Modulated lattice relaxation in β-based premartensitic phase

Abstract

Recent X-ray studies on a TiNi(Fe) alloy by Shapiroet al. show that the incommensurability of satellite reflections changes from Brillouin zone to Brillouin zone, giving an overall swirl-like shift pattern in the reciprocal space, which precludes any simple incommensurate wave model. We have succeeded in reproducing the intriguing shift pattern observed, based on two simple assumptions: (i) existence of a dip in TA phonon dispersion atq = 1/3[110] and (ii) existence of embryos of low temperature martensite phase. The proposed features of the premartensitic phase suggest a possible microscopic mechanism of martensite transformation in general as well as of w-phase formation. fa]This paper is based on a presentation made in the symposium “Pretransformation Behavior Related to Displacive Transformations in Alloys” presented at the 1986 annual AIME meeting in New Orleans, March 2–6, 1986, under the auspices of the ASM-MSD Structures Committee.