Preparation method of titanium alloy / aluminum alloy composite mobile phone middle frame material

Abstract

The invention discloses a preparation method of a high-efficiency and low-cost titanium-clad aluminum mobile phone middle frame material, which comprises the following steps: carrying out cladding extrusion on TC4 alloy (Ti-6Al-4V) and 6013 aluminum alloy at 480-520 DEG C according to an extrusion ratio of 6.5-11.5 to obtain a rectangular profile with the specification of 160-180 * (70-90) mm, the titanium outside the rectangular profile and the aluminum inside the rectangular profile, and the thickness of the titanium alloy on the outer layer is about 0.5-0.8 mm. And then the titanium-clad aluminum extrusion profile is cut into square blocks with the thickness being 10-15 mm in the direction perpendicular to the extrusion direction, diffusion annealing is carried out, titanium atoms and aluminum atoms are mutually diffused on a boundary layer, stable metallurgical bonding is formed, the annealing temperature is 500-620 DEG C, and the annealing time is 5-8 hours. Compared with other existing technical approaches, the method has the advantages of high production efficiency, low cost, short technological process, high yield, high titanium-aluminum interface bonding strength and the like.

Description

Field of the Invention

[0001] The invention discloses a method for preparing a high-efficiency and low-cost titanium-clad aluminum mobile phone middle frame material, belonging to the field of material processing. Background Art

[0002] Aluminum alloy materials have the advantages of light weight, good thermal conductivity, no fingerprints, anti-static, and beautiful appearance, so they are widely used in electronic product shells. For example, Apple uses the higher-strength 7-series aluminum alloy, and Samsung Galaxy S6 uses 6013 aviation-grade aluminum alloy.

[0003] Although aluminum alloy materials such as 6013 are widely used in the production of mobile phone middle frames, their disadvantages are also very obvious. First of all, this kind of material has a strong impact on the quality of Cl - It has no resistance to ion corrosion, and long-term use will cause varying degrees of intergranular corrosion on the surface of the mobile phone's middle frame; secondly, the strength and hardness of aluminum alloy are relatively low, and it is easy to deform or leave scratches under the action of external forces, affecting the appearance of the mobile phone.

[0004] Based on the above technical problems, a new type of mobile phone middle frame-titanium-aluminum composite material came into being. Its structure is titanium outside and aluminum inside. It not only has the excellent corrosion resistance and high surface strength of titanium alloy, but also has the advantages of lightweight and portability of aluminum alloy. Apple launched the titanium alloy version of iPhone 15pro mobile phone on March 15, 2023. The middle frame of this mobile phone used titanium-aluminum layered composite material (6013-T6 / Ti-6Al-4V(TC4)) for the first time, which instantly became the eye-catching point of the mobile phone.

[0005] The existing titanium-aluminum composite technology of mobile phone middle frame materials is mainly based on the principle of interface atomic diffusion, such as hot isostatic pressing and hot pressing technology of titanium-aluminum layered composite. The above technology has disadvantages such as low production capacity, high cost and low yield rate, which affects the production and sales of titanium alloy mobile phone products. Based on the current production technology status of titanium-clad aluminum mobile phone middle frames, a titanium / aluminum middle frame extrusion composite technology has been developed, which has the advantages of high production capacity, high yield rate, low cost, short production process and high interface bonding strength. Summary of the invention

[0006] The present invention proposes a technical solution of extrusion composite + diffusion annealing of TC4 alloy and 6013 aluminum alloy for titanium / aluminum mobile phone middle frame, and its specific contents and features are as follows:

[0007] A method for preparing a titanium-aluminum composite material, comprising the following steps:

[0008] 1) Encapsulate the raw aluminum in a shell of raw titanium; the shell is tightly fitted to the surface of the core material;

[0009] In some preferred embodiments, the raw aluminum includes an aluminum alloy, and in some more preferred embodiments, the raw aluminum is a 6013 aluminum alloy;

