Surface Characteristics of Machined NiTi Shape Memory Alloy: The Effects of Cryogenic Cooling and Preheating Conditions
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This experimental study focuses on the phase state and phase transformation response of the surface and subsurface of machined NiTi alloys. X-ray diffraction (XRD) analysis and differential scanning calorimeter techniques were utilized to measure the phase state and the transformation response of machined specimens, respectively. Specimens were machined under dry machining at ambient temperature, preheated conditions, and cryogenic cooling conditions at various cutting speeds. The findings from this research demonstrate that cryogenic machining substantially alters austenite finish temperature of martensitic NiTi alloy. Austenite finish (A f) temperature shows more than 25 percent increase resulting from cryogenic machining compared with austenite finish temperature of as-received NiTi. Dry and preheated conditions do not substantially alter austenite finish temperature. XRD analysis shows that distinctive transformation from martensite to austenite occurs during machining process in all three conditions. Complete transformation from martensite to austenite is observed in dry cutting at all selected cutting speeds.
Keywordscryogenic machining DSC analysis NiTi shape memory alloy surface integrity XRD analysis
Support from the NASA EPSCOR Program under Grant No. NNX11AQ31A and the NASA FAP Aeronautical Sciences Project are greatly acknowledged.
- 2.S.A. Shabalovskaya, On the Nature of the Biocompatibility and on Medical Applications of NiTi Shape Memory and Superelastic Alloys, Biomed. Mater. Eng., 1996, 6, p 267–289Google Scholar
- 13.Y. Kaynak, H. Karaca, and I.S. Jawahir, Cryogenic Machining of NiTi Shape Memory Alloy, 6th International Conference and Exhibition on Design and Production of Machines and Dies/Molds, 2011, p 23–26Google Scholar
- 18.A.P. Stebner, S.C. Vogel, R.D. Noebe, T.A. Sisneros, B. Clausen, D.W. Brown, A. Garg, and L.C. Brinson, Micromechanical Quantification of Elastic, Twinning, and Slip Strain Partitioning Exhibited by Polycrystalline, Monoclinic Nickel-Titanium During Large Uniaxial Deformations Measured via In-Situ Neutron Diffraction, J. Mech. Phys. Solids, 2013, 61, p 2302–2330CrossRefGoogle Scholar
- 26.B.D. Cullity and S.R. Stock, Elements of X-Ray Diffraction, Prentice Hall, Upper Saddle River, 2001Google Scholar
- 34.Y. Kaynak, Process-Induced Surface Integrity in Machining of NiTi Shape Memory Alloys, University of Kentucky. Ph.D. Dissertation (2013)Google Scholar
- 38.Y. Liu and Z. Xie, Detwinning in Shape Memory Alloy, Progress in Smart Materials and Structures, P.L. Reece, Ed., Nova Science Publishers Inc, NY, 2007, p 29–65Google Scholar
- 40.J.T. Lim and D.L. McDowell, Degradation of an Ni-Ti Alloy During Cyclic Loading, 1994 North American Conference on Smart Structures and Materials, International Society for Optics and Photonics, 1994, p 326–341Google Scholar