Stacking faults (SFs) have received a growing attention in recent years, and are currently incorporated in microstructure design to achieve a synergistic enhancement of strength and ductility for critical applications. However, unlike extensively studied nanotwins, the full potential of SFs in face-centered-cubic (fcc) metallic alloys, particularly in high stacking fault energy fcc Al-based materials, has remained less-explored and unutilized. In the present work, we engineered SFs-containing high-strength ultrafine-grained Al-Mg based alloys by extrusion deformation of mechanically alloyed powder compacts. These SFs tend to emit from grain boundaries (GBs) and matrix/precipitate interfaces during the extrusion deformation, exhibiting a heterogeneous spatial distribution in the resultant microstructures. Through theoretical analysis of the strengthening effects associated with diverse structural elements and detailed microscopic observations of SFs in the macroscopically yielded specimens, we find that GB- and hetero-interface-emitted SFs are incapable of providing substantial strengthening, but can effectively improve the plasticity of the materials. This finding is fundamentally inconsistent with the reported Al-based materials with SFs in which SFs are proposed to simultaneously enhance materials’ strength and plasticity. Hence, our results advance the current understanding of the role of SFs in modulating ductility of high-strength Al-based alloys by interface-emitted SFs.

中文翻译：

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超细晶粒铝合金的变形断层：成核机制和强化-延展化贡献的关键评估


近年来，堆叠故障 （SF） 越来越受到关注，目前已被纳入微观结构设计中，以实现关键应用的强度和延展性的协同增强。然而，与广泛研究的纳米孪生不同，SF 在面心立方 （fcc） 金属合金中的全部潜力，特别是在高堆叠故障能量 fcc Al 基材料中，仍然很少被探索和利用。在本工作中，我们通过机械合金粉末压块的挤压变形设计了含有 SFs 的高强度超细晶粒 Al-Mg 基合金。在挤压变形过程中，这些 SF 倾向于从晶界 （GB） 和基体/沉淀物界面发射，在所得微观结构中表现出异质空间分布。通过对与不同结构元件相关的强化效应的理论分析和对宏观样品中 SF 的详细显微镜观察，我们发现 GB 和异质界面发射的 SF 不能提供实质性的增强，但可以有效提高材料的塑性。这一发现与已报道的具有 SFs 的 Al 基材料根本不一致，其中 SF 被提议同时提高材料的强度和塑性。因此，我们的结果促进了目前对 SF 在界面发射 SF 调节高强度 Al基合金延展性中的作用的理解。