WINNING ENTRIES: 2007 APMI INTERNATIONAL PM METALLOGRAPHY COMPETITION, PART I

摘要

The evolution of the onion ring structure and the changes in the carbon content in the carbonyl iron powder were investigated in this study. In the as-received powder, the carbon was present mostly as free carbon, with small amounts of Fe_3C and Fe_2C, as measured using the self-designed current settings in the C/S analyzer and X-ray diffraction. As the powder was heated in the N_2-15 v/o H_2 atmosphere, decarburization occurred. Both the amounts of Fe-C compound and free carbon decreased, and the onion ring structure disappeared at about 600 deg C. After heating to 900 deg C, only some nanoscale Fe_3C and Fe_2C particles were present, and grain growth was obvious.