A modified titanium alloy, profile and preparation method thereof for improving cutting performance

Abstract

The present invention discloses a modified titanium alloy with improved cutting performance, a profile, and a preparation method thereof. The modified titanium alloy with improved cutting performance comprises the following components by mass percentage: Al 0.3-3%, Zr 0.4-3.0%, Si 0.05-0.3%, Fe 0.25-0.5%, O 0.25-0.4%, with the balance being Ti. Based on the standard TA4 titanium alloy, the present invention adds Si, Zr, and Al elements. Since Al and Si distributed at grain boundaries are easily precipitated at grain boundaries, Si and Zr act to hinder dislocation movement, thereby improving the rigidity of the workpiece material during CNC machining, suppressing elastic deformation and vibration during workpiece machining, and reducing tool sticking. The excellent chip breaking properties allow a large amount of chips to be carried away with the cutting coolant, reducing the occurrence of hardness reduction and wear caused by tool bit sticking and heat storage, thereby improving tool life and workpiece machining quality.

Description

Technical Field

[0001] The present invention belongs to the field of metal materials, and in particular relates to a modified titanium alloy with improved cutting performance, a profile and a preparation method thereof. Background Art

[0002] TA4 titanium alloy has excellent mechanical properties and corrosion resistance, making it suitable for applications in aerospace, chemical engineering, and medical applications. However, TA4 titanium alloy is relatively expensive, has poor machinability, and is prone to cold welding. Cold welding must be avoided during processing, and appropriate lubrication and machining methods must be employed. It is widely used in the manufacture of high-strength and corrosion-resistant parts.

[0003] In the existing standard TA4 titanium alloy products: O < 0.4% (conventional product content 0.3%), Fe < 0.5% (conventional product content 0.3%). In the downstream processing industry, the high processing cost of TA4 titanium alloy has always been an industry pain point. The reason is that the titanium alloy material itself has the following common characteristics:

[0004] (1) Poor thermal conductivity. The cutting heat is not easy to dissipate during the cutting process, and is concentrated in a small area near the cutting zone and the cutting edge, resulting in increased cutting temperature, accelerated tool wear, and reduced surface quality.

[0005] (2) It has active chemical properties and is easy to react with nitrogen, oxygen in the air and carbon in grease at high temperatures to form a hardened layer, which increases cutting resistance and accelerates tool wear;

[0006] (3) Small elastic modulus and large elastic deformation. Titanium alloy has a small elastic modulus and is prone to elastic deformation under the action of cutting force, causing vibration, resulting in reduced processing accuracy, reduced quality, and frequent tool breakage and other abnormalities. Summary of the Invention

[0007] In view of this, the technical problem to be solved by the present invention is to propose a modified titanium alloy with improved cutting performance. Referring to the existing standard TA4 titanium alloy, the metal components are increased and the alloy microstructure is optimized by combining corresponding forging and rolling processes. The hardness and strength of the material are increased without significantly reducing its plasticity and toughness. This improves the material's cutting performance, increases the service life of CNC machining tools, and improves the surface quality of the processed products. The titanium alloy material of the present invention has mechanical properties and cost comparable to standard TA4 titanium alloy, but with lower machining costs.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0009] A modified titanium alloy with improved cutting performance, comprising the following components in percentage by mass:

[0010] Al 0.3-3%, Zr 0.4-3.0%, Si 0.05-0.3%, Fe 0.25-0.5%, O 0.25-0.4%, and the balance is Ti. The modified titanium alloy also includes inevitable impurities.

[0011] The present invention primarily adds elements such as Al, Zr, and Si to existing standard alloy compositions, and selects appropriate amounts of Fe and O to ensure that the material's mechanical properties are comparable to or slightly superior to those of standard TA4, thereby improving processing performance and reducing material processing costs. By increasing the material's thermal strength, it improves tool sticking during processing and reduces cutting resistance. Refining the microstructure inhibits cutting deformation during processing, improving processing stability. By adding trace elements such as Al, Zr, and Si, the material's lubricity and chip breaking properties during cutting are adjusted (cutting heat is carried away by the cutting fluid along with the broken chips), reducing cutting resistance, effectively slowing tool wear caused by chip sticking and untimely heat dissipation, and extending tool life.

[0012] In the present invention, the addition of Al, an α-stabilizing element, increases the α-solution bonding strength and forms an intermetallic compound with Ti, thereby improving the thermal strength of the titanium alloy. It also refines the grain size, increasing the alloy's elastic modulus and deformation resistance. Al strongly segregates at grain boundaries, with the concentration at these boundaries exceeding the concentration within the grain by more than one times. This uneven distribution of Al across the grain volume reduces the alloy's plasticity. Considering the influence of Al on the alloy's material properties, an addition range of 0.3 to 3% was selected, which not only increases the alloy's strength and elastic modulus, but also improves its cutting performance, while minimizing its impact on the material's plasticity.

