Clearly, you have some specific alloy issues possibly relating to an engineering or design problem you are working on. It appears to me then you are seeking some free consultation. I will cover some basics but you need to be talking to a local metallurgical engineer who can help with the specifics of your problem.

First, you mention two different alloys A-479 is a type 405 ferritic alloy, 11.5 - 14.5 Cr, 0.8 C, and no nickel. This single-phase BCC alloy is not heat treatable. The XM-19 alloy is a type 209 austenitic stainless steel, sometimes called Nitronic 50, 20.5 - 23.5 Cr, 0.6 C, 4 - 6 Mn, 11.5 - 13.5 Ni, plus all kinds of minor alloying elements. This stable, single-phase FCC alloy is also not heat treatable but gets its strengthening from cold work.