Bainite kinetic transformation of austempered AISI 6150 steel

This research studies the kinetic transformation and austempering temperature effect on the morphologies of bainite for AISI 6150 steel. A minimum of 10 different holding times for each austempering temperature were utilized. All the AISI 6150 steel samples with original spheroidal pearlite were austenized at 855 °C for 20 min, followed by a lower temperature salt bath for austempering at various holding times. The hardness for each austempered temperature and holding time was measured, and the microstructures were observed by optical microscopy. The kinetic energy for needle like lower bainite and granular like upper bainite was analyzed by using kinetic transformation equations. The aim of this research was to study the transformation of bainite, in particular lower bainite, to obtain improved mechanical properties and higher ductility of AISI 6150 steel, and then apply AISI 6150 steel to more applications.