Aluminum Alloy Properties
Versatility - Cost Effectiveness - Precision Dimension Control
Shelmet Precision Casting, Inc pours many different metals and alloys. However, it's impossible to process with every metal and alloy available. As an example, the 6061 is a bar stock designation which is not a casting alloy. 360 and 383 are only poured in the die casting industry. Other metals like 343 have different chemical makeups that make it suitable for work in other methods besides investment castings. The information of additional metals and alloys is provided for educational and comparative requirements of the many customers Shelmet Precision Casting, Inc services.
Do you have questions regarding the process that best fits your needs? Contact your Shelmet Precision Casting Process Expert for a no cost evaluation. The Investment casting method is often the best choice, but when it isn't your process expert can help identify options that can save you much research time.
Aluminum alloy properties, the mechanical and physical characteristics of the alloy, experience change when exposed to elevated (max. 400°C) and extremely low (cryogenic, -195°C) temperatures. These temperature-related changes are not as obvious as they are with steel and other metals.
Additionally, the types of changes evidenced by aluminum alloys due to extreme temperatures are greatly influenced by the actual temper and chemical composition of the metal.
The best room-temperature tensile properties are found in aluminum alloy investment casting ingots of the 7xxx-series alloys.
Unfortunately, exposure to high temperatures causes that strength to rapidly weaken due to the fin precipitates coarsening. And while series 2xxx aluminum alloys do well at elevated temperatures, theyre not usually employed in such applications.
There have been some promising developments at improving the high-temperature (100-200°C) strength of aluminum alloys. One development has employed rapid solidification technology producing foils with high iron or chromium supersaturations. These slowly diffuse in the solid aluminum. Exciting creep properties at temperatures to 350°C are being demonstrated by some cutting-edge alloys. One such alloy is an Al-Cu-Mg alloy to which silver has been added, another is an aluminum alloy which includes iron.
Extremely low temperatures (sub-zero) have very little impact on most aluminum alloys. In fact, tensile strength and yield may actually increase. Impact strength appears to remain unchanged, although there may be a slight decrease in elongation. It is this ability to endure extremely low temperatures without experiencing structural changes that makes aluminum alloys the preferred material for many applications.
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2124 and 2024 are similar in characteristics, but 2124 has a better fracture toughness due to more pure base and its special processing. Subzero temperatures have a similar impact on the tensile properties of both 2124-T851 and 2024-T851.
2214, 2419, 7050 and 7475, as well as other aluminum alloys have a superior fracture toughness at room-temperature when compared to other 2xxx and 7xxx aluminum alloys.
Another of the aluminum alloy properties to be considered is fatigue strength. Tests of different aluminum alloys at 106 cycles indicate that fatigue strength is actually better the lower the temperature.
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Low Temperatures and Specific Alloys
Here are just some of the aluminum alloy properties and their temperature-related characteristics:
5083 & 5456: exhibit a 30-40% increase in tensile strength, 5-10% in yield strength and 60-100% elongation at temperatures from room temp to -195°C. The ASME has approved these alloys for pressure vessels.
1100, 2014, 2024, 2219, 3003, 6061, 7005, 7039 and 7075: wrought alloys, in addition to 5083 and 5456, employed in low-temperature applications; with 5083-O being most commonly used for cryogenic uses.
Alloy 5083-O has a fracture toughness that is significantly greater than the other alloys. With this alloy, a decrease in exposure temperature actually increases the fracture toughness.
2219-T87: of all weldable alloys displays the best yield strength and fracture toughness from room temperatures down to -196°C
6061-T651: as good a fracture toughness as 2219-T87 in the same temperature ranges, but with a lower yield strength.
7039: another weldable aluminum alloy with good yield strength and fracture toughness from room temperatures down to -196°C
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