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CN-122012990-A - Niobium-containing yttrium titanium alloy plate, preparation method and battery shell

CN122012990ACN 122012990 ACN122012990 ACN 122012990ACN-122012990-A

Abstract

The invention discloses a niobium-containing yttrium titanium alloy plate, a preparation method and a battery shell. Through the synergistic process of cryogenic rolling and plasma assisted surface nanocrystallization, the titanium alloy plate forms a three-layer microstructure with continuously gradient change of grain size and hardness along the thickness direction. The ultra-thin wall titanium alloy plate has high strength, high plasticity, corrosion resistance and welding performance, and is suitable for manufacturing the shell of the 3C product battery.

Inventors

  • CHEN HAIFENG
  • FU JINGQIN

Assignees

  • 苏州中科瑞龙科技有限公司

Dates

Publication Date
20260512
Application Date
20260415

Claims (12)

  1. 1. The niobium-containing yttrium titanium alloy plate is characterized in that the titanium alloy plate is prepared from the following niobium-containing yttrium titanium alloy materials in percentage by mass: 0.08% -0.25% of niobium; 0.01% -0.08% of yttrium; 0.01% -0.04% of iron; no more than 0.01% carbon; No more than 0.01% nitrogen; No more than 0.005% hydrogen; 0.05% -0.20% of oxygen; Not less than 99.5% titanium; The titanium alloy plate forms a three-layer microstructure with grain size and hardness changing continuously in gradient along the thickness direction, and each layer has the following structure: (1) The surface nanocrystalline layers are positioned on the surface layers at two sides of the thickness direction of the plate, the depth of each layer is 2-8 mu m inwards from the surface of the plate, the layer is a nanocrystalline alpha-Ti structure, the average grain size is 50-200 nm, and the Vickers hardness of the layer is 380-480; (2) The intermediate superfine crystal layer is connected with the two surface nanocrystalline layers and is 8-60 mu m inwards at the surface nanocrystalline layers, is an superfine crystal alpha-Ti structure, has an average grain size of 0.5-3 mu m, and is internally dispersed with an Nb-Y enriched phase and a Ti-C composite precipitated phase, and the Vickers hardness of the layer is HV 280-360; (3) The core layer is positioned in the central area of the thickness direction of the plate, takes an equiaxial alpha-Ti phase as a main matrix, has an average grain size of 5-10 mu m and hardness HV 200-250, and forms continuous hardness transition with the middle superfine crystal layer; The total thickness of the plate is 0.03-0.5 mm, and the grain size is gradually increased and the hardness is gradually reduced from the surface nanocrystalline layer to the core layer along the thickness direction of the plate, so that continuous transition is realized, and no abrupt interface exists.
  2. 2. The niobium-containing yttrium titanium alloy sheet according to claim 1, wherein the Nb-Y enrichment phase is an intermetallic compound formed by Nb and Y, the size is 20-80 nm, the Ti-C composite precipitation phase comprises at least one of TiC and Ti-C solid solution, and the size is 10-40 nm.
  3. 3. The niobium-containing yttrium-titanium alloy sheet according to claim 1 or 2, wherein the titanium alloy sheet has a tensile strength of 480-480 mpa, a yield strength rp 0.380-480 mpa, a elongation after break of not less than 30%, a plastic strain ratio r of not less than 3.5, a limiting draw ratio LDR of not less than 4.0, and a work hardening exponent n of not less than 0.18 under room temperature tensile test conditions.
