强流脉冲电子束辐照诱发的AISI 304奥氏体不锈钢中的空位簇缺陷

Microstructure of defect clusters in AISI 304 austenitic stainless steel induced by high-current pulsed electron beam

利用强流脉冲电子束技术对AISI304奥氏体不锈钢进行辐照处理,采用透射电子显微镜详细地分析了辐照诱发的空位簇缺陷结构。1次辐照未产生空位簇缺陷结构;5、10次辐照后诱发大量的空位簇缺陷结构,缺陷尺寸通常小于10nm,随辐照次数增加,缺陷簇数量明显增加,但尺寸增加不明显;小缺陷簇主要由空位型位错圈和少量的堆垛层错四面体(SFT,stacking fault tetrahedral)组成,SFT占整个缺陷簇的比例低于1%;少量的孔洞缺陷在孪晶片附近出现。10次辐照后,孪晶片前沿或附近形成大量的大尺寸SFT,其最大尺寸可达250nm,这些大尺寸SFT的形成机制与小尺寸SFT的有所不同,通过1/3<111>位错攀移在孪晶片前沿和孪晶界上的台阶处形成的压杆位错核心吸收周围丰富的空位而长大可能是大尺寸SFT形成的原因。

AISI 304 austenitic stainless steel specimens were irradiated with high current pulsed electron beam （HCPEB） for 1, 5 or 10 pulses. The defect cluster rnicrostructures were investigated by transmission electron microscopy （TEM）. While the 1-pulse HCPEB irradiated specimen dose not show any microstructure change, the original microstructure changed completely after the repeated HCPEB irradiation. Dense small defect clusters in sizes of a few nanometers were introduced in the sample, and part of them can be resolve as stacking fault tetrahedral （SFT）. For 10-pulse HCPEB irradiation, large-size SFTs normally located at the tip of twin lamellae, and sometimes located in or inside twin lamellae were formed. The largest SFTs were 250 nm approximately. The formation mechanism of large-size SFTs is different from that of the small counterpart. There is a close relationship between large-size SFTs and twin lamellae.