Structural and Mechanical Characteristics of AISI 420 Stainless Steel After Annealing

The temperature influence on the structural and mechanical properties of AISI 420 stainless steel is studied. The iron-based alloy underwent normalizing at three temperatures 975, 1025, and 1075°C for 1 h, followed by annealing at temperatures ranging from 250 to 650°C for 2 h. At both treatment stages, steel is air-cooled. The material was examined with nanoindentation, macrohardness, scanning electron microscopy, light microscopy, and X-ray diffraction. For each normalizing temperature, the two stages of the mechanical behavior were observed. At the first stage, in which macrohardness and nanohardness decrease slightly over temperature range of 250–450°C, and the second one is characterized by a significant loss of these mechanical properties corresponding to 550 and 650°C temperatures. At the microstructural level, softening of AISI 420 steel occurs due to dissociation of large cementite into smaller spheroids.