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对经淬火+回火(QT)与淬火+两相区淬火+回火(QLT)工艺处理后的9Ni钢中的逆转变奥氏体含量和其对原位拉伸时裂纹形成和扩展时所起到的作用进行了观察和分析。结果表明:经QT工艺处理的钢中的逆转变奥氏体含量为2%,在裂纹扩展过程中,裂纹尖端成锐角,加剧了应力集中;经QLT处理后,钢中的逆转变奥氏体含量提高为6%,在裂纹扩展的过程中,裂纹尖端成钝角,弱化了应力集中。逆转变奥氏体并不能直接阻碍裂纹的扩展,通过提高基体的韧性,间接地阻碍裂纹的扩展,从而优化实验钢的低温韧性。
In the quenched + tempering (QT) and quenching + two-phase quenching and tempering (QLT) process 9Ni steel after reverse austenite content and its in-situ tensile crack growth and formation of the time The role of play was observed and analyzed. The results show that the content of reverse-transformed austenite in the steel treated by QT is 2%, and the crack tip becomes acute at the crack growth, which aggravates the stress concentration. After QLT treatment, the reverse-transformed austenite The content increased to 6%. During the crack growth, the crack tip became obtuse, weakening the stress concentration. Reverse transformation of austenite does not directly hinder the expansion of the crack, by increasing the toughness of the matrix indirectly hinders the expansion of the crack, so as to optimize the low temperature toughness of the experimental steel.