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Properties, Weldability, and Applications of Aluminum 6063
Aluminum alloy 6063 is frequently called an “architectural alloy” because of its moderate strength and intricate extrusion capabilities. When exposed to high temperatures, aluminum alloys tend to lose their strength. However, they can be made stronger at sub-zero temperatures, making them suitable for low-temperature applications. Moreover, aluminum alloys possess high corrosion resistance. In particular, the 6063 alloy is widely used for extrusion purposes.
Typical Applications of 6063 T6 aluminum
Commercial applications of T6 6063 aluminum for this engineering material include:
- Window frames
- Extrusions
- Roofs
- Architectural
- Balustrading
- Doors
- Irrigation tubing
We carry aluminium alloy 6063 T6 in various shapes and sizes, including flats, round and hexagon bars, round plates, rectangular, hollow bars, square tubes, and channels.
Alloy Designations
Aluminum alloy 6063/6063A may not be a direct equivalent to the following standard designations and specifications:
Al Mg0.7Si
AA6063
GS10
A-GS
AlMgSi0.5
3.32206
ASTM B210
ASTM B221
ASTM B241 (Pipe- Seamless)
ASTM B345 (Pipe- Seamless)
ASTM B361
ASTM B429
ASTM B483
ASTM B491
MIL G-18014
MIL G-18015
MIL P-25995
MIL W-85
HE19
SAE J454
QQ A-200/9
UNS A96063
Weldability
Alloy 6063 is suitable for all common welding techniques. It is recommended to use either alloy 5183 or alloy 4043 for welding. If you require maximum electrical conductivity, it’s better to use alloy 4043. On the other hand, if you need strength and conductivity, you are advised to use alloy 5346. However, in this case, you need to increase the size of the weld to compensate for lower conductivity.
| Process | Performance |
| Working Ability – Cold | Good |
| Machining Ability | Good |
| Welding Ability – Gas | Good |
| Welding Ability – Arc | Excellent |
| Welding Ability – Resistance | Good |
| Brazing Ability | Excellent |
| Soldering Ability | Good |
The Chemical Composition Of 6063 Aluminum
| Element | % Composition |
| Si | 0.2-0.6 |
| Fe | 0.35 |
| Cu | 0.1 |
| Mn | 0.1 |
| Mg | 0.45-0.9 |
| Zn | 0.1 |
| Ti | 0.1 |
| Cr | 0.1 |
| Al | Balance |
Tempers for Aluminium 6063
The most common tempers for aluminum 6063 are:
- Annealed wrought alloy
- 6063 T4 – Solution heat-treated and naturally aged
- 6063 T6 – Solution heat-treated and artificially aged
Properties
| Physical Property | Value |
| Melting Point | 655 °C |
| Density | 2.70 g/cm³ |
| Thermal Expansion | 23.5 x10^-6 /K |
| Modulus of Elasticity | 69.5 GPa |
| Thermal Conductivity | 201 W/m.K |
| Electrical Resistivity | 52 % IACS |
| Electrical Resistivity | 0.033 x10^-6 Ω .m |
Element Optimization of Aluminum 6063
6063 T5 aluminum profiles used in construction must possess specific mechanical properties. When all other conditions are the same, the profiles’ yield and tensile strength increase with a higher magnesium and silicon content. In 6063 alloys, the strengthening phase is primarily the Mg2Si phase.
The optimal amount of magnesium, silicon, and Mg2Si is essential. The Mg2Si phase comprises two magnesium atoms and one silicon atom, with a relative atomic mass of 24.3l for magnesium and 28.09 for silicon. Therefore, the magnesium-to-silicon mass ratio in Mg2Si compounds is 1.73:1.
If the magnesium-to-silicon content ratio is bigger than 1.73, the alloy has excess magnesium besides forming the Mg2Si phase. Conversely, if the ratio is less than 1.73, it indicates residual silicon and the formation of the Mg2Si phase.
Excessive magnesium is harmful to the mechanical properties of alloys. Typically, magnesium is controlled at around 0.5%, and the total amount of Mg2Si is controlled at 0.79%. When there is an excess of 0.01% silicon in the alloy, the mechanical property of the alloy, measured by σ B, is about 218Mpa, which exceeds the national standard performance. When the excess silicon increases from 0.01% to 0.13%, σ B can be increased to 250Mpa, which is an increase of 14.6%.
