OBSERVATION OF PSEUDOELASTC BEHAVOR NULTRAF NEGRANED FE-10NI-7MN (WT 6) STEELDUE TO REVERSE MARTENSITE TRANSFORMATION

Fe-10Ni-7Mn (wt.%) steel is a member of ultrahigh strength steels which shows good ductility in solution annealed condition and excellent age harden ability. In the current research, this alloy was subjected to heavy cold rolling. Reverse martensitic transformation was occurred during deformation. The stored energy through heavy cold rolling process and required driving force for austenite formation was calculated by mechanical and thermodynamic equations, respectively. The result of calculations showed that straining more than 0.92 leads to displacive austenite formation. Stability of austenite at room temperature is related to ultrafine grain size of austenite after deformation which prevents the austenite to martensite transformation. The presence of ultrafine austenite formed by displacive mechanism leads to observation of new mechanical properties during cyclic tensile test. This behavior is known as pseudoelastic phenomenon. In this behavior, during loading-unloading tensile cycle, the shape of the specimen return to its original configuration with a hysteresis loop in its path to the Zero strainpoint.

کلیدواژه ها:

Fe-10Ni-7Mn (wt %) alloy ، cold rolling ، reverse transformation ، Pseudoelastic