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Variation of free volume with deformation and relaxation for copper- and zirconium based bulk metallic glasses

Kanungo, Biraja Prasad
http://rave.ohiolink.edu/etdc/view?acc_num=osu1092922080

Abstract Details

2004, Master of Science, Ohio State University, Materials Science and Engineering.
Variation of free volume with deformation plays an important role in strain localization in shear bands. However, the details of this structural change, in case of inhomogeneous flow of metallic glasses, are unclear. This study investigates the effect of deformation and relaxation on the amount and distribution of free volume in Cu60Zr30Ti10 and Zr58.5Cu15.6Ni12.8Al10.3Nb2.8 bulk metallic glasses using positron annihilation spectroscopy (PAS) and differential scanning calorimetry (DSC). Both the studies show an increase in the amount of free volume with deformation and decrease in free volume with relaxation. However, large amount of deformations result in nano-void formation via free volume coalescence. Therefore it is suggested that there is a critical amount of deformation re-quired to favor nano-void formation. PAS results indicate that there are multiple size open volume sites; however, all of them are of the same type. Annealing at higher tem-peratures decreases both the small sites (shallow traps) and large sites (deep traps). Whereas, annealing at lower temperature decreases mostly the deep traps. The free volume changes for the Zr-based glass are successfully simulated using van den Beukel and Sietsma’s glass transition model. However, the Cu-based glass can not be simu-lated using the above model due to the presence of a drastic exothermic event at ~ 683K. High resolution TEM analysis is carried out on the Cu glass in order to investigate the drastic exotherm. It is observed that the as-cast Cu-glass has very less (~ 0.5%) vol-ume fraction of nano-crystals, which are rich in Cu. It is suggested that these nano-crystals transform in to more stable CuZr phase at ~ 683K giving rise to the drastic exo-thermic event. It is also observed that this exothermic event arises as a batch to batch variation.
Katharine Flores (Advisor)
116 p.
FREE VOLUME; METALLIC GLASSES; specimen; GLASSES; positron; rolled; shear bands

Recommended Citations

Citations

  • Kanungo, B. P. (2004). Variation of free volume with deformation and relaxation for copper- and zirconium based bulk metallic glasses [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1092922080

    APA Style (7th edition)

  • Kanungo, Biraja. Variation of free volume with deformation and relaxation for copper- and zirconium based bulk metallic glasses. 2004. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1092922080.

    MLA Style (8th edition)

  • Kanungo, Biraja. "Variation of free volume with deformation and relaxation for copper- and zirconium based bulk metallic glasses." Master's thesis, Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1092922080

    Chicago Manual of Style (17th edition)

osu1092922080
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This open access ETD is published by The Ohio State University and OhioLINK.