Question: The group that we are in is called Zirconium, which is said to be used for artificial limbs, how do they make artificial limbs? If you have an artificial limb made from zirconium wouldnt it become a liquid if the temperature is a little below room temperature?

John Welford answered on 3 Jul 2012:

Zirconium is a metal that has a melting point of 1855 °C. At all temperatures below that it is a solid. So if you had an artificial limb with zirconium in it the rest of you would be pretty frazzled before it started to melt!

There are not many metals that are liquid near room temperature, mercury is the most common one – perhaps you are thinking of that?

Zirconium has been shown to have no adverse effect on living organisms, this is called “biocompatibility”. It is also very resistant to corrosion and can be made quite hard and tough. This makes it very good for use in artificial limbs, particularly in joints.

One of the most common joints that requires artificial replacement in humans is the hip joint. This is a ball-and-socket type joint that takes a lot of load and can get worn and damaged. A hip replacement removes the bone ball and socket and screws a new manmade ball and socket in their place.

Commonly the socket is made from a plastic material and the ball and connection to the leg bones is made from metal. The metal was originally stainless steel, but the body can react badly to this, so titanium or chromium alloys are now commonly used. Zirconium is a relatively new option for this but seems quite promising due to its biocompatibility, strength and smoothness.