Aluminum has been the preferable metal in the aerospace industry since the first air crafts were made because of its ease of fabrication, corrosion resistance, strength, lightweight, and relatively low cost.
Aluminum heat treating increases the hardness and strength of specific precipitation hardenable cast and wrought alloys. Precipitation hardenable alloys include the 8XXX, 7XXX, 6XXX, and 2XXX series.
Each series has unique features that are improved through aluminum heat treating. The 2XXX series is widely used in the aerospace industry because it has copper, giving it extra strength.
The 6XXX series has magnesium and silicon, improving its corrosion resistance, and is primarily used in the automotive industry.
The 7XXX series has magnesium, zinc, and either copper or chromium. This makes it extra strong, making it the most preferred series in the aerospace industry. Finally, the 8XXX series has silicon, iron, copper, and vanadium, also making it highly used in the aerospace industry.
Values Of Heat Treating Aerospace Industry Aluminum
While aluminum heat treating is used in many industries for different purposes, it is mainly used in the aerospace industry. The following are some of the benefits of aerospace aluminum heat treating.
Strength-to-weight ratio
This is one of the main reasons behind aerospace aluminum heat treating. The aerospace industry requires metals that are strong enough to withstand natural elements but light enough to ensure aircraft can safely take off and land.
Depending on the aerospace aluminum heat treating method, aluminum can be forged to become stronger than some steel metals. An added advantage of using heat-treated aluminum is that even with the newly achieved strength, it remains among the lightest metals.
This means that the aerospace industry can use thicker aluminum than steel or any other metal without worrying about weight.
Improved mechanical properties
Heat treating aerospace industry aluminum results in metal with higher mechanical properties and lower metal stresses in castings, making it easier to machine and weld. Aerospace aluminum heat treating is consistent and generates almost uniform properties throughout the process.
The following are additional benefits that aerospace aluminum heat treating offers.
- Higher thermal conductivity
- Better corrosion resistance
- Good surface finish
Types Of Aluminum Heat Treating
There are different aerospace aluminum heat treating methods depending on the alloy and the intended use in the aerospace industry. The most important thing people observe during areospace heat treating is the temperature and duration to ensure the end product has the suitable properties and required strength.
Annealing
This aluminum heat treating method is applicable for non-heat-treatable and heat-treatable alloys. It reduces the metal’s strength by heating it close to the melting point, then letting it cool. This makes it more malleable, making it easier to form into different shapes.
Different annealing aluminum heat treating methods depend on the alloy type, temperature condition, and final microstructure. The most essential thing in this aluminum heat treating method is determining the proper aluminum heat because temperature highly affects how soft the end product will be.
Full annealing aluminum heat treating produces the most ductile and softest end products. Stress relief is another annealing method that eliminates the strain-hardening effects in cold-worked alloys. Other annealing aerospace aluminum heat treating methods include partial annealing and recrystallization aluminum heat treating.
Homogenizing
This aerospace aluminum heat treating method helps to redistribute precipitating elements throughout the aluminum evenly. It involves the most aluminum heat and is mainly used to improve workability for cast alloys.
Once the heated metal starts cooling, the outer edges touching the molds cool first, resulting in a layer of aluminum crystals or grains. As the cooling continues, it results in fairly pure aluminum close to the skin and the center.
Solution heat treatment
This aluminum heat treating method is similar to annealing. However, the cooling rate in solution heat treatment is less significant than in annealing. This areospace heat treating dissolves the elements responsible for age hardening that make it challenging to work with the metal over time.
These dissolved elements become spheroids, resulting in a homogenized structure. The heated metal must be quenched or cooled rapidly to prevent the alloys from separating or precipitating. Solution aluminum heat treating improves the metal’s flexibility and strength and relieves stress, making it easier to machine.
The temperature in this aluminum heat treating method depends on the aluminum alloy composition but is mostly between 825 and 980 degrees F.
Natural aging
After solution aerospace aluminum heat treating and quenching, most heat-treatable aluminum alloys experience age hardening at room temperature. This is when the dissolved elements begin to precipitate over time, making the grains lock in position and increasing the aluminum’s natural strength.
This is referred to as natural aging, which happens over four to five days, with about 90% of the hardening happening on the first day. This means that aluminum must be shaped fast in the aerospace industry.
The rate and extent of the hardening vary among different alloys. Natural aging does not include micro-structural changes.
Precipitation/ artificial aging
Some aluminum alloys require that the dissolved elements are fully precipitated out to attain maximum hardness. Some of the alloys cannot reach the maximum hardness through natural aging, which is where precipitation or artificial hardening comes in.
In this aerospace aluminum heat treating method, the alloys are heated to specific temperatures between 240 and 460 degrees F and within 35 degrees F of the required temperature.
The alloys are left to soak for between six and 24 hours, then cooled at room temperature. This results in a metal with more yield and tensile strength plus reduced ductility.
Tensilemill Tensile Testers
Tensile testers also called pull testers, are electromechanical test systems that apply tensile or pull force to materials to determine their tensile strength and deformation behaviors until they break.
One of the main benefits of aerospace aluminum heat treating is increasing the alloys’ tensile strength. This means that they become more resistant to breaking under tension.
The aerospace industry needs to understand precisely how much tensile strength they need for different purposes, and TensileMill CNC is here to help with state-of-the-art tensile testers.
TensileMill CNC has partnered with reputable and certified tensile testing equipment manufacturers around Europe and North America, ensuring all clients nothing but the highest quality. Click here to get to an easy submission form to get a quote from TensileMill CNC.
