Low cycle fatigue and post fatigue tensile behavior of a non-conventional austenitic stainless steel

Abstract

Traditionally, stainless steels find a wide range of applications, which include pipelines, automobiles, engine and gear parts etc. In many of these applications, structures and components go through fatigue loading ranging for low cycle to high cycle. ISO/TR 15510 X12CrMnNiN17-7-5 is a special grade of austenitic stainless steel, which is developed to conserve nickel and is used in automobile parts such as automotive trim, automobile wheel covers, flat conveyer chains, railroad passenger car bodies. The aim of this project is to explore the low cycle fatigue behaviour and its effect on the tensile properties of the abovementioned non-conventional stainless steel, which is unavailable in literature. Attempts have also been made to understand the microstructural variation due to deformation in the steel, as the structure is austenitic, hence metastable in nature. For these purposes a set of non-conventional austenitic stainless steel rods were annealed by soaking at 1000°C for one hour these were followed by water quenching prior to machining.The fatigue studies have been carried out at four different strain amplitudes (at ambient temperature) up to 100 cycles, which have been followed by tensile tests on the fatigued samples at constant crosshead speed of 1mm/minute. The low cycle fatigue results include that the steel undergoes cyclic softening behavior, which has also been reflected from the post-fatigue tensile results X-ray diffraction studies indicate that deformation induced phase transformation takes place in the steel due to combined effects of fatigue and tensile loading. The extent of phase transformation has been estimated and is correlated with the extent of deformation.