Alloy

[Dave Plowman (News)]

I'd always thought an alloy was a mixture of metals. Seems some dictionaries reckon it's just a metal mixed with anything. And by that definition, steel is an alloy.

Comments?

[John Laird]

My preferred Chambers says "extended to mean a mixture of metals and non-metals". I've always personally thought of steel as an alloy of iron, the alternative nomenclature presumably being a mixture (it's not technically a compound). Especially as many steels do contain other metals.

[Dave Baker]

Technically anything other than 100% pure metal element is an alloy. Steels are routinely classified as high carbon alloys, low carbon alloys etc. Carbon is a non metallic element but the term alloy has always applied.

I would say that provided the majority of the material is metallic then it's an alloy. If the majority is non metallic I suppose the term composite might be better.

[Mary Fisher]

All steels contain other elements.

Mary

[Dave Plowman (News)]

Steel isn't an element. It's basically iron and carbon.

But you get some described as 'alloy steel' - which seems strange if it's already classified as an alloy.

[Set Square]

The term seems to be used these days to describe a metal with additives to improve/strengthen it.

Time was when the term meant impure or debased - as "So may we with holy joy, Pure, and free from sin's *alloy*, All our costliest treasures bring, Christ, to Thee, our heavenly King."

There, I bet you wish you'd never asked!

[OldScrawn]

I'd disagree with that, Dave. Alloy steel usually means steel containing chromium or other elements to increase corrosion resistance, strength, creep resistance, etc. People talk of high carbon steels, which are hardenable and difficult to weld, and low carbon steels which are not hardenable, but easy to weld. Mild steel has pretty low carbon, but if it is made from scrap it may contain traces of all sorts of alloying elements.

[Mary Fisher]

Well, that's Time Was. Nowadays I'm not sure that just because something isn't pure it's debased ...

In the case of iron you can have some far superior alloys for specific purposes.

Not at all. It's one interpretation.

Mary

[Andy Dingley]

Not just anything - carbon and silicon (and a few others) are honorary metals in this case. As carbon and iron are mutually soluble, then steel is an alloy.

The definition of "alloy" depends on what period you're talking about, and what industry. Throughout the 19th century the question of whether steel was truly an alloy or not (and where the carbon was hiding) flip-flopped both ways.

[Mary Fisher]

metalloids

[G&M]

I would regard an alloy as any mixture of elements where the metallic crystalline structure is maintained. For instance the Silicon Germanium mix used in some semiconductors is an alloy but silicon in it's natural oxidised state - sand - isn't an alloy.