Abstract: Based on the standard composition of 316 L alloy， a type of Cr， Ni， and Nb strengthened austenitic stainless steel （denoted as 0.03C-XCr-14Ni-2.3Mo-0.35Nb-Fe steel） was designed. Analytical techniques such as optical microscopy （OM）， scanning electron microscopy （SEM）， transmission electron microscopy （TEM）， tensile testing， and impact testing were employed to investigate the microstructures and mechanical properties of hot-rolled plates with three Cr contents （16%， 18%， and 21%） in both solution-treated and aged states （aged at 400 ℃for 1 000 hours）. The results indicate that the main precipitated phases in the alloy are NbC and delta-ferrite. With increasing Cr content， the volume fraction of delta-ferrite significantly increases， while the quantity of NbC remains nearly unchanged. After thermal aging for 1 000 hours， the delta-ferrite phase remains stable， and no new phases are observed， with minor fluctuations in mechanical properties. As Cr content increases， the room-temperature and 350 ℃tensile yield strength and ultimate tensile strength of both solution-treated and aged alloys show slight upward trends. However， the elongation and impact energy exhibit minor variations from 16Cr to 18Cr but sharply decrease in the 21Cr alloy. The higher Cr content promotes the precipitation of delta-ferrite， leading to the formation of localized cleavage regions during fracture. This alters the fracture mode from ductile to brittle， resulting in a rapid decline in elongation and impact energy for the 21Cr alloy.

Key words: Austenitic Stainless Steel, δ-Ferrite, Thermal Aging, Cr Content, Mechanical Properties

摘要： 基于316 L合金标准成分，设计了一种Cr、Ni、Nb强化型的奥氏体不锈钢（记0.03C-XCr-14Ni-2.3Mo-0.35Nb-Fe钢）。利用 OM、SEM、TEM、拉伸和冲击等分析和检测技术，对三种不同Cr含量（16%、18%和21%）的奥氏体不锈钢热轧板材固溶态、时效态（400°C时效1 000 h）的显微组织及力学性能进行了研究。结果表明，合金中的主要析出相为NbC和δ-铁素体，随着Cr含量的增加，合金中的δ-铁素体析出量增多，NbC的数量几乎未发生变化。在相同Cr含量下，热时效1 000 h后，合金中δ-铁素体依旧稳定，析出相类型未发生变化，合金的力学性能波动较小。随着Cr含量增加，固溶态和时效态合金的室温和350 ℃高温拉伸屈服强度、抗拉强度波动较小，总体呈小幅增高趋势；而伸长率、冲击功由16Cr合金到18Cr合金的小幅波动，到21Cr合金的迅速降低。较高的Cr含量导致δ-铁素体析出量的增多，使0.03C-XCr-14Ni-2.3Mo-0.35Nb-Fe钢断裂时出现了少量的解理区，改变了合金的断裂模式，使合金的伸长率和冲击功迅速下降。

关键词: 奥氏体不锈钢, δ-铁素体, 热时效, Cr含量, 力学性能