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利用XRD、SEM及EBSD等分析手段研究不同回火试样在深冷处理后奥氏体含量以及形貌、分布位置和尺寸不同的逆转变奥氏体的变化规律,以此来探讨回火温度,奥氏体的形貌、分布位置与尺寸以及奥氏体稳定化元素的含量等对奥氏体稳定性的影响。结果表明,随着回火温度的升高,逆转变奥氏体体积分数先升高后下降,且650℃回火试样经过深冷处理后逆转变奥氏体体积分数急剧降低。逆转变奥氏体位于小角度晶界上或马氏体板条间时稳定性最高,大角度晶界上次之,位于大角度三叉晶界处的奥氏体最不稳定。在大角度三叉晶界处,逆转变奥氏体晶粒尺寸越小,其稳定性越高。逆转变奥氏体的稳定性还与其中的C、Mn与Ni等稳定化元素相关,稳定化元素的含量越高,奥氏体的稳定性越高。
The changes of austenite content, shape, distribution location and size of different austenite after cryogenic treatment were studied by means of XRD, SEM and EBSD. The effects of tempering temperature, The influence of austenite morphology, distribution location and size, austenite stabilizing element content on the austenite stability. The results show that with the increase of tempering temperature, the volume fraction of retrograded austenite increases first and then decreases, and the volume fraction of retrograded austenite decreases sharply after tempering at 650 ℃. Retrograde austenite is the most stable at the low-angle grain boundaries or between the martensite laths, the last at the high-angle grain boundaries, and the most unstable austenite at the large-angle trigeminal grain boundaries. At the large angle of the trigeminal grain boundary, the smaller the size of the retrograded austenite grain, the higher its stability. The stability of retrograded austenite is also related to the stabilizing elements such as C, Mn and Ni. The higher the content of stabilizing elements, the higher the stability of austenite.