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CN-121976097-A - Low-density high-specific-strength rare earth aluminum alloy and preparation method thereof

CN121976097ACN 121976097 ACN121976097 ACN 121976097ACN-121976097-A

Abstract

The invention discloses a low-density high-specific strength rare earth aluminum alloy and a preparation method thereof, belonging to the technical field of aluminum alloy materials. The aluminum alloy comprises, by mass, 3-5wt% of Zn, 3-6wt% of Mg, 0-1.5wt% of Cu, 0-0.2wt% of rare earth elements, 0.08-0.12wt% of Mn, 0.03-0.05wt% of Cr, 0.05-0.07 wt% of Ti, and the balance of Al and unavoidable impurities. The preparation method comprises smelting and casting, hot rolling, solution heat treatment, quenching, stretching and subsequent aging heat treatment. According to the invention, the Zn/Mg proportion is cooperatively regulated to reduce the density, rare earth elements and Zr microalloy are introduced, grains are refined, a nano-scale dispersed phase is formed, and an optimized step solid solution and double-stage aging heat treatment process is adopted, so that the material density is reduced to below 2.69g/cm 3 (which is reduced by about 5 percent compared with the traditional 7xxx system), the tensile strength is kept at 475-505 MPa, the specific strength is excellent, the fracture toughness and the corrosion resistance are obviously improved, and the method is suitable for the fields of material weight reduction such as aerospace and rail transit, and has outstanding practicability and industrialization value.

Inventors

  • HUANG LIANG
  • WEI YI
  • Ling Zejie
  • WU ZHENYU
  • LI YONGDI
  • QIN SHANLI
  • ZHONG YONGLI
  • HUANG HAOBIN

Assignees

  • 广西产研院新型功能材料研究所有限公司

Dates

Publication Date
20260505
Application Date
20260206

Claims (10)

  1. 1. The low-density high-specific strength rare earth aluminum alloy is characterized by comprising, by mass, 3-5wt% of Zn, 3-6wt% of Mg, 0-1.5wt% of Cu, 0-0.2wt% of rare earth elements, 0.07-0.09 wt% of Zr, 0.08-0.12 wt% of Mn, 0.03-0.05 wt% of Cr, 0.05-0.07 wt% of Ti, and the balance of Al and unavoidable impurities.
  2. 2. The low-density high-specific strength rare earth aluminum alloy according to claim 1, wherein the content of Zn is 4.0-4.8%, the content of Mg is 3.2-4.0% and the mass ratio of Zn to Mg is 1.2-1.5:1.
  3. 3. The low-density high-specific strength rare earth aluminum alloy according to claim 1, wherein the rare earth element comprises at least one of Sc, er, la, pr, nd and the total rare earth element content is 0.2 wt.% or less.
  4. 4. A method for preparing the low-density high-specific strength rare earth aluminum alloy according to any one of claims 1 to 3, comprising the steps of: (1) Smelting and casting, namely proportioning according to the component proportion, heating and smelting industrial pure aluminum and intermediate alloy, sequentially adding alloy elements, and standing and semi-continuously casting after refining to obtain an ingot; (2) Step homogenization treatment, namely raising the temperature and preserving the temperature of the cast ingot in stages, and then air-cooling; (3) Hot rolling, namely milling the surface of the homogenized cast ingot, preserving heat, carrying out multi-pass hot rolling in a set temperature interval, and controlling the total deformation; (4) Step solid solution treatment, namely adopting a two-stage heating solid solution system to heat and preserve heat of the plate after hot rolling; (5) Prestretching, namely applying permanent stretching with set deformation to the quenched plate; (6) And (3) performing two-stage ageing treatment, namely performing ageing treatment on the pre-stretched plate by adopting a low-temperature and high-temperature two-stage ageing system, and cooling along with a furnace to obtain a finished product.
  5. 5. The method for producing a low-density high-specific strength rare earth aluminum alloy according to claim 4, wherein in the step (1), the melting temperature is 740 to 760 ℃ and the refining temperature is 720 to 740 ℃.
  6. 6. The method for preparing a low-density high-specific strength rare earth aluminum alloy according to claim 4, wherein in the step (2), the step-type homogenization treatment parameters are that the temperature is raised to 400 ℃ at a rate of 50 ℃ per hour for 4-6 hours, the temperature is raised to 450 ℃ for 18-22 hours, and the temperature is raised to 470 ℃ for 10-14 hours.
  7. 7. The method for preparing a low-density high-specific strength rare earth aluminum alloy according to claim 4, wherein in the step (4), the step solid solution treatment parameters are that the temperature is raised to 470 ℃ at a rate of less than or equal to 50 ℃ per hour for 0.5-2 h, and then raised to 480 ℃ at a rate of less than or equal to 30 ℃ per hour for 0.1-1.5 h.
  8. 8. The method for producing a low-density high-specific strength rare earth aluminum alloy according to claim 4, wherein the amount of permanent set applied in step (5) is 1.2 to 1.8%.
  9. 9. The method for preparing a low-density high-specific strength rare earth aluminum alloy according to claim 4, wherein in the step (6), the first-stage aging temperature is 121+/-2 ℃, the temperature is kept for 4-6 hours, and the second-stage aging temperature is 174+/-2 ℃ and the temperature is kept for 15-20 hours.
  10. 10. A low density high specific strength rare earth aluminum alloy prepared according to the method of any one of claims 4-9.

