Fe-Al-N合金の内部摩擦および窒化物の析出

Abstract

Snoek peaks of nitrogen in Fe-Al-N ternary alloys were measured with the torsional pendulum at temperatures ranging from −30 to 120°C. Besides the normal nitrogen peak of Fe-N alloys, an additional peak was found at higher temperatures. The activation energies were determined as 17.7 and 19∼20 kcal/mol for low and high temperatures respectively. It is considered that the low temperature peak is due to the stress-induced diffusion of N atoms in Fe-Fe interstices and the high temperature peak due to that in Al-Fe interstices. Although the shape of the normal nitrogen peak of Fe-N binary alloys is in good agreement with that calculated as the internal friction has a single relaxation time, the low temperature peaks in Fe-Al-N ternary alloys are slightly broader than that of the Fe-N binary alloys, and the high temperature peaks are much broader. The broadening can be explained by introducing the relaxation times which have an appropriate error functional distribution.The precipitation of iron nitrides (Fe16N2, Fe4N) and AlN in Fe-Al-N ternary alloys was investigated by measuring the electrical resistivity. The Snoek peaks were also measured to clarify the precipitation process of AlN. Though the precipitation of Fe16N2 at about 150°C is accelerated very slightly with increasing Al content, that of Fe4N at about 250°C is not affected by Al. On the other hand, the precipitation of AlN is accelerated by increasing the Al content. The precipitation process of AlN in specimens of above 0.5%Al is divided into two stages which are characterised as large and small decrements of both electrical resistivity and the Snoek peak. The former and the latter stages are assumed to be due to the pre-precipitation clustering of Al and N and the growth of hexagonal AlN, respectively.