1. Classification by Chemical Composition
Based on the content and type of alloying elements in titanium, it is divided into two main categories: pure titanium and titanium alloys. This is the primary basis for grade selection in production.
- Pure Titanium (Commercial Pure Titanium)
Contains only trace impurities (e.g., Fe, C, N, O, H) with no intentionally added alloying elements. It offers good plasticity, excellent corrosion resistance, and moderate strength. Suitable for components requiring high corrosion resistance but not high strength (e.g., base material for joint prostheses in medical implants, chemical pipelines).
Graded based on oxygen content (affecting strength and plasticity). The correspondence between International (ISO) and Chinese (GB/T) standards is as follows:
| International Standard (ISO 5832-2) | Chinese Standard (GB/T 2965) | Oxygen Content O (%) | Main Characteristics | Typical Applications |
| Grade 1 | TA1 | 0.18 | Good plasticity, low strength | Thin-walled parts requiring high corrosion resistance, medical sutures |
| Grade 2 | TA2 | 0.25 | Good balance of strength and plasticity | Common medical titanium grade (artifical bones, dental implants), chemical containers |
| Grade 3 | TA3 | 0.35 | High strength, slightly lower plasticity | Medium-strength corrosion-resistant structural parts (e.g., heat exchanger tubes) |
| Grade 4 | TA4 | 0.40 | High strength, low plasticity | High-strength corrosion-resistant parts (e.g., valve spools) |
- Titanium Alloys (Classified by Main Alloying Elements)
Strength, heat resistance, corrosion resistance, or biocompatibility are improved by adding elements such as Al, V, Mo, Zr, Nb. These are commonly used materials in high-end fields (aviation, medical). Classified into 4 major systems by alloy element type:
(1) α-Type Titanium Alloys (Low-temperature stable, excellent corrosion resistance)
Alloying elements: Mainly α-stabilizers (e.g., Al, Sn, Zr), with no or minimal β-stabilizers.
Characteristics: α single-phase structure at room temperature, good weldability, corrosion resistance close to pure titanium, strength higher than pure titanium, but lower high-temperature strength (≤500°C).
Typical grades:
Grade 5 (Ti-6Al-4V ELI): Common medical titanium alloy grade (ELI stands for “Extra Low Interstitial,” with lower C/O/N content, offering better biocompatibility), used for artificial joints, spinal internal fixators.
Grade 9 (Ti-3Al-2.5V): High strength, high plasticity, used for aviation tubing, medical interventional devices (e.g., stents).
Grade 23 (Ti-6Al-4V ELI): Further reduces interstitial elements compared to Grade 5, suitable for long-term human implants.
- β-Type Titanium Alloys (High-temperature stable, high strength)
Alloying elements: Mainly β-stabilizers (e.g., Mo, Nb, Ta, V) in high content (≥10%).
Characteristics: Can obtain β single-phase or α+β dual-phase structure at room temperature through quenching/aging treatment. Offers high strength (tensile strength ≥1100 MPa), good cold workability, and good biocompatibility (contains no toxic elements).
Typical grades (medically related):
Ti-13Nb-13Zr: Contains no V or Al, avoiding toxic metal ion release, used for dental implants, artificial joints.
Ti-29Nb-13Ta-4.6Zr (TNZT alloy): Elastic modulus close to human bone (approx. 60 GPa, lower than Ti-6Al-4V’s 110 GPa), reducing “stress shielding” effect, a development direction for medical titanium alloys.
Ti-15Mo: Strong corrosion resistance, used for chemical corrosion-resistant parts, medical orthopedic instruments.
(3) α+β-Type Titanium Alloys (Good overall performance)
Alloying elements: Contains both α-stabilizers (Al) and β-stabilizers (V, Mo). α+β dual-phase structure at room temperature.
Characteristics: Microstructure proportion can be adjusted through heat treatment (annealing, solution and aging), balancing strength (higher than α alloys), plasticity (better than β alloys), and high-temperature performance (≤600°C). Widely used in aerospace and medical fields.
Typical grades:
TC4 (Grade 5, Ti-6Al-4V): Non-ELI version, used for aerospace structures (fuselage, wings), low-medium temperature sections of engine fans/compressors, biological implants, naval components.
Grade 22 (Ti-6Al-4V ELI): Higher purity than Grade 5 ELI, used for high-demand medical implants.
Ti-6Al-2Sn-4Zr-2Mo: Higher high-temperature strength than Ti-6Al-4V, used for aero-engine blades (≤550°C).
(4) Near α-Type Titanium Alloys (Excellent high-temperature strength)
Alloying elements: Predominantly α-stabilizers with a small amount of β-stabilizers (≤2%).
Characteristics: Structure mainly α-phase with a small amount of β-phase. Offers high high-temperature strength (≤650°C) and good oxidation resistance, suitable for high-temperature environments.
Typical grades:
Ti-8Al-1Mo-1V: Used for aero-engine combustion chambers, high-temperature fasteners.
Ti-6Al-2Sn-4Zr-6Mo: High high-temperature strength, used for aerospace vehicle components.
