Titanium wire is widely used in aerospace, hydrogen energy equipment, consumer electronics and other fields due to its excellent corrosion resistance, lightweight and good mechanical properties. There are significant differences in the strength performance of titanium wires with different diameters, and these differences are closely related to the type of titanium material, processing technology, and heat treatment method. Accurately understanding the strength characteristics of titanium wires with different diameters is the key to achieving precise selection and ensuring the safe and stable operation of equipment. Starting from the strength characteristics of pure titanium wire and titanium alloy wire, this article deeply analyzes the correlation between diameter and strength, and provides targeted selection suggestions.
1、 Strength characteristics of pure titanium wire: balancing basic strength and excellent plasticity
The most commonly used grades of pure titanium wire are TA1 and TA2, both of which belong to industrial pure titanium. The main difference lies in the oxygen content, which directly affects its strength and plasticity performance. Although the strength of pure titanium wire is lower than that of titanium alloy wire, it has better elongation and formability, making it suitable for scenarios that require high flexibility, corrosion resistance, and relatively mild load-bearing pressure.

Tensile strength: Purity and processing technology dominate, and the influence of diameter shows a differentiated trend
The tensile strength of pure titanium wire is not a fixed value, but is within the range of 240-550 MPa. The specific value is influenced by factors such as purity grade, cold work hardening degree, annealing process, etc., and the change in diameter will further exacerbate the fluctuation of strength.
Purity and process determine the basic strength range:
TA1, as a low oxygen pure titanium, has a lower limit of tensile strength of ≥ 240 MPa and an upper limit usually not exceeding 400 MPa. It focuses more on plasticity and welding performance and is suitable for manufacturing components that require multiple bending; TA2 has a slightly higher oxygen content and can be strengthened through cold processing technology. The upper limit of tensile strength can reach 450-550 MPa, which can withstand higher static loads while ensuring a certain plasticity. It is commonly used as a sealing gasket skeleton for hydrogen energy equipment and a conductive connecting wire for electronic devices.
The bidirectional effect of diameter on strength:
For pure titanium wire, the diameter is not simply “larger, stronger” or “smaller, stronger”, but rather forms a linkage effect with the processing technology. Under the cold working process, pure titanium wires with smaller diameters have further refined metal grains and higher lattice distortion, resulting in more significant cold work hardening effects. Their tensile strength is 10% -15% higher than that of pure titanium wires with the same grade and diameter of 3.0-5.0mm. However, when the diameter is too small, stress concentration is prone to occur during the processing, and the impact of surface defects on strength is amplified, leading to an increase in strength fluctuations and even brittle fracture when subjected to small external forces. Customized processes such as multiple annealing and surface polishing are needed to reduce the risk.

Elongation: The core advantage of pure titanium wire is that its diameter has a relatively mild impact
Elongation is a key indicator for measuring material plasticity, and the elongation of pure titanium wire is significantly better than that of titanium alloy wire, which is also the reason why it cannot be replaced in flexible demand scenarios. The elongation of TA1 pure titanium wire is generally ≥ 15%, and the elongation of TA1 wire after partial annealing treatment can reach 20% -25%, which can easily achieve multiple bending without fracture; TA2 pure titanium wire has a slightly higher oxygen content and a slightly lower elongation than TA1, usually between 12% -18%, but still much higher than TC4 titanium alloy wire.
From a diameter perspective, the elongation of pure titanium wire is less affected by diameter: TA2 wire with a diameter of 1.0-5.0mm usually has an elongation difference of no more than 3%; Only when the diameter is ≤ 0.3mm, due to the difficulty in uniformly controlling the degree of cold work hardening, the elongation may decrease to 8% -10%, and plasticity needs to be restored through intermediate annealing process. This excellent plastic stability makes pure titanium wire widely used in flexible connecting components of medical devices and precision instruments.
2、 Strength characteristics of titanium alloy wire: perfect combination of high strength and lightweight
TC4 is the most typical titanium alloy wire, which is strengthened by solid solution and aging precipitation of alloy elements. Its strength far exceeds that of pure titanium wire, while retaining the advantage of lightweight titanium material. It is the core material for high load-bearing scenarios such as aerospace and high-end equipment.