[0013] Zr is a substitutional neutral strengthening element that forms a continuous solid solution with Ti, lowering the transition temperature and nucleation activation energy, promoting the nucleation of silicides on the matrix. Without reducing the bonding strength of titanium, it increases the static lattice distortion of Ti, thereby strengthening it and improving the thermal strength of titanium. The addition of Zr allows the α phase to crystallize in more directions, thereby reducing the width of the lamellar α phase and refining the grains. Coarse-grained structures have smaller grain boundaries, allowing cutting deformation to easily extend along them. Fine-grained structures have larger grain boundaries, which can hinder the development of cutting deformation. Zr compounds precipitated at the grain boundaries act as lubricants, effectively reducing tool sticking and lowering cutting resistance.

[0014] Si is an interstitial fast-eutectoid β-stabilizing element, present in the alloy in the form of solid solution or silicide. Due to Si's solid solution strengthening, DSA (dynamic strain aging) effect, and silicide dispersion strengthening, it improves the creep resistance of titanium alloys. It also refines grains, forming finely dispersed silicides within the alloy. These silicides, distributed at grain boundaries, inhibit grain boundary movement and grain growth. Due to the significant atomic size difference between Si and Ti, Si in solid solution tends to aggregate at dislocations, inhibiting dislocation motion, reducing material toughness, and improving chip breaking during cutting, thereby enhancing the alloy's strength, hardness, and heat resistance. When Si coexists with Zr, it forms dispersed complex silicides that deposit on active dislocations, hindering dislocation motion and improving the alloy's creep resistance.

[0015] In the present invention, in the production of titanium alloy, titanium and silicon or iron are added to the titanium alloy in the form of intermediate alloys of titanium-silicon alloy and titanium-iron alloy, and the preparation of titanium-silicon alloy and titanium-iron alloy is usually produced by smelting method. After being crushed into particles, the particles of sponge titanium and other alloying elements are mixed and then pressed into electrodes. In order to ensure the uniformity of the mixture, the particle size difference of all added elements cannot be too large, otherwise they will be concentrated in certain parts of the electrode block during the electrode pressing process. Fe is easy to segregate in titanium, and the amount of Si added is very small, and it is impossible to mix the materials uniformly mechanically. Therefore, the method of adding titanium and silicon or iron in the preparation as intermediate alloys is mainly to ensure the uniformity of the alloy material composition (to avoid segregation) and the consistency of mechanical properties and microstructure.

[0016] The addition of interstitial element O forms an interstitial solid solution with titanium, causing lattice distortion, hindering dislocation movement, and playing a role of solid solution strengthening. It can also increase the lattice constant c / a value, reduce its plasticity and toughness, and improve its chip breaking properties during cutting.

[0017] Trace amounts of Fe form substitutional solid solutions with titanium, which can refine grains, increase strength and hardness, and improve cutting and chip breaking properties.

[0018] The method for preparing a profile from a titanium alloy material of the present invention comprises the following steps:

[0019] The process involves batching, mechanical mixing, electrode pressing, electrode welding, electron beam cold-bed melting (EB melting), followed by vacuum consumable arc melting (VAR melting), or two VAR melting steps: peeling, forging, peeling, rolling, annealing, peeling, profile finishing, cold drawing, and annealing. In this method, EB melting combined with VAR melting is preferred, as EB melting has a high temperature and good impurity removal effect. However, two VAR melting steps essentially meet the requirements of the present invention, with the advantage of not requiring additional equipment, saving cost and time.

[0020] When preparing the ingredients, aluminum beans Al 0.3-3%, sponge zirconium Zr 0.4-3.0%, Si (added in the form of titanium silicon alloy) 0.05-0.3%, Fe (added in the form of titanium iron alloy) 0.25-0.5%, O (added in the form of titanium dioxide) 0.25-0.4%, and the rest is sponge titanium.

[0021] During the mechanical mixing process, silicon and iron are crushed into particles and mixed with sponge titanium and other alloying element particles before pressing the electrode. To ensure the uniformity of the mixture, the particle size difference of all added elements cannot be too large, otherwise they will be concentrated in certain parts of the electrode block during the electrode pressing process, resulting in uneven mixing.

[0022] Selection of ferrotitanium alloy: Select ferrotitanium alloy with an iron content of 30% to 35% and Ti as the balance, and a particle size of 2 to 6 mm (obtained by vacuum induction melting using high-purity iron with a purity greater than 99.99% and grade 0 sponge titanium. Other impurity content requirements in ferrotitanium alloy are: Al < 0.2%, V < 0.1%, Si < 0.1%, C < 0.1%, O < 0.2%);

[0023] Selection of titanium silicon alloy: Select titanium silicon alloy with Si content of 45% to 55% and Ti as the balance in the particle size range of 2 to 6 mm (obtained by vacuum induction melting using high-purity silicon with a purity greater than 99.999% and grade 0 sponge titanium. The requirements for other impurity contents in the titanium silicon alloy are: Fe < 0.4%, C < 0.2%, O < 0.2%).

