Here's a short course in Welding Metallurgy & The Basics of Metallurgical Principals fro the NRC which covers the basics in a concise and easy to understand manner... I recommend this .pdf for those who need to learn more of these topics, but doesn't want to purchase an expensive book... Mainly because it's tailored for welding students, yet thorough enough for some engineers who do not have or did not take metallurgy while in school... Management personnel could find this useful also: