by George Langford, Sc.D., Massachusetts Institute of Technology, Cambridge, MA, 1966
2005 by George Langford

"answers" email address
The first set of unknowns is based on photomicrographs I made of eight specimens that are in the M.I.T. collection.  In order to build up your confidence and test your ability to interpret microstructures, only minimal help and hints are given in this section.  At the end of the description of each unknown specimen, there will be a link to the answer.  However, the answers are individually password protected; you can email me at the address imaged above to get a Username and Password to access those answers.  Naturally, I'll expect some small proof that you have made an effort to work out some answers, in the form of an included written outline of your analysis.  There is no charge for this.  These unknowns and others like them were doled out one at a time at M.I.T., one each week to each student, so you should not expect that your analysis will just leap out at you from the computer screen.  It takes time (or experience) for that to happen.
I made the color photomicrographs presented here of a prepared set of specimens of known history collected by the staff of M.I.T. in the years prior to 1959.  They were made by me with Kodachrome KA135 Professional, but the color temperature of the illumination was still way too low for proper rendition of the color of the light reflected from the specimens.  I have therefore adjusted the color balance to approximate better what I remember seeing through the eyepieces of the microscope.  The microscope objective lenses used were achromatic (corrected for two colors) and, as the appropriate green filter was not used, there are sometimes color fringes and reduced resolution as a result of the use of the panchromatic color film.
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. 
Return to main Introduction.
Unknowns - First Set - Iron-Based
Second Set - Non Ferrous (do this second -- it's harder)