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利用XRD、TEM、SEM研究了铸态和600、800、1000℃不同温度退火8 h后微纳结构304不锈钢的微观组织,并测试了力学性能,探讨了两者之间的变化关系。结果表明:铸态和退火处理后的钢都由纳米晶、微米晶奥氏体和少量纳米晶高温铁素体组成。随退火温度升高,纳米奥氏体平均晶粒尺寸没有变化,而铁素体晶粒尺寸、微米晶奥氏体体积分数增大,δ-铁素体体积分数减少。800℃退火后,最高的抗拉强度能达到800 MPa,伸长率是8.3%,位错滑移机制占主导地位,800℃退火后的纳米晶/微米晶304不锈钢获得最好的力学性能。
The microstructure of micro / nano structure 304 stainless steel after as-cast and annealed at 600, 800 and 1000 ℃ for 8 h was investigated by XRD, TEM and SEM. The mechanical properties were also tested. The results show that as-cast and annealed steels consist of nanocrystalline, micro-crystalline austenite and a small amount of nanocrystalline high-temperature ferrite. With the increase of annealing temperature, the average grain size of nano-austenite did not change, while the ferrite grain size, the volume fraction of micro-grain austenite increased and the volume fraction of δ-ferrite decreased. After 800 ℃ annealing, the highest tensile strength can reach 800 MPa, the elongation is 8.3%, and the dislocation slip mechanism dominates. The nanocrystalline / microcrystalline 304 stainless steel annealed at 800 ℃ obtains the best mechanical properties.