Harmonic Structure Design of a SUS329J1 Two Phase Stainless Steel and Its Mechanical Properties

In the pursuit of creating new structures with improved overall mechanical properties, we produced a duplex stainless steel with both high strength and good plasticity, which combines in a harmonized way a refined microduplex structure with a coarse structure. This is accomplished by applying a mixed process of mechanical milling followed by spark-plasma sintering for a duplex steel powder, leading to a microstructure with a gradual and continuous transition between coarse and ultra-fine-grained regions at the microscale. This type of structure is referred to as Harmonic. The grain refinement at the surface of the milled powder particles occurs through the recrystallization of the severely-deformed surface layers during sintering, and results in a microduplex structure which gradually transitions to a coarse duplex structure away from the particles surface. Both the recrystallization mechanism and the effect of this refined structure on the sinterability and final mechanical properties of the compacts are investigated.