Introduction and Acknowledgements
|When I was a
senior in the [then] Metallurgy Department at the Massachusetts
Institute of Technology (M.I.T.) in 1959, I took an innocuously named
course, Physical Metallurgy III or 3.33. The class lectures
were a little boring and had something to do with the current
industrial metallurgical treatments of metals such as nitriding ... but
the laboratory was something else entirely. Each week we met for
three hours in a room fully equipped with metallurgical microscopes -
each student in the class - a heavy investment even then. The
first hour was spent looking at a set of polished & etched
metallurgical cross sections, nicely prepared by Metallographer Nicholas
Lab Instructors Walter Johnson and the late Arthur J. Gregor. We
the specimens one at a
notes, asking questions of our instructors (Profesor David A. Thomas,
and Instructors Marc
Richman, George Krauss, and Vince Sciuta) and then passing each
room. We all got first-hand looks at each and every
specimen. Then we were each given an unknown specimen; and we
were expected to examine it, then prepare a suitable cross section, and
figure out all by ourselves (a) what it was, (b) how it was made and
processed metallurgically, (c) what (if anything) was wrong with it,
and (d) what should have been done to make it right. We then
wrote short reports, usually a page or two with one or two illustrative
photomicrographs which we also made ourselves, using 3-1/4 by 4 inch
glass negatives and contact prints, in which we put forth our
analyses. The instructors graded those before the next class, so
another part of the following class was spent discussing our findings
with the instructor who had graded it. Usually the instructors
didn't know any more than we did about the history of each unknown, so
it was excellent practice for everyone.
The following year I had graduated, entered graduate school at M.I.T., and had been appointed Instructor in Metallurgy. Charlie McMahon also joined the fray as Instructor in Metallurgy. I was the eager new purchaser of a Miranda single lens reflex camera and a microscope attachment for it. Arthur Gregor picked an Asahi (later, Honeywell) Pentax at the same time. He was luckier than I - the Miranda Camera Company soon sank from the sheer weight of its cast-brass camera bodies. I was fortunate to be assigned as the lab instructor for 3.33 along with Charlie. In 1962 I took advantage of this opportunity to make color transparency photomicrographs of all the known specimens each week just prior to class, and I also made suitable photomicrographs of the unknowns that I graded each week. I used Kodachrome KA-135 Professional film (at Arthur Gregor's knowing urging) and I also took the trouble to make and calibrate my own through-the-lens exposure meter, using a cadmium sulfide photoresistive cell whose resistance I measured with a multimeter. I also tried Ektachrome, but that was a disaster, as the much shorter exposures caused the inevitable mirror bounce of the SLR to ruin the sharpness of nearly every image that I made with that film. The exposures with the far slower Kodachrome Professional film were so much longer - several seconds - that the bounce died out long before most of the image was recorded. These images have stood the test of time - and now, 45 years later, they are still as bright and clear as they were back in 1962. Note, however, that I have had to adjust the color balance of many of the images (using the PhotoStudio image-editing software that came bundled with my Sony Mavica digital camera) in order to approximate what I remember seeing directly through the microscope eyepiece. The next year I was again an instructor in the course, and so I continued the process, filling in the blanks and omissions of the previous year. I eventually exposed more than thirty, 36-exposure rolls of film, with about a 90% success rate as to exposure and sharpness. In all images shown here, the microscope was a Leitz Metallux set up for reflected light.
Then, almost twenty years later in 1979 and 1980, I was an eager professor at Drexel University and took it upon myself to shoehorn my slide collection into the Metallurgy curriculum there by creating (with the help of John Gregory and his staff in Drexel's Audio-Visual Department) a self-paced instruction set based on filmstrips and audio cassette tapes. These were well received by the undergraduate students in the one year that I had remaining there. The present narrations are based on the notes that I prepared for that instruction set.
The exceptional value of M.I.T.'s 3.33 lab course to me personally was that it forced me to bring together all the knowledge and understanding of metallurgy to which I had been exposed. I developed confidence in my work and in my interpretation of microstructures. It made me grow up. I am now placing all of it out in the open Internet in the hope that others may gain from seeing and reading about the microstructures that I had been shown and had discussed with my colleagues and instructors at M.I.T. I am doing this in the spirit of M.I.T.'s recent decision to make available much of the M.I.T. course material that the staff prepares electronically for instructional purposes, free, to the general public. This material, both M.I.T.'s and mine, is presented with the understanding that it is not a substitute for and not an equivalent to a college education.
Virtually all the specimens depicted in my photomicrographic images are part of the collection of the M.I.T. Metallurgy Department; I am grateful to M.I.T. for their acquiescence in permitting me the time from my studies and from my duties as an instructor to record what I saw. I paid for the film and its development myself, however. The blame for any errors and omissions is entirely mine. Do not endeavor to base any design or structure to which the public may be exposed on what you learn here. This material is not a substitute for a professional analysis of your current task.
Non Ferrous Alloys
Second Section: Low Alloy Steels
Third section: Cast Irons, High Alloy Steels, and Superalloys
Fourth Section: Unknowns