AI 中文总结
研究316H不锈钢纳米划痕中竞争马氏体转变途径，采用原位同步加速器X射线纳米衍射结合纳米划痕测试及有限元建模，揭示压力驱动途径选择，解释合金擦伤性能差异，解决瞬态微观结构状态测量问题。
AI 中文摘要
摩擦接触下的局部表面变形会产生一个摩擦层，其微观结构和性能与基体不同。在奥氏体不锈钢中，这个摩擦层通过两种竞争的马氏体转变途径形成。在此，利用原位同步加速器X射线纳米衍射结合纳米划痕测试，在316H不锈钢中分离出这些途径，共同产生单个滑动微凸体下方演化应变场的空间图。有限元建模解释了马氏体相的最终分布，揭示了压力驱动的途径选择，即接触前方的静水压力抑制α′形成并有利于γ→ε转变，而横向滑动缓解了这种约束并引入剪切应变驱动ε→α′，在摩擦层中产生整体顺序γ→ε→α′途径。在静水约束持续存在的地方，ε-马氏体被保留；在材料堆积且表面上方无约束的地方，转变直接进行到α′。与α′-马氏体相邻的γ-奥氏体显示出位错密度升高，表明α′形成由周围基体中的塑性变形来适应。这种差异可以解释铁基和钴基堆焊合金之间擦伤性能的差异，其中形成ε-马氏体的钴合金具有优异的抗擦伤性。所提出的方法解决了宏观多微凸体接触静态测量无法获得的瞬态微观结构状态，为更广泛地深入了解摩擦学现象建立了一条途径。
英文摘要
Localised surface deformation beneath frictional contacts generates a tribolayer whose microstructure and properties differ from the bulk. In austenitic stainless steels, this tribolayer forms through two competing martensitic transformation pathways. Here, these pathways are isolated in 316H stainless steel using in-situ synchrotron X-ray nanodiffractometry combined with nanoscratch testing, which together yield spatial maps of the evolving strain field beneath a single sliding asperity. Finite element modelling interprets the resulting distribution of martensitic phases, revealing a pressure driven pathway selection where hydrostatic compression ahead of the contact suppresses $α'$ formation and favours the $γ\rightarrow \varepsilon$ transformation, while lateral sliding relieves this constraint and introduces a shear strain driving $\varepsilon \rightarrow α'$ , producing an overall sequential $γ\rightarrow \varepsilon \rightarrow α'$ pathway in the tribolayer. Where hydrostatic constraint persists, $\varepsilon$-martensite is retained; where material piles up and is unconstrained above the surface, the transformation proceeds directly to $α'$. The $γ$-austenite adjacent to $α'$- martensite shows elevated dislocation density, indicating that $α'$ formation is accommodated by plastic deformation in the surrounding matrix. This distinction could explain differences in galling performance among iron-based and cobalt-based hardfacing alloys, where the $\varepsilon$-martensite forming cobalt alloys offer superior galling resistance. The methodology presented resolves transient microstructural states inaccessible to static measurements of macroscale, multiple asperity contacts, establishing a route to mechanistic insight across tribological phenomena more broadly.
