Previous studies showed that internal friction peaks appear around 130℃ and 150℃ in the process of tempering of high-carbon and low-carbon martensite respectively. These peaks have been assumed to be associated with the coherency existing between the decomposition product and the parent phase. In the present work, systematic studies are made on the appearance and disappearance of the respective internal friction peaks in correlation with the formation and the destruction of the coherent decomposition products of high-carbon and low-carbon martensite.Results show that these peaks are definitely related with the coherency of the decomposition products.Experimental results show further that, in the case of high-carbon as well as low-carbon martensite, the position of the internal friction peaks (when expressed as a function of temperature) does not change with a change of the frequency of measurement, but the height of the peaks increases with a raise of the stress amplitude used in the measurement. This indicates that the observed internal friction does not involve a relaxation process, and this may be characteristic for all internal friction peaks associated with a coherency phenomenon. On the basis of the behaviour of the peaks, we may assume that the peaks are associated with the stress-induced movement of the coherent boundaries. The origin of the temperature variation of this internal friction is discussed.
下载:
