A nanolaminated surface layer was produced on interstitial-free steel by surface mechanical rolling treatment. While the microstructure showed relatively high thermal stability during annealing at 500°C, significant grain boundary (GB) migration occurred in the nanolaminated surface layer during chromizing at the same temperature. GB diffusion of Cr was observed under the Harrison B-type regime in the chromized surface layer. The accelerated GB migration was discussed to be influenced by enhanced GB energy and mobility due to the GB diffusion and enrichment of Cr in nanolaminated structures. Meanwhile, the high stresses introduced during sample preparations also enhance the coarsening kinetics.

Impact statement

Different from enhanced thermal stability by regular GB segregation, GB enrichment of Cr due to fast GB diffusion from a Cr-coating can accelerate the GB migration in nanolaminated IF steel.

通过表面机械轧制处理在无间隙钢上制备了纳米层合表面层。尽管在500°C的退火过程中，显微组织显示出相对较高的热稳定性，但在相同温度下的铬化过程中，纳米层压的表面层中发生了明显的晶界（GB）迁移。在哈里森B型态下，在铬化表面层中观察到Cr的GB扩散。讨论了加速的GB迁移受纳米层状结构中GB扩散和Cr富集而增强的GB能量和迁移率的影响。同时，样品制备过程中引入的高应力也增强了粗化动力学。

影响陈述

与通过规则的GB偏析增强的热稳定性不同，由于Cr涂层中GB的快速扩散而导致的GB的Cr富集可加速GB纳米复合IF钢的迁移。