INTERNAL FRICTION OF BAINITE TRANSFORMATION IN 18CrNiWA STEEL
CHEN Shuchuan; ZHANG Jihua; ZHANG Shoubo; XU Zuyao (T. Y. Hsu) (Shanghai Jiaotong University)
Cite this article:
CHEN Shuchuan; ZHANG Jihua; ZHANG Shoubo; XU Zuyao (T. Y. Hsu) (Shanghai Jiaotong University). INTERNAL FRICTION OF BAINITE TRANSFORMATION IN 18CrNiWA STEEL. Acta Metall Sin, 1986, 22(5): 23-28.
Abstract By using of a new type low frequency internal friction instrument controlled through a microcomputer, the change in internal friction during the course of phase transformation under continuous cooling and isothermal holding in 18CrNiWA steel is measured. Under continuous cooling, two internal friction peaks are observed around 400—430 and 320℃ (M_s) respectively. In the specimen after decarbonized with wet-hydrogen, the peak temperature changes to 600℃. The peak temperature is independent with frequency and its height increases with the decrease of frequency. Under isothermal holding the value of internal friction is always the highest at the beginning of holding and gradually decreases to a base-value with holding time in specimen whether it is decarbonized or not. Experimental results shows that the effect of frequency on the internal friction peak in bainite transformation is the same as that in martensitic transformation; within the incubation period the prebainitic transformation occurs basically with the nucleation process rather than with the diffusion of carbon; and in the initial stage of the incubation period, there exists a great number of bainitic nucleus, so the incubation period usually measured in supercooled austenite only is the time at which the grown up bainite can be observed under a specified experimental conditions.
