Biffro
editNearing the end of my degree in Materials Science I felt that I should give something back to a resource I have used so frequently to give me background knowledge in a topic.
Cheers wikipedia
Gum Metal Article Under construction
editAlloy Composition
editGum metal is a new beta phase titanium alloy that has been developed within the last decade that has been shown to exhibit excellent mechanical properties that include a low youngs modulus, a high tensile strength, a large ductility, superelasticity at room temperature and also elivar and invar properties [1] [2]. For a titanium alloy to exhibit these properties it must consist of group IVa and group Va elements that simultaneously satisfy the following electronic numbers : -
- An average compositional valence electron number (e/a) ~4.24
- A bond order number (Bo) ~2.87 based on the DV-X cluster method
- A "d" electron orbital energy level (Md) ~2.45eV
As well as adherering to these electronic parameters the alloy must also receive a substantial amount of cold working and must also contain a minimum of 0.7at% of oxygen[3]. The base composition of these alloys has been cited as Ti-24( Ta+ Nb+ V)-(Zr, Hf) - O (at%) and a standard alloy that follows the electronic numbers it Ti-36Nb-2Ta-3Zr-0.3O (wt%). However it has been shown that designing a titanium alloy solely on the electronic numbers does not always yield the excellent mechanical properties that are attributed to Gum metal [4] As a result of this there is a continued amount of research being performed to refine the composition of this new family of metal alloys and hopefully further enhance it's properties.
There is a large amount of interst in the development of these alloys because of their unique properties including a Young's Modulus ~60GPa and a high strength >1GPa. These properties make the alloy system an ideal candidate for biomedical implants for multiple reasons. Since the alloy will be able to withstand reasonably large loads and has an elastic modulus similar to bone (~30GPa), which will help to ease the problem of "stress shielding" that occurs when the implant material has a large difference in the elastic modulus with the bone[5]. This has been a major issue for alpha + beta phase titanium alloys such as Ti 6Al-4V which has an elastic modulus close to 110GPa. There has also been a large concern over the toxicity and long term affects of using Ti-6Al-4V in biomedical applications due to the aluminium and vanadium ions, however the standard composition for Gum metal alloys is seen as an alternative with the alloying elements being non toxic and also bio-inert[6]
- ^ T.Furuta et al, Development of multi functional titanium alloy, "gum metal".Titanium 2003 science & technology 2004 pg 1519-1526
- ^ T. Saito et al, Multifunctional alloys obtained via a dislocation-free plastic deformation mechanism, Science vol. 300 pg. 464-467
- ^ T.Furuta et al, Development of multi functional titanium alloy, "gum metal".Titanium 2003 science & technology 2004 pg 1519-1526
- ^ R.J.Talling et al, Compositional variability in gum metal, Scripta Material 2009
- ^ M.Niinomi, Recent metallic materials for biomedical applications,Materials transactions A 2002 44 pg. 477-486
- ^ M Long et al, Titanium alloys in total joint replacement - a materials science perspective Biomaterials 1998 19 pg. 1621-1639