Phase fraction, texture and strain evolution in superelastic NiTi and NiTi–TiC composites investigated by neutron diffraction

Samples of superelastic NiTi and superelastic NiTi reinforced with 10 vol.% TiC particles were deformed under uniaxial compression to 975 MPa while neutron diffraction spectra were simultaneously collected. Despite the presence of stiff TiC particles, a macroscopic strain of 3% was obtained in the composite on loading and was fully recovered on unloading. The diffraction spectra were analyzed by Rietveld refinement that included a spherical harmonic description of the texture and a lattice plane (hkl) dependent formulation of the elastic strain. The experiments provided bulk, phase-specific measurements of the evolution of phase fractions, texture and strains during the reversible stress-induced austenite to martensite transformation responsible for the large recoverable strains. For the composite, Eshelby elastic theory is used to predict the discrete phase strains measured by neutron diffraction. The observed behavior suggests that the martensite accommodates the mismatch with the transforming austenite (while they co-exist) and the TiC particles (in the case of the composite).

[1]  H. Rietveld.  A profile refinement method for nuclear and magnetic structures , 1969 .

[2]  L. Schetky.  Shape-memory alloys , 1979 .

[3]  T. W. Duerig,et al.  Engineering Aspects of Shape Memory Alloys , 1990 .

[4]  Parag A. Pathak,et al.  Massachusetts Institute of Technology , 1964, Nature.

[5]  Arthur W. Sleight,et al.  Materials for smart systems: By S. Trolier-McKinstry, K. Uchino, M. Wun-Fogle, E.P. George and S. Takahashi (eds.). Materials Research Society, Pittsburgh, 1995, 559 pages, price $57 MRS member, $67 U.S. list, $72 foreign. ISBN 1-55899-261-8 , 1995 .

[6]  David C. Dunand,et al.  Neutron diffraction measurement of stress-induced transformation in superelastic NiTi , 1996 .

[7]  W. Assmus,et al.  Elastic properties of NiTi , 1991 .

[8]  Mark R. Daymond,et al.  Use of Rietveld refinement for elastic macrostrain determination and for evaluation of plastic strain history from diffraction spectra , 1997 .

[9]  E. G. Wolff,et al.  An introduction to metal matrix composites , 1995 .

[10]  H. Bunge.  Texture Analysis in Materials Science , 1982 .

[11]  大塚 和弘,et al.  Solid - solid phase transformations , 1999 .

[12]  C. M. Wayman,et al.  Shape-Memory Materials , 2018 .

[13]  M. Daymond,et al.  Use of Rietveld refinement to fit a hexagonal crystal structure in the presence of elastic and plastic anisotropy , 1999 .

[14]  A. Krawitz,et al.  Measurement of residual and applied stress using neutron diffraction , 1992 .

[15]  A. Reuss,et al.  Berechnung der Fließgrenze von Mischkristallen auf Grund der Plastizitätsbedingung für Einkristalle . , 1929 .

[16]  K. Ehrlich,et al.  Strength differential effect in pseudoelastic NiTi shape memory alloys , 1997 .

[17]  S. Shtrikman,et al.  On some variational principles in anisotropic and nonhomogeneous elasticity , 1962 .

[18]  L. Graham,et al.  Low-Temperature Elastic Properties of ZrC and TiC , 1966 .

[19]  Morris Cohen,et al.  On the thermodynamics of thermoelastic martensitic transformations , 1979 .

[20]  R. Dreele.  Quantitative texture analysis by Rietveld refinement , 1997 .

[21]  G. Gremaud,et al.  Single‐crystal elastic constants of the equiatomic NiTi alloy near the martensitic transformation , 1980 .

[22]  James F. Shackelford,et al.  The CRC Materials Science And Engineering Handbook , 1991 .