[0024] During the preparation of the modified titanium alloy of the present invention, iron and silicon are added to titanium as an intermediate alloy. Titanium-silicon and titanium-iron alloys are typically produced during the smelting process. The addition of iron and silicon as an alloy is primarily to ensure uniformity of the alloy's composition (to avoid segregation) and consistency of mechanical properties and microstructure. A secondary reason is that iron readily segregates in titanium, and the small amount of silicon added prevents uniform mechanical mixing.

[0025] The modified titanium alloy of the present invention can be used for frames or housings of smart electronic devices, such as frames or housings of mobile phone products, frames or housings of tablet products, frames or housings of watch products, etc.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The modified titanium alloy of the present invention is based on the standard TA4 titanium alloy. Mainly by adding trace elements of Si, Zr and Al, the room temperature strength of the material is slightly improved, the plasticity index is slightly reduced, and the elastic modulus, thermal strength and creep resistance are improved. Since Al and Si distributed on the grain boundaries are easy to precipitate at the grain boundaries, Si and Zr play a role in hindering dislocation movement. With the appropriate forging and rolling process, an ultrafine grain microstructure is obtained. Through the joint action of the above elements, the rigidity of the workpiece material during CNC machining is improved, elastic deformation and vibration during the workpiece machining process are suppressed, and the occurrence of tool sticking is reduced. The trace added elements concentrated at the grain boundaries can reduce the plasticity of the material and improve the chip breaking property of the workpiece during the machining process. The excellent chip breaking property allows a large amount of chips to be carried away with the cutting coolant, reducing the hardness reduction and wear of the tool head caused by material sticking and heat storage, thereby extending the service life of the tool and improving the workpiece machining quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a metallographic image (200×) of the modified titanium alloy of Example 4 of the present invention;

[0029] Figure 2 is a binary image of the modified titanium alloy of Example 4 of the present invention;

[0030] Figure 3 This is the metallographic image of standard TA4 titanium alloy (200×);

[0031] Figure 4 It is the binary image of standard TA4 titanium alloy;

[0032] Figure 5 This is the appearance and size of chip breaking during CNC machining of standard TA4 titanium alloy profiles;

[0033] Figure 6 The chip breaking appearance and size diagram of the modified titanium alloy profile during CNC machining according to Example 4 of the present invention;

[0034] Figure 7 This is a milling cutter diagram for CNC machining of standard TA4 titanium alloy profiles (with sticking cutter);

[0035] Figure 8 This is a milling cutter diagram for CNC machining of the modified titanium alloy profile of Example 4 (without sticking tool);

[0036] Figure 9 Graph showing the results of the number-induced cutting force tests on the standard TA4 titanium alloy (TA4) and the modified titanium alloy of Example 4 (modified alloy). DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to understand the present invention more clearly and intuitively, the present invention will be further described below with reference to the accompanying drawings.

[0038] The modified titanium alloy with improved cutting performance of the present invention comprises the following components in percentage by mass:

[0039] Al 0.3~3%, Zr 0.4~3.0%, Si 0.05~0.3%, Fe 0.25~0.5%, O 0.25~0.4%, and the balance is Ti.

[0040] The present invention mainly adds elements such as Al, Zr, and Si to the existing standard TA4 titanium alloy, and selects the appropriate amount of Fe and O added to ensure that the material's mechanical properties are equivalent to or slightly better than those of the standard TA4 titanium alloy, thereby improving processing performance and reducing material processing costs. By improving the thermal strength of the material, the sticking phenomenon during material processing is improved, and cutting resistance is reduced; the microstructure is refined to inhibit cutting deformation during the processing process, improving processing stability, and by adding trace elements such as Al, Zr, and Si to adjust the lubricity and chip breaking properties of the material during cutting (cutting heat is carried away by the cutting fluid along with the broken chips), reducing cutting resistance, effectively slowing down the tool wear rate caused by chip sticking and untimely heat removal, and improving tool life.

[0041] The addition of the α-stabilizing element Al increases the α-solution bonding force and forms intermetallic compounds with Ti, thereby improving the thermal strength of the titanium alloy. It also refines the grains, increasing the alloy's elastic modulus and deformation resistance. Al is strongly concentrated at grain boundaries, with the Al concentration at grain boundaries being more than 1 times higher than the concentration within the grains. This uneven distribution of Al by grain volume reduces the alloy's plasticity. Considering the influence of Al on the alloy's material properties, an addition range of 0.3-3% was selected, which not only increases the alloy's strength and elastic modulus, but also improves the alloy's cutting performance, while having minimal impact on the material's plasticity.

