Distribution of the Inclusion Particles in Ferritic Spheroidal Graphite Cast Irons

Abstract

To reveal the distribution of the inclusion particles in ferritic spheroidal graphite cast irons, an electrochemical etching process was developed in this investigation using the Morries solution. Two series of test materials, one with approximate 2.0 mass% silicon and 2.0 to 3.5 mass% carbon (hypo-eutectic to approximate eutectic campositions), the other with approximate 3.5 mass% carbon and 2.0 to 3.9 mass% silicon (approximate eutectic compositions), were chosen for the study. The results indicate that the metallographic features can be revealed successfully after the specimens were etched at 5 V etching voltage for 30 min. The area and length of eutectic cell wall which inclusion particles clustered are varied with the chemical composition of the test materials. For the materials containing approximate 2.0 mass% silicon, the degree of inclusion clustered in the eutectic cell wall increases with decreasing carbon concentration. For those containing approximate eutectic composition, the degree of inclusion clustering increases with increasing silicon content. Comparison with the degree of inclusion clustering, it was concluded that the tensile embrittlement occurs at the materials containing large area (length) of the eutectic cell wall regions.