Why magnesium alloy????

Started Apr 19, 2013 | Discussions thread
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trekkeruss Veteran Member • Posts: 3,899
Re: Titanium vs. aluminum strength to weight ratios...

Joseph S Wisniewski wrote:

trekkeruss wrote:

leicaman wrote:

Magnisium is hard, light and cheap... it can be cast.

Aluminum must be machined and is heavier.

Titanium is the best, lighter and stronger but is hard to machine and hugely expensive.

Titanium is heavier than both aluminum and magnesium.

And that matters why?

I suppose it doesn't; I was merely stating a fact.

Titanium has a strength to weight ratio of  288 kN·m/kg, nearly twice that of magnesium at 158 kN·m/kg. So, something the same weight is twice as strong when made from titanium. Or, if you're aiming for a specific strength, the titanium part is half the weight,

It is more commonly used as a lighter weight replacement for steel.

Except that it's not. Most steels have a higher strength to weight ratio than titanium. So it's worse if you're designing to a particular strength or a particular weight. Where titanium shines is that it's half the density of steel, so if you're designing to a particular volume, it may be adequately strong for your purpose, although weaker than a  steel part of the same volume.

That's why I said it is more commonly used as a replacement for steel, because for a given volume, it is much closer to steel in strength than aluminum or magnesium. But the way a camera chassis is designed, it wouldn't make much sense to use titanium. If made the same exact way, it would be stronger, but a lot heavier. If it was made thinner to offset the weight, the strength would be compromised.

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