To form a certain amount of Mg2Si, it is essential first to consider the silicon loss caused by impurities such as Mn and Fe, ensuring a certain amount of excess silicon. To fully match magnesium with silicon in 6063 alloys, it is necessary to consciously ensure that Mg: Si<1.73 during actual batching. Extra magnesium can weaken the strengthening effect and increase product costs.
Therefore, the composition of 6063 alloy is typically controlled to have 0.45%-0.65% magnesium and 0.35%-0.50% silicon, with a Mg: Si ratio of 1.25-1.30. Iron impurities should be kept below 0.10%-0.25%, and manganese levels should be less than 0.10%.
Pseudo-binary Al-Mg2Si phase diagram for a Mg:Si weight ratio of 1.73:1. The displacement of the average composition of the solid under nonequilibrium conditions corresponding to industrial solidification practices is shown.
Annealing Process Of Aluminum 6063
When producing civilian extruded profiles, the high-temperature homogenization annealing of 6063 alloy is 560 ± 20 ℃, with insulation for 4-6 hours. The cooling method is either forced air cooling out of the furnace or rapid water spraying.
The homogenization treatment of alloys can increase the extrusion speed and reduce the extrusion force by approximately 6% -10 % compared to ingots without homogenization treatment. The cooling rate after homogenization treatment has a significant impact on the precipitation behavior of the organization. For ingots that are rapidly cooled after being uniformly heated, Mg2Si can almost completely dissolve in the matrix, and excess Si will also dissolve or exist as dispersed precipitated small particles. This type of ingot can be quickly extruded at lower temperatures and achieve excellent mechanical properties and surface brightness.
By replacing resistance-heating furnaces with fuel or gas-heating furnaces, significant energy-saving and consumption-reduction effects can be achieved in the extrusion production of aluminum profiles. Proper selection of furnace type, burner, and air circulation mode can achieve a uniform and stable heating performance of the furnace, stabilizing the process and improving parts quality.
After many years of operation and continuous improvement, combustion-type ingot heating furnaces with combustion efficiency higher than 40% have been introduced in the market. After being loaded into the stove, the ingot rapidly heats up to above 570 ℃, and after a period of insulation, it is cooled in the discharge area to near the extrusion temperature before being extruded. The ingot undergoes a semi-homogenization process in heating furnace, called semi-homogenization treatment, and meets the needs of the 6063 alloy hot extrusion process. This process can save a separate homogenization process, significantly reduce equipment investment and energy consumption, and is worth promoting.
Heat Treatment and 6063 Extrusion
1, Ingot Heating
When it comes to extrusion production, the temperature is the most important factor that can affect the quality of the product, production efficiency, energy consumption, mold life, and more. The control of metal temperature is the most critical issue in the extrusion process. It is essential to ensure the soluble phase structure doesn’t precipitate from the solid solution or exhibit dispersed precipitation of small particles from heating the ingot to quenching the extruded profile.
The heating temperature for al 6063 ingots is generally set within the temperature scope of Mg2Si precipitation, and the heating time significantly impacts the precipitation of Mg2Si. Rapid heating can reduce the possible precipitation time. The heating temperature for uneven ingots is between 460-520 ℃, and for uniformly cast ingots, it is between 430-480 ℃.
The temperature in the deformation zone increases gradually as the extrusion process is completed.To prevent extrusion cracks, the extrusion speed should gradually decrease as the process progresses and the temperature of the deformation zone increases. The extrusion temperature is adjusted based on the product and unit pressure.
2, Extrusion Speed
It’s essential to control the extrusion speed carefully during the extrusion process. The speed significantly affects various aspects of the product, such as the thermal effect of deformation, deformation uniformity, recrystallization and solid solution processes, mechanical properties, and surface quality.
If the extrusion speed is too fast, the product’s surface may show signs of pitting, cracks, and other problems. Moreover, excessive extrusion speed can result in uneven metal deformation. The extrusion flow rate depends on alloy type, profile geometry, size, and surface conditions.
