Effects of graphene nano-platelets (GNPs) on the microstructural characteristics and textural development of an Al-Mg alloy during friction stir processing

SURFACE & COATINGS TECHNOLOGY

卷:335

Article

Khodabakhshi, F.¹  Nosko, M.²  Gerlich, A. P.³ 

[1] Univ Tehran, Coll Engn, Sch Met & Mat Engn, POB 11155-4563, Tehran, Iran

[2] Slovak Acad Sci, Inst Mat & Machine Mech, Dubrayska Cesta 9-6319, Bratislava 84513, Slovakia

[3] Univ Waterloo, Dept Mech & Mechatron Engn, Waterloo, ON, Canada

关键词: Al-Mg alloy;    Friction-stir processing;    Graphene;    Microstructure;    Texture;   

DOI  :  10.1016/j.surfcoat.2017.12.045

来源: Elsevier

【 摘 要 】

The aim of this research is to characterize the unique microstructural features of Al-matrix nanocomposites reinforced by graphene nano-platelets (GNPs), fabricated by multi-pass friction-stir processing (FSP). During this process, secondary phase GNPs were dispersed within the stir zone (SZ) of an AA5052 alloy matrix, with a homogenous distribution achieved after five cumulative passes. The microstructural characteristics and crystallographic textures of different regions in the FSPed nanocomposite, i.e., base metal (BM), heat affected zone (HAZ), thermo-mechanical affected zone (TMAZ), and SZ, were evaluated using electron back scattering diffraction (EBSD) and transmission electron microscopy (TEM) analyses. The annealed BM consisted of a nearly random crystal orientation distribution with an average grain size of 10.7 pm. The SZ exhibited equiaxed recrystallized grains with a mean size of 2 pm and a high fraction of high-angle grain boundaries (HAGBs) caused by a discontinuous dynamic recrystallization (DDRX) enhanced by pinning of grain boundaries by GNPs. The sub-grains and grain structure modification within the HAZ and TMAZ regions are governed by dislocation annihilation and reorganization in the grain interiors/within grains which convert low-angle to high-angle grain boundaries via dynamic recovery (DRV). The FSP process and incorporation of GNPs produced a pre-dominantly {100} < 100 > cube texture component in the SZ induced by the stirring action of the rotating tool and hindering effect of nano-platelets. Although, a very strong {112} < 110 > simple shear texture was found in the HAZ and TMAZ regions governed by additional heating and deformation imposed by the tool shoulder. These grain structure and texture features lead to a hardness and tensile strength increases of about 55% and 220%, respectively.

【 授权许可】

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