[AlwaysQuestioning]

Hi guys. According to wikipedia,"Tungsten with minor amounts of impurities is often brittle[5] and hard, making it difficult to work. However, very pure tungsten, though still hard, is more ductile, and can be cut with a hard-steel hacksaw." My question is , when is tungsten hard, which since hardness means the ability to deform something, means that tungsten isn't malleable. But how does it translate to ductility? Isn't ductility and malleability similar to an extent that both have to do with the ability of the orderly layers of atoms to slide over one another when a force is applied?


Or does it have to do with the high density of tungsten?


Thanks in advance!

[Corribus]

Malleability and ductility are similar properties but not identical, because they are responses to different types of mechanical stress.  Often a ductile material is also malleable, but not always.

http://en.wikipedia.org/wiki/Malleability

[curiouscat]

Lead is malleable but not ductile.

What's a reverse example, I wonder.

[Corribus]

It's all relative, right?

According to An Introduction to the Study of Metallurgy By Sir William Chandler Roberts-Austen, "Malleable metals are also ductile, but they do not possess the two properties in the same order. Arranged according to their malleability, the most important metals follow this order: 1. Gold, 2. Silver, 3. Copper, 4. Tin, 5. Platinum, 6. Lead, 7. Zinc, 8. Iron, 9. Nickel.  The order of ductility, on the other hand, is: 1. Gold, 2. Silver, 3. Platnium, 4. Iron, 5. Nickel, 6. Copper, 7. Zinc, 8. Tin, 9. Lead."

So it would I guess be appropriate to say that copper is far more malleable than iron, but iron is more ductile than copper.  These properties depend a lot on temperature and probably also the rate at which force is applied.  I believe zinc is pretty brittle at room temperature but heated up slightly, it can be pounded out into thin sheets. Like anything else, it's rarely simple.

[curiouscat]

True, but can one make lead wires? In any reasonable size.

I know one gets lead sheets.

Conversely, I wonder if someone can name a case where wires are easy but sheets not. That's what I meant.

Additionally, when your Reference ordered them wonder how he measured those properties. I'd be curious to know of a quantitative measure of ductility and malleability.

[Corribus]

Honestly I couldn't tell you.  Solid mechanics is not really my area of expertise.  I assume ductility is measured by elongation at break or something of the sort.