Heat Treatment of Titanium Alloys vs Aluminum Alloys: Process, Differences, and Applications
Heat treatment is a critical process for enhancing the mechanical properties, microstructure, and service life of metals. In industries such as aerospace, automotive, and medical, titanium alloys and aluminum alloys are among the most commonly used materials. Each requires specific heat treatment methods to meet high-performance demands.
Why Do Titanium and Aluminum Alloys Need Heat Treatment?
Heat treatment significantly improves the properties of titanium and aluminum alloys in the following ways:
Increases tensile strength, ductility, and fatigue life
Tailors mechanical properties for specific applications
Enhances corrosion resistance and machinability
Eliminates residual stress from forming or welding
However, due to differences in crystal structure and thermal stability, the heat treatment processes for titanium alloys differ significantly from those of aluminum alloys.
Heat Treatment of Titanium Alloys
Titanium alloys are generally classified into three types: α (alpha), β (beta), and α+β alloys. The choice of heat treatment depends on the alloy’s phase structure and performance requirements.
Common Heat Treatment Methods for Titanium Alloys:
Annealing
Performed at 600–800°C to relieve internal stress, improve ductility, and stabilize the microstructure. Common for α and α+β alloys.Solution Treatment + Aging
Used mainly for α+β and β alloys. The alloy is heated to 900–980°C (e.g., ~950°C for Grade 5) to dissolve alloying elements, then rapidly quenched to form a supersaturated solution. Followed by aging at 500–600°C to precipitate strengthening phases.Beta Annealing
Suitable for β alloys; conducted above the β transus temperature (usually >1000°C) to refine grains and enhance high-temperature performance.Stress Relieving
Typically at 500–650°C, this treatment is applied after forming or machining to minimize the risk of deformation in complex parts.
Application Examples:
Ti-6Al-4V (Grade 5): Common in aircraft engine blades and medical implants; processed by solution treatment + aging.
Ti-3Al-2.5V (Grade 9): Used in heat exchangers and aerospace hydraulic tubes; typically annealed.
Ti-6Al-4V ELI (Grade 23): A high-toughness version for medical applications, with similar heat treatment as Grade 5.
Key Process in Titanium Alloy Heat Treatment
Let's take Grade 5 titanium alloy as example:
Solution Treatment: Heat to ~950°C to dissolve alloy elements, then rapidly quench.
Aging: Hold at 500–600°C for several hours to precipitate strengthening phases.
Annealing (for α alloys): Heat to 700–800°C to relieve stress without altering structure.
These steps significantly improve tensile strength, creep resistance, and fatigue life, making them ideal for aerospace and high-performance applications.
Heat Treatment of Aluminum Alloys
Aluminum alloys are divided into heat-treatable alloys (e.g., 6061, 7075) and non-heat-treatable alloys (e.g., 5052, 3003). The former are strengthened via solution treatment and aging, while the latter rely on cold working for strength enhancement.
Typical Heat Treatment Tempers:
| Temper | Heat Treatment | Process Summary | Common Use Case |
|---|---|---|---|
| O (Annealed) | ✅ Yes | Fully annealed for maximum ductility | Deep drawing, aerospace forming parts |
| T1 | ✅ Yes | Cooled from hot working and naturally aged | Moderate-strength extrusions |
| T3 | ✅ Yes | Solution treated → cold worked → naturally aged | 2024 aluminum sheet for aerospace |
| T351 | ✅ Yes | T3 + stress relieved by stretching | Thick 2024/7075 plates |
| T4 | ✅ Yes | Solution treated → naturally aged | 6061, 2024 before welding/forming |
| T6 | ✅ Yes | Solution treated → artificially aged | 6061-T6 for structural components |
| T651 | ✅ Yes | T6 + stress relieved by stretching | 6061-T651, 7075-T651 for machining |
| T6511 | ✅ Yes | T6 + stress relieved + straightened | 6061 extruded bars and profiles |
| T7351 | ✅ Yes | Solution treated → overaged → stress relieved | 7075/7050 aerospace plates |
| T73511 | ✅ Yes | T7351 for extrusions | 7075/7050 extruded profiles |
| T8 | ✅ Yes | Solution treated → cold worked → artificially aged | High-strength, fatigue-resistant parts |
| T851 | ✅ Yes | T8 + stress relieved by stretching | Precision machining parts |
Application Examples:
6061-T6: Common in aircraft structures, marine parts, and automotive components.
7075-T651: Very high strength; used in aerospace load-bearing parts and molds.
2024-T3: Excellent fatigue resistance; ideal for wing skins and other structural panels.
Key Process in Aluminum Alloy Heat Treatment
Solution Heat Treatment
Heat to 500–530°C to dissolve alloying elements like Mg, Si, and Zn.Quenching
Rapid cooling to room temperature to form a supersaturated solid solution.Aging
Natural Aging (e.g., T3, T4): Performed at room temperature over several days.
Artificial Aging (e.g., T6, T8): Heated to 160–200°C for several hours to precipitate strengthening phases.
Stress Relieving
Common in tempers like T651 and T7351 to reduce machining deformation.
Heat treatment temperature, holding time, and cooling method directly influence strength, dimensional stability, and corrosion resistance.
Key Differences of Titanium and Aluminum Heat Treatment:
| Comparison Aspect | Titanium Alloy | Aluminum Alloy |
|---|---|---|
| Heat Treatment Types | Annealing, Solution + Aging, Beta Annealing | Solution treatment, Aging, Stress relief |
| Temperature Range | 600–1000°C | 160–530°C |
| Performance Focus | Fatigue life, creep resistance, high strength | Balanced strength and workability |
| Cooling Methods | Air cooling or water quenching | Water or polymer quenching |
| Key Applications | Aerospace, medical implants | Aerospace, automotive, structural components |
Conclusion
Heat treatment is a fundamental process in defining the performance of titanium and aluminum alloys. From the solution + aging treatment of Grade 5 titanium to the carefully managed steps of aluminum heat treatment, each stage must be precisely controlled to ensure stable and reliable final parts.
Whether you're selecting materials for aircraft components or industrial structures, understanding heat treatment principles helps you make informed decisions on material type and temper.
Shenzhen Chinalco Metal supplies heat-treatable titanium and aluminum alloys, including 6061-T6 aluminum plates, 7075-T651 plates, Ti-6Al-4V (Grade 5), and Grade 23 titanium alloys, widely used in aerospace, automotive, and high-performance manufacturing.
👉 Contact us today for expert material selection advice and reliable supply support!