[0042] Zr is a substitutional neutral strengthening element that forms a continuous solid solution with Ti, lowering the transition temperature and nucleation activation energy, promoting the nucleation of silicides on the matrix. Without reducing the bonding strength of titanium, it increases the static lattice distortion of Ti, thereby strengthening it and improving the thermal strength of titanium. The addition of Zr allows the α phase to crystallize in more directions, thereby reducing the width of the lamellar α phase and refining the grains. Coarse-grained structures have smaller grain boundaries, allowing cutting deformation to easily extend along them. Fine-grained structures have larger grain boundaries, which can hinder the development of cutting deformation. Zr compounds precipitated at the grain boundaries act as lubricants, effectively reducing tool sticking and lowering cutting resistance.

[0043] Si is an interstitial fast-eutectoid β-stabilizing element, present in the alloy in the form of solid solution or silicide. Due to Si's solid solution strengthening, DSA (dynamic strain aging) effect, and silicide dispersion strengthening, it improves the creep resistance of titanium alloys. It also refines grains, forming finely dispersed silicides within the alloy. These silicides, distributed at grain boundaries, inhibit grain boundary movement and grain growth. Due to the significant atomic size difference between Si and Ti, Si in solid solution tends to aggregate at dislocations, inhibiting dislocation motion, reducing material toughness, and improving chip breaking during cutting, thereby enhancing the alloy's strength, hardness, and heat resistance. When Si coexists with Zr, it forms dispersed complex silicides that deposit on active dislocations, hindering dislocation motion and improving the alloy's creep resistance.

[0044] The amounts used in the examples and comparative examples of the present invention are nominal amounts, indicating that reasonable deviations are permitted.

[0045] Example 1

[0046] The modified titanium alloy of this embodiment includes the following components in percentage by mass:

[0047] Al 0.3%, Zr 0.5%, Si 0.05%, Fe 0.25%, O 0.25%, and the balance is Ti.

[0048] Example 2

[0049] The modified titanium alloy of this embodiment includes the following components in percentage by mass:

[0050] Al 0.5%, Zr 2.0%, Si 0.12%, Fe 0.4%, O 0.35%, and the balance is Ti.

[0051] Example 3

[0052] The modified titanium alloy of this embodiment includes the following components in percentage by mass:

[0053] Al 0.4%, Zr 1%, Si 0.08%, Fe 0.38%, O 0.32%, and the balance is Ti.

[0054] Example 4

[0055] The modified titanium alloy of this embodiment includes the following components in percentage by mass:

[0056] Al 0.3%, Zr 0.4%, Si 0.08%, Fe 0.35%, O 0.3%, and the balance is Ti.

[0057] Example 5

[0058] The modified titanium alloy of this embodiment includes the following components in percentage by mass:

[0059] Al 0.8%, Zr 1.5%, Si 0.15%, Fe 0.3%, O 0.32%, and the balance is Ti.

[0060] Example 6

[0061] The modified titanium alloy of this embodiment includes the following components in percentage by mass:

[0062] Al 1.0%, Zr 1.8%, Si 0.18%, Fe 0.35%, O 0.35%, and the balance is Ti.

[0063] Example 7

[0064] The modified titanium alloy of this embodiment includes the following components in percentage by mass:

[0065] Al 1.5%, Zr 2.5%, Si 0.20%, Fe 0.4%, O 0.38%, and the balance is Ti.

[0066] Example 8

[0067] The modified titanium alloy of this embodiment includes the following components in percentage by mass:

[0068] Al 2.0%, Zr 3.0%, Si 0.25%, Fe 0.45%, O 0.4%, and the balance is Ti.

[0069] Example 9

[0070] The modified titanium alloy of this embodiment includes the following components in percentage by mass:

[0071] Al 2.5%, Zr 2.8%, Si 0.28%, Fe 0.45%, O 0.35%, and the balance is Ti.

[0072] Example 10

[0073] The modified titanium alloy of this embodiment includes the following components in percentage by mass:

[0074] Al 3.0%, Zr 1.2%, Si 0.3%, Fe 0.5%, O 0.4%, and the balance is Ti.

