Abstract True bulk nanostructured composites promising for a wide range of applications however being difficult to produce using established engineering techniques. Most of previous works aimed to design of Cu graphene composite used the approach of high temperature sintering inevitably associated with growth of Cu grains. Another advantageous approach of composites consolidation allowing to avoid heating of the sample is shear deformation under high pressure that has been earlier used for Al – graphene composite. Our work reports the first attempt of Al-graphene composite consolidation by means of is high pressure torsion (HPT). Two-step processing by constrained and non-constrained HPT was applied to produce bulk Cu-graphene composite with nanoscaled Cu grains laminated by graphene. After the constrained HPT high and low graphene content layers were interspersed in the microstructure. The second step of not-constrained HPT led to the refinement of graphene agglomerates to the range of 10 nm and Cu grains to the range of 100 nm with quite uniform distribution of graphene, preserving the equiaxial shape of the grains seldom in case of the composite structure. The process significantly increased microhardness of Cu-graphene composite from 1450 to 1900 MPa in the edge region after consolidation with even more pronounced increase from 1900 to 2950 after following constrained HPT. However, infusion of graphene resulted in a prominent decrease of both ductility from 15 to 4% and strength of the material. Brittle failure with low value of critical fracture stress should be related to the role of graphene as an obstacle for the dislocation movement. The dynamic recrystallization in the Cu-graphene composite during severe plastic deformation by not-constrained HPT suggests also that dispersed graphene may play role in the dislocation sinking at the micro-grains boundaries. The obtained results contribute to figuring out the major issues of Cu and graphene interaction under pressure and can be helpful in validation of prospective research plan in this field.

中文翻译：

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两种高压扭转工艺制备的Cu-石墨烯复合材料的微观结构和力学性能

摘要 真正的块状纳米结构复合材料有广泛的应用前景，但难以使用已建立的工程技术生产。以前的大部分工作旨在设计 Cu 石墨烯复合材料，使用高温烧结的方法不可避免地与 Cu 晶粒的生长相关。另一个避免加热样品的复合材料固结方法是高压下的剪切变形，早先用于铝-石墨烯复合材料。我们的工作报告了通过高压扭转（HPT）对铝-石墨烯复合材料固结的首次尝试。应用约束和非约束 HPT 的两步处理来生产块状 Cu-石墨烯复合材料，其中纳米级 Cu 颗粒由石墨烯层压。在受约束的 HPT 后，石墨烯含量高和低的层散布在微观结构中。非约束 HPT 的第二步导致石墨烯团聚体细化到 10 nm 的范围和 Cu 晶粒到 100 nm 的范围，石墨烯的分布非常均匀，在复合材料的情况下很少保留晶粒的等轴形状结构体。该过程显着增加了固结后边缘区域 Cu-石墨烯复合材料的显微硬度从 1450 MPa 到 1900 MPa，在遵循约束 HPT 后从 1900 增加到 2950 更加显着。然而，石墨烯的注入导致材料的延展性和强度从 15% 显着降低至 4%。临界断裂应力值低的脆性破坏应该与石墨烯作为位错运动障碍的作用有关。非约束 HPT 在严重塑性变形期间 Cu-石墨烯复合材料中的动态再结晶表明，分散的石墨烯可能在微晶界处的位错下沉中起作用。获得的结果有助于找出压力下铜和石墨烯相互作用的主要问题，有助于验证该领域的前瞻性研究计划。