[0010] In some preferred embodiments, the raw aluminum comprises an aluminum alloy core ingot; in some more preferred embodiments, the core ingot has a specification of diameter×length of The outer diameter tolerance is -0.25~0mm;

[0011] In some preferred embodiments, the raw titanium comprises a titanium alloy, preferably a TC4 titanium alloy; in some more preferred embodiments, the raw titanium comprises a titanium alloy round tube and a round plate, the diameter of the round plate is The wall thickness is 1.2-1.6mm; the length of the round tube is 380-420mm, and the inner diameter is The inner diameter tolerance is 0~+0.25mm and the wall thickness is 1.2~1.6mm.

[0012] In some preferred embodiments, before packaging, the raw aluminum and / or raw titanium are pretreated to remove surface oil and oxide film;

[0013] In some preferred embodiments, the pretreatment method includes: alkali boiling to remove oil, pickling to remove oxide film, and washing and drying after the fresh surface is exposed;

[0014] In some preferred embodiments, the packaging method includes: using a tungsten inert gas arc welding process with argon protection;

[0015] 2) After the encapsulation is completed, an isolation dielectric layer is applied on the outer surface of the titanium layer of the cladding;

[0016] In some preferred embodiments, the composition of the dielectric layer includes molybdenum disulfide and / or graphite; in some more preferred embodiments, the dielectric molybdenum disulfide powder and graphite powder are fully and completely mixed; more preferably, in the dielectric layer, the mass ratio of molybdenum disulfide to graphite is 7:3 to 8:2;

[0017] 3) Wrapping the titanium-clad aluminum ingot coated with the dielectric layer with copper foil, performing an extrusion operation to form a metallurgical bond between the titanium alloy shell and the aluminum alloy core ingot at the interface, and removing the surface copper foil after the extrusion is completed;

[0018] In some preferred embodiments, the extrusion temperature is 480-550°C, and the extrusion ratio is 6.5-11.5;

[0019] In some preferred embodiments, after extrusion, the specifications of the titanium / aluminum composite profile are 160-180 mm in width × 70-90 mm in height; more preferably, the thickness of the titanium layer after extrusion is 0.5-0.8 mm.

[0020] 4) Cut the titanium-clad aluminum extruded profile into blocks with a thickness of 10 to 15 mm perpendicular to the extrusion direction, and wrap them with copper foil for diffusion annealing; so that titanium and aluminum atoms diffuse with each other in the boundary layer to further form a stable metallurgical bond;

[0021] In some preferred embodiments, the annealing temperature is 500-620° C., and the annealing time is 5-8 hours;

[0022] 5) After annealing, the titanium / aluminum middle frame material is cooled to room temperature by strong wind for aging hardening treatment;

[0023] In some preferred embodiments, two-stage aging (double-stage aging treatment) is preferred;

[0024] In some preferred embodiments, the first stage aging temperature is 170-180°C and the time is 4-6 hours;

[0025] In some preferred embodiments, the second stage aging temperature is 200-210° C., and the time is 1-2 hours.

[0026] The beneficial effects of the present invention are:

[0027] To sum up, compared with traditional technical means, this technical solution innovatively and comprehensively utilizes technical means such as cladding extrusion and boundary layer diffusion annealing, which not only greatly improves the production capacity and production efficiency of titanium-clad aluminum mobile phone middle frames and reduces production costs, but also significantly improves the metallurgical bonding quality and strength of the titanium-aluminum interface, and greatly improves the yield of finished products.

