Fatigue cracks analysis in high-strength bainitic steel

M.C. MARINELLI; M.C. MARINELLI; U. KRUPP; U. KRUPP; M. BALBI; M. BALBI

Darmstadt

Congreso; Materials Science and Engineering; 2018

DGM - Deutsche Gesellschaft fur Materialkunde e. V

Nowadays, the most modern bainitic steels are designed with much reduced carbon and other alloying element concentrations exhibiting excellent mechanicalproperties and are widely applied in the automobile industry as crash reinforcement bars to protect against sidewise impact and for injection lines (underpulsating loads) in common rail diesel engines [Ca09]. Although most applications of high-strength bainitic steels as structural materials are exposed to dynamiccyclic loading, only a limited amount of research has been reported concerning the fatigue induced damage in these types of steels. According to some authors[Zh15, Bh12, So14], fatigue microcracks nucleate at the interface between the bainitic ferrite and the retained austenite regardless of the strain amplitudeimposed. Other authors [Zh16, Br12, Re15, Ma17] reported that microcracks initiate along slip bands and show transgranular propagation and eventually form acoalescence of short cracks. In order to understand the behavior of microcracks, it is proposed a gradual monitoring of them during low cycle fatigue at di×erentplastic strain amplitudes by means of optical and electron microscopy along with EBSD data analysis.