Neutron scattering study of the martensitic transformation in a Ni-Alβ-phase alloy

Abstract

A high-resolution neutron scattering study of Ni62.5Al37.5 shows that the martensitic transformation is associated with a homogeneous distortion and a nearly sevenfold modulation of the cubic lattice which is predicted by an observed phonon anomaly above TM-In the low-temperature IR phase a nonuniform spacing of superlattice reflections and unusual line shapes are observed which are believed to arise from stacking faults.

Martensitic and Related Transformations in Ni-Al Alloys

“…2) on a transformed region in the stress field near a microcrack [20]. Recently neutron diffraction studies by Shnpiro, Yang, Shirane, Noda & Tanner indicated that there most probably exist two distinct versions of this long period superstructure [21,22]. The existence of these two versions was attributed by Yamada, Noda & Fuchizaki to small local density fluctuations [23].…”

Three intrinsic relationships of lattice parameters between intermediate monoclinicMCand tetragonal phases in ferroelectricPb[(Wang1 2006Phys. Rev. B771200View full textAdd to dashboardCite

“…Khachaturyan et al 42 developed an adaptive phase theory to explain the experimental observation of self-adjusting intermediate ferroelastic ͑martensitic͒ states with variable crystal lattice parameters depending on temperature and applied stress in martensitic crystals. 43 This concept has recently been further developed to explain the behaviors of intermediate monoclinic phases in ferroelectric PMN-xPT and PZN-xPT. [29][30][31] It has been shown that averaging the twin-related tetragonal nanodomains gives rise to the monoclinic M C lattice symmetry, with monoclinic lattice parameters a m , b m , and c m uniquely related to the tetragonal lattice parameters a t and c t .…”

Some questions on the structure of martensite and precursor in Ni(<63at%)-Al alloys

“…In the late eighties, and more recently, a number of reports [14][15][16][17][18] based on HREM and neutron scattering studies consider 7R to be the martensitic structure in Ni-AI alloys with nickel contents less than 63 at%.…”