Microstructures And Mechanical Properties Of Equal Channel Angular Pressed Ultra-low Carbon Steel

With the developments of society and economy in China, requirements of steel materials are increasing, which results in some problems, such as environmental pollution and decrease of energy and resources. Only researching and developing new generation of steel materials can resolve these problems. Microstructure refinement can lead to an increase in both strength and toughness in the methods enhancing the mechanical properties of steel materials, so the microstructure refinement is a important direction of material research.The methods and mechanism of the microstructure refinement in steel materials are introduced in the paper. A new method of microstructure refinement -Equal Channel Angular Pressing (ECAP) is discussed with emphasis. On this basis, microstructures and mechanical properties of equal channel angular pressed ultra-low carbon steel (0. 001%C) are studied by the means of optical microscope, transmission electron microscope and electronic tensile equipment.The ultra-low carbon steel (0.001%C ) is subject to a strain of ~ 10 by utilizing equal channel angular pressing of ten passes with route C at room temperature. The grain size is refined to ~0.3m and the resultant steel exhibited the yield strength over 678MPa with a reasonable good elongation of 47.4%. The test results show that the grain sizes do not reduce further after 6 passes of ECAP ,the slip systems of ferrite is mainly belonging to {110} < 111 >and {112}<111>slip system family during the first and the second pass of the ECAP with route C , and under the annealing conditions of 300℃~550℃ X lh,ultrafme grains are thermally stable. The tensile deformation behavior of the UFG resultant steel is characterized by the absence of strain hardening.