This investigated how silicon contents (varied from 2.1 wt. Percent to 5.2 wt. Percent Si) affect the fracture behavior of ferritic spheroidal graphite (SG) cast irons under resonant vibration. Experimental results indicated that the initial deflection amplitude of specimens increase with increasing silicon contents. The D-N curves (Deflection amplitude vs. Number of vibration cycles) of all test materials show two-steps manner, i.e., region I and region II. The vibrational fracture behavior can be concisely divided into four steps, namely (1) crack initiation, (2) crack linking, (3) the major cracks formation, and (4) deepening of the major cracks in the through-thickness direction of specimen. The initial three steps correspond to the region I period of the D-N curves, and the fourth step occurs in the region II period. As increasing silicon contents (excepting 5.2 Si specimen), the eutectic cell wall inclusions are more crowded and the crack propagation path is more tortuous. So, the vibration fracture resistance can be enhanced by decreasing the silicon content and with dispersive inclusions in the eutectic cell wall.
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