Welcome to the forum Trav

Hey  I'm a welding instructor for 15 years now and must admit I struggle with phase diagrams...   Most folks start out with the Iron-Carbon diagram and try to understand Eutectic/Eutectiod behavior.

But only 200 words?    Thats really not even enough for a preamble.

Why don't you tell us a little about what your textbook says when they describe these diagrams and what you "don't" understand about it...  I think this will help some of the experts on the forum to give you a starting point.

Here You go Travis:

http://en.wikipedia.org/wiki/Phase_diagram

Here's another pretty good explanation but like Larry mentioned previously, 200 words really isn't enough to give an explanation where anyone could have even a basic understanding of what phase diagrams are and their uses which are many!!! :)

http://www.metallurgy.nist.gov/phase/papers/applic_sol.html

Here's another good website which could help you formulate your own abstract based on learning how phase diagrams work and learning all you can from this site:

http://www.soton.ac.uk/~pasr1/

This one is from Answers.com and it gives you three separate definitions of what phase diagrams are. So it will be up to you in describing how phase diagrams are used in relation to welding and metallurgy:

http://www.answers.com/topic/phase-diagram

Here is a link to a power point presentation on phase diagrams:

http://aurora.wells.edu/~ctb/solidstate/Phase.ppt

Here's a very good .pdf from the University of Virginia:

http://people.virginia.edu/~lz2n/mse209/Chapter9c.pdf

Here's another good .pdf also:

http://sorcerer.ucsd.edu/ERTH50/Lect05_Supp.pdf

I like using this one to explain to students just how phase diagrams are used and it begins from the very basics all the way down to covering different types of materials including Iron and Steel...

http://physics.info/phases/

This one is from the University of Tennessee:

http://web.utk.edu/~prack/mse201/Chapter%209%20%20Total.pdf

This one is one of the best ones I have in my own reference material to use in describing phase diagrams in general:

http://webpages.charter.net/ericbeaton/powerpt/chpt9.pdf

Here's a definition from about.com:

http://physics.about.com/od/glossary/g/phasediagram.htm

This one is from Encyclopedia Britannica:

http://www.britannica.com/EBchecked/topic/455315/phase-diagram

I'm going to stop here because right now, you have more than enough reference material available for you to come up with a very simplified 200 word abstract describing basically what phase diagrams are...

I'm not going to write it out for you because that's your job which I just made a little bit easier for you to do... SO GO DO IT!!! :) :) :)

Respectfully,
Henry