两相区淬火对9Ni钢中逆转变奥氏体的影响

淬火+两相区淬火+回火(QIT)能显著的提高9Ni钢的低温韧性。利用扫描电镜(SEM)、透射电镜(TEM)、电子背散射衍射(EBSD)、X射线衍射(XRD)和电子探针(EPMA)对QIT处理的9Ni钢中逆转变奥氏体的含量、形貌、分布以及两相区淬火对逆转变奥氏体的影响进行了研究。结果表明,QIT处理的9Ni钢中逆转变奥氏体的含量约为10%,以块状和薄膜状形态分布在基体中;两相区淬火的9Ni钢中的大角度晶界增多,有利于逆转变奥氏体的形核;基体上某些区域的C、Mn和Ni元素含量较高,利于逆转变奥氏体长大和稳定化。

Effect of quenching in dual-phase region on the reversed austenite in 9Ni steel

The reversed austenite in quenching+intercritically quenching+tempering(QIT) treated 9Ni steel was studied by means of scanning electron microscopy(SEM),transmission electron microscopy(TEM),electron back scatter diffraction(EBSD),X-ray diffraction(XRD) as well as electron probe micro-analysis(EPMA).The results show that about 10.9% reversed austenite forms in the QIT-treated 9Ni steel.TEM observation demonstrates that the reversed austenite is in the shape of block and films.Thirty percent of reversed austenite are located within grains,and uneven distribution of C,Mn and Ni elements is detected for the steel after quenching in intercritical region.Intercritically quenching can facilitate the reversed austenite to form by providing more nucleation sites through increasing percent of large-angle grain boundaries,as well as stabilize the reversed austenite via enriching C,Mn and Ni in reversed austenite.