Metalllurgy question
Metalllurgy question
Since I work with aluminum most of the time, I ponder the use of different aluminum alloys. If I want strength, I go with a 7xxx series like 7075; for less strength, but good formability, I go with a 2xxx series, like 2024 and for average quality (strength/machinability), I go with 6061. That's about all the alloys I use, but I was wondering about 2024 alloy as I understand it work hardens. Will work hardening occur on a piece that is being machined? 2024 also known as duralumin was used for the skin of aircraft like the DC-3 and performed well over the years. Some DC-3's are still flying somewhere in the world. Would work hardening cause the material to eventually fail due to brittleness?
Mr.Ron from South Mississippi
Re: Metalllurgy question
I'm not sure that it work hardens like some steel or bronze alloys do when machined, but it does have a fatigue life.
Glenn
Operating machines is perfectly safe......until you forget how dangerous it really is!
Operating machines is perfectly safe......until you forget how dangerous it really is!
Re: Metalllurgy question
I guess I worded this wrong. I wanted to know if the type of machining would induce work hardening. For example; would milling a slot cause it to work harden?
Mr.Ron from South Mississippi
- tornitore45
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Re: Metalllurgy question
Never noticed a problem machining 2024, I use it for con-rods and heads and machines much nicer than 6061.
Mauro Gaetano
in Austin TX
in Austin TX
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Re: Metalllurgy question
2024 (and other aluminum alloys) are precipitation hardening. That means given temperature an time, alloying elements will migrate within the metal and form tiny clumps, which strengthen the alloy. Some alloys do this at room temperature. The upshot is, that unlike some CRES alloys, aluminum alloys don’t apreciably work harden. You should be able to machine without fear. ( of course, don’t overheat it)
Kelly Jones, PE
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Re: Metalllurgy question
Kelly Jones writes:
2024 (and other aluminum alloys) are precipitation hardening. That means given temperature an time,
alloying elements will migrate within the metal and form tiny clumps, which strengthen the alloy.
Some alloys do this at room temperature.
I recall reading of a vendor who shipped aluminum alloy rivets packed in dry ice. They were dead soft until they had been at room temperature for a few hours.
2024 (and other aluminum alloys) are precipitation hardening. That means given temperature an time,
alloying elements will migrate within the metal and form tiny clumps, which strengthen the alloy.
Some alloys do this at room temperature.
I recall reading of a vendor who shipped aluminum alloy rivets packed in dry ice. They were dead soft until they had been at room temperature for a few hours.
Re: Metalllurgy question
Those were DD rivets. (2024)
Glenn
Operating machines is perfectly safe......until you forget how dangerous it really is!
Operating machines is perfectly safe......until you forget how dangerous it really is!
- tornitore45
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Re: Metalllurgy question
But. but, but were they kept in dry ice since the bar was extruded and through the forming process?I recall reading of a vendor who shipped aluminum alloy rivets packed in dry ice. They were dead soft until they had been at room temperature for a few hours.
Mauro Gaetano
in Austin TX
in Austin TX
Re: Metalllurgy question
No, they were kept on dry ice after they were quenched.
I've seen small table top furnaces about the size of a beer mug that are used to re-heat treat the rivets just prior to use.
The manufacturer will also do that for you and then ship them via air freight packed in dry ice.
I've seen small table top furnaces about the size of a beer mug that are used to re-heat treat the rivets just prior to use.
The manufacturer will also do that for you and then ship them via air freight packed in dry ice.
Glenn
Operating machines is perfectly safe......until you forget how dangerous it really is!
Operating machines is perfectly safe......until you forget how dangerous it really is!
Re: Metalllurgy question
Yep, what Glenn said. In order for aluminum to age harden, it must first be solution annealed, which is a process by which the items in question are heated to the proper temperature (very near the melting point for aluminum), then quickly quenched. Quenching "locks", for lack of a better description, in an evenly distributed state, the portion which is precipitated . The process of aging begins immediately, and is lengthened by super cooling. The process can be repeated by another solution anneal, which causes the precipitated constituents to, once again, be evenly distributed in the material.GlennW wrote: ↑Sat Sep 22, 2018 2:06 pm No, they were kept on dry ice after they were quenched.
I've seen small table top furnaces about the size of a beer mug that are used to re-heat treat the rivets just prior to use.
The manufacturer will also do that for you and then ship them via air freight packed in dry ice.
H
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