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The Effects of Ultrasonic Nano-crystal Surface Modification on Residual Stress, Microstructure and Fatigue Behavior of Low-Modulus Ti-35Nb-7Zr-5Ta-0.3O Alloy

Jagtap, Rohit
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479823317088871

Abstract Details

2016, MS, University of Cincinnati, Engineering and Applied Science: Materials Science.
In this study, the effects of Ultrasonic Nanocrystal Surface Modification (UNSM) on residual stress, near surface microstructure, hardness, high cycle fatigue, biocompatibility and corrosion behaviour of a low-modulus beta Ti-35Nb-7Zr-5Ta-0.3O (wt %) was studied. The UNSM is novel mechanical surface treatment which effectively improves mechanical properties, fatigue life and wear of engineering components. UNSM causes severe plastic deformation on the surface, thus inducing deep compressive stresses and a surface nano-crystalline layer in the component which improves hardness, yield strength and fatigue life. At first, the as-received specimens were solution treated at 850º C for 1 hour and water quenched to obtain a single phase ß structure. The solution treated specimens were then subjected to UNSM treatment with two different static (20N and 50N) and dynamic loads (20% and 50%). The microstructure after UNSM was characterized by optical, scanning electron microscope (SEM), Electron Backscattered Diffraction (EBSD) and transmission electron Microscopy (TEM). Nanoindentation test was also performed to determine local properties like hardness with distance from the treated surface. The UNSM treated specimen induces compressive residual stresses as high as -1600 MPa and shows significant increase in surface hardness from 4.5 GPa to 6 GPa. The residual compressive stresses and hardness increases with increase in static load. The severe plastic deformation caused by UNSM produces nanocrystalline layer of about 1 µm from the treated surface and a gradient microstructure of deformation bands and high dislocation density which was confirmed by transmission electron microscopy. The deformation mechanism after UNSM was also studied. The deformation mechanism in this alloy is dominated by dislocation movement and occurrence of deformation bands with high dislocation density. Three-point bending fatigue tests were also performed to study improvement in fatigue life through S-N Curves. UNSM treated specimen shows improvement in fatigue endurance limit by 30%. The improvement in fatigue life is mainly resulted from near surface hardening caused by grain refinement, high dislocation density and high magnitude of compressive residual stresses. A biocompatibility and potentiodynamic polarization tests were also carried out after UNSM to assess the cell adhesion and corrosion response of Ti-35Nb-7Zr-5Ta-0.3O% alloy after UNSM. UNSM treated specimen shows improvement in cell adhesion and minor improvement in corrosion rate owing to increase in surface roughness after UNSM. Thus, UNSM proves to be promising technique for improving fatigue and wear performance of biomedical alloys without compromising low elastic modulus and superior corrosion resistance.
Vijay Vasudevan, Ph.D. (Committee Chair)
Ashley Paz y Puente, Ph.D. (Committee Member)
Rodney Roseman, Ph.D. (Committee Member)
118 p.
Materials Science
Ultrasonic Nanocrystal Surface Modification; Low Modulus Beta Titanium; Fatigue Performance; Nanocrystalline-layer; Residual Stress; Biocompatibility

Recommended Citations

Citations

  • Jagtap, R. (2016). The Effects of Ultrasonic Nano-crystal Surface Modification on Residual Stress, Microstructure and Fatigue Behavior of Low-Modulus Ti-35Nb-7Zr-5Ta-0.3O Alloy [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479823317088871

    APA Style (7th edition)

  • Jagtap, Rohit. The Effects of Ultrasonic Nano-crystal Surface Modification on Residual Stress, Microstructure and Fatigue Behavior of Low-Modulus Ti-35Nb-7Zr-5Ta-0.3O Alloy. 2016. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479823317088871.

    MLA Style (8th edition)

  • Jagtap, Rohit. "The Effects of Ultrasonic Nano-crystal Surface Modification on Residual Stress, Microstructure and Fatigue Behavior of Low-Modulus Ti-35Nb-7Zr-5Ta-0.3O Alloy." Master's thesis, University of Cincinnati, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479823317088871

    Chicago Manual of Style (17th edition)

ucin1479823317088871
254
© 2016, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.