Tensile strength: Heat treatment process dominates, diameter affects focusing stability
The tensile strength of TC4 titanium alloy wire is extremely outstanding, with a basic range of 900-1300 MPa. Through differentiated heat treatment processes, the upper limit of strength can be further broken, and the influence of diameter on strength is mainly reflected in cross-sectional uniformity and defect control.
The heat treatment process determines the upper limit of strength:
Solid solution treatment can uniformly dissolve alloy elements in the titanium matrix, forming a supersaturated solid solution. At this time, the tensile strength of TC4 titanium alloy wire can reach about 1100 MPa, and it has good toughness, suitable for fasteners in aviation engines and lightweight connectors in automotive chassis; If aging treatment is carried out after solid solution treatment, small β – phase particles will precipitate in the matrix, producing a strong precipitation strengthening effect. The tensile strength can exceed 1500 MPa, and even reach 1600 MPa. This high-strength TC4 wire is commonly used in extreme load-bearing scenarios such as the stress skeleton of spacecraft and the high-pressure valve core of hydrogen energy storage tanks.
The influence of diameter on strength stability:
Unlike pure titanium wire, when the diameter of TC4 titanium alloy wire increases, its strength does not decrease, but may become more stable due to improved cross-sectional uniformity. For example, TC4 wire with a diameter of 2.0mm is prone to local stress concentration during cold drawing, resulting in a fluctuation range of tensile strength of approximately 1050-1150 MPa; TC4 wire with a diameter of 5.0-8.0mm can be rolled through multiple passes and uniformly annealed to ensure the consistency of the microstructure at all parts of the section, reduce the fluctuation of tensile strength to 1080-1120 MPa, and have better fatigue performance. However, it should be noted that when the diameter exceeds 10mm, a “temperature difference between the core and the surface” is prone to occur during the heat treatment process, resulting in coarse core tissue and a 5% -8% decrease in strength. Therefore, the large-diameter TC4 wire needs to adopt a segmented heating and slow cooling heat treatment process to avoid internal defects caused by thermal stress.

Strength advantage: the core competitiveness of lightweight scenarios
Specific strength is a key indicator for measuring the lightweight performance of materials. The specific strength of TC4 titanium alloy wire is as high as 23.5, far exceeding ordinary alloy steel and aluminum alloy, which gives it an irreplaceable advantage in scenarios that require “weight reduction+high strength”.
Taking the aviation industry as an example, the aircraft seat frame connector made of TC4 titanium alloy wire with a diameter of 4.0mm reduces weight by 35% compared to alloy steel connectors of the same specification. A single aircraft can reduce weight by about 80kg and reduce fuel consumption by about 5000L per year. In the automotive industry, TC4 titanium alloy wire with a diameter of 6.0mm is used to manufacture suspension system springs, which reduces weight by 40% and increases fatigue life by 2 times compared to traditional steel springs, effectively improving the handling and endurance of automobiles.
3、 The correlation between diameter and strength: a deep analysis of classification and scenarization
The influence of diameter on the strength of titanium wire is not a single law, but requires comprehensive analysis based on the type of titanium material, processing technology, and application scenarios. The diameter strength correlation characteristics vary significantly in different scenarios.

Pure titanium wire: The smaller the diameter, the more significant the cold processing strengthening, but caution should be taken against the brittleness of ultrafine wires
The core correlation between the diameter and strength of pure titanium wire lies in the “cold work hardening effect”, which exhibits different effects in different diameter ranges:
Medium to coarse diameter range:
The pure titanium wire in this range is the main application object of cold processing technology. The smaller the diameter, the greater the deformation during the cold drawing process, the higher the degree of metal grain refinement, and the more obvious the strength improvement. Taking TA2 pure titanium wire as an example, the tensile strength of cold drawn wire with a diameter of 3.0mm is about 480 MPa, and the elongation rate is 16%; The tensile strength of cold drawn wire with a diameter of 1.0mm has been increased to 520 MPa, and the elongation rate has decreased to 13%; The tensile strength of cold drawn wire with a diameter of 0.5mm can reach 550 MPa, and the elongation rate is further reduced to 11%. The strength of pure titanium wire in this range is significantly negatively correlated with its diameter, and the strength fluctuation is small, making it suitable for scenarios such as catheter wires in medical devices and pins in electronic devices.
Ultra fine wire interval:
When the diameter is less than 0.3mm, the processing difficulty of pure titanium wire increases sharply, and the phenomenon of “wire breakage” is prone to occur during the cold drawing process. In order to ensure forming, higher cold processing deformation is usually required, resulting in high concentration of internal stress in the metal. At this point, the strength fluctuation amplitude of pure titanium wire increases, and the tensile strength of some ultrafine wires may reach as high as 600 MPa, but the elongation rate drops sharply to below 8%, and the brittleness significantly increases, making them prone to fracture when subjected to minor bending or vibration. Therefore, the application of ultra-fine wires requires a customized “multi pass cold drawing+intermediate annealing” process, with each cold drawing deformation controlled at 10% -15%, and surface microcracks removed through electrochemical polishing to ensure strength stability and fatigue life.

