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PROCESSING, MECHANICAL BEHAVIOR AND BIOCOMPATIBILITY
OF ULTRAFINE GRAINED ZIRCONIUM FABRICATED
BY ACCUMULATIVE ROLL BONDING
by
Ling Jiang
___ ________
A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(MECHANICAL ENGINEERING)
December 2008
Copyright 2008 Ling Jiang
Object Description
| Title | Processing, mechanical behavior and biocompatibility of ultrafine grained zirconium fabricated by accumulative roll bonding |
| Author | Jiang, Ling |
| Author email | ljiang79@gmail.com; lingjian@usc.edu |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Mechanical Engineering |
| School | Viterbi School of Engineering |
| Date defended/completed | 2008-09-29 |
| Date submitted | 2008 |
| Restricted until | Unrestricted |
| Date published | 2008-11-09 |
| Advisor (committee chair) |
Kassner, Michael E. Perez-Prado, Maria-Teresa |
| Advisor (committee member) |
Nutt, Steven Phares, Denis Goo, Edward |
| Abstract | The aim of this study is to produce large quantities of bulk zirconium with an ultrafine grained microstructure and with enhanced properties. Accumulative roll bonding (ARB), a severe plastic deformation technique based on rolling, is chosen due to its availability in industrial environment. The texture, microstructure and mechanical behavior of bulk ultrafine grained (ufg) Zr fabricated by accumulative roll bonding is investigated by electron backscatter diffraction, transmission electron microscopy and mechanical testing. A reasonably homogeneous and equiaxed ufg structure, with a large fraction of high angle boundaries (HABs, ~70%), can be obtained in Zr after only two ARB cycles. The average grain size, counting only HABs (θ>15°), is 400 nm. (Sub)grain size is equal to 320 nm. The yield stress and ultimate tensile stress (UTS) values are nearly double those from conventionally processed Zr with only a slight loss of ductility. Optimum processing conditions include large thickness reductions per pass (~75%), which enhance grain refinement, and a rolling temperature (T ~ 0.3T_m) at which a sufficient number of slip modes are activated, with an absence of significant grain growth. Grain refinement takes place by geometrical thinning and grain subdivision by the formation of geometrically necessary boundaries. The formation of equiaxed grains by geometric dynamic recrystallization is facilitated by enhanced diffusion due to adabatic heating. Optical microscopy examination and shear testing suggest accepted bonding quality compared to that achieved in materials processed by diffusion bonding and that obtained in other ARB studies. Biocompatibility of ultrafine grained Zr processed by large strain rolling is studied by evaluating the behavior of human osteoblast cells. It is suggested that ultrafine grained Zr has a similar good biocompatibility as Ti6Al4V alloy and conventional Zr with a large grain size have.; The improved mechanical properties together with an excellent biocompatibility make ultrafine grained Zr a promising biomaterial for surgical implants. |
| Keyword | accumulative roll bonding; biocompatibility; shear testing; texture; ultrafine grained materials; zirconium |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m1759 |
| Rights | Jiang, Ling |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | http://www.usc.edu/isd/libraries/services/ask_a_librarian/email/ |
| Filename | etd-Jiang-2496 |
| Archival file | uscthesesreloadpub_Volume23/etd-Jiang-2496.pdf |
Description
| Title | Page 1 |
| Full text | PROCESSING, MECHANICAL BEHAVIOR AND BIOCOMPATIBILITY OF ULTRAFINE GRAINED ZIRCONIUM FABRICATED BY ACCUMULATIVE ROLL BONDING by Ling Jiang ___ ________ A Dissertation Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (MECHANICAL ENGINEERING) December 2008 Copyright 2008 Ling Jiang |
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