Effect of thermal aging on the room temperature tensile properties of AISI type 316LN stainless steel

摘要

Round tensile specimens of AISI type 316LN stainless steel, thermally aged at 1123 K for 0, 2, 10, 25, 100, 500 and 1000 h, were tested for tensile properties at room temperature at a strain rate of 7.7 x 10~(-3) s~(-1). The changes in tensile properties were correlated to the transmission electron microscopic studies. The various stages of nitrogen repartitioning including Cr-N cluster formation, intragranular and subsequent cellular precipitation of Cr_2N were found to have a strong influence on the yield strength (YS) and ductility of the material. However, the changes in ultimate tensile strength (UTS) with aging were negligible. The results of electrochemical extraction of secondary phases clearly indicated a two-slope behavior. X-ray diffraction analysis of electrochemically extracted residue suggested that the initial smaller sloped line corresponded to the precipitation of the Cr_2N phase while the line with larger slope at longer aging time corresponded to the domination of chi phase precipitation.