Is Magnesium considered a soft metal??

B

Bob Litt

Joined
Feb 7, 1999
Messages
94
And how does it compare to Titanium in terms of stiffness - more or less flex?

Thanks in advance for any comment
 
Originally posted by GarageBoy
Mg is softer than Ti, it's also flammable and brittle, so good luck with heat treatment
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its only flammable in shavings or as fine powder. solid blocks of Mg will not burn
 
Mg also has very little corrosion resistance. Old magnesium (not aluminum "mag") wheels would literally turn into dust in the wet
 
Hey Gollnick...

Yup,, you are correct.. LOL

They do burn,, and boy Do They!

We use to pull the Mag rods out of old water heaters,, stick them in the middle of the back yard and light'M up with a blowtorch at parties...

2 or 3 of them, and it would be like daylight...

A 3 foot bar would last quite awhile ...

No I'm Scrounging for the stuff.. LOL

ttyle

Eric...
 
Wow, these are some excellent information....I appreciate all the responses.

The reason for my question was there's this company making snowboard bindings out of magnesium rather than the traditional aluminum or polymer.

I'm thinking the advantage of magnesium is light weight, dampen virbration, but at the same since it's a softer metal, it should flex more than aluminum - which means less responsive in terms of energy transfer.

Also, the part about Magnesium having very little corrosion resistance is a bit disconcerting, because the bindings will be in constant contact with snow.
 
The Mg has been painted or coated in ski bindings. Trust me, Mg does not like water. (an old Chem experiment is to place Mg in water and watch bubbles form as metal ionizes)
 
There was an Intro To Chemistry class that I used to student teach in college. One of the labs involved strips of Mg, and some other things, teaching the art of observation. Someone disposed of the Mg strips in the trash can with some wet paper towels, and we had a nice little fire going! Freaked some of the kids out, but I learned my lesson!
 
Oops, double post. I always wondered how that happens...

First time for everything.:p

DD
 
There is a similarity between Ti and Mg, they both have a hexagonal crystal structure. They use Mg on ships as sacrificial anodes (anodes dissolve instead of hull).So mixing with other metals with moisture is not a good idea. Yes it burns ,thats why they make flares and incindiery bombs with Mg. Machining Mg requires special safety precautions. For the bindings you would of course be using an alloy, perhaps with Al. And I'm sure there would be a corrosion resistant coating also.
 
Fun fact - the Army had a tank named the Sheridan that had a turret made of Magnesium. Once it got going, those turrets would burn and burn and burn....
 
Magnesium is less stiff than aluminum (magnesium has a Young's modulus of 6.4 Mpsi vs 10 for aluminum). The primary advantage of magnesium is that it is light (it has a specific gravity of 1.74 vs 2.70 for aluminum). I used to file magnesium bar stock to make powdered mangesium for fireworks. Magnesium feels more brittle and aluminum feels more ductile.

Titanium is stiffer and heavier than either of the above. It has a Young's modulus of 16 Mpsi and a specific gravity of 4.54. So titanium is 2.5 times stiffer than magnesium and is about 2.6 times heavier.
 
Magnesium won´t burn if you put it in the oven, but everybody knows it will if you "flame" it. That kind of substances are said to be pyrophoric. The pyrophoric metals are magnesium and calcium, and if finely shreded aluminium, zinc and nickel too. ¿why do yo think the Concorde went to hell, lost half a wing without an explosion and flipped over by unbalanced sustentation?. As simple and tragic as that: a wing was burnt.
Gollnick is right, no matter how big a magnesium block is, it may burn.
By the way, that Concorde thing only happened because the engines were right under the wing, with no space in between. If you look at any other commercial aircraft you will notice that the engine is attached to the wing via a "bar". No problem with those, don´t worry.
 
Hi Bob. More than likely, the magnesium used in ski equipment is not pure mag. AZ91E is the alloy most often used for auto racing wheels, cel phone covers, etc, and it's cast. I would guess that is what is being used for the ski equipment. We have a prototype knife made from AZ91E and it is a most impressive material.

It's stiff, strong doesn't burn and must be anodized to prevent moisture problems. It is also ligher than Titan.

sal
 
In our foundry we cast aluminum at about 730 Celsius. At this temperature some of the magnesium burns off. We use A356 with an optimum Mg content of .33% When it is necessary to add Mg to compensate for burn-off, we add alloy sheets of 75% Al and 25% Mg. the low Mg concentration is for safety and stability, but even these will burn in a hotter furnace.

A356 is 92% Al, 7% Silicon, .33% Mg, not less than .10% Ti and not more than .25% Fe. The balance is trace amounts of Chromium, Nickel, Manganese, Copper and Tungsten. By contrast with the Mg, Titanium tends to settle out of the molten bath at about the same rate the Magnesium burns off. The metal must be "stirred" to re-suspend the Ti in the alloy.

If you have a compound bow with a cast riser, odds are it is made of an aluminum-magnesium alloy with the mag being around 10% (IIRC). I'm sure there are different alloys used in machined-riser bows.
 
I have a pair of shades made from Magnesium alloy with a ceramic coating. I would have never bought em if it wasnt my facination with metals and alloys. Great for shades....light and strong.
 
They still make water heaters like that. I don't remember how to remove the Mg rod, but they should be relatively easy to do since they are replacable.
 
Well, just down the street a water heater appeared. The liquid rust comming out as I rolled it home was a harbinger of unfortunate things to come.
After cutting away some sheet metal so the wrench wouldn't slip, and resorting to banging on the wrench handle with a hammer, I finally got the darn thing to come loose (another forboding event).

To my disgust, the rod was gone, completely eroded away, leaving a nubin of pitted steel rod. :grumpy: :mad:

While beating on the tank in frustration, I figured out the story: Because the sacrafical cathode had been completely consumed and not replaced, the water heater rusted out, and so was discarded.

So I rolled the bloody thing back up the street to where I got it from.
 
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