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IVIechanical Behavior of a CrMo Steel vith Tempered Martensite. and Ferrite-. Bainite-martensite. microstructure. . I. A. Salemi 1, A. Abdollah-zadeh2,. H. Assadi2, M. Mirzaei3. IDepartment. of Materials. Eng., Islamic. Azad. University-Karaj. Branch, P. O. Box:. 31485-313,.
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IVIechanical Behavior of a CrMo Steel \vith Tempered Martensite and Ferrite-. Bainite-martensite microstructure \ I . A. Salemi 1, A. Abdollah-zadeh2, H. Assadi2, M. Mirzaei3 IDepartment of Materials Eng., Islamic Azad University-Karaj Branch, P. O. Box: 31485-313, Karaj-Iran 2Department of Materials Eng., Tarbiat Modares Lniversity, P. O. Box: 14115-143, Tehran-Iran 3Department of Mechanical Eng., Tarbiat Modares University, P. O. Box: 14115-143, Tehran- Iran Abstract This study is concerned with a correlation between the microstructure and mechanical properties of 42CrMo4 steel, used for press~re vessels applications, with two different microstructtlres. Quench tempering and step quenching heat treatment produced a tempered martensite and an equiaxed Ferrite- Bainite-Martensite (F-B-M) microstructure, respecti\ely. Tensile test results indicated a yield drop effect in F-B-M microstructure with ferritic matrix. This effect was not observed on the specimens with tempered martensite and F-B-M microstructure with hard phase B-M matrix. This effect can be attributed to dislocation generation in ferrite phase during bainitic and martensitic transformations. Fr~ctographic investigations indicated intergranular cleavage in F-B-M microstructure and micro void coalescence in tempered martensite microstructure can be attributed'to carbide formation in martensitic structure during tempering micro void coalescence in tempered martensite microstructure. Keywords: Microstructure, CrMo steel, Mechanical Behavior, Cleavage fracture Introduction The influence of microstructure on mechanical property behavior in steels has been a subject of considerable research interest for many yearsl-5. The microstructure of co:nventional steels often makes it impossible to obtain concurrently good ductility, toughness and high strength. Evolution of newer steel with improved combinations of strength, ductility and toughness has led to the emergence a series of mixed or multi-phase structure in which Advanced High Strength (AHS), so repre~ent a distinguished class6-12. Some applications, especially transportations require economical high strength steel with good ductilit:. and formability. AHS steels were developed to satisfy an increasing need, primarily in the automobile industry, for new high strength steels that permit weight reduction without dramatically increasing costsI2-17.The mechanical property of