《搅拌摩擦加工制备GNPs/Al复合材料的微观结构与力学性能》

Microstructure and mechanical properties of GNPs/Al composites fabricated by friction stir processing

摘要:

本文以纯铝为基体，利用搅拌摩擦加工(FSP)制备GNPs/Al复合材料，研究了复合材料基体组织、增强相与界面等微观结构与力学性能，探讨了其增强机理。结果表明，添加GNPs并经FSP后复合材料基体晶粒得到明显细化且晶界由小角度为主转变为大角度为主；FSP制备过程致使GNPs片层一定程度剥离的同时，较大片径的GNPs被破碎而形成众多边缘缺陷，使其易发生Al-C原子扩散，结果在GNPs边缘与基体形成界面过渡；GNPs加入量约1.8vol%时，复合材料的屈服强度和抗拉强度达到72MPa和147MPa，较同等条件FSP的基体分别提高了89.5%和79.3%，理论计算界面载荷传递、Orowan和细晶强化依次是复合材料的主要增强机制；随着GNPs加入量的增加，复合材料屈服强度实验值与理论值的增长趋势一致，且偏差也略有提高，但可能因GNPs在复合材料中的杂乱排布，界面载荷传递强化不能充分发挥，实际的复合材料屈服强度与理论值尚有差距。

Abstract:

In this paper, GNPs/Al composites were fabricated by friction stir processing(FSP) used pure aluminum as the matrix materials. The microstructure (including the matrix, reinforcement and interface) and mechanical properties were investigated, and the reinforcing mechanism of the composites was analyzed. The results showed that the matrix was?obviously refined, and many high angle grain boundaries were generated. The GNPs tended to be exfoliated and broken resulting in large amounts of GNPs edges during FSP. The Al-C atomic-sacle diffusion is easy owing to C atoms activity at the GNPs edges, as a result the interface transitions were formed between the GNPs edges and Al matrix. The yield strength and ultimate tensile strength of 1.8 vol% GNPs/Al composites were 72MPa and 147MPa. Compared to that of unreinforced Al, they increased by 89.5% and 79.3%, respectively. One by one, interface load transfer, Orowan and grain refinement were the principal reinforcing mechanism according to the theoretical calculation，and the calculated and experimental yield strength of the composites increase with the graphene content, concurrently, the deviations between the experimental and calculated strengths also slightly increased. However, the interface load transfer can not be well achieved owing to GNPs disorder distribution in the composites, therefore there is still a gap between the actual yield strength and theoretical calculation.