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A super-hard metal has been made in the laboratory by melting together titanium and gold.
The alloy is the hardest known metallic substance compatible with living tissues, say US physicists.
The material is four times harder than pure titanium and has applications in making longer-lasting medical implants, they say.
Conventional knee and hip implants have to be replaced after about 10 years due to wear and tear.
Details of the new metal - an alloy of gold and titanium - are revealed in the journal, Science Advances.
Prof Emilia Morosan, of Rice University, Houston, said her team had made the discovery while working on unconventional magnets made from titanium and gold.
The new materials needed to be made into powders to check their purity, but beta-Ti3Au, as it is known, was too tough to be ground in a diamond-coated mortar and pestle.
The material "showed the highest hardness of all Ti-Au [titanium-gold] alloys and compounds, but also compared to many other engineering alloys", said Prof Morosan.
She said the hardness of the substance, together with its higher biocompatibility, made it a "next generation compound for substantively extending the lifetime of dental implants and replacement joints".
Source: http://www.bbc.com/news/science-environment-36855705
(Score: 3, Interesting) by DECbot on Tuesday July 26 2016, @12:26AM
I thought on this a little more.... By no means am I a weld engineer or materials engineer, but I did some quick references to see the feasibility of welding this new alloy. Gold has a melting point of 1064°C and a boiling point of 2700°C while titanium melts at 1668°C and boils and temperatures higher than I care about for this thought problem (in excess of 5900°C for those curious folks). When welding this alloy, you're likely to hit the boiling point of the gold during the weld and due to the low melting point of the gold. This will result in gold vapor escaping from the base material and cause expulsions, spatter, and porosity in the weld. AKA a really bad weld. Imagine making a knee replacement, and right where the tendon goes over the weldment, there is a tiny 0.5mm ball of spatter rubbing against the tendon than no regular grinding disk could remove. You would essentially feel a tiny knife slowly cutting your tendon every time it moves over this spatter ball. So the process window for welding is very tiny and the process to remove spatter and bad welds very expensive. Now the article [sciencemag.org] does mention that the intermetallic TiAu alloys have lower melting point than Ti, but no details were listed in the article and I wasn't bothered to look up the referred article (footnote 64 [sciencemag.org] for those with more determination than I). Perhaps the process window is greater than I'm imagining. However, if your goal in life is to avoid the spatter completely, you could try brazing--where you melt the gold to your filler metal, but never melt the titanium. This will make a strong bond, but it won't be as strong as the base material. Here at least the spatter would be cheap to remove (well, as cheap as grinding gold away--I mean what's the inherent value of gold dust?) and the brazes easy to cut out if needed. In regards to melting, the only thing I saw the article suggest is casting, frankly due to the machining costs. Less face it, machining something harder than most industrial grinding an milling tools and the value of the dust is likely worth more per pound than the person machining the final product really detracts from the possibility of becoming a viable industrial process.
Again, I'm not an expert, but I happen to work with some experts. Correct me if you have insight that I may be ignorant of.
cats~$ sudo chown -R us /home/base
(Score: 2) by butthurt on Tuesday July 26 2016, @02:57AM
I don't know much about metallurgy, but I think sintering (fusing metallic powder) might lend itself to the manufacturing of implants. It allows creation of porous metal bodies. Living tissues could grow into the pores in an implant. I would assume people are using sintering for that purpose already.
https://en.wikipedia.org/wiki/Sintering [wikipedia.org]
(Score: 0) by Anonymous Coward on Tuesday July 26 2016, @07:38AM
Gold has a melting point of 1064°C and a boiling point of 2700°C while titanium melts at 1668°C and boils and temperatures ...
Oh come on, it's over 1000°C of margin for both of them to remain in liquid phase!