中文摘要：

将超低碳无取向电工钢冷轧板在γ单相区加热，分别在H2和N2中使其发生α→γ→α相变，对超低碳无取向电工钢中的相变组织特征进行表征，并对其形成机理进行分析与讨论。结果表明，H2退火板中形成了强{100}取向单层饼状晶，且{100}取向晶粒的尺寸达到1mm以上；而N2退火板表层为近{100}和{110}取向柱状晶，中心层则主要为{111}和{114}取向等轴晶。弱晶界普遍出现在发生取向择优的相变组织中，其形成机制与表面效应作用下诱发变体选择时所遵循的K-S关系密切相关；在N2退火板的柱状晶内部出现了近似线性的取向梯度，应为表层晶粒沿板材法向（ND）依靠γ→α相变长大受阻引起的相变应变累积造成的。

英文摘要：

At present, the quality of commercial non-oriented electrical steels is improved mainly by optimizing deformation and recrystallization textures, but the most desirable {100} texture for the magnet- ic properties of sheets is normally no more than 20% in volume fraction. Through α→γ→α transformation, however, the percentage of {100} texture can be up to 50%, even as high as 80% or more. The character- istics of transformation microstructure in ultra-low carbon non-oriented electrical steel are basically re- vealed in this work, and the formation mechanisms are analyzed and discussed. The cold-rolled sheets of electrical steels are heated in ysingle phase region, α→γ→α transformation occurs in hydrogen and ni- trogen atmosphere, respectively. The results indicate that strong {100} texture with monolayer pancake grains is developed in hydrogen, and the size of {100} oriented grains reaches more than 1 mm; whereas near {100} and {110} textured columnar grains are formed at the surface layer of the sheets in nitrogen, and the equal-axed grains with {111} and {114} textures in the center layer are obtained finally. 23 grain boundaries generally appear in the transformation microstructure where grain orientations are preferred, and its formation mechanism is closely related to K-S relationship which is followed during variant selec- tion induced by surface-effect. There is an approximate linear orientation gradient in the columnar grains at the surface of the sheet annealed in nitrogen, and this phenomenon should be resulted from the accu- mulation of transformation strain induced by the suppression of the growth of surface grains with γ→α transformation along the normal direction.