  4. 4. A method for producing a niobium-containing yttrium-titanium alloy sheet as claimed in any one of claims 1 to 3, wherein the gradient structure in the thickness direction of the sheet is controlled by a synergistic process of cryogenic rolling and plasma-assisted surface nanocrystallization, comprising the steps of: (1) Alloy smelting and homogenizing treatment, namely mixing raw material powder, carrying out vacuum consumable arc smelting to obtain an ingot, homogenizing for 4-8 hours at 900-1000 ℃, and air-cooling to obtain an alloy ingot with uniform components; (2) Thermo-mechanical deformation, namely forging and cogging the cast ingot obtained in the step (1) at 800-900 ℃, and then carrying out multi-pass hot rolling at 700-800 ℃ until the thickness is 3-5mm, and then carrying out recrystallization annealing at 550-650 ℃ for 1-2 hours to obtain an intermediate blank with a uniform equiaxial structure; (3) Performing cryogenic rolling, namely performing multi-pass cryogenic rolling on the intermediate blank obtained in the step (2) in a liquid nitrogen environment with the temperature of-150 ℃ to-196 ℃ until the total thickness of the target plate is reached, wherein the single-pass rolling reduction is 10% -25%, the total rolling reduction is 85% -95%, the rolling speed is 5-20 m/min, and the roller temperature is controlled to be-100 ℃ to-150 ℃; (4) And (3) carrying out plasma assisted surface nanocrystallization, namely carrying out high-density plasma bombardment treatment on the thin plate obtained in the step (3), adopting pure argon or helium as working gas, wherein the gas flow is 20-40L/min, the plasma power density is 500-1500W/cm < 2 >, the treatment time is 10-30 min, the treatment temperature is less than or equal to 150 ℃, and inducing the surface layer to be subjected to severe plastic deformation through high-energy plasma particle bombardment, further refining surface layer crystal grains to nano-scale, and simultaneously promoting Nb and Y atoms to form nano precipitated phases by means of grain boundary segregation, so that the target titanium alloy plate with continuous gradient change of grain size and hardness along the thickness direction is finally obtained.
  5. 5. The preparation method of the cold-rolling mill according to claim 4, wherein in the deep cold-rolling process of the step (3), the blank is soaked in liquid nitrogen for 15-30 min before each pass of rolling, the temperature of the blank is ensured to be uniformly reduced below-150 ℃, and the contact area between a roller and the blank is cooled by adopting liquid nitrogen direct injection in the rolling process, so that a low-temperature environment is maintained.
  6. 6. The method according to claim 4, wherein the surface roughness Ra of the titanium alloy sheet material after the treatment in the step (4) is less than or equal to 0.2 μm, the thickness of the surface nanocrystalline layer is 2-8 μm, the width of the hardness transition zone between the surface nanocrystalline layer and the intermediate ultrafine grain layer is less than or equal to 10 μm, and no obvious interface mutation is generated.
  7. 7. The method according to claim 4, wherein the deep cold rolled sheet obtained in the step (3) is subjected to non-destructive inspection, has no internal cracks and hole defects, has no coarse second phase particles in the crystal, and has a matrix grain size uniformity coefficient of not less than 0.90.
  8. 8. A battery case prepared from the niobium-containing yttrium-titanium alloy sheet material according to any one of claims 1 to 3 or prepared by the method for preparing the niobium-containing yttrium-titanium alloy sheet material according to any one of claims 4 to 7.
  9. 9. The battery case according to claim 8, wherein the case has a cylindrical shape with one end opened, or the case has a ring shape with both ends opened.
  10. 10. The battery housing of claim 8, wherein the wall thickness of the housing is 0.03mm to 0.5mm.
  11. 11. The battery housing of claim 8, wherein the housing has a helium leak detection leak rate of 1 x 10 - 10 Pa-m 3/s or less, a corrosion rate of 0.0015 mm/year or less under 60 ℃ conditions of LiPF 6 /ec+dmc electrolyte, and no pitting, intergranular corrosion, and stress corrosion cracking phenomena on the surface.
  12. 12. The battery shell according to claim 8, wherein after the shell circulates 3000 times within a temperature range of-40 ℃ to 150 ℃, no phenomena of cracks, liquid leakage and bulge occur, and the shell bursting pressure is more than or equal to 3.5MPa.

