I get really pissed off when I see consumer products marketed that are constructed of "surgical grade" or "aircraft grade" alloy/steel/aluminum/titanium. The inkling that this stuff is made out of some kind of advanced superalloy is totally bogus and misleading assertion.
First things first.
The two greatest criteria in selecting a metals for use within the body are:
1) that it is inert to blood and other body fluids
2) it will not undergo corrosion in the time from manufacture, sterilization, and aging. Or in the body if it's implantable.
Strength is often an afterthought for most medical materials. Fitting into the "almost never a consideration" category would be weight. Oh yeah, and stainless steel is relatively cheap.
Check this out. They should really be calling it Cutlery steel. This is from 1915, when most surgery was generally performed with a hacksaw.
The greatest criteria in selecting a metal for use in an airplane are
1) Strength to weight ratio (specific strength, for you geeks out there)
2) Fatigue resistance
3) Creep resistance (for the layman, creep is an engineering term for the weakening of a metal at high temperatures over long periods. I'm not talking about that guy mumbling to himself on a downtown street corner, that is an entirely different creep resistance -- a steely gaze and big biceps are the best in this regard)
4) ability to form into complex shapes
5) corrosion resistance - although aircraft often employ complex coating systems as well.
Anways, generally you hear "aircraft grade" applied to 6061-T6 and 6Al-4V titanium. Incidentally, these are the most common alloys of the two respective base elements you'll find.
Here's something you probably didn't know. simple carbon steel is stronger than pure titanium, most titanium alloys, and almost all aluminum alloys. Care to know what you add to aluminum to make it as strong as steel? Guess! I bet you're wrong! Answer: Copper. about 3% by weight and then a sophisticated heat treatment.
Even better yet, sometimes 6Al-4V is sometimes reffered to "military grade!" That's gotta have every basement nerd jizzing their pants in ecstasy. Actually, 6Al4V is by design almost identical in property to common stainless steel, just lighter. That's about it.
Here's what you'll never see. Some company hocking a "surgical grade" gadget made out of Nickel Titanium, MP35N, Cobalt Chrome, Tantalum, Tungsten, 17-4PH(my favorite flavor of stainless steel), or Platinum.
sidebar: Speaking of Platinum, I don't understand the fascination. Platinum is not an attractive metal -- its a dull grey, nor can it become shiny unless you alloy it with something -- Iridium is generally the choice. But even then it can't hold a mirror polish like stainless steel can, and it's not nearly as hard, and will scratch & mar quite easily.
I bet you've never seen an "aircraft grade" doohicky made from Hastelloy, Waspalloy, Inconel, or CMSX single crystal alloys.
Now. Let me tell you about some cool metals. Brace yourself, this is going to be AWESOME.
Palladium - indistinguishable from platinum but about 1/3 the price, it absorbs up to 900 times its volume of hydrogen under standard conditions.
Beryllium- the lightest of all (mostly) non-reactive metals, it is also extremely stiff. Used primarily in satellites, missles, and supersonic aircraft.
Rhenium - the last metal on the periodic table to be discovered; it is about as dense as platinum, has a melting point second only to tungsten, and its one of the most rare metals on the planet - many times more rare than platinum or gold.
Indium-a relatively weak metal that makes high pitched screams when you bend it.
Astatine- Its isotopes have half lifes of between 8 hours and 125 nanoseconds, so you could have kilos of it in your hand, and it would dissappear before your eyes. Actually, it would emit so much radiation that it would probably cook you down to charcoal in the process, but that's cool, right? Too bad that in all of North & South America to a depth of 10 miles deep, there's probably only about 1 trillion At atoms at any given time. (found that on wikipedia)
Tellurium- a metal that when exposed to humans, even in very low concentrations, gives them a garlicly smelling breathe.
Thermite - a mixture of steel and aluminum that gets so hot that when ignited, a dollop of it could pass through the block of a V8 engine.
So now you can laugh the same way I do when you hear all this nonsense.
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