| The effect of cooling rate from the intercritical annealing temperature on the mechanical properties of dual-phase steel was investigated using a Fe/1.8Mn/1.4Si/0.07C alloy and the results were explained in terms of the microstructures. It was found that within the range of cooling rates studied, better property-combinations were obtained as the cooling rate was slower. Microstructures of the specimen slow-cooled at 5℃/sec. were characterized as fine dispersion of martensite, considerable amount of the retained austenite up to 8% in volume, most of which transformed to martensite upon tensile strain in the strain range 2-6%, and low dislocation density in the ferrite matrix. Those microstructural characteristics in 5℃/sec. cooled specimen were considered responsible for higher strain hardening rate than that of water-quenched specimen during the post elongation after initial 2%, and hence resulted in larger elongation in 5℃/sec. cooled specimen. |
|
