In this study, in situ surface nanocomposites based on Mg-CuO and Mg-Cu systems were developed via six passes of friction stir processing (FSP) on the surface of AZ91 magnesium casting alloy. In-situ phase evolution during FSP with the addition of Cu and CuO micro-powders was studied by x-ray diffraction (XRD) analysis and microstructural investigations. Here, AZ91/Cu nanocomposite was reinforced by the in situ formation of Mg₂Cu intermetallic compound. In AZ91/CuO nanocomposite, CuO particles were reduced and MgO and MgCu₂ reinforcing particles alongside Mg₂Cu intermetallic compounds were formed during FSP. Grain refinement and in situ formation of reinforcement particles with different sizes ranging from nano- to micro-scale significantly improved mechanical performance of the specimens. Dynamic recrystallization was found to be the main mechanism of grain refinement. After six passes of FSP, the hardness values of AZ91/Cu and AZ91/CuO nanocomposites were increased by 69.1% and 91%, respectively. Besides, AZ91/CuO nanocomposite exhibited the best tensile strength and wear resistance among all the samples. The dominant wear mechanisms were abrasive and delamination wear in AZ91 magnesium alloy, while nanocomposite specimens were worn mainly by abrasive mechanism.

在这项研究中，基于 Mg-CuO 和 Mg-Cu 系统的原位表面纳米复合材料是通过六道次搅拌摩擦处理 (FSP) 在 AZ91 镁铸造合金表面开发的。通过 X 射线衍射 (XRD) 分析和微观结构研究，研究了添加 Cu 和 CuO 微粉的 FSP 过程中的原位相演变。在这里，AZ91/Cu 纳米复合材料通过Mg ₂ Cu 金属间化合物的原位形成得到增强。在AZ91/CuO纳米复合材料中，在FSP过程中，CuO颗粒减少，MgO和MgCu ₂增强颗粒与Mg ₂ Cu金属间化合物一起形成。晶粒细化和原位形成从纳米级到微米级的不同尺寸的增强颗粒，显着提高了试样的机械性能。发现动态再结晶是晶粒细化的主要机制。经过6道FSP后，AZ91/Cu和AZ91/CuO纳米复合材料的硬度值分别提高了69.1%和91%。此外，AZ91/CuO纳米复合材料在所有样品中表现出最好的拉伸强度和耐磨性。AZ91镁合金的主要磨损机制是磨粒磨损和分层磨损，而纳米复合材料试样的磨损主要是磨粒机制。