Thermodynamic prediction of M-s in Fe-Mn-Si shape memory alloys associatedwith fcc(gamma)-> hcp(epsilon) martensitic transformation

By means of X-ray diffraction profile analysis of three different compositi on Fe-Mn-Si alloys, the relationship between stacking fault probability P-s f with the concentrations of constituents in alloys, 1/P-sf = 540.05 + 23.7 0 x Mn wt% -138.74 x Si wt%, was determined. According to the nucleation me chanism by stacking fault in this alloy, the equation between critical driv ing force Delta G(c) and P-sf, Delta G(c) = 67.487 + 0.177 5/P-sf(J/mol), w as made. Therefore, the relationship between critical driving force and com positions was established. Associated with the thermodynamic calculation, t he M-s of fcc(gamma)-->hcp(epsilon) martensitic transformation in any suita ble composition Fe-Mn-Si shape memory alloys can be predicted and results s eem reasonable as compared with some experimental data.