取向硅钢高温退火时内氧化层与MgO反应过程研究

Study on reaction process between inner oxide layer and MgO during high temperature annealing of grain-oriented silicon steel

对取向硅钢高温退火工艺进行实验室模拟,采用聚焦离子束显微镜(FIB)观察了氧化层中二氧化硅和氧化镁反应的微观形貌演变过程,采用能谱仪(EDS)分析了试样截面近表层Mg、Al、Si等元素的分布规律,最后采用透射电镜(TEM)分析了对成品试样硅酸镁底层的结构特征。结果表明:(1)Mg离子的扩散速度是影响硅酸镁底层反应的主要因素;(2)Mg离子最初沿着二氧化硅颗粒与铁基体之间的界面扩散,逐渐将二氧化硅颗粒包覆;随着温度的进一步升高,Mg离子开始向二氧化硅颗粒内部扩散,并与之反应;(3)随着温度的升高,特别是在AlN分解后,钢基中的Al会逐渐将钉扎部位的硅酸镁(Mg_(2)SiO_(4))完全转化成为镁铝尖晶石(MgO·Al_(2)O_(3))。

The microstructure evolution process of the reaction between silicon oxide and magnesium oxide in oxide layer was observed by focused ion beam microscope(FIB)in simulating the high temperature annealing process of grain-oriented silicon steel in laboratory.Then the distribution of Mg,Al and Si in the near surface layer of the sample section was analyzed by energy dispersive spectrometer(EDS).Finally,the structure of the magnesium silicate glass film was analyzed by transmission electron microscopy(TEM).The results showed that:(1)the diffusion rate of Mg ions is the major factor affecting the reaction of magnesium oxide and silica;(2)Mg ions diffuse firstly along the interface between silica oxide and iron matrix,and gradually coat the silica particles,and then Mg ions begin to diffuse into and react with the silica particles as the further increase of temperature;(3)as the temperature increasing,the Al decomposed by AlN gradually converts the magnesium silicate(Mg_(2)SiO_(4))at the pinning site into magnesium aluminum spinel(MgO·Al_(2)O_(3)).