Description

Niobium-containing yttrium titanium alloy plate, preparation method and battery shell Technical Field The invention relates to the technical field of titanium alloy materials and battery shell manufacturing, in particular to a niobium-containing yttrium-titanium alloy plate, a preparation method and a battery shell. Background With the development of 3C products (such as smart phones, tablet computers, smart watches, etc.) toward light and thin and high energy density, extremely severe comprehensive performance requirements are put forward for battery shell materials. The battery case needs to have high strength (prevention of bulge deformation), high plasticity (satisfaction of deep drawing molding requirements), excellent corrosion resistance (resistance to electrolyte corrosion), good weldability (ensuring sealability), and extremely light weight (improvement of energy density) at the same time under ultra-thin wall thickness conditions. In the prior art, stainless steel (such as SUS 316L) has high strength and good corrosion resistance, but has high density, low specific strength, low plastic strain ratio r value and poor deep drawing performance, and is difficult to prepare a deep cylindrical ultrathin-wall shell. Industrial pure titanium (such as TA1/TA 2) has the following technical defects although the density is low and the corrosion resistance is excellent: (1) The strength-plasticity contradiction is that the industrial pure titanium has low strength, the work hardening index n value is extremely low, the bulge forming performance is poor, and the partial thinning and cracking are easy to occur when the complex shape is formed; (2) The welding performance is insufficient, namely, hydrogen, oxygen and nitrogen gas are easy to be absorbed during welding of pure titanium, so that air holes and brittle phases are formed, and the plasticity of a welding joint is obviously reduced; (3) The surface performance is weak, the surface hardness of pure titanium is low (HV 180-220), the wear resistance is poor, and the surface oxide film is easy to damage under extreme working conditions. In order to improve the performance of titanium materials, the prior art tries to add alloy elements to form titanium alloys, but the conventional titanium alloys have high strength, obviously reduced plasticity (elongation after fracture is usually less than 15 percent), poor cold working performance and difficulty in preparing ultrathin plates. In addition, the hardened layer can be formed on the surface of the titanium material by a surface modification technology (such as shot blasting and ion implantation), but the hardened layer has the problems of abrupt interface between the hardened layer and a matrix, poor binding force, easy peeling and the like. Accordingly, there is a need for an improvement over the prior art to overcome the deficiencies described in the prior art. Disclosure of Invention The invention aims to provide a niobium-containing yttrium titanium alloy plate, a preparation method and a battery shell, so as to improve the comprehensive performance of the material. In order to achieve the above object, in a first aspect, the present invention provides a niobium-containing yttrium-titanium alloy sheet material, which is prepared from the following niobium-containing yttrium-titanium alloy materials in percentage by mass: 0.08% -0.25% of niobium; 0.01% -0.08% of yttrium; 0.01% -0.04% of iron; no more than 0.01% carbon; No more than 0.01% nitrogen; No more than 0.005% hydrogen; 0.05% -0.20% of oxygen; Not less than 99.5% titanium; The titanium alloy plate forms a three-layer microstructure with grain size and hardness changing continuously in gradient along the thickness direction, and each layer has the following structure: (1) The surface nanocrystalline layers are positioned on the surface layers at two sides of the thickness direction of the plate, the depth of each layer is 2-8 mu m inwards from the surface of the plate, the layer is a nanocrystalline alpha-Ti structure, the average grain size is 50-200 nm, and the Vickers hardness of the layer is 380-480; (2) The intermediate superfine crystal layer is connected with the two surface nanocrystalline layers and is 8-60 mu m inwards at the surface nanocrystalline layers, is an superfine crystal alpha-Ti structure, has an average grain size of 0.5-3 mu m, and is internally dispersed with an Nb-Y enriched phase and a Ti-C composite precipitated phase, and the Vickers hardness of the layer is HV 280-360; (3) The core layer is positioned in the central area of the thickness direction of the plate, takes an equiaxial alpha-Ti phase as a main matrix, has an average grain size of 5-10 mu m and hardness HV 200-250, and forms continuous hardness transition with the middle superfine crystal layer; The total thickness of the plate is 0.03-0.5 mm, and the grain size is gradually increased and the hardness is gradually reduced from the surface nanocrystalline layer t