High temperature mechanical behavior of an harmonic structured AISI 304L stainless steel

Harmonic structured materials are constituted by a network of fine grains surrounding coarse grained cores. This peculiar microstructure ensures a good combination of strength and ductility. The harmonic microstructure is obtained via powder metallurgy through a controlled ball milling process followed by a Spark Plasma Sintering consolidation. Different studies investigated the room temperature mechanical behavior of harmonic structured materials, focusing on the role of the different grain size parts in determining strength and ductility, but rather scarce literature is present on their mechanical properties at higher temperature. In the present study, the behavior of an harmonic structured austenitic stainless steel (AISI 304L) has been investigated at high temperature (400°C - 600°C), under both tensile and compressive stresses, comparing its behavior with the one of the same material having a conventional coarse grained microstructure. Better properties were found for the harmonic material, at both 400°C and 600°C.