[0075] Example 11

[0076] The modified titanium alloy material of Examples 1-10 is prepared into a profile, comprising the following steps:

[0077] S1. Ingredients

[0078] According to the raw material requirements of Examples 1-10, the ingredients are prepared, and aluminum beans, sponge zirconium, titanium silicon alloy, ferrotitanium alloy, titanium dioxide, and sponge titanium raw materials are prepared, and each raw material is crushed. The particle size of each raw material particle must be the same or similar; specifically, sponge titanium with a particle size range of 2-12.7 mm (generally used in aviation / military product production) is used, and ferrotitanium alloy and titanium silicon alloy use products with a particle size range of 2 to 6 mm, which is conducive to uniform mechanical mixing of the materials. Among them, the selection criteria for titanium-ferroalloy are: titanium-ferroalloy with an iron content of 30% to 35% and Ti as the balance, and a particle size range of 2 to 6 mm (obtained by vacuum induction melting using high-purity iron with a purity greater than 99.99% and grade 0 titanium sponge, and the requirements for other impurity contents in the titanium-ferroalloy are: Al < 0.2%, V < 0.1%, Si < 0.1%, C < 0.1%, O < 0.2%); the selection criteria for titanium-silicon alloy are: titanium-silicon alloy with an Si content of 45% to 55% and Ti as the balance, and a particle size range of 2 to 6 mm (obtained by vacuum induction melting using high-purity silicon with a purity greater than 99.999% and grade 0 titanium sponge, and the requirements for other impurity contents in the titanium-silicon alloy are: Fe < 0.4%, C < 0.2%, O < 0.2%); commercially purchased materials are selected according to the requirements of titanium-ferroalloy and titanium-silicon alloy.

[0079] S2, mechanical mixing, electrode pressing and welding

[0080] Mechanically mix the raw material particles, then complete the electrode pressing and welding;

[0081] S3, VAR smelting

[0082] Vacuum consumable electrode arc melting is performed twice to produce an ingot of φ440mm*L, which is then peeled to remove surface defects such as pores.

[0083] S4, Forging

[0084] The forging temperature range is 800℃~1180℃. The ingot is forged into a φ120mm*L round bar through more than three alternating axial and radial deformations. The bar is then peeled to remove the surface oxide layer and forging defects.

[0085] S5, rolling

[0086] The coils are rolled using a high-speed linear rolling mill with a rolling temperature of 850°C ± 50°C and a rolling line speed of 8m ± 3m / s. Annealing treatment is then performed at 720°C ± 20°C for 1 hour to remove processing stress and adjust the structure. The coils are then peeled to remove surface defects and adjust the dimensional accuracy of the coils.

[0087] S6, finishing rolling and drawing

[0088] The required specifications of the profiles are produced through multiple passes of finishing rolling and multiple passes of drawing, and then the profiles are annealed to eliminate processing stress and adjust the structure.

[0089] Three profile samples made of standard TA4 titanium alloy and three profile samples made of modified titanium alloy produced in three different batches represented by Example 4 were tested:

[0090] Hardness test data comparison:

[0091]

[0092] Comparison of mechanical properties test data:

[0093] Mechanical properties test data of standard TA4 titanium alloy

[0094] Sample 1 Sample 2 Sample 3 average value Yield strength (MPa) 627.00 625.00 620.00 624.00 Tensile strength (MPa) 700.00 698.00 699.00 699.00 Elongation (%) 26.28 26.12 26.04 26.15

[0095] Mechanical properties test data of the modified titanium alloy of Example 4

[0096] Sample 1 Sample 2 Sample 3 average value Yield strength (MPa) 642.00 638.00 643.00 641.00 Tensile strength (MPa) 717.00 715.00 718.00 716.67 Elongation (%) 25.40 25.04 24.44 24.96

[0097] Comparison of metallographic test data (typical metallographic diagram):

[0098] The results are as follows Figure 1-4 As shown. From the metallographic diagram, the organization of the standard TA4 titanium alloy and the modified titanium alloy of Example 4 are both uniform equiaxed crystals, and the organization is uniform and consistent. Calculated by metallographic analysis software (Matlab), the modified titanium alloy is superior to the standard TA4 titanium alloy in terms of both maximum grain size and average grain size. The binary diagram is a picture of the metallographic diagram processed by analysis software (Matlab) and is used for quantitative metallographic analysis. In the present invention, it is mainly used for the determination of the grain size of the material (grain size, generally expressed as the number of grains per unit test area). Grain size directly affects the mechanical properties of the material.

[0099] Standard TA4 titanium alloy grain grading data: maximum grain size (μm) 33.660, average grain size (μm) 12.325; modified titanium alloy grain grading data: maximum grain size (μm) 25.670, average grain size (μm) 6.608.

[0100] The grain data of the modified titanium alloy of Example 4 are as follows:

[0101] Maximum grain size (μm) 25.670 Average grain size (μm) 6.608 Standard deviation 3.486

[0102] The grain data of standard TA4 titanium alloy are as follows:

[0103] Maximum grain size (μm) 33.660 Average grain size (μm) 12.325 Standard deviation 4.359

[0104] In summary, the average hardness of the modified titanium alloy profile in Example 4 of the present invention is increased by about 10HV (the hardness reaches 273HV) compared with the standard TA4 titanium alloy, the yield strength is increased by about 20Mpa (reaching 641MPa) compared with the standard TA4 titanium alloy, the tensile strength is increased by about 15MPa (reaching 716.67MPa), and the elongation is about 25%.

