Austenite in stainless steel is meta-stable. So, when it deformed, it transforms to the more stable phase, martensite. This transformation is a function of temperature and degree of deformation. The stability of the austenite is expressed as the temerature at which 30% deformation (uniaxial tension) produces 50% transformation. It is related to composition in the following way: Md30(C)=413-462(C+N)-9.2Si-8.1Mn-13.7Cr-9.5Ni-18.5Mo Any alloy addition lowers the Md30 and stabilizes the austenite.