Description

Low-density high-specific-strength rare earth aluminum alloy and preparation method thereof Technical Field The invention relates to the technical field of aluminum alloy materials, in particular to an aluminum alloy and a preparation process thereof, and particularly relates to a rare earth-containing Al-Zn-Mg aluminum alloy with low density, high specific strength and high damage tolerance and a preparation method thereof. Background High performance aluminum alloys, particularly 7xxx series (Al-Zn-Mg-Cu) alloys, have long taken the importance of aerospace primary load bearing structural materials due to their excellent specific strength, good processability and relatively mature application systems. The high strength of conventional 7xxx series aluminum alloys, such as 7075, 7050, etc., is primarily dependent on the relatively high levels of Zn (5.0-8.0 wt%), mg (1.8-2.8 wt%), and Cu (1.2-2.0 wt%). Although the addition of these heavy metal elements brings about a remarkable effect of precipitation strengthening (the main strengthening phases are eta' -MgZn 2 and eta-MgZn 2 and T-Al 2Mg3Zn3), the density of the alloy is too high, and is generally 2.83g/cm 3. With the development of aerospace equipment towards longer endurance, higher load and lower energy consumption, the requirement on the weight reduction of structural materials is increasingly severe, and the density of the traditional high-zinc aluminum alloy has become a bottleneck for restricting the further application of the traditional high-zinc aluminum alloy. In order to reduce the structural weight, researchers at home and abroad mainly explore from two directions, namely, adopting a material system with lower density, such as aluminum lithium alloy, magnesium alloy or composite material, and optimizing in the existing high-performance aluminum alloy system to reduce the density. The former often faces problems such as high cost, complex process, or anisotropy. The latter has more economic and inheriting advantages, but the core challenge is that lowering the density (mainly lowering the content of high density element Zn) generally results in a significant loss of alloy strength, especially yield strength. For example, simply reducing the Zn content from 7% to 4%, the tensile strength of the alloy may be reduced by more than 15% and the performance requirements of the critical structure may not be met. In the prior art, researchers have tried various methods in order to maintain strength under low zinc conditions. Patent CN105296823a discloses an Al-Mg-Si based alloy containing Sc, which improves properties by fine-grain strengthening and dispersion strengthening of Sc, but the alloy belongs to the 6xxx series of medium and low strength, and the difference between the strength level (tensile strength is usually lower than 400 MPa) and the high-strength 7xxx series is obvious, and the latter cannot be replaced in the main load-bearing structure. Patent CN101076613a focuses on controlling the internal stress of Al-Zn-Cu-Mg alloys by thermo-mechanical processes, the composition of which still belongs to the traditional high zinc category, without involving the problem of density reduction. Patents US4618382, US5939967, etc. also mainly surround the corrosion resistance or process optimization development of high strength aluminum alloys of conventional composition. There are reports in the prior art that the performance of aluminum alloys is improved by adding rare earth elements (such as Sc, er, etc.). The rare earth element can form Al 3 M-type nano-grade coherent precipitated phase (such as Al 3Sc、Al3 Er), dislocation and crystal boundary are effectively pinned, recrystallization and crystal grain growth are inhibited, and fine crystal strengthening and dispersion strengthening are realized. However, these studies are mostly improved based on the conventional high zinc component, aiming at further improving the strength or improving the corrosion resistance and the thermal stability, and the idea is to "add flowers on the market" instead of "weight reduction and synergy". The rare earth microalloying technology is systematically applied to the design of low-zinc Al-Zn-Mg alloy aiming at reducing density, and a heat treatment process which is matched with the low-zinc Al-Zn-Mg alloy and can give consideration to high strength and high damage tolerance is cooperatively developed, so that a mature and effective technical scheme is not yet available. In particular, while low density, high specific strength is sought, aerospace structural materials must also possess excellent damage tolerance properties, i.e., high fracture toughness and stress corrosion cracking resistance. The traditional high-strength aluminum alloy often has contradiction between strength and toughness inversion. How to significantly improve the toughness of a material while reducing density and maintaining strength is a more challenging problem. In the prior art, the collabo