Thermo-mechanical processing, microstructure and bending rotation fatigue of ultra-fine grained NiTiCr-wires (bibtex)

by M. Frotscher, J. Burow, M.F.-X. Wagner, K. Neuking, G. Eggeler, P. Schön, R. Böckmann

@InProceedings{Frotscher,
  Title                    = {{Thermo-mechanical processing, microstructure and bending rotation fatigue of ultra-fine grained {NiTiCr}-wires}},
  Author                   = {Frotscher, M. and Burow, J. and Wagner, M.F.-X. and Neuking, K. and Eggeler, G. and Sch\"{o}n, P. and B\"{o}ckmann, R.},
  Booktitle                = {Proc. of SMST 2007},
  Year                     = {2007},

  Address                  = {Tsukuba, Japan},
  Pages                    = {149--157},

  Abstract                 = {The addition of Cr to NiTi-alloys results in an improvement of tensile strength, stiffness and torqueability. There is a need for a better understanding of microstructural and mechanical aspects of fatigue especially with regard to medical applications. The properties of pseudoelastic NiTiCr shape memory alloy (SMA) wires (0.25 wt.% Cr) were studied. The microstructure of the material was characterized in the as-received condition and after a number of different heat treatments using scanning and transmission electron microscopy (SEM and TEM). A prominent feature of the microstructure of our wires is ultra fine grains (UFG) of about 40 nm grain size. We performed mechanical loading-unloading tensile tests at temperatures ranging from 20°C to 80°C. Moreover, bending-rotation fatigue (BRF) tests were conducted in air and in oil. The influence of surface conditions on fatigue life was studied. Results are reported and compared with data from binary NiTi wires. The effects of testing and microstructural parameters like the type of loading, temperature, and the presence of inclusions are discussed. The results obtained in the present study contribute to a better understanding of the microstructure and fatigue of ternary NiTi-alloys.}
}