Microstructural Evolution of High Phosphorus Steel Using Warm Multiaxial Deformation

Abstract

High phosphorus steel is deformed by warm multi-axial deformation (MAD) process under severe plastic deformation technique to investigate the microstructural evolution and mechanical properties. In this process high phosphorus steel is multi-axially deformed under warm condition at temperature of 600⁰C. Microstructural evolution during different MAD passes is characterized by light optical microscopy. The mechanical properties have been investigated using tensile and Vickers hardness tests, and the fractographs of the fracture surface were observed by scanning electron microscope. The substructure was formed, as the number of MAD passes increased. The fragmentation starts as the MAD passes increased from 6 to 9, further the subgrains were formed in 12 MAD passes. Additionally, with increasing the MAD passes to 15, the subgrains were further refined and equiaxed fine grained material with more dense grain boundaries was observed. This microstructural evolution occurs due to sub division of grains results grain refinement, and grain size reduced from initial average grain size of 184µm to 22µm. It is also observed that the mechanical properties are enhanced such as tensile strength increased from 187 MPa to 644 MPa, and the hardness increased from 132 VHN to 343 VHN.