오스테나이트계 스테인리스강의 강도와 자성 특성에 미치는 적층결함에너지 및 상안정도의 영향

Abstract

In this study, the effects of stacking fault energy and phase stability on the mechanical and magnetic properties of austenitic stainless steels have been investigated using conventional 301 STS and newly designed stainless steels. While 301 STS has high strength with the formation of martensite phase in cold-rolled specimen, it is not suitable for the foldable smartphone components due to the magnetic properties. In order to achieve non-magnetic properties while having high strength, stacking fault energy and MD30 value were adjusted. Specimens were prepared by hot rolling and cold rolling. The prepared specimens were subjected to optical microscope observation, EBSD, X-diffraction, tensile test, delta ferrite measurement, and magnetic measurement experiment. As the result of the tests, with lower value of Md30, non-magnetic properties appeared by suppressing martensite transformation, but that led to the dramatic decrease of the strength. By increasing stacking fault energy value to compensate the decreased strength, strain hardening rate has increased with the formation of twins while satisfying the nonmagnetic properties. Therefore, in order to improve strength while having non-magnetic characteristics, it is necessary to satisfy low stacking falutenergy and low Md30 value.