Aluminum 7129 Alloy (UNS A97129) – Composition, Properties and Uses
Aluminum 7129 is a heat-treatable alloy that offers an exceptional combination of strength and toughness. UNS A97129 is often used in the aerospace, automotive, and defence industries, as it provides superior corrosion resistance and heat resistance without requiring complex machining or welding processes. Let’s take a look at the properties of 7129 Alloy and how they make this alloy so versatile.
7129 Alloy Composition
| Element | Content (%) |
|---|---|
| Aluminum, Al | 90.9 – 94 |
| Zinc, Zn | 4.2 – 5.2 |
| Magnesium, Mg | 1.3 – 2 |
| Copper, Cu | 0.50 – 0.90 |
| Iron, Fe | ≤ 0.30 |
| Titanium, Ti | ≤ 0.050 |
| Vanadium, V | ≤ 0.050 |
| Gallium, Ga | ≤ 0.030 |
| Silicon, Si | ≤ 0.15 |
| Chromium, Cr | ≤ 0.10 |
| Manganese, Mn | ≤ 0.10 |
| Remainder (each) | ≤ 0.050 |
| Remainder (total) | ≤ 0.15 |
7129 Alloy Physical Properties
| Properties | Metric | Imperial |
|---|---|---|
| Density | 2.78 g/cm³ | 0.100 lb/in³ |
7129 Alloy Mechanical Properties
| Properties | Metric |
|---|---|
| Density | 2.78 g/cm³ |
| Youngs modulus | 69 GPa |
| Elongation at Break | 9.0 % to 9.1 % |
| Fatigue Strength | 150 to 190 MPa |
| Shear Modulus | 26 GPa |
| Shear Strength | 250 to 260 MPa |
| Tensile Strength: Ultimate (UTS) | 430 MPa |
| Specific Heat Capacity | 880 J/kg-K |
| Thermal Conductivity | 150 W/m-K |
7129 Alloy Uses
Due to its high strength-to-weight ratio, aluminium 7129 is ideal for applications where weight savings are crucial. It has been used in the aerospace industry for aircraft components since the 1970s due to its ability to provide superior corrosion resistance in harsh environments. It is also commonly used in automotive applications such as pistons and cylinder heads and in defence applications such as armour plating.
Corrosion Resistance
Aluminium 7129 has excellent corrosion resistance when exposed to saltwater or other corrosive environments. Its high chromium content makes it especially resistant to pitting and crevice corrosion. Additionally, its low carbon content makes it very resistant to stress corrosion cracking. This makes it an ideal choice for parts that will be exposed to harsh environments or extreme temperatures.
Heat Resistance
Aluminium 7129 has excellent thermal conductivity, making it suitable for use in high-temperature applications up to 315°C (600°F). Its exceptionally high melting point also makes it suitable for use in cryogenic applications down to -195°C (-320°F).
Heat Treatment
Aluminium 7129 can be heat treated using either precipitation hardening or solution annealing processes depending on the desired outcome of the treatment. Precipitation hardening involves heating the material at temperatures between 550 – 630°C (1022 – 1166°F) followed by rapid quenching before being aged at 160 – 190°C (320 – 374°F). Solution annealing involves heating the material at temperatures between 500 – 540°C (932 – 1004°F) followed by slow cooling before being aged at room temperature. Both processes result in increased strength and improved fatigue properties with minimal loss of ductility or toughness compared to untreated material.
Machining
Aluminium 7129 can be machined using conventional machining techniques such as turning, milling, drilling, tapping, reaming etc., although cutting speed should be kept relatively low due to its harder nature compared with other aluminum alloys. It can also be machined using EDM techniques if necessary for more intricate shapes or geometries that cannot be achieved through conventional methods.
Welding
aluminum 7129 can be welded using GTAW (TIG) welding process, provided that appropriate filler materials are used along with preheating and post-weld heat treatment steps during the fabrication process for better weldability and improved mechanical properties after welding operations have been completed successfully.
Conclusion:
In summary, aluminium 7129 is a versatile alloy with excellent mechanical properties that make it suitable for use in a wide variety of applications, including aerospace components, automotive parts, armour plating and many more demanding uses which require superior corrosion resistance and/or heat resistance without sacrificing ductility or toughness too much after undergoing various thermal treatments like solution annealing or precipitation hardening during manufacturing process utilizing conventional machining methods like turning or milling along with GTAW (TIG) welding operations while following preheating/post-weld heat treatment steps accordingly. Moreover, its higher cost compared to other aluminium alloys is offset by its superior performance characteristics, making it an attractive option when selecting the right alloy material for your specific application needs, especially ones involving harsh environments where weight savings are important considerations too!
A passionate metal industry expert and blogger. With over 5 years of experience in the field, Palak brings a wealth of knowledge and insight to her writing. Whether discussing the latest trends in the metal industry or sharing tips, she is dedicated to helping others succeed in the metal industry.
