Fe-Cr-N合金の内部摩擦および窒化クロムの析出

Abstract

Nitrogen diffusion peaks in iron chromium alloys containing less than 1.5 atomic pct chromium were measured at the frequencies of 1.0 and 102 c/s. Two abnormal peaks were observed on both temperature sides of the usual nitrogen peak in unalloyed iron. From peak shifts, activation energies for the low and the high temperature peak were calculated as 16 kcal/mol and 20 kcal/mol, respectively. The high temperature peak is put down as being due to nitrogen atoms in the vicinity of chromium atoms, while the mechanism of the low temperature peak is interpreted as jumps of nitrogen atoms in strained Fe-Fe interstices which are produced by the addition of chromium atoms. Although it is not obvious whether the high temperature peak is describable in terms of a single relaxation time or not, it is reasonable for the low temperature peak to introduce a distribution of relaxation times. Precipitation of nitride phases, Fe8N, Fe4N and CrN, from Fe-Cr-N alloys were investigated by measuring electrical resistivity. Internal friction peaks were also measured after the precipitation of the chromium nitride as a function of chromium contents. Precipitation of the chromium nitride was clearly observed even in 0.2 atomic pct chromium alloy. Consequently, soluble nitrogen atoms in alpha iron-chromium alloys are decreased due to the precipitation of the chromium nitride.