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四种不同Ti浓度的Fe-Ti合金,加氮到N/Ti>1之后,发现有两个内耗峰,并且随氮浓度之增加而同时升高。20℃处的峰是氮的Snoek峰,160℃附近的是s-i峰。s-i峰的峰高和Ti浓度成线性关系,表明起峰的反应只涉及孤立的Ti原子,与Ti-Ti原子对或杂质原子团都无关系。提出了产生s-i峰的二种缺陷中心——Ti-N对缺陷和N-Ti-N仨缺陷——的模型(图7)。氮占Ti位就构成对缺陷,其中的Ti,N原子亲和力很强,只要合金中尚存有自由Ti原子,就不可能存有自由氮原子,因此N/Ti≤1以下,不会出现Snoek峰或s-i峰。N/Ti>1之后,多余氮原子要在对缺陷的OⅡ位和T_3位之间以约1:10的比例进行分配,直到绝大部分的对缺陷转化为仨缺陷。N/Ti(?)2以后,几乎所有的多余氮都进入了仨缺陷的OⅡ位,此时s-i峰的弛豫强度突然增加10倍。淬火时冻结在α-Fe基体中的过饱和氮、要扩散到OⅡ位(扩散距离～10(?)),以期达到室温下的再分配,因此引起Snoek峰室温下的迅速衰减。s-i峰的形状,只取决于多余氮的浓度,与淬火温度、冷却速度无关。
Four kinds of Fe-Ti alloys with different Ti concentrations, after adding nitrogen to N / Ti> 1, found two internal friction peaks and increased at the same time as the nitrogen concentration increased. The peak at 20 ° C is a nitrogen Snoek peak, and the vicinity of 160 ° C is the s-i peak. The peak height of s-i peak is linear with Ti concentration, indicating that the peak reaction only involves isolated Ti atoms, which is not related to Ti-Ti atom pairs or impurity atomic groups. Two models of defect centers that generate s-i peaks-the Ti-N pair defect and the N-Ti-N 仨 defect-are presented (Figure 7). Nitrogen accounted for Ti bit on the defect, which Ti, N atoms affinity is strong, as long as there is free Ti atoms in the alloy, it is impossible to have free nitrogen atoms, so N / Ti ≤ 1 below, does not appear Snoek Peak or si peak. After N / Ti> 1, excess nitrogen atoms are distributed in a ratio of about 1:10 between the O ¢ ò and T_3 positions of the defect until most of the defects are converted to 仨 defects. After N / Ti (?) 2, almost all of the excess nitrogen entered the Ⅱ defect O Ⅱ position, at which point the relaxation strength of the s-i peak suddenly increased 10-fold. The supersaturated nitrogen that is frozen in the α-Fe matrix during quenching is diffused into the OⅡ position (diffusion distance ~10 (?)) In order to achieve redistribution at room temperature, thus causing rapid decay of the Snoek peak at room temperature. s-i peak shape, only depends on the concentration of excess nitrogen, and quenching temperature, cooling rate has nothing to do.