I'm looking at a bike.
The Fork is described as CRMO.
1) Is this aluminum or steel?
2) What does "alloy" mean? Aluminum or steel?
Thanks

CroMo, crmo, etc are cro molly steel alloy. Alloy can be any combination of metals , like two different types of aluminum making it a new grade, like 6010.

CrMo, also called Cromolly, etc., is a steel. Usually at least a decent steel fork, compared to ones with stickers that say Hi-Ten, 1020, High Carbon, etc.

Technically an alloy can be all kinds of things. Pretty much any metallic bicycle part will be an alloy, whether it's mainly aluminum, steel, titanium, magnesium, beryllium (I think the last two would be alloyed, anyways, not sure).

In olde bicycle marketing parlance, alloy referred to aluminium alloy. Still alive today, I reckon.

Chromium Molybdenum steel- usually alloy 4130.

Just to repeat the above, almost any metal used in a bicycle (and perhaps other manufacturing) is an alloy of some sort. Iron, aluminum etc are apparently not suitable in their pure forms for bicycles.

Steel is by definition an alloy (usually of iron and carbon)... different steels add other materials (such as carbon, chromium etc)

If someone says alloy in reference to bikes, they do often mean aluminum... or more precisely aluminum alloy as opposed to steel alloy.

CROMO is good steel but there are also other good steel alloys. (See? Alloy is not just aluminum.)

Chro-molly steel is baseline for a quality fork. Hi-ten steel is really low-end.
Next up from Chro-molly steel is the same material in "butted" tube profile

Cromoly steel is inexpensive these days... mainly because high end air hardened steels have taken over the premium end of the market once commanded by cromoly.

Double butted cromoly makes for a sweet compliant ride.

Just to make it more confusing.

In the steel world, they divide steels (all of which are alloys) into three basic classes. Carbon, Alloy, and Stainless steels. In this context, the alloy steel category includes steels with various alloying elements, such as chrome, molybdenum (ie. CrMo), nickel, manganese, vanadium, etc. added in significant quantities to improve strength toughness or other desired properties.

These are usually used in combinations and the steel will be classed by the the elements mixed in highest quantities, such as Chromoly, nickel/chrome/moly, boron, manganese, or one that was popular for bikes a while back; nivachrome (nickel/vanadium/chrome).

BITD, the term alloy was popularized in the bicycle world as light alloy, meaning aluminum which is a relatively recent innovation (50s/60s) when it began to supplant steel in things like hubs, handlebars and cranks. Later, light alloy was shortened to alloy, and I still consider it shorthand for aluminum when used alone.

So alloy is another of those words with multiple meanings depending on the context.

Mixing more than 1 elemental Mineral , molten, in a Metal is called alloying . Industry assigns Numbers to differentiate what is in the Alloy Mix.

The common designation for Chrome Moly Steel .. is 4130.. Trade marked Products have other names they chose.

Aluminums also have Numbers.. 6065 is specific as is 7001 the first number of the group tells you the largest % of non aluminum added.

the 1000 group is pretty much all aluminum OTOH 7000 adds Zinc.

GENERAL ALUMINUM INFORMATION from Aircraft Spruce