Austempering Ce-La inoculated solution strengthened ferritic ductile cast irons

Abstract

The influence of austempering conditions on the microstructure, hardness, tensile strength, and impact toughness of Ce-La inoculated solution-strengthened ferritic ductile irons was analyzed. The austempering was performed at temperatures 280, 320, 420, 520, and 620◦C for periods of 1.5 and 2.5 h. Metallurgical characterization of the samples was determined using scanning electron microscopy, optical microscopy, X-ray diffraction, microhardness, impact, and tensile test. The fracture surfaces of the tensile samples were examined by scanning electron microscopy. Austempering heat treatment significantly enhanced the mechanical characteristics of solution-strengthened ferritic ductile cast iron. This led to the birth of solutionstrengthened Ce-La inoculated ferritic cast iron, a new spheroidal graphite cast iron family member with a unique microstructure in an ausferritic matrix. Samples austempered for low temperature exhibited higher impact toughness and tensile strength due to the nano-sized ausferrite phase. Austempering for high temperatures displayed higher elongation.