Effect of matrix structure on the impact properties of an alloyed ductile iron

• Published in: Materials characterization 2006-12, Vol.57 (4), p.290-299
• Main Authors: TOKTAS, Gülcan, TAYANC, Mustafa, TOKTAS, Alaaddin
• Format: Article
• Language: English
• Subjects: Applied sciences; Cross-disciplinary physics: materials science; rheology; Ductile iron; ELONGATION; Exact sciences and technology; FERRITIC STEELS; FRACTURES; HARDNESS; HEAT TREATMENTS; HYDROGEN 7; Impact energy; IRON; MATERIALS SCIENCE; Matrix structure; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; MICROSTRUCTURE; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; SCANNING ELECTRON MICROSCOPY; Solidification; SURFACES; TEMPERATURE RANGE 0273-0400 K; TENSILE PROPERTIES; YIELD STRENGTH
• ISSN: 1044-5803; 1873-4189
• DOI: 10.1016/j.matchar.2006.02.008

An investigation was performed to examine the influence of the matrix structure on the impact properties of a 1.03% Cu, 1.25% Ni and 0.18% Mo pearlitic ductile iron. Specimens were first homogenized at 925 °C for 7 h and a fully ferritic structure was obtained in all ductile iron samples. Then, various heat treatments were applied to the homogenized specimens in order to obtain pearlitic/ferritic, pearlitic, tempered martensitic, lower and upper ausferritic matrix structures. The unnotched charpy impact specimens were tested at temperatures between − 80 °C and + 100 °C; the tensile properties (ultimate tensile strength, 0.2% yield strength and elongation) and the hardnesses of the matrix structures were investigated at room temperature. The microstructures and the fracture surfaces of the impact specimens tested at room temperature were also investigated by optical and scanning electron microscope. The results showed that the best impact properties were obtained for the ferritic matrix structure that had the lowest hardness, yield and tensile strength. Ductile iron with a lower ausferritic matrix had the best combination of ultimate tensile strength, percent elongation and impact energies of all structures.