Cu合金化6.5%Si高硅钢中有序相的调控机制及增塑机理研究

6.5%Si high silicon steel exhibits excellent magnetic properties. However, because of the formation of the ordered phases B2 and D03, 6.5%Si high silicon steel is brittle with almost zero ductility at room temperature. How to improve the plasticity of 6.5%Si high silicon steel is a hot and difficult research issue. Previous research of the applicant shows that the addition of a suitable amount of Cu can increase the plasticity of 6.5%Si high silicon steel and also maintain its excellent magnetic properties. In this project, the first-principles calculation method is to be used to clarify the location site of Cu in the ordered phases, and to calculate the electronic structure of 6.5%Si high silicon steels with various amounts of Cu addition, to study the effect of Cu on the bonding characteristics of 6.5%Si high silicon steels. TEM and Mössbauer Spectroscopy are to be applied to analyse and quantitatively characterize the ordered phases in the Cu-alloyed high silicon steel, and the effect of Cu content on the content and degree of long-range order of the ordered phases are to be studied. Based on the study of the effect of Cu content on the microstructure and plasticity, the relationships among plasticity of 6.5%Si high silicon steels with various Cu additions, its ordered phases, bonding characteristics and microstructure are to be clarified. Such results will be used to unveil the controlling mechanism of the formation of ordered phases in the Cu-alloyed 6.5%Si high silicon steels and the mechanism by which its plasticity is increased. In combination with the studies on the effects of Cu additions on the magnetic properties, the optimum Cu addition is to be determined, leading to the provision of a theoretical basis for establishing a rolling process for large scale production of 6.5%Si steel thin sheets and for their practical applications.

6.5%Si高硅钢具有优异的磁性能，但由于B2和D03有序相的形成，其室温延伸率几乎为零，提高其塑性是该领域的研究热点和难点。本项目针对前期研究发现，添加Cu在保持优异磁性能的同时能提高6.5%Si高硅钢塑性，拟通过第一性原理研究Cu在有序相中的占位，并获取不同Cu含量高硅钢的电子结构，阐明Cu添加量对键合特征的影响规律；采用TEM和穆斯堡尔谱仪定量表征含Cu高硅钢中有序相，阐明Cu添加量对有序相的含量及其长程有序度的影响规律；研究6.5%Si高硅钢微观组织、塑性随Cu添加量的变化规律，探讨不同Cu含量高硅钢中有序相、键合特征、微观组织与塑性之间的关系。项目将解决“Cu对6.5%Si高硅钢中有序相的调控机制及增塑机理”的科学问题，并结合Cu添加量对磁性能的影响规律，明确Cu的最佳添加量，为实现这类薄板的轧制法生产提供理论指导。

Cu合金化可以抑制6.5%Si高硅钢中脆性有序相的形成，而提高其塑性。然而Cu对6.5%Si高硅钢中有序相的影响规律与机制及其增塑机理尚不明确。本项目通过微观组织、织构、有序相及力、磁性能研究，并结合第一性原理研究了Cu添加量与6.5%Si高硅钢中有序相形成的相关性，以及6.5%Si高硅钢塑性与有序相、键合特征、微观组织之间的关系。主要结论如下：.1. Cu在6.5%Si高硅钢中的固溶度大于等于0.3wt.%且小于0.5wt.%。当Cu添加量≤0.5wt.%时，添加的Cu基本固溶在6.5%Si高硅钢中，固溶的Cu可以抑制有序相的形成，且随着Cu添加量增加，钢中有序相的含量和长程有序度均降低。当Cu添加量>0.5wt.%时，超过了Cu在6.5%Si高硅钢中的固溶度，会形成粗大的晶界偏聚物和大量细小-Cu析出。.2. 6.5%Si高硅钢的塑性随Cu含量增加呈先增加后降低的趋势，当Cu的添加量达到0.3wt.%时，Cu对6.5%Si高硅钢塑性的改善作用最显著；Cu含量达到0.7wt.%时，Cu对塑性有恶化作用，且Cu含量越高，恶化作用越明显。Cu对6.5%Si高硅钢的增塑作用主要是由于固溶的Cu降低了钢中有序相的含量和长程有序度，而一旦Cu的添加量超过了其在6.5%Si高硅钢中的固溶度，会形成粗大的晶界偏聚物，导致晶界脆性而严重降低钢的塑性。.3. 6.5%Si高硅钢的磁性能随Cu含量增加呈先增加后降低的趋势，当Cu的添加量达到0.5wt.%时，磁性能达到最优；Cu含量达到1.0wt.%时，Cu对6.5%Si高硅钢的磁性能有恶化作用。结合Cu对6.5%Si高硅钢力学性能和磁性能的影响规律，明确了最佳Cu添加量为0.3-0.5wt%，这对轧制法生产6.5%Si高硅钢具有重要的指导意义。