The Study On Fabrication Of ZrO₂/Al5083 Surface Composites Based On Friction Stir Processing

Friction stir processing?FSP?,as a new solid phase processing technology,make use of the high-speed friction of the mixing head and the workpiece surface to generate heat to cause the metal material plastic deformation,which is used to improve the material defects,and also used to prepare metal matrix surface composites.As one of the key materials in modern engineering and high-tech development,aluminum alloy surface composite material with good strength and easy to be formed by adding reinforcing particles to the surface of aluminum alloy has become a hot research direction.In this paper,ZrO₂/Al5083 surface composites were prepared with 5083aluminum alloy as the substrate and ZrO₂ as the reinforcing particle by FSP.The effects of FSP parameters on the macrostructure,mechanical properties and microstructure of surface composites were studied.The microhardness and tensile properties of surface composites were analyzed by Vickers hardness and universal tensile testing machine.The microstructure of surface composites and the dispersion of ZrO₂ nanoparticles were analyzed by optical microscope?OM?,scanning electron microscope?SEM/EDS?,X-ray diffraction?XRD?and other modern characterization methods,and the results are as followed:ZrO₂/Al5083 surface composites can be successfully prepared by FSP.Higher rotation speed,lower processing speed and multi-pass processing lead to more flash of surface composites.At the same time,it can improve internal organization holes defect,and ZrO₂ nanoparticles are uniformly dispersed on Al5083.When the rotation speed is800 rpm,the processing speed is 50 mm/min and 4 times of processing pass,the surface composite material obtained is well formed.The addition of ZrO₂ nanoparticles significantly improved the microhardness of ZrO₂/Al5083 surface composites.Higher rotation speed,lower processing speed and multi-pass processing are conducive to the improvement of microhardness and stable distribution change.The average hardness of the forward side of the mixing zone is up to 110.6 HV.Compared with the base material,the microhardness of the surface composites at the retreating side of the stirring zone and the friction stir boundary zone is decreased.The tensile strength of ZrO₂/Al5083 surface composite is lower than that of the base material,and higher rotation speed,lower processing speed and multi-pass processing are beneficial to improve the tensile strength.When the processing speed is50 mm/min and 4 times of processing,the tensile strength?308 MPa?with the rotation speed of 800 rpm is better,which can reach 94%of the base metal and the elongation is9.57%.The tensile strength?315 MPa?with a rotation speed of 1000 rpm shows optimal results,which can reach 96%of the base metal,but the elongation is 8.89%.In addition,the fracture mode of ZrO₂/Al5083 surface composite is ductile fracture.The well-formed ZrO₂/Al5083 surface composite has good structure and no defects.The ZrO₂ nanoparticles in the advancing side of the stirring zone are dispersed evenly and no new phase is generated.ZrO₂ nanoparticles will not appear in the retreating side of the stirring zone.The grains in the friction stir boundary area are bent and a part of the grains in the base material area are coarsened.