For the metallurgists among us: What happens to cast aluminium when...
07-11-2012, 02:19 PM
#16
Rennlist Member
Wow wish I had seen this sooner.
Yeah nothing will happen.
Banana, let me know if you need anyone to bounce some MSE stuff off of -- I got my degrees in it and I miss it (don't do it for my day job).
0.4*MP @ std pressure is a good rule of thumb. This correlates nicely to the creep temperature (or "Hot temperature" if you're in industry), which is largely considered to be ~.4*MP in metals and slightly higher in most ceramics (~0.5x).
Yeah nothing will happen.
Banana, let me know if you need anyone to bounce some MSE stuff off of -- I got my degrees in it and I miss it (don't do it for my day job).
0.4*MP @ std pressure is a good rule of thumb. This correlates nicely to the creep temperature (or "Hot temperature" if you're in industry), which is largely considered to be ~.4*MP in metals and slightly higher in most ceramics (~0.5x).
07-11-2012, 02:34 PM
#17
Rennlist Member
I should note that "something happening" at 0.4*MP is only really even relevant to metals experiencing prolonged exposure (an hour, ish, at least usually) to either heat and/or force application.
It is possible to force changes in microstructure to a material at lower temperatures than this "magical" 0.4x. However, this is often accompanied by prior heat treating.
Examples: Tempering/annealing (in metals) is used to relieve stresses in crystal structure, thereby softening the metal and increasing toughness. Another example is age-hardening (aluminum is an age-hardenable metal, most steels are not). However, in order to induce age hardening (AKA Precipitation Hardening), the metal must be brought to a single-phase solid solution first.
Ever seen Age-Hardening Rivets? These are aluminum rivets requiring constant refrigeration, because they age-harden at room temperature! But again -- this hardening will not be an "immediate" change. Remember, temperature aids kinetics, so if a change is possible (negative Gibbs) it will go more slowly at lower temperatures.
OK I'm done -- thanks for letting me get it out of my system, for now.
It is possible to force changes in microstructure to a material at lower temperatures than this "magical" 0.4x. However, this is often accompanied by prior heat treating.
Examples: Tempering/annealing (in metals) is used to relieve stresses in crystal structure, thereby softening the metal and increasing toughness. Another example is age-hardening (aluminum is an age-hardenable metal, most steels are not). However, in order to induce age hardening (AKA Precipitation Hardening), the metal must be brought to a single-phase solid solution first.
Ever seen Age-Hardening Rivets? These are aluminum rivets requiring constant refrigeration, because they age-harden at room temperature! But again -- this hardening will not be an "immediate" change. Remember, temperature aids kinetics, so if a change is possible (negative Gibbs) it will go more slowly at lower temperatures.
OK I'm done -- thanks for letting me get it out of my system, for now.
07-11-2012, 03:08 PM
#18
Three Wheelin'
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Uh yeah, Collin, got a test next week!
hahah just kidding
But I do enjoy when this technical conversation comes up on RL, really affirms my decision in Mechanical Engineering!
hahah just kidding
But I do enjoy when this technical conversation comes up on RL, really affirms my decision in Mechanical Engineering!