[0028] In the present invention, titanium and aluminum have excellent thermodynamic affinity, and the two quickly form a solid solution and a compound phase at the interface at high temperature. The technical solution forms a large number of atomic diffusion channels composed of dislocations at the interface of TC4 and 6013 aluminum alloys through severe extrusion deformation in the temperature range of 480-550°C, which greatly accelerates the mutual diffusion of Ti atoms and Al atoms at the interface, causing TC4 alloy and 6013 aluminum alloy to quickly form a metallurgical bond at the interface; further annealing in the temperature range of 500-620°C causes the concentration gradient of Ti atoms and Al atoms in the boundary layer of the two to be more gentle and broad, and the interface bonding strength is greatly improved. DETAILED DESCRIPTION

[0029] The following examples further illustrate the significant advancement of the present invention over the prior art:

[0030] 1) Specifications of 6013 aluminum alloy core ingots: The thickness of the outer cladding titanium layer is 1.2-1.6 mm. The specifications of the extruded titanium cladding aluminum are 160-180×70-90 mm, the extrusion ratio is maintained in the range of 6.5-11.5, and the extrusion temperature is 480-550°C. The high extrusion ratio and extrusion temperature create favorable conditions for the metallurgical bonding of TC4 alloy and 6013 aluminum alloy at the interface. In addition, the TC4 alloy tubes, plates and 6013 aluminum alloy core ingots used for cladding have all undergone strict surface alkali boiling and degreasing (sodium hydroxide: 20-30 g / L, sodium carbonate: 30-40 g / L, trisodium phosphate: 30-40 g / L, temperature: 60-70°C) and pickling (HF: 15-20 g / L, HNO3: 340-360 g / L, 15-35°C, 1-2 Min) to remove the oxide film. The titanium alloy shell and the aluminum ingot are tightly fitted together, and the argon arc welding package prevents air from mixing into the interface between the two. The above measures greatly improve the metallurgical bonding quality of the titanium alloy shell and the aluminum alloy core ingot interface;

[0031] 2) Cut the titanium-clad aluminum extruded profile into blocks with a thickness of 10 to 15 mm perpendicular to the extrusion direction, and then wrap the blocks with copper foil for diffusion annealing at a temperature of 500 to 620°C for 5 to 8 hours, so that titanium and aluminum atoms diffuse with each other in the boundary layer, further forming a stable metallurgical bond, and the concentration gradient of Ti atoms and Al atoms in the boundary layer becomes smoother and wider, and the interface bonding strength is greatly improved;

[0032] 3) After annealing, the titanium-clad aluminum mobile phone middle frame material is cooled to room temperature by strong wind, so that the 6013 alloy core material obtains a complete solid solution structure, and the subsequent double-stage aging (170-180℃×4-6h+200-210℃×1-2h) significantly improves the strength of the 6013 alloy;

[0033] 4) Apply a layer of molybdenum disulfide + graphite lubricant (mixed in a mass ratio of 7:3 to 8:2) on the TC4 titanium alloy shell, and then coat its surface with a layer of copper foil to prevent titanium metal from sticking to the mold during the extrusion of the titanium-clad aluminum ingot. Apply molybdenum disulfide + graphite lubricant on the outside of the titanium cladding layer to prevent unnecessary adhesion between the copper foil layer and the titanium metal during the extrusion process.

[0034] Example 1

[0035] The specifications of extruded 6013 aluminum alloy core ingot are After the surface is boiled with alkali to remove oil and pickled to remove the oxide film, it is cleaned and dried after the fresh surface is exposed. Then it is packaged in a In the TC4 titanium alloy shell with a wall thickness of 1.2mm and a length of 400mm, the inner surface of the titanium alloy shell is tightly fitted with the outer surface of the aluminum core ingot. The titanium alloy shell must be boiled in alkali to remove oil and pickled to remove the oxide film before packaging. The packaging process is carried out by tungsten inert gas welding with argon protection; a layer of molybdenum disulfide + graphite lubricating medium is applied to the TC4 titanium alloy shell, and the mass ratio of molybdenum disulfide powder to graphite powder is 8:2. Then a layer of copper foil is wrapped on its surface and enters the extrusion process. The extrusion temperature is 500℃, the extrusion ratio is about 7.0, and a rectangular profile with a specification of 180×80mm outer titanium and inner aluminum is obtained, in which the thickness of the outer titanium alloy is about 0.5mm. After extrusion, the copper foil layer outside the titanium-clad aluminum profile is torn off; the titanium-clad aluminum extruded profile is cut into a 15mm thick block perpendicular to the extrusion direction, and then the block is wrapped with copper foil for diffusion annealing. The annealing temperature is 520℃ and the annealing time is 6 hours. After annealing, the titanium-clad aluminum mobile phone middle frame material is cooled to room temperature by strong wind; finally, the titanium-clad aluminum mobile phone middle frame material is subjected to double-stage aging, with the first stage aging temperature at 170°C and the time being 6 hours; the second stage aging temperature at 200°C and the time being 2 hours.

