One of the most significant breakthroughs in cast aluminum of the past 30 years has been the development of a high property and castable alloy, 205-T7. This new alloy offers a significant material option for engineers to design lightweight structural shapes that will enhance the affordability and reliability of their products.
The family of 200-Series Aluminum Copper alloys is well known for being heat-treatable to very high properties. But because of the propensity of these alloys to “hot tear” during solidification the Investment Casting Industry generally considers the 200-Series to be “un-castable”.
Prevalent instead in the Investment Casting Industry are the highly castable 300-Series of Aluminum-Silicon alloys. These are outstanding alloys in most applications but their physical properties are unable to compete with the higher properties of some wrought alloys. Although the foundry industry has, over the years, develop a number of special solidification technologies to boost the physical properties of alloys such as D357 and E357 those properties remain far less than what can be attained from a 200-Series alloy.
The breakthrough came at Aeromet International PLC with their development of 205-T7 cast aluminum alloy. This alloy couples the high properties that characterize of a 200-Series aluminum with a castability that is similar to a 300-Series.
O’Fallon Casting is licensed by Aeromet International PLC to manufacture castings from their patented A20X / 205 aluminum alloy.
Design Standards are available for 205-T7. The FAA added 205-T7 to the MMPDS in 2013. SAE International has issued specification AMS 4471A for the Investment Casting of 205-T7 alloy. The minimum physical properties of AMS 4471A (205-T7) exceed those of other cast alloys such as A201-T7 (AMS 4229), A357 (AMS 4219), D357-T6 (AMS 4241) and E357-T6 (AMS 4288). With a Yield Strength that is 50% greater than that of D357-T6, 205-T7 will rival those alloys for use in what are considered to be “Structural Castings”.
Although 205-T7 is unlikely to replace standard alloys such as A356-T6 in everyday applications, its attractive strength to weight ratio provides Engineers & Designers with a major new material for the manufacture lightweight castings. Moreover as the physical properties of 205-T7 are very comparable to those of many wrought alloys, so structures that are difficult or impossible to machine from solid can now be investment cast.
In addition to its high properties at Ambient Temperature, 205-T7 also retains its strength at elevated temperatures better than C355 aluminum, has better Fatigue Strength than A201 or A357, and offers excellent Corrosion Resistance.