[0105] The average grain size reaches grade 11.5, with an average grain size of 6.6μm. The average grain size of TA4 titanium alloy is usually grade 9-10 (GB / T 6394-2002): grade 9 corresponds to an average grain size of 15.9μm, and grade 10 corresponds to an average grain size of 11.2μm.

[0106] In addition, if Figure 5 and 6 As shown, the chip length of the modified titanium alloy of Example 4 is about 70% to 80% of that of the standard TA4 titanium alloy.

[0107] In summary, it can be seen that the present invention changes the properties of titanium alloy by adding elements such as Al, Zr, and Si. For example, the addition of Al improves the hardness and tensile strength of titanium alloy. By controlling the amount of Al added, a new balance is achieved between the processing difficulty and the life of the milling cutter, that is, the life of the milling cutter will not be excessively affected by the increase in the hardness of the titanium alloy material. Generally speaking, increasing the hardness of a material can easily cause thermal deformation of the material during processing, resulting in a decrease in processing accuracy and even causing other problems. In order to solve this problem, the present invention improves the thermal strength of titanium alloy by adding Zr, overcomes the deformation resistance of titanium alloy materials at high temperatures, and the addition of Zr also provides lubricity during milling cutter processing, reduces the binding force between the milling cutter and the chips when processing titanium alloy, so that the chips can be more easily separated from the milling cutter, and the added Si reduces the toughness of the titanium alloy material to a certain extent, improves the chip breaking property of the titanium alloy material during cutting, reduces the length of the chips generated by processing, and the shorter chips are easier to separate from the milling cutter. The rapid separation of chips from the milling cutter can reduce the contact time of high-temperature chips with the milling cutter, and takes away the heat of the milling cutter and the processing position through the chips, reducing the impact of continuous high heat on the milling cutter, thereby increasing the number of milling cutter processing times.

[0108] Therefore, the present invention fully utilizes the effects of the added elements to improve the material properties of the titanium alloy, and strictly controls the amount of each element added to prevent the added elements from increasing the processing difficulty and prevent increasing the cost of the titanium alloy material itself and the processing cost of the titanium alloy. On the contrary, the present invention reduces the material processing difficulty through the combined effect of the added elements, increases the number of times the milling cutter can be used, and reduces the processing cost.

[0109] Using the same CNC machining parameters (spindle speed 10,000 rpm, feed rate 2 m / min, feed amount 0.6 mm), the same cutting tools and cutting cooling conditions, the tool life was improved by 10%. That is, the length and weight of the modified titanium alloy machined during the tool life were twice that of the standard TA4 titanium alloy. Each 1 m of length processed was considered a milling process. The workpiece machining process was monitored by an inductive cutting force measurement and monitoring system installed on the CNC equipment, and the following data was obtained:

[0110] The cutting force of the standard TA4 titanium alloy profile increased sharply (greater than 200N, and the cutting force measured in the second experiment reached 420N) when the cutting force of the 5th, 48th and 29th times was processed respectively. Inspection found that the milling cutter head had a lot of sticking material, such as Figure 7 shown.

[0111] The modified titanium alloy profile of Example 4 only experienced a slight increase in the induced cutting force (<150N) during the entire processing process, and in the subsequent processing, the induced cutting force dropped to a stable level (75-90N), solving the problem of the milling cutter head sticking. Figure 8 shown.

[0112] like Figure 9 As shown in the figures, through data comparison, the cutting performance of the modified titanium alloy of Example 4 is significantly better than that of the standard TA4 titanium alloy. The average induced cutting force during the processing is about 82% to 90% of that of the standard TA4 titanium alloy, and the stable processing length is 2.5-3 times that of the standard TA4 titanium alloy.

[0113] The hardness, strength and elongation of the present invention are all improved, and the Zr-based compounds precipitated at the grain boundaries play a lubricating role between the tool and the material, reducing material sticking to the tool during cutting and reducing the processing load on the tool.

[0114] Machinability results: Reduced machining load, reduced tool tip load by 15%-25%

[0115]

[0116] After evaluation, the number of machining times of the modified titanium alloy machining tool of Example 4 increased: (mass production) 46 times / (modification) more than 100 times, reducing the sticking phenomenon between the tool and the material.

[0117] Since the effect of the present invention is mainly achieved by adding elements such as Al, Zr, and Si, a new balance is formed between the performance and processing difficulty of the titanium alloy through the newly added elements, thereby improving the performance of the titanium alloy material while reducing its processing cost. Therefore, based on the same principle, the modified titanium alloys of the remaining embodiments obviously have similar effects to the modified titanium alloy of Example 4, which has also been confirmed through verification of other embodiments during the research process.

