Influence of Pearlite Formation on the Ductility Response of Commercial Hadfield Steel

Abstract

This manuscript presents the singular event of pearlite occurrence in commercially produced Hadfield steel. A detailed characterization of the microstructure is performed and its influence on the mechanical properties of the material is analyzed. The found microstructure may be interpreted as carbide formation if observed at the optical microscope. However, it consists of an extremely fine lamellae structure ranging from 40 to 130 nm of thickness. Experimental evidence of pearlite formation is supported by microhardness measurements, X-ray diffraction and secondary electron microscopy. The pearlite is located on the austenitic grain boundaries and within by means of intragranular islands. The occurrence of this phase is detrimental for the ductility response of the material assessed by means of uniaxial tensile testing and reduction of area determination. It is observed that a pearlite fraction of 20 % is responsible for a reduction of 90 % in elongation at fracture and a drop of 80 % in reduction of area. A short heat treatment performed at 1050°C allows recovering the ductility response of the material keeping grain size and chemical composition unchanged.