One key challenge for tailoring microstructure of high-speed steel (HSS) is to obtain small-sized carbides with a homogeneous distribution. Although diffusion annealing followed by post-deformation offers an opportunity to refine carbides, it requires high annealing temperatures and large strains. In this study, we employ a pre-compression step and examine its role in following carbide decomposition and spheroidization. The result shows that pre-deformation may introduce dislocations into M₂C carbides and hence triggers a significant enhancement of M₂C decomposition into M₆C and MC. Structural defects in M₂C act as potential nucleation sites of new precipitates and activate an alternative decomposition pathway via nucleation along dislocations or intersections of stacking faults and dislocations. The decomposition enhancement effect exhibits a dependence on strain and temperature, which may originate from a temperature-mediated balance between dislocation densities and element diffusion rates in M₂C carbides. Compared with post-deformation, pre-deformation facilitates carbide spheroidization and enables smaller carbides as well as higher tempered hardness. This may offer an alternate pathway for carbide refinement in HSS.

定制高速钢（HSS）显微组织的一个关键挑战是获得具有均匀分布的小尺寸碳化物。尽管扩散退火后进行变形可提供细化碳化物的机会，但它需要较高的退火温度和较大的应变。在这项研究中，我们采用了预压缩步骤，并研究了其在碳化物分解和球化之后的作用。结果表明，预形变可将位错引入M ₂ C碳化物中，从而触发M ₂ C分解为M ₆ C和MC的显着增强。M ₂ C中的结构缺陷充当新沉淀物的潜在成核位点，并通过以下途径激活替代分解途径沿着错位或堆积断层和错位的相交成核。分解增强效应表现出对应变和温度的依赖性，这可能源于M ₂ C碳化物中位错密度与元素扩散速率之间的温度介导平衡。与后变形相比，预变形有利于碳化物的球化，并能使碳化物变小以及回火硬度更高。这可能为HSS中的碳化物细化提供了替代途径。