SCr420H齿轮钢中AlN的析出行为

Precipitation behavior of AlN in SCr420H gear steel

通过Thermo-Calc热力学计算软件对SCr420H钢中第二相Al N析出的热力学进行计算,通过建立Avrami模型对Al N的析出动力学进行分析,利用扫描电镜研究了不同温度和时间下Al N析出的大小、形貌及分布,并对其尺寸进行了统计。结果表明:SCr420H齿轮钢中Al N相的开始析出温度为1180℃,以均匀、晶界和位错3种形核机制形核的鼻点温度分别为927、1127和892℃,从析出开始到结束所需时长分别为15s、57min和58s。试验钢在850℃和900℃温度下等温1 h足以析出大量Al N,扫描电镜下观察到Al N相的析出形貌有四边形、近球状和长棒状,还有少数Al N为不规则形状,这些大量弥散细小的Al N粒子,大多分布在晶界上及晶界附近处。随着等温温度的提高和保温时间的延长,第二相Al N粒子的尺寸有明显长大的趋势。

The precipitation thermodynamics of secondary phase AlN was calculated by the Thermo-Calc thermodynamic calculation software,and the precipitation kinetics of AlN was analyzed by Avrami modeling.The size,morphology and distribution of AlN precipitates at different temperatures and time were studied by using of scanning electron microscope,and the precipitate size data was also statistically analyzed.The results show that the initial precipitation temperature of AlN phase in SCr420 H gear steel is 1180℃,and for the homogeneous,grain boundary,and dislocation nucleation mechanisms of AlN,the fastest precipitation temperature is 927,1127 and 892℃,respectively,and the precipitation time from start to the end is 15 s,57 min and 58 s,respectively.At 850℃and 900℃,isothermally holding for 1 h is enough for large amount of AlN to precipitate in the tested steel.It is observed by scanning electron microscopy that the precipitation morphologies of AlN are quadrangular,near spherical and long rod,and a few are irregular shape.The large number of dispersed and fine AlN particles are mostly distributed in the grain boundary and near the grain boundary.With the increase of the isothermal temperature and holding time,the size of the secondary phase AlN particles has a tendency to increase significantly.