[0036] Under the current process conditions, a production line can normally produce about 1,500 titanium-clad aluminum middle frame materials a day, with a processing cost of about 51.7 yuan per piece, a yield rate higher than about 93.5%, and a titanium-aluminum interface shear strength of about 54 MPa.

[0037] Example 2

[0038] The specifications of extruded 6013 aluminum alloy core ingot are After the surface is boiled with alkali to remove oil and pickled to remove the oxide film, it is cleaned and dried after the fresh surface is exposed. Then it is packaged in a In the TC4 titanium alloy shell with a wall thickness of 1.2mm and a length of 400mm, the inner surface of the titanium alloy shell is tightly fitted with the outer surface of the aluminum core ingot. The titanium alloy shell must be boiled in alkali to remove oil and pickled to remove the oxide film before packaging. The packaging process is carried out by tungsten inert gas welding with argon protection; a layer of molybdenum disulfide + graphite lubricating medium is applied to the TC4 titanium alloy shell, and the mass ratio of molybdenum disulfide powder to graphite powder is 7:3. Then a layer of copper foil is wrapped on its surface and enters the extrusion process. The extrusion temperature is 550℃, the extrusion ratio is about 7.0, and a rectangular profile with a specification of 180×80mm with titanium outside and aluminum inside is obtained, in which the thickness of the outer titanium alloy is about 0.5mm. After extrusion, the copper foil layer outside the titanium-clad aluminum profile is torn off; the titanium-clad aluminum extruded profile is cut into a 15mm thick block perpendicular to the extrusion direction, and then the block is wrapped with copper foil for diffusion annealing. The annealing temperature is 580℃ and the annealing time is 5 hours. After annealing, the titanium-clad aluminum mobile phone middle frame material is cooled to room temperature by strong wind; finally, the titanium-clad aluminum mobile phone middle frame material is subjected to double-stage aging, with the first stage aging temperature at 180°C and the time being 4 hours; the second stage aging temperature at 210°C and the time being 1 hour.

[0039] Under the current process conditions, a production line can normally produce about 1,480 titanium-clad aluminum middle frame materials a day, with a processing cost of about 53.6 yuan per piece, a yield rate of more than 92.8%, and a titanium-aluminum interface shear strength of about 56.1 MPa.

[0040] Comparative Example 1

[0041] The specification is The 6013 aluminum alloy ingots are extruded into 80×15mm thick plates at 500±10℃, and then cut into rectangular blocks with specifications of 180×80×15mm. After finishing and polishing, the surface is boiled and degreased by alkali, and the surface oxide film is removed by pickling. A circle of TC4 metal rings is tightly put on the edge of the 6013 aluminum alloy rectangular block. The width of the square metal ring is 15mm and the thickness is 0.5mm. The titanium metal ring needs to go through the pre-alkali boiling and degreasing and pickling process to remove the oxide film. Then the 6013 aluminum alloy middle frame material with the titanium alloy ring is placed in a vacuum isostatic pressing furnace. The hot isostatic pressing temperature is 500-620℃, the pressure is about 8.0MPa, and the time is 10-12 hours. After leaving the furnace, it needs to be subjected to 520℃×40min solid solution treatment, cooled to room temperature by strong wind, and finally subjected to double-stage aging (180℃×4h+200℃×2h).

