Microstructure and mechanical properties of annealed SUS 304H austenitic stainless steel with copper

An experimental investigation into the effect of Cu on the mechanical properties of 0 and 3 wt.% Cu added SUS 304H austenitic stainless steel upon annealing at 700 °C for up to 100 h was conducted. Optical microscopy reveals grain coarsening in both the alloys upon annealing. Observations by transmission electron microscopy revealed the precipitation of nanometer-sized spherical Cu particles distributed within the austenitic grains and the presence of carbides at the dislocations. Both the yield and ultimate tensile strengths of the alloys were found to remain invariant with annealing. Tensile ductility and the threshold stress intensity factor range for fatigue crack growth for 3 wt.% Cu added alloy increase with annealing. These are attributed to the grain coarsening with annealing. In all, the addition of Cu to SUS 304H does not affect the mechanical performance adversely while improving creep resistance.

Research highlights
► SUS 304H austenitic stainless steel containing 3 wt.% Cu was annealed at 700 °C for up to 100 h.
► Microstructure and mechanical properties of annealed alloys are examined.
► Nano-sized Cu-rich precipitation upon annealing.
► Strength of the alloy remains invariant with annealing whereas ductility improves.
► Fatigue crack growth threshold of 3 wt.% Cu added alloy increases with annealing.