‘Modulated lattice relaxation’ in β-based premartensitic phase

Abstract

Recent X-ray studies on TiNi(Fe) alloy by Shapiro et al. show that incommensurability of satellite reflections changes from Brillouin zone to Brillouin zone, giving overall ‘swirl’ like shift pattern in the reciprocal space which precludes any simple incommensurate wave model. We have succeeded to reproduce the intriguing shift pattern observed, based on two simple assumptions: (i) existence of soft phonons at q = 1 3 [110] (ii) existence of ‘embrios’ of low temperature martensite phase. The proposed features of premartensitic phase suggest a possible microscopic mechanism of martensite transformation in general as well as of ω-phase formation.