by George Langford, Sc.D., Massachusetts Institute of Technology, Cambridge, MA, 1966
2005 by George Langford
INTRODUCTION - Set 1 - Unknowns

There is no set logical procedure to be followed in solving microstructural riddles, since a lot of "educated guessing" and "detective work" are involved.  However, there are some key questions which you should address:

* How was the specimen made? For example, was it forged, cast, machined, made from powder, welded, etc. ...

* Was the processing done correctly ?
     * In what order were the steps followed ?
     * Was any processing step omitted ?
     * Was something done to an extreme ?

* Is there anything "wrong," or was the specimen simply abused or overloaded ?

* Was there an environmental interaction ?
     * Overheating
     * Chemical attack, as by corrosion or by cementation (i.e., gain of any component) ?

* Is there evidence of mechanical damage ?
     * Cracks
     * Surface deformation
     * Deformation pattern (as by bending)

* Is there an interaction or synergism between the damage and the microstructure ?
    * Intergranular vs. transgranular cracks
    * Corrosion or carburization along grain boundaries
    * Phase changes near the insult

* Can anything be done metallurgically ?
    * How would you change the processing procedure or the environment to which the material is being exposed ?
    * Can this particular specimen be saved, or can another one like it be altered in order to perfoem adequately ?
    * Is there a better material or alloy to use in this application ?
Good luck !  Be sure to commit yourself to a well thought out explanation before "peeking" at the answers.  The value of this learning process will be much greater the first time you go through it than in any subsequent session.
Allow plenty of time to study and to take good notes about each specimen.  About two hours per lesson would be appropriate.  You will be expected to interpret some of these specimens during the final examination.  Feel free to use the Internet to find additional information about the alloys and applications mentioned here.
Whenever the narrator asks a question, be sure to commit yourself to an answer before going to the next page.  You can backtrack with your browser's BACK button at any time, of course.  Just be sure to click the FORWARD button to return to the proper page before proceeding so that you don't get lost.