OT- can someone tell me what this metal is??

True, inthe case of a pure Fe-C system. Quenching some low-alloy content stainless steels fast enough (granted, not possible with large billets) should keep the microstructure intact, but it will put the FCC austenite into a "metastable" situation, but transitions of less then

50% to martensite over long periods of time are typical. As you mention below, in high-Ni or certain Ni-Cr ratios, austenite is stable to room temperature, demonstrating the effect of austenite stabilization.

You are quite right, I tied my thoughts up in a knot here and called them non-related when they were. Alloying and impurity control are critical to most material systems. Materials and thermo 201 there...don't know what happened in the gray matter.

I'm not sure this disagrees with my above paragraph, as martensite is not truly aviodable in a pure Fe-C system, but in Fe-Ni-Cr-C systems it is. But I think we say that depending on the alloying, and cooling rate, we can get either martensite or austenite. Some restrictions may apply. :-)

This one still has me thinking...can all austenitic stainless steels even be hardened by heat treatment? If the microstructure can not be changed appreciably, and we can not achieve grain refinement, what will the hardening mechanism be?

I believe I straightened myself out, now.

Don't forget pearlite/ferrite. Martensite is hard to create in iron-iron carbide alloys containing carbon up to .5%, and impossible to create when the carbon is below .2% like in "mild steel". Over .8% (eutectic) martensite is easy to create. But, regardless of the iron alloy, martensite can only be created if quench fast enough to transform the austenite to martensite. Inversely, and alloy than can form martensite, can be annealed to completely eliminate it.

...or pearlite, ferrite, bainite, trootsite... and most importantly, Fe3C

You're not kidding there. I've been doing this for longer than I will admit, and I still get metallurgical "issues I don't predict.

Other than some "freaky" supper alloys, the answer is no. Austenitic stainless steel alloys can not be hardened by heat treat (quenching).

The only way to harden austenetic stainless steels is to workharden them. Some stainless steels, like 17-4PH can be age-hardened. This is a type of low-heat heat treatment. But still, the hardening is not created by quenching, its a precipitation mechinisim.

Not if you're into metallurgy. You'll never be straight. It's 99% science,

1% magic.

Doc