GutZ Posted November 9, 2006 Share Posted November 9, 2006 I should know this really for the field I am in but since I am still a student, and we don't really cover it well, I have a question. Take Steel (Iron/Carbon), When it's brought to a temperature of "A" or so it changes phase. What phase, doesn't really matter I just know that at certian phases the structure of the metal atoms changes from like BCC, FCC and HCP to another. I was wondering what sets those states? Like is it an specfic energy level where the structure changes to HCP, or whatever? I am not making sense probably but I am sure one of you will get it. Link to comment Share on other sites More sharing options...
YT2095 Posted November 9, 2006 Share Posted November 9, 2006 those are Crystaline stuctures you`re talking about, not atoms, atoms stay the same. as for phases there are only 5 that we know of anyway, Solid, Liquid, Gas, Plasma, Bose Einstein condensate. in chem we deal only with the 1`st 3 mostly. so "Phase" isn`t the correct wording either. using this data, can you re-define your question again please? Link to comment Share on other sites More sharing options...
GutZ Posted November 9, 2006 Author Share Posted November 9, 2006 No. Well I should of said Iron sorry. I had steel on the mind. http://en.wikipedia.org/wiki/Ferrite_%28iron%29 In pure iron, ferrite is stable below 910°C. Above this temperature the face-centered cubic form of iron, austenite (gamma-iron) is stable. Above 1390°C, up to the melting point at 1534°C, the body-centred cubic crystal structure is again the more stable form (delta-iron). Structure FCC-->BCC Phase Austentite--->Delta Iron (eek) I guess the Phase is irrelvant...I just want to know what causes a cystalline structure to change. Link to comment Share on other sites More sharing options...
Tetrahedrite Posted November 10, 2006 Share Posted November 10, 2006 I think I know what you are trying to ask, and the answer (nearly always) has to do with thermodynamics. The iron will always react so that it has the lowest possible energy. When you heat iron (or it's alloys) up to certain temperatures, it will rearrange itself to give a lower lattice energy. If it did not do this, it would not be in thermodynamic equilibrium. To put it another way....... You'll probably find that the reaction from from BCC iron to FCC iron is endothermic, and when you heat the system up, it reacts in such a way to try and counteract that heat (stress) ie it reacts in the endothermic direction, BCC to FCC. This is not at all dis-similar to Le Chatelier's principle. Link to comment Share on other sites More sharing options...
psynapse Posted November 10, 2006 Share Posted November 10, 2006 ^Good answer, IMO. Link to comment Share on other sites More sharing options...
GutZ Posted November 10, 2006 Author Share Posted November 10, 2006 Yeah that's it, perfect! thank you. Thermodynamics...*shudders*, I guess I should read into that. Link to comment Share on other sites More sharing options...
Tetrahedrite Posted November 13, 2006 Share Posted November 13, 2006 Yeah that's it, perfect! thank you. Thermodynamics...*shudders*, I guess I should read into that. No problem. Thermodynamics is the fundamental driving force behind all chemistry so it really is a good thing to learn, even in a basic sense. Link to comment Share on other sites More sharing options...
insane_alien Posted November 13, 2006 Share Posted November 13, 2006 yeah thermodynamics is pretty important. even if its as boring as hell. and i mean reallly BORING. on a side note, guess what class i'm in just now Link to comment Share on other sites More sharing options...
jdurg Posted November 14, 2006 Share Posted November 14, 2006 Yes, but thermodynamics classes typically have the most interesting and exciting demos. Link to comment Share on other sites More sharing options...
GutZ Posted November 15, 2006 Author Share Posted November 15, 2006 I want to get as much information as I can now, being a Metal Casting Technician (glorified titles ) , and wanting to advance my education later, it will help me make that leap when I get the money or assistance to do it. Plus...it impress people Thermodynamics is interesting for me, it's just like, they purposely find the most boring way to present it (well in books anyway). Link to comment Share on other sites More sharing options...
insane_alien Posted November 15, 2006 Share Posted November 15, 2006 do you want to go to my thermo lectures then? Link to comment Share on other sites More sharing options...
GutZ Posted November 15, 2006 Author Share Posted November 15, 2006 Do I have to take notes for you? Link to comment Share on other sites More sharing options...
insane_alien Posted November 15, 2006 Share Posted November 15, 2006 yes and the must be surrounded by a border of amusing doodles as they would be if i was taking notes. Link to comment Share on other sites More sharing options...
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