[0118] The above examples confirm that adding elements such as Al, Zr, and Si to the titanium alloy of the present invention can achieve processing properties that the standard TA4 titanium alloy does not have. Furthermore, by adjusting the addition amounts of different components during the preparation process of the modified titanium alloy material in Example 4, different comparative proportions are obtained to study the effect of changes in the specific amount of each element on the processing properties of the titanium alloy material.

[0119] Comparative Example 1

[0120] The titanium alloy of this comparative example includes the following components in percentage by mass:

[0121] Al 0.27%, Zr 0.4%, Si 0.08%, Fe 0.35%, O 0.3%, and the balance is Ti.

[0122] Comparative Example 2

[0123] The titanium alloy of this comparative example includes the following components in percentage by mass:

[0124] Al 3.3%, Zr 0.4%, Si 0.08%, Fe 0.35%, O 0.3%, and the balance is Ti.

[0125] The addition of Al has a crucial influence on the hardness of titanium alloy materials. Too much or too little Al addition affects the processing performance of titanium alloys. In Comparative Example 1, Al addition is too low, and the hardness of the titanium alloy material is not significantly improved compared to the standard TA4 titanium alloy (about 265HV). During processing, the titanium alloy profile is more likely to deform than the modified titanium alloy profile of Example 4, and because Al and Ti can form intermetallic compounds to improve the thermal strength of the titanium alloy, when Al is added too little, the thermal strength of the titanium alloy material is not sufficiently improved during processing. The chip length during cutting is similar to that of the standard TA4 chip length (measured, the chip length exceeds 1 cm, mostly between 1.1 and 1.2 cm), resulting in insufficient cutting performance of the profile. Subsequently, during the processing of the titanium alloy material, the heat cannot be quickly and promptly discharged by relying on the chips. The number of times the milling cutter is used is not significantly increased compared to when processing the standard TA4 titanium alloy profile, and the service life of the milling cutter is not significantly extended. In Comparative Example 2, too much Al is added, and the hardness of the titanium alloy material is increased too much (reaching about 280HV). The direct result is that the extremely hard titanium alloy material is too difficult to process. The high hardness causes the titanium alloy material to generate more heat during processing, and the milling cutter is more affected by the heat during processing, resulting in not only no significant extension of the life of the milling cutter, but also a sharp shortening of the service life of the milling cutter due to the long-term operation of the milling cutter under high temperature conditions (the total number of processing times is about 35 times).

[0126] Comparative Example 3

[0127] The titanium alloy of this comparative example includes the following components in percentage by mass:

[0128] Al 0.3%, Zr 0.36%, Si 0.08%, Fe 0.35%, O 0.3%, and the balance is Ti.

[0129] Comparative Example 4

[0130] The titanium alloy of this comparative example includes the following components in percentage by mass:

[0131] Al 0.3%, Zr 3.3%, Si 0.08%, Fe 0.35%, O 0.3%, and the balance is Ti.

[0132] The addition of Zr not only increases the static lattice distortion of Ti and strengthens it, thereby improving the thermal strength of titanium, but also acts as a lubricant, effectively reducing the sticking phenomenon and reducing cutting resistance. In Comparative Example 3, the amount of Zr added is controlled to be lower than the 0.4% Zr amount used in Example 4, while the addition of Al element improves the hardness of the titanium alloy material (combined with the hardening of the titanium alloy material, the hardness reaches about 270HV), resulting in an increase in the heat when the titanium alloy is heated. Due to the low amount of Zr added in Comparative Example 3, the thermal strength of the titanium alloy is insufficient, resulting in weakening of the strength at high temperatures during processing, resulting in defects such as cracks. At the same time, the material has insufficient lubricity during the cutting process, resulting in a milling cutter sticking phenomenon similar to that in the processing of standard TA4 titanium alloy (the milling cutter sticking phenomenon is alleviated compared to the processing of standard TA4 titanium alloy, but it still exists). In Comparative Example 4, the amount of Zr added is controlled to be higher than 3.0%. This is because as the Zr element content in the titanium alloy increases, the microstructure first becomes finer and then coarser, the precipitated phase gradually increases, the segregation becomes serious, and the strength first increases and then decreases. Therefore, the excessive addition of Zr in Comparative Example 4 not only results in excessively high cost, but also reduces the strength, reduces the toughness of the titanium alloy during post-processing, and has a low cost-performance ratio.

[0133] Comparative Example 5

[0134] The titanium alloy of this comparative example includes the following components in percentage by mass:

[0135] Al 0.3%, Zr 0.39%, Si 0.045%, Fe 0.35%, O 0.3%, and the balance is Ti.

