固溶时效对节镍型高氮奥氏体不锈钢组织的影响

对热轧态节镍型高氮奥氏体不锈钢进行固溶及时效处理,利用光学显微镜、电子背散射衍射,结合相图系统分析该材料固溶处理及时效后组织变化规律。结果表明,1050 ℃固溶处理后,试验钢基体为奥氏体,存在少量的铁素体,奥氏体晶粒形状偏等轴,晶粒内部存在大量孪晶。时效后,析出相主要为Cr₂N、CrN、Cr₂₃C₆。在时效时间为5 h不变的条件下,温度由650 ℃升高至800 ℃,碳化物及氮化物数量呈现先增长后降低的趋势,在750 ℃时数量最多。而在750 ℃时效5~10 h范围内,随着时效时间的增加,析出相数量变化不大。析出相的析出过程为:先在晶界交叉处析出胞状析出物,随时间的延长,在晶界逐渐析出条状析出物,在晶内开始出现并逐渐长大,最终形成类珠光体的片层状析出。

Effect of solution treatment and aging on microstructure of low-nickel high nitrogen austenitic stainless steel

Solid solution treatment and aging of hot rolled low-nickel high nitrogen austenitic stainless steel were carried out.Metallographic microscope,electron backscatter diffraction and phase diagram were used to systematically analyze the microstructure changes of the steel after solid solution treatment and aging. The results show that after solid solution treatment at 1050 ℃,the steel matrix is austenite with nearly equiaxial grains containing a large number of twins,and with a small amount of ferrite. After aging,the precipitated phases are mainly Cr2 N,CrN,and Cr23C6. With the increase of aging temperature from 650 ℃ to 800 ℃ under the same aging time of 5 h,the amounts of carbides and nitrides increase first and then decrease,reaching to the maximum at 750 ℃ . With the increase of aging time in the range of 5-10 h at 750 ℃,the amount of precipitates has little change. The precipitation process of the precipitated phases is as follows: Firstly,cellular precipitation occurs at the triple junctions of grain boundaries. With the extension of aging time,strip precipitates are gradually precipitated at the grain boundaries,and begin to appear and grow up inside the grains,finally form pearlite-like lamellar precipitates.