Understanding the Role of Aluminum in High Temperature Super Alloys

In summary, adding aluminum to nickel helps create a higher melting point, which can be beneficial for creating superalloys.
  • #1
Pkruse
466
2
Is anyone interested in starting a discussion on this topic? I use them in designs, but don't understand the metallurgy very well.

In particular, how does adding Al to Ni increase the melting point of Ni? It also improves a number of other desirable characteristics. The peak of the melting temperature curve on the phase diagram is at a 50-50 mixture. (Counting moles, not weight.) The resulting mixture is half aluminum, which we who work with refractory metals call "butter" due to its incredibly low melting point; yet the melting point of this mixture is much higher than pure Ni.
 
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  • #2
Pkruse said:
Is anyone interested in starting a discussion on this topic? I use them in designs, but don't understand the metallurgy very well.

In particular, how does adding Al to Ni increase the melting point of Ni? It also improves a number of other desirable characteristics. The peak of the melting temperature curve on the phase diagram is at a 50-50 mixture. (Counting moles, not weight.) The resulting mixture is half aluminum, which we who work with refractory metals call "butter" due to its incredibly low melting point; yet the melting point of this mixture is much higher than pure Ni.
Superalloys is an extraordinarily interesting topic, and in fact TMS (The Metallurgical Society) has hosted a conference Superalloys on a three year period. One of the key editors of the series, Ed Loria, passed away recently (https://www.physicsforums.com/showthread.php?t=402572).

TMS Superalloys Archive - http://knowledge.tms.org/superalloys.aspx

See also - http://www.tms.org/meetings/specialty/superalloys2000/superalloyshistory.html

The high melting point can be attributed to NiAl, an intermetallic compound.

See the Ni-Al phase diagram here - http://www.ias.ac.in/sadhana/Pdf2003Apr/Pe1064.pdf

The challenge is that there are several different phases that can form during the freezing of a melt, so one possibility is to produce a rapid solidified powder, which then must be hot pressed.
 
  • #3
Thanks, Joe. Now I have to go do some studying before I can ask further questions.
 

1. What are high temperature super alloys?

High temperature super alloys are a class of metal alloys that exhibit exceptional strength and resistance to creep (deformation under high temperatures). They are typically used in applications where materials are exposed to high temperatures, such as jet engines and gas turbines.

2. What properties make high temperature super alloys suitable for high temperature applications?

High temperature super alloys are known for their high strength, good resistance to corrosion and oxidation, and their ability to maintain their mechanical properties at elevated temperatures. They also have a low coefficient of thermal expansion, making them less prone to thermal stress.

3. What elements are typically included in high temperature super alloys?

High temperature super alloys are usually composed of a combination of nickel, cobalt, iron, and chromium, along with other elements such as molybdenum, tungsten, and titanium. These elements contribute to the alloy's high temperature strength and resistance to corrosion and oxidation.

4. What are some common applications for high temperature super alloys?

High temperature super alloys are commonly used in aerospace and industrial gas turbine engines, as well as in chemical processing equipment, nuclear reactors, and heat exchangers. They are also used in automotive and electronic industries.

5. How are high temperature super alloys manufactured?

High temperature super alloys are typically produced using a variety of techniques such as vacuum arc melting, electron beam melting, and powder metallurgy. These processes allow for precise control over the composition and microstructure of the alloy, resulting in the desired properties for high temperature applications.

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