[0042] Due to the complexity of hot isostatic pressing equipment operation (such as vacuuming, gas pressurization) and its high cost, a production line can only produce 200 to 300 titanium-clad aluminum middle frame materials a day, with a processing cost of about 180 yuan per piece, a yield of about 70%, and a titanium-aluminum interface shear strength of only about 30MPa.

Claims

1. A method for preparing a titanium / aluminum composite mobile phone middle frame, the steps are as follows: 1) Encapsulating the raw aluminum core ingot in a raw titanium shell; 2) After the encapsulation is completed, an isolation dielectric layer is applied to the outer surface of the raw titanium, and then a layer of copper foil is placed on the titanium alloy shell; 3) Performing extrusion operation on the titanium-clad aluminum ingot, and removing the outer copper foil protective cover after extrusion; 4) Cutting the titanium-clad aluminum extruded profile into sheet-shaped middle frame materials perpendicular to the extrusion direction, wrapping them with copper foil, and performing diffusion annealing; 5) After annealing, the middle frame material is cooled to room temperature by strong wind, and then subjected to aging hardening treatment.

2. The method for preparing a titanium-aluminum composite material according to claim 1, wherein: In the step 1), the raw aluminum comprises an aluminum alloy, preferably a 6013 aluminum alloy; and / or The raw aluminum includes an aluminum alloy core ingot, preferably, with a specification of diameter×length of The outer diameter tolerance is -0.25~0mm; and / or The raw titanium comprises a titanium alloy cladding layer, preferably TC4 titanium alloy; and / or The raw titanium comprises a round tube and two round plates. Preferably, the diameter of the round plates is The wall thickness is 1.2-1.6mm; the length of the round tube is 380-420mm, and the inner diameter ranges from The tube wall thickness is 1.2-1.6 mm; the inner diameter and length of the titanium tube are consistent with those of the aluminum core ingot, and the inner diameter tolerance is 0-+0.25 mm to ensure that the inner surface of the titanium tube fits closely with the circumferential surface of the aluminum core ingot.

3. The method for preparing a titanium-aluminum composite material according to claim 1, wherein: Before packaging in step 1), the raw aluminum and / or raw titanium are pretreated to remove oil and oxide film from the surface; Preferably, the pretreatment method includes: alkali boiling to remove oil, pickling to remove oxide film, and cleaning and drying after the surface is activated; Preferably, the packaging method comprises: inserting the aluminum core ingot into a titanium tube, and welding two circular titanium plates to both ends of the titanium tube by tungsten inert gas welding under argon protection, and packaging the aluminum core ingot in a titanium alloy shell.

4. The method for preparing a titanium-aluminum composite material according to claim 1, wherein: The components of the isolation dielectric layer in step 2) include molybdenum disulfide and / or graphite; preferably, the isolation dielectric layer is obtained by fully mixing molybdenum disulfide powder and graphite powder; more preferably, in the dielectric layer, the mass ratio of molybdenum disulfide to graphite is 7:3 to 8:

2.

5. The method for preparing a titanium-aluminum composite material according to claim 1, wherein: The extrusion temperature in step 3) is 480-550° C. and / or The extrusion ratio is 6.5 to 11.5; and / or After extrusion, the specifications of the titanium / aluminum composite profile are 160-180×70-90mm in width and height; and / or After extrusion, the thickness of the titanium cladding layer is 0.5 to 0.8 mm.

6. The method for preparing a titanium-aluminum composite material according to claim 1, wherein: In the step 4), the titanium-clad aluminum extruded profile is cut perpendicularly to the extrusion direction to a thickness of 10 to 15 mm; and / or The annealing temperature is 500-620° C.; preferably, the annealing time is 5-8 hours.

7. The method for preparing a titanium-aluminum composite material according to claim 1, wherein the aging treatment process is preferably a two-stage process; Preferably, the first stage aging temperature is 170-180°C and the time is 4-6 hours; Preferably, the aging temperature in the second stage is 200-210° C., and the aging time is 1-2 hours.

8. A titanium / aluminum composite mobile phone middle frame material prepared by the preparation method according to claims 1 to 7.