Jan_AMP_Digital

3 7

A D V A N C E D M A T E R I A L S & P R O C E S S E S | J A N U A R Y 2 0 1 6

PHASE TRANSFORMATIONS Bain joined the newly formed Re- search Laboratory of U.S. Steel in 1928. His first assignment was to design and equip a laboratory in a vacant building in Kearney, N.J. Here he undertook re- search on the transformation of austen- ite to pearlite in 0.80% carbon steel. This steel had the carbon content that formed only pearlite, called the eutectoid com- position. He hired a young metallurgist, E.S. Davenport, to help with his research. The experiment was unique in that they studied the formation of pearlite over time at a constant temperature. This was the first time anyone had studied a metal reaction as a function of time. It had been assumed that only temperature was important in transfor- mation. They heated very thin samples to the austenitic phase, and quenched them in a bath heated to the transfor- mation temperature. At various time intervals, a sample was removed and quenched in a room temperature water bath to form martensite in the untrans- formed austenite. The microstructure was then examined to measure the amount of pearlite that had formed at the constant higher temperature. Plotting the percent transforma- tion against time on a logarithmic scale for transformation to start, to progress, and to end provided the rate of trans- formation. The resulting curves started Isothermal transformation diagram for an iron- carbon alloy of eutectoid composition (0.80%C), including austenite to pearlite and austenite to bainite transformations. Courtesy of ASM.

Aerial view of U.S. Steel’s Research Center showing the Edgar C. Bain Laboratory for Fundamental Research on the left. Courtesy of Historic Pittsburgh, images. library.pitt.edu/pittsburgh.

slowly, progressed rapidly, and ended slowly. Plotting the beginning and end- ing times for many different tempera- tures resulted in a curve with a c-shape. At the highest temperatures, the start and end of transformation was delayed in time. As temperature decreased, the reaction was faster until about 1100°F. At even lower temperatures, the reac- tion rate decreased again and a newmi- crostructure formed that was not pearl- ite. This new phase was named bainite in his honor. The paper published by Davenport and Bain in 1929 received worldwide at- tention, and with his previous research on tool steels, alloy steels, and his pio- neering work in x-ray diffraction, he was recognized as America’s leading metals scientist. During his active research ca- reer at U.S. Steel, Bain and his coauthors published 20 technical papers between 1929 and 1939. He also coauthored a book on tool steels with Marcus Gross- mann in 1931 and published his book Functions of the Alloying Elements in Steel in 1939. He was promoted to vice president of research and technology of the Carnegie-Illinois Steel Corp. in 1943 and moved to Pittsburgh where he later became vice president of research and technology for the entire U.S. Steel Corp. The corporation built a research campus in 1956 in Monroeville, Pa., which includ- ed the Edgar C. Bain Laboratory for Fun- damental Research.

Granular bainite. Courtesy of EWI.

AWARDS AND HONORS

Bain was active in many technical societies, served as president of ASM in 1937, was elected into the Nation- al Academy of Sciences in 1954, and received many other honors. He also earned several awards for his career in metals research. These include the Rob- ert W. Hunt Medal in 1929, Henry Mari- on Howe Medal in 1931, Albert Sauveur Achievement Award in 1946, ASM Gold Medal in 1949, and the Franklin Insti- tute’s John PriceWetherill Medal in 1949. Edgar Bain suffered a stroke in 1959 that left him partially paralyzed. He contin- ued to consult from his home and wrote his autobiography, Pioneering in Steel Research: A Personal Record, published by ASM in 1975 after his death in 1971. For more information: Charles R. Simcoe can be reached at crsimcoe1@ gmail.com.