Macro and microscopical approach to the damaging micromechanisms in a ferritic ductile cast iron

The influence of the graphite nodules morphology (shape, dimension and distribution) on ductile cast irons (DCIs) mechanical properties is experimentally confirmed both in static, quasi static and cyclic loading conditions. According to the most recent results, these graphite elements cannot be merely considered as ‘‘microvoids embedded in a metal matrix’’, but their presence implies a modification of the damaging micromechanisms, depending on the metal matrix microstructure. In this work, a fully ferritic DCI has been investigated: tensile tests have been performed on notched mini tensile specimens. Specimens lateral surfaces have been observed by means of a Scanning Electron Microscope (SEM) during the tests (‘‘in situ’’ tests) at different magnifications. Considering the results obtained at low magnification, quantitative image analysis has been applied in order to investigate the triaxiality evolution during the test.