ing temperature as well as with an additional share of pearlite in the matrix, while it significantly increases with rising strain rate. Simultaneously, elongation af- ter fracture is significantly reduced by increasing strain rate, decreasing temperature and increasing pearlite share. The corresponding characteristic values – de- termined from the technical stress-strain curves – are shown in Figs. 5-8.


While strength is slightly reduced with a growing graph- ite particle diameter (to which an increasing ferrite grain


size corresponds), ductility does not show a variation (see Figure 9). This demonstrates that a distinctive consider- ation of ductility and even strength is not possible based on the graphite particle size as a single graphite morphol- ogy parameter.


Similarly, strength and ductility are not sensitive to the product of graphite particle shape and distance, which has proven to be an appropriate representation of the graph- ite particles notch effect and the ductility of the ferrite matrix (Figure 10). In contrast, the fracture mechanical


Figure 1. Influence of strain rate on true stress-strain curves of ferritic EN-GJS-400f at room temperature.


Figure 2. Influence of strain rate on true stress-strain curves of ferritic EN-GJS-400f at -40°C.


Table 2. Microstructural Parameters (NA – particle count per area, λ - mean distance between graphite particles [nearest neighbor distance], f – shape factor, dG – mean value of particle diameter in different directions, dF


– ferrite grain size).


28


International Journal of Metalcasting/Volume 8, Issue 2, 2014


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