Effect of Aging Time and Temperature on Mechanical Properties and Microstructural Evolution of 2205 Ferritic-Austenitic Stainless Steel

Duplex stainless steels (DSS) with ferritic-austenitic microstructures offer good combination of resistance to. pitting corrosion and high strength that are not concomitantly attainable using conventional single phase austenitic or ferritic stainless steels. The DSS used in this investigation was 2205 alloy having a stable microstructure consisting of about 45% ferrite and 55% austenite at ambient temperature. In order to investigate aging behavior of this steel and the influences on mechanical properties, different aging treatments were conducted at temperatures of 350-950 degrees C for various aging time of 15, 30, 60 and 180 min The aged specimens were subjected to impact testing and hardness measurements Finally, the changes in microstructure due to aging were studied by optical and scanning electron microscopy The results showed that aging at temperatures lower than 550 degrees C for different time had negligible effects on mechanical properties. Besides, no considerable changes in term of precipitation of harmful intermetallic particles were observed in microstructure below this temperature However, a critical temperature range, 550-650 degrees C, was introduced here. Aging in this range led to a significant decrease in toughness and notable increase in hardness The formation of intermetallic phases such as sigma was recognized as the major reason for the observed changes.