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采用DIL805A膨胀仪测定15-5PH不锈钢马氏体相变点,通过透射电镜和金相显微镜观察了等温处理后的组织。结果表明,等温温度的提高会导致马氏体相变点升高,在700~800℃之间等温时,Ms点变化更为明显;等温处理后基体中出现了第二相NbC,且随等温温度的升高,NbC的数量和尺寸都有所增加。随等温时间延长,Ms点先下降后升高,等温30 min时达到最低值,而Mf点的变化不明显。
The martensitic transformation point of 15-5PH stainless steel was measured by DIL805A dilatometer. The isothermal treated tissues were observed by transmission electron microscope and metallographic microscope. The results show that the increase of isothermal temperature leads to the increase of martensitic transformation temperature. The Ms point changes more obviously when the temperature is between 700 and 800 ℃. The second phase NbC appears in the matrix after isothermal treatment, As the temperature rises, the number and size of NbC increase. With the extension of isothermal time, Ms decreased first and then increased, reaching the lowest value at isothermal 30 min, while the change of Mf was not obvious.