenly with a stainless steel stick, remove the slag, and keep it warm for 10 minutes; remove the slag again, cast it in a mold, and after 10 minutes, take it out and air cool it; 4) Double-stage homogenization heat treatment: the first stage is to heat the alloy ingot to 580℃ and keep it for 24h; the second stage is to heat it to 600℃-630℃ and keep it for 24-48h. Preferably, the temperature is kept at 630°C for 24-48 hours, and then cooled to room temperature by water quenching.

2. The process according to claim 1, characterized in that The second stage is kept at 630°C for 24-48h, preferably 48h.

3. The process according to claim 1, characterized in that The composition of the alloy is: 0.09wt.% Er, 0.08wt.% Yb, 0.16wt.% Sc, 1.33wt.% Li, impurities ≤ 0.3wt.%, and the balance is Al.

Images