Method for measuring transformation energy and quantitative characterization of transformation-induced plasticity

A method for measuring transformation energy (E,,) of strain-induced martensite (SIM) and quantitative characterization of transformation-induced plasticity is developed using characteristics of the tensile curve of three metastable austenitic stainless steels, 10Cr18.5Ni8.5Mn1.9SiO.9, 19Cr17.5Ni7.4Mn2.3Si1.0, and 10Cr16.2Ni11.8Mn1.2Si0.7. The results show that the E-pt of tested materials at - 196 degreesC is 11.3, 14.7, and 20.1 X 10(6) J/m(3), respectively; E-pt remains constant in the stages of elasto-plastic instability and stress plateau of tensile curves. As the E-pt, which mainly depends on chemical composition of materials, increases, M-s decreases, but the minimum strain-producing M transformation, e(ph), increases. The average plasticity increment (D) induced by M transformation is 0.17 to 0.20 for the metastable austenitic stainless steels, and it decreases with increasing carbon content of steels. The decrease of stacking fault energy (SFE) is beneficial to the D value.