Titanium alloy wire: moderate diameter, optimal strength and stability
The core correlation between the diameter and strength of TC4 titanium alloy wire lies in “cross-sectional uniformity and heat treatment effect”, and the performance is best in the medium diameter range:
Medium diameter range:
The TC4 titanium alloy wire in this range can achieve high uniformity of cross-sectional structure, stable strength, and excellent fatigue performance through the process of “rolling+cold drawing+uniform heat treatment”. Taking solid solution TC4 wire as an example, the tensile strength of wire with a diameter of 2.0mm is ≥ 1000 MPa, and the fatigue strength is about 520 MPa; The tensile strength of a wire with a diameter of 5.0mm is ≥ 1050 MPa, and the fatigue strength is increased to 550 MPa; The tensile strength of a wire with a diameter of 8.0mm is ≥ 1080 MPa, and the fatigue strength can reach 580 MPa. The strength of TC4 wire in this range slightly increases with the increase of diameter, and the fluctuation is small, making it the preferred choice for aviation fasteners and high-pressure components of hydrogen energy equipment.
Fine diameter range:
The processing difficulty of thin diameter TC4 titanium alloy wire is relatively high. During the cold drawing process, local excessive deformation is prone to occur, resulting in excessive roundness of the cross-section. In addition, during heat treatment, it is easy to cause uneven organization and increased strength fluctuations due to “small heat capacity and fast cooling”. For example, the tensile strength of TC4 wire with a diameter of 0.8mm may fluctuate between 950-1030 MPa, and the surface is prone to oxide scale. It needs to be improved in performance through vacuum heat treatment and sandblasting process, and is suitable for micro medical devices, but its fatigue life needs to be strictly verified.
Coarse diameter range:
The main problem with the coarse diameter TC4 titanium alloy wire is the poor uniformity of heat treatment, where the surface temperature is higher than the core during heating, resulting in coarse grains in the core and a decrease in strength. For example, a TC4 wire with a diameter of 12mm has a surface tensile strength of about 1080 MPa, a core tensile strength of only 980 MPa, and a cross-sectional strength difference of up to 100 MPa, which can easily lead to core cracking due to stress concentration during loading. Therefore, the thick diameter TC4 wire needs to be subjected to a heat treatment process of “segmented heating+isothermal insulation”, and internal defects should be detected through ultrasonic testing, which is suitable for low stress scenarios such as support shafts of large industrial equipment and ship connectors.
4、 Selection suggestion: Accurate matching based on scene requirements
Different diameters and types of titanium wires have significant differences in strength, plasticity, and processing performance. The selection should be closely combined with the “strength requirements, flexibility requirements, processing difficulty, and cost budget” of the application scenario to achieve a balance between performance and economy.

High flexibility demand scenario: Prioritize the selection of medium to thick diameter pure titanium wire
If the application scenario requires frequent bending and forming, and the bearing pressure is low, TA2 pure titanium wire is preferred, and the specific diameter needs to be determined based on flexibility requirements:
Medical devices: Flexibility and formability need to be taken into account. It is recommended to choose TA2 cold drawn wire with a diameter of 0.5-2.0mm, a tensile strength of 450-520 MPa, an elongation of 13% -16%, which can achieve multiple bending, and has excellent resistance to body fluid corrosion, avoiding postoperative abnormal reactions.
Flexible connection of electronic devices: requires a small diameter and easy welding. It is recommended to choose TA2 annealed wire with a diameter of 0.1-0.5mm, tensile strength of 300-350 MPa, elongation of 18% -22%, good welding performance, and light weight, suitable for miniaturized devices.

High load scenario: Prioritize the selection of medium diameter titanium alloy wire
If the application scenario requires high load, high-frequency vibration, and high lightweight requirements, TC4 titanium alloy wire is preferred, and the specific diameter needs to be determined based on the bearing strength and processing technology:
Aerospace: High strength and high fatigue performance are required. It is recommended to choose TC4 solid solution aging wire with a diameter of 2.0-8.0mm, tensile strength ≥ 1200 MPa, fatigue strength ≥ 550 MPa, and aviation standard certification to ensure long-term stability in high temperature and vibration environments.
Hydrogen energy equipment: High strength and hydrogen embrittlement resistance are required. It is recommended to choose TC4 solid solution wire with a diameter of 4.0-10.0mm, a tensile strength of ≥ 1050 MPa, and hydrogen embrittlement testing to avoid brittle fracture caused by hydrogen atom infiltration.

Application scenarios of ultra-fine wires: customized process+strict verification
If the application scenario requires ultra-fine wires, such as micro sensor electrodes and small transmission components of surgical robots, customized processes should be combined with titanium material types, and performance should be strictly verified:
Pure titanium ultrafine wire: suitable for low load and high flexibility scenarios, requiring the use of “multi pass cold drawing+intermediate annealing” process, with deformation controlled within 10% per pass, final tensile strength ≥ 350 MPa, elongation ≥ 12%, and passing fatigue testing.
Titanium alloy ultrafine wire: suitable for low load and high-precision scenarios, requiring vacuum cold drawing+vacuum heat treatment process to avoid surface oxidation, with a final tensile strength of ≥ 950 MPa and a cross-sectional roundness of ≤ 0.03mm, and ensuring tissue uniformity through metallographic testing to prevent local brittleness.

Cost sensitive scenarios: balancing performance and economy
If the application scenario is cost sensitive and the intensity requirement is moderate, a more cost-effective solution can be selected based on the demand:
Alternative to stainless steel wire: If lightweight and corrosion-resistant, TA2 pure titanium wire with a diameter of 3.0-6.0mm can be chosen. Compared to stainless steel wire of the same specification, it reduces weight by 40% and improves corrosion resistance by three times. Although the initial cost is 30% higher, the total lifecycle cost is reduced by 50%.
TC4 wire with simplified process: If higher strength is required but the budget is limited, TC4 solid solution wire with a diameter of 5.0-8.0mm can be selected. Compared with TC4 wire treated by aging, the cost is reduced by 20% and the processing performance is better. It is suitable for industrial equipment scenarios with less extreme fatigue life requirements.