Project Proposal - Stuart Kennedy

MECH3402 Project Proposal, Semester 2-2010
Corrosion of beta Ti produced by SLM
Stuart Kennedy, 20356129
Benjamin Kotovski-Steele, 20352455
Dr. Tim Sercombe

Project Summary

Biomedical research and implementation has become an important part of our society with the
capabilities of material substitutes for specific parts within the human body. Engineers are
challenged with finding an appropriate material with sufficient strength, elasticity and
corrosion resistance. Beta (b) Titanium (in particular Ti-5Al-5Mo-5V-3Cr or Ti5553) is a
Titanium alloy which is currently used in the aerospace industry for landing gear applications,
but has recently garnered much attention in the biomedical field due to its overall low
modulus, superior biocompatibility and enhanced corrosion resistance, making it a suitable
candidate for orthopedic implant applications (Nag 2008). However, not a great deal is known
about the corrosion properties of Ti5553. This project aims to identify these properties by
testing both the wrought and manufactured material (pertaining to Selective Laser Melting) in
various environments and constructing polarisation curves to further benefit current research
of Ti5553.

Project Description

Introduction

Due to various demographic changes, there is now a worldwide increase in the number of
surgical procedures involving prosthesis implantation. This has resulted in an urgent need for
improvement in the very biomaterial technologies used in these orthopedic implants (Nag
2008). The ability to provide a much more effective alloy to the biomedical forefront is an
impressive advancement in technology. To achieve this, corrosive properties of Ti5553 must
be discovered, catalogued and (if applicable) recommended for biomedical advancements.

Titanium alloys have proven to be an invaluable material used in the biomedical area due to
their lack of toxicity, high strength and low elastic modulus (Hao & Yang, 2010). Although
Ti5553 is generally used for aerospace applications, its ability to be applied as a
biomechanical member within the body is evident, as it has “shown to exhibit excellent static
strength and equivalent castability properties to Ti-6Al-4V” (an already popular biomedical
material) (Rivard, K 2006).

Discovering the corrosive properties of the Ti5553 alloy will enable scholars and researchers
to broaden their studies to a greater spectrum. If the corrosive properties of Ti5553 are
adequate for biomedical application, this paper could aid the medical field in helpful ways.


Research/Design/Model Development/Investigation Plan

Investigating the corrosion resistance of Ti5553 is the primary aim of this project. To
complete this goal, the beta Titanium alloy must be observed and tested in several
“environments” in order to completely grasp the corrosive characteristics of Ti5553. The
environments were selected after conferring with Dr Sercombe. These include: seawater,
water, a weak acidic solution, a weak basic solution and a body fluid-like substance. These


<Stuart Kennedy, 20356129>

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MECH3402 Project Proposal, Semester 2-2010
substances were chosen on completely general terms; more specific testing of this alloy
should incur more specific choices of corrosive test environments. Testing the Ti5553 alloy in
the chosen solutions will be promptly followed by the creation of polarization curves under
the direction of Dr Stachowiak.

The testing procedure is as follows: we shape the wrought and processed material into
‘coupons’ (a circular or rectangular shape with a hole in the middle) and it’s left in a small
container with the specific liquid in it. Measurements are taken of the mass, surface area and
density. After a certain “elapsed time”, the mass is re-measured and calculations/polarisation
curves are calculated/constructed thereof. Polarization curves, presented as E vs log i plots,
can be used to evaluate the corrosion behaviour of a material in a specific environment
(Stachowiak 2010).


Project Timeline

The primary information that needs to be gained is the results from the experiments. These are
the crucial milestones, as they will answer the bulk of the questions proposed in the project.
The Ti alloy will be tested in different solutions every week and will be tested in those
particular solutions for two.

See the attached Gantt Chart for clarification.


References

Hao, Y & Yang, R, 2010. ‘Biomedical Titanium Alloy with Ultralow Elastic Modulus and
High Strength’. Materials Science Forum Journal, vols 654 – 656, PRICM7. Available from:
http://www.scientific.net/MSF.654-656.2130 [August 15, 2010].

Nag, S 2008, ‘Influence of beta instabilities on the early stages of nucleation and growth of
alpha in beta titanium alloys’. Ph.D. diss., The Ohio State University ,2008. In Dissertations
& Theses: Full Text [database on-line]. Available from:
<http://www.proquest.com.ezproxy.library.uwa.edu.au> [August 15, 2010].

Rivard, K.L, 2006. “DePuy Orthopaedics’, Internation Titanium Association. Available from:
< http://www.titanium.org/files/ItemFileA3361.pdf>

Stachowiak, G 2010, Corrosion testing and rate measurement with coupons (Exposure tests),
lecture notes distributed in Structural Integrity MECH3405 at The University of Western
Australia, Crawley on 29 August 2010.

Watson, D, Bayha, T, Hofmann, T & Festeau, G 2007, ‘Titanium takes off: The art and
science of milling titanium to make aerospace parts’, Allegheny Technologies, Journal, vol.
59, no. 3. Available from: <http://www.ctemag.com/pdf/2007/0703-Titanium_in_Aero.pdf>
[August 17, 2010].






<Stuart Kennedy, 20356129>

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MECH3402 Project Proposal, Semester 2-2010
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<Stuart Kennedy, 20356129>

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