[0136] Comparative Example 6

[0137] The titanium alloy of this comparative example includes the following components in percentage by mass:

[0138] Al 0.3%, Zr 3.1%, Si 0.33%, Fe 0.35%, O 0.3%, and the balance is Ti.

[0139] Si tends to accumulate at dislocations in the solid solution, preventing dislocation movement, reducing material toughness, and improving chip breaking during cutting. In Comparative Example 5, the amount of Si added is too little, so the effect of Si is not prominent enough, and the machinability of the titanium alloy material is insufficiently improved. However, due to the addition of Al, the hardness of the titanium alloy material is improved compared to the standard TA4 titanium alloy. The heat generated during processing is greater, and the change in the length of the chips generated during processing is not significantly different from the chip length of the standard TA4 (after measurement, the chip length is about 1 cm). The heat at the processing position cannot be quickly taken away with the chips, and the service life of the milling cutter is shorter than when processing the standard TA4 titanium alloy (comprehensively about 40 times of processing). In Comparative Example 6, the amount of Si added is too much, and the toughness and plasticity of the titanium alloy material are reduced. Since the plasticity of the titanium alloy is small, it significantly affects its plastic deformation during cutting. The deformation coefficient of the titanium alloy is only 1 or even less than 1. During cutting, the chips have a very small contact surface with the milling cutter, which makes the pressure and local temperature in the contact area high, and the tool wears quickly, thus affecting the service life of the milling cutter (comprehensively about 42 times of processing) and increasing the processing cost.

[0140] Similarly, comparative proportions of Fe below 0.25% and above 0.5%, and comparative proportions of O below 0.25% and above 0.4% are set respectively. Since appropriate Fe and O can ensure that the mechanical properties of the material are equivalent to or slightly better than those of the standard TA4 titanium alloy, improve the processing performance and reduce the material processing cost, too much or too little Fe and O elements make the titanium alloy have no obvious advantages over the standard TA4 titanium alloy in terms of plasticity, toughness and machinability.

[0141] In summary, in the present invention, the selection of the amount of Al, Zr, Si, Fe, and O each has a decisive influence on the processing properties of the titanium alloy material. The elements play a role of mutual support and complementation in the processing properties of the titanium alloy. Too much or too little addition of a certain element will break this new balance, affecting the processing properties of the titanium alloy and failing to achieve the purpose of reducing processing costs.

[0142] The above description of the embodiments is intended to facilitate understanding and application of the present invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the embodiments described herein, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention should fall within the scope of protection of the present invention.

Claims

1. A modified titanium alloy with improved cutting performance, characterized in that: The modified titanium alloy comprises the following components in percentage by mass: Al 0.3-3%, Zr 0.4-3%, Si 0.05-0.3%, Fe 0.25-0.5%, O 0.25-0.4%, and the balance Ti. The preparation method of the modified titanium alloy comprises the following steps: S1. Ingredients Prepare the ingredients according to the content requirements of each element, prepare aluminum beans, zirconium sponge, titanium silicon alloy, ferrotitanium alloy, titanium dioxide, and titanium sponge, and crush the raw materials into particles; S2, mechanical mixing, electrode pressing and welding Mechanically mix the raw material particles, then complete the electrode pressing and welding; S3, smelting Electron beam cold bed melting combined with vacuum consumable arc melting to obtain ingots for use; or two vacuum consumable arc melting to obtain ingots for use; S4. Forging the ingot The forging temperature range is 800℃~1180℃, and the ingot is forged into a round bar through more than three alternating axial and radial deformations; S5, rolling The coils were rolled using a high-speed linear rolling mill and then annealed to remove processing stress and adjust the structure. The rolling conditions were: feed temperature 850°C ± 50°C, rolling line speed 8 m / s ± 3 m / s. S6, finishing rolling and drawing After finishing rolling and drawing, the required specification profiles are produced, and then the profiles are annealed to eliminate processing stress and adjust the structure.

2. The modified titanium alloy according to claim 1, characterized in that In step S1 , the particle sizes of the raw material particles are the same or similar; the particle size of the titanium sponge is 2 to 12.7 mm, and the particle size of the titanium-iron alloy and the titanium-silicon alloy is 2 to 6 mm.

3. The modified titanium alloy according to claim 1, characterized in that In step S3, the ingot obtained by smelting further includes a scalping step to remove the surface oxide layer and defects.

4. The modified titanium alloy according to claim 1, characterized in that After steps S4 and S5, a peeling step is also included to remove the surface oxide layer and defects.

5. Use of the modified titanium alloy according to any one of claims 1 to 4 in preparing frames or shells of mobile phone products, frames or shells of tablet products, and frames or shells of watch products.

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