A study of laves phase in high Nb non-oriented silicon steel for electric automobiles

In the study of precipitates in high-Nb non-oriented silicon steel for the rotor of electric automobiles, it was found that mass dispersed Nb-rich precipitates were formed during the rolling process of the steel, these precipitates are presumed to be Laves phases in published literatures. In this regard, two types of Laves phases of high-Nb non-oriented silicon steel for electric automobiles and their crystallographic relationship with the Fe matrix were determined using SAED, FFT and IFFT, and calculation of steel strength enhancement by precipitation strengthening. The results showed the elliptical Laves phase is Fe16Nb6Si7 and the rectangular strip Laves phase is Nb7P4, and the orientation relationship between Fe16Nb6Si7 phase and Fe matrix is : [001](Fe16Nb6Si7)parallel to[001](Fe), [101](Fe16Nb6Si7)parallel to[110](Fe), [113](Fe16Nb6Si7)parallel to[112](Fe), the orientation relationship between Nb7P4 phase and Fe matrix is : [130](Nb7P4)parallel to[001](Fe), [102](Nb7P4)parallel to[110](Fe), [110](Nb7P4)parallel to[112](Fe); Both Fe16Nb6Si7 and Nb7P4 precipitates have a good coherent relationship with the Fe matrix; The calculation results show that Fe16Nb6Si7, Nb7P4 and other precipitates can improve the yield strength of non-oriented silicon steel, but at the same time, the magnetic properties of the steel are expected to be negatively impacted. The research results can provide important theoretical guidance on the influence of thermo-mechanical processing on balancing the mechanical and magnetic properties of high niobium non-oriented silicon steel for electric vehicle rotor.