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Influence of compression aging on phase transition temperatures in single crystalline Ni‐rich NiTi shape memory alloys
Author(s) -
Michutta J.,
Yawny A.,
Carroll M. C.,
Somsen Ch.,
Eggeler G.
Publication year - 2004
Publication title -
materialwissenschaft und werkstofftechnik
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.285
H-Index - 38
eISSN - 1521-4052
pISSN - 0933-5137
DOI - 10.1002/mawe.200400750
Subject(s) - materials science , nickel titanium , nucleation , martensite , shape memory alloy , crystallite , single crystal , diffusionless transformation , grain boundary , metallurgy , microstructure , phase (matter) , crystallography , alloy , composite material , thermodynamics , chemistry , physics , organic chemistry
The present paper considers the phase transition behavior of a single crystal Ni‐rich NiTi alloy which was compression aged to produce one single family of Ni 4 Ti 3 precipitates. The single crystal material was produced in a two stage process. Polycrystalline material was first melted under an inert atmosphere and remelted when single crystals were produced. Compression aging treatments in <111>‐orientation were carried out in order to suppress all but one family of Ni 4 Ti 3 ‐precipitates which nucleate and grow on {111}‐planes of the B2 matrix. The objective of this study is to investigate the influence of Ni 4 Ti 3 ‐precipitates on the martensitic transformation behavior. It was previously shown that grain boundaries provide heterogeneous nucleation sites for the formation of Ni 4 Ti 3 ; this results in heterogeneous microstructures which undergo multiple step martensitic transformations. Single crystals avoid grain boundaries and the present study aims at clarifying how homogeneously precipitated particles affect martensitic transformations.