摘要
用热膨胀法和X射线衍射法研究了60Si2Cr VAT弹簧钢在Q-I-Q-T(Quenching-Isothermal-Quenching-Tempering)新工艺的Q-I阶段,即材料奥氏体化后短时淬火再等温这一过程中的亚稳态残留奥氏体的等温转变动力学。实验表明:随等温温度的升高,残留奥氏体含量先升后降。不同温度短时淬火等温冷却后均得到马氏体、贝氏体和残留奥氏体的复相组织。随等温温度的升高,发生完全转变的时间明显缩短,转变量明显减少,转变孕育期也从280℃的54 s减少到500℃的0.96 s。实验获得的亚稳奥氏体等温阶段的TTT曲线呈近C型特征。从亚稳奥氏体的转变量与等温时间的关系曲线可知曲线分为2个阶段,其中第Ⅰ阶段亚稳奥氏体的转变速率明显大于第Ⅱ阶段的转变速率,其等温转变动力学可以用对数曲线进行描述。
The isothermal transformation kinetics of metastable austenite in the novel Q-I-Q-T（ Quenching-Isothermal-QuenchingTempering） process were studied by means of dilatometric technique and XRD（ X-ray diffraction）. Results show that the volume fraction of residual austenite increases at first and then decreases with the isothermal temperature increasing. After short-time quenching and isothermal treatment at different temperatures,all the samples have complex microstructure containing martensite,bainite and austenite.The TTT curve has near-C characteristic,in which the transition time is short and the transformation amount reduces significantly with the isothermal temperature increasing and the start time of the transition decreases from 54 s at 280 ℃ to 0. 96 s at 500 ℃. According to the curve of transformation amount of metastable austenite versus isothermal time,two stages can be clearly watched where the transformation speed of metastable austenite in the first stage is distinctly greater than that in the second stage. The law curve of isothermal transformation kinetics can be given accord with logistic curve.
出处
《材料热处理学报》
EI
CAS
CSCD
北大核心
2016年第3期132-138,共7页
Transactions of Materials and Heat Treatment
基金
贵阳市科技计划项目(筑科合同[2013101]1-3)
贵州省科技厅工业攻关项目(黔科合GZ字[2014]3018号)
贵州省科技计划项目(黔科合LH字[2015]7646号)