2. Classification by Processing Condition
For the same titanium grade, mechanical properties (strength, plasticity) vary significantly due to different rolling, forging, and heat treatment processes. This must be clearly specified in production. Common processing conditions are as follows:
| Processing Condition Codes (GB/T 3620.1) | Processing Description | Main Characteristics | Typical Applications |
| R(Hot Rolled) | Hot rolling performed at high temperature without subsequent heat treatment. | Moderate strength, good plasticity. | Semi-finished products(e.g., hot-rolled plates, bars) requiring further processing. |
| M(Annealed) | Fully annealed (held at 650-800°C) after hot rolling. | Uniform microstructure, good plasticity, stable mechanical properties. | Common condition for medical titanium materials (e.g., dental implant bars, artificial joint forgings). |
| Y (Cold Worked) | Rolling/drawing at room temperature with ≥15% deformation. | High strength, low plasticity. | High-strength components (e.g., medical screws, springs). |
| CS (Solution Treated) + A (Aged) | High-temperature solution treatment (above β transus) + low-temperature aging. | High strength, high hardness. | Strengthening process for β-type titanium alloys (e.g., orthopedic bone plates). |
3. Classification by Application Field
Different fields have varying performance requirements for titanium materials. The following shows grade matching for core application fields:
| Application Field | Core Requirements | Recommended Grades | Specific Products |
| Medical Implants | Biocompatibility, Low Elastic Modulus, Corrosion Resistance | Grade 2 (Pure Ti), TC4 (Grade 5), TC4 ELI (Grade 5 ELI), Ti-13Nb-13Zr, TNZT | Artificial joints, Dental implants, Spinal rods and screws |
| Aerospace | High Strength, High-Temperature Performance, Lightweight | TC4 (Grade 5), Ti-6Al-2Sn-4Zr-6Mo, Ti-10V-2Fe-3Al | Aircraft fuselage frames, Engine blades |
| Chemical & Corrosion Resistance | Resistance to Acids/Alkalis, Seawater Resistance | Grade 1/2 (Pure Ti), Ti-15Mo, Ti-32Mo | Chemical reactors, Seawater desalination equipment, Oil pipelines |
| Medical Devices | High Strength, Easy Processing, Corrosion Resistance | Grade 9, TC4 (Grade 5), Grade 23, Ti-6Al-4V ELI | Surgical instruments (hemostatic forceps), Medical stents, Ultrasound probe housings |
| Sports Equipment | Lightweight, High Strength, Aesthetics | TC4 (Grade 5), Ti-6Al-4V | Golf club heads, Bicycle frames, Trekking poles |
4. Grade Comparison Table
Production often requires aligning international orders (e.g., ASTM, ISO standards) with domestic procurement (GB standards). The following shows the correspondence of core grades:
| Chinese Standard (GB/T 2965/3620) | American Standard (ASTM B265) | International Standard (ISO 5832-2) | Type |
| TA1 | Grade 1 | Grade 1 | Pure Titanium |
| TA2 | Grade 2 | Grade 2 | Pure Titanium |
| TA3 | Grade 3 | Grade 3 | Pure Titanium |
| TA4 | Grade 4 | Grade 4 | Pure Titanium |
| TC4 | Grade 5 | Grade 5 | α+β Alloy |
| TC4 ELI | Grade 5 ELI | Grade 23 | α+β Alloy (medical) |
| TC11 | Ti-6Al-2Sn-4Zr-6Mo | – | Near α Alloy |
| TB6 | Ti-15Mo | – | β Alloy |
5. Special Requirements for Medical Titanium Grades
For medical titanium material production, the following two points require additional attention:
Interstitial Element Control: Medical grades (e.g., Grade 5 ELI, TNZT) require stricter limits than industrial grades: C≤0.08%, O≤0.13%, N≤0.05%, H≤0.015%. Strict control is needed during the melting process (Vacuum Arc Remelting furnace).
Biocompatibility Certification: Must pass ISO 10993-1 (Biological evaluation of medical devices) testing to ensure no cytotoxicity or sensitization. Grade selection must comply with the YY/T 0640 (Wrought titanium and titanium alloy for surgical implants) standard.
Article Sources:
Chinese National Standards: GB/T 3620.1-2016 “Designation and chemical composition of titanium and titanium alloys”, GB/T 2965-2023 “Titanium and titanium alloy bars”, GB/T 13810-2017 “Wrought titanium and titanium alloy for surgical implants”.
International Standards: ISO 5832-2 “Implants for surgery – Titanium and titanium alloys – Part 2: Wrought titanium”, ASTM B265 “Standard Specification for Titanium and Titanium Alloy Strip, Sheet, and Plate”.
Industry Materials: “Analysis of GB/T 2965-2023 ‘Titanium and Titanium Alloy Bars’ Standard” (Baoji Kehui Titanium Industry Co., Ltd.), “Total Materia Material Database – Titanium Material Standards”, “Titanium Material Grades and Chemical Composition Query Methods and Standard System Analysis”.
Enterprise & Industry News: Sichuan News Broadcast “Pangang: Successfully Rolled Southwest China’s First Coil of TC4 Titanium Alloy”, Guangming Online “Filling Domestic Gaps, Major Technological Breakthrough Achieved in Chongqing New Material R&D”, China Nonferrous Metals Network “Nanjing Baotai Successfully Develops TC4 Titanium Alloy Casting Double-Layer Blade Impeller”, Securities Daily “Ti-Gold Technology Releases Q3 Report, Layout in High-End Titanium Alloys Opens Long-Term Growth Space”, The Paper “World’s First: Changzheng Hospital Replaces Patient’s Entire Cervical Vertebrae with 3D-Printed Titanium Alloy”, National Medical Products Administration “Biological Knee Prosthesis System Approved for Market”.