TITLE:
Mechanical Behaviour of Duplex Phase Structures in a Medium Carbon Low Alloy Steel
AUTHORS:
K.K. Alaneme, S. Ranganathan, T. Mojisola
KEYWORDS:
duplex phase steel; intercritical annealing; fatigue behaviour; microscopy
JOURNAL NAME:
Journal of Minerals and Materials Characterization and Engineering,
Vol.9 No.7,
July
20,
2010
ABSTRACT: The mechanical behaviour of duplex phases produced in a medium carbon low alloy steel with potentials for use as machine body parts and vehicle panels, has been investigated. A representative composition of the steel (C: 0.3; Si: 0.28; Mn: 0.97; Cr: 0.15) was utilized to produce ferrite – martensite duplex phases of varied proportions by intercritical annealing treatment. The tensile, hardness, and rotating bending fatigue behaviour of the structures were studied; and optical and SEM microscopy utilized to characterize the microstructures and their fracture characteristics. The duplex phase structures exhibited continuous yielding behaviour; and were characterised by high strain hardenability, high tensile strength, total elongation, toughness and superior fatigue strength (endurance limit) in comparison with the normalised structure. The fatigue fracture was observed to be characterized by mixed mode of ductile (dimple) fracture and intergranular brittle cleavage for the duplex structures. Superior tensile and fatigue property combinations were better harnessed when treatment was performed at 760℃ and 780℃ in comparison to 740℃.