For 6063 alloy profiles, the extrusion speed (metal flow rate) can be set between 20-100 meters per minute. With modern technology, programs or simulated programs can control the extrusion speed, and new technologies such as isothermal extrusion and CADEX have been developed. We can achieve rapid extrusion without cracking by automatically adjusting the speed to maintain a constant temperature range in the deformation zone.
Many measures can be taken during the process to improve production efficiency. For example, when using induction heating, we can balance the deformation heat by facing the high-temperature end towards the extrusion die and the low-temperature end towards the extrusion pad. Some use water-cooled molds, which require forced cooling with water at the back of the mold. Experiments have shown that this can increase the extrusion speed by 30%-50%.
In recent years, nitrogen or liquid nitrogen cooling molds have been used to increase extrusion speed, improve mold life, and enhance the surface quality of profiles. During the extrusion process, nitrogen is introduced to the outlet of the extrusion die to cool the product, extrusion die, and the metal in the deformation zone and remove the deformation heat. At the same time, the nitrogen atmosphere at the mold outlet is controlled, reducing the oxidation of aluminum and the adhesion and accumulation of aluminum oxide. Therefore, the cooling of nitrogen improves the surface quality of the product and can greatly enhance the extrusion speed.
CADEX is a new process that maximizes extrusion speed and efficiency while ensuring the best performance. This process involves a closed-loop system that adjusts the extrusion temperature, speed, and pressure accordingly.
3, Quenching
6063-T5 quenching is a process that helps to retain Mg2Si, which is solidly dissolved in the base metal at high temperatures. The process involves rapidly cooling the metal to room temperature after it exits the mold hole. The cooling rate is crucial as it is directly proportional to the content of the strengthening phase. For 6063 alloys, the minimum cooling rate required for strengthening is 38 ℃/min. It makes it suitable for air-cooling quenching. By changing the fan and fan speed, the cooling intensity can be adjusted, and the temperature of the product can be reduced to below 60 ℃ before tension straightening.
4, Tension Straightening
Once the profile is shaped, it is typically pulled by a traction machine. The traction machine applies a specific tension to the extruded product and moves in sync with the product’s flow rate. The traction machine is used to decrease uneven length and scratches that can occur during multi-line extrusion. It also helps to prevent twisting and bending of the profile after it leaves the mold hole, which can cause issues during tension straightening. Tension straightening eliminates any longitudinal shape irregularities in the products, reduces residual stress, improves strength characteristics, and maintains a suitable surface.
5, Artificial Time Efficiency
The aging process involves maintaining a consistent temperature, with a temperature difference of no more than ±3-5 ℃. For 6063 alloys, the recommended artificial aging temperature is 200 ℃, with an aging and insulation time of 1-2 hours. To enhance mechanical properties, some may age at 180-190 ℃ for 3-4 hours, which can reduce production efficiency.
FAQs
Which one is stronger: 6063 or 6061?
Both alloys are highly formable, workable, and heat-treatable. Alloy 6061 has a slight strength advantage over 6063.
Which one is cheaper, 6061 or 6063?
When considering the cost of a 6063 extruded aluminum part, using the 6063 alloy in a solid shape is the most cost-effective method.
Is 6063 aluminum resistant to corrosion?
Alloy 6063 provides excellent corrosion resistance, which can be further enhanced with an appropriate surface finish. It is also easily weldable, brazeable, and workable while possessing moderate tensile strength and machinability.
What is the difference between 6061 T6 and 6063 T5?
Aluminum 6063-T5 is widely used in architectural applications due to its exceptional aesthetic properties. It can be easily colored and anodized to meet the user’s requirements. On the other hand, Aluminum 6061-T6 is not commonly used for aesthetic purposes but for its strength and durability.
Can 6063 aluminum be forged?
6063 is an aluminum alloy with magnesium and silicon as alloying elements. It possesses good mechanical properties and can be done by forging and heat-treated processes.
Like 6061 aluminum, 6063 is one of the most commonly used alloys for aluminum forging. It allows for the creation of complex shapes with smooth surfaces that are perfect for anodizing, making it popular for visible architectural applications. However, applications that require higher strength typically opt for 6061 or 6082 instead.
Summary
The article presents the properties, weldability, heat treatment, extrusion, and applications of aluminum 6063. If you have any questions, please don’t hesitate to contact us.
