In the present work, an ultrahigh strength 300 M steel was treated by the surface plastic deformation with surface cryogenic grinding treatment (SCGT) technique. The SCGT was carried out by rotational grinding wheel embedded with numerous zirconium corundum abrasive grits, which contributes to a decreasing distribution of strain, strain rate and strain gradient from the treated surface to the matrix. The depth-dependent microstructural evolution was systematically evaluated from micrometer to nanoscale and in particular, the deformation mechanisms and texture alternation were addressed. It was identified that the microstructural evolution starts from the formation of dislocation structures, that is subsequently followed by the distorted microstructures featured as the origination and evolution of ultrafine laminates and ultrafine grains in the form of dislocation activities. Nanocrystalline was generated in the topmost surface region and nanoparticle precipitates induced by the SCGT process occur within a few microns of the treated surface. In SCGT, a very high strain rate of over 10⁶ s⁻¹ and a strain gradient of over 0.2 μm⁻¹ were induced on the topmost surface of 300 M steel sample, which impels the martensite-matrix lamella extended into the elongated structure and finally transformed into the nanosized grains during processing. A dislocation slip-dominated process that was supplemented by the mechanical twinning governs the microstructural evolution pattern during the SCGT process, the nucleus of dynamic recrystallization initiated from the pre-existing dislocation cells were observed, and the transformation from martensite to austenite was effectively suppressed. The increase of grain size from nanoscale to submicron and finally microscale contributes to a decrease of microhardness by 25.6% (from 7.8 GPa at the treated surface to 5.8 GPa at a depth of over 100 μm from the processed surface).

在目前的工作中，超高强度 300 M 钢通过表面塑性变形和表面低温研磨处理 (SCGT) 技术进行处理。SCGT 是通过嵌入大量锆刚玉磨粒的旋转砂轮进行的，这有助于减少从处理表面到基体的应变分布、应变速率和应变梯度。从微米到纳米尺度系统地评估了与深度相关的微观结构演变，特别是解决了变形机制和纹理交替。确定微观结构演化始于位错结构的形成，随后是扭曲的微观结构，其特征是超细层压板和超细晶粒以位错活动的形式的起源和演变。在最顶部的表面区域产生了纳米晶体，并且通过SCGT工艺诱导的纳米颗粒沉淀发生在处理过的表面的几微米之内。在 SCGT 中，应变率非常高，超过 10⁶  s ^-1和超过 0.2 μm ^-1的应变梯度在 300 M 钢样品的最上表面诱导，这促使马氏体-基体薄片延伸到细长结构中，并最终在加工过程中转变为纳米尺寸的晶粒。SCGT过程中以位错滑移为主的过程控制着机械孪生的微观结构演化模式，观察到由预先存在的位错细胞引发的动态再结晶核，有效抑制了从马氏体向奥氏体的转变。晶粒尺寸从纳米级到亚微米级和最终微米级的增加导致显微硬度降低 25.6%（从处理表面的 7.8 GPa 到距处理表面超过 100 μm 深度的 5.8 GPa）。