Formability of Ultrafine Grained Steel

Ultrafine grain refinement to 1 m deteriorates the uniform elongation in the tensile tests of steels. Such loss of ductility has been argued to be an inherent feature of the ultrafine-grained steels. While uniform elongation is a measure of ductility of the material, reduction in area in tensile tests is also an important measure of ductility. Ultrafine grained steels with different carbon contents from ultralow carbon to high carbon were produced through warm caliber rolling and evaluated for their stress-strain behavior along with the reduction in area. It was found that the reduction in area- tensile strength balance is far better than the conventional ferrite+pearlite steels and even superior to bainitic steels for all materials tested in the present study. Formability of ultrafine grained steel is examined by applying to make a micro screw. Good formability was verified by this process.