Effect Of Er-Zr And Graphene On Microstructure And Properties Of 6082 Aluminum Alloy

The 6-series aluminum alloys are the mainstream aluminium alloy materials for vehicle lightweight application,boasting high strength,good corrosion resistance,and excellent formability,and widely used in aluminum alloy plates and stamping parts.With increasingly light automobiles,the research on lightweight,tough,and excellent formability 6082 aluminum alloy has become a hot spot.The introduction of in-situ nano-phase（adding Er and Zr）and foreign nano-phase（graphene,abbreviated as Gr）to realize the synergistic optimization of microstructure and strength is a viable strategy for comprehensive properties improvement.In this paper,6082,Er+Zr/6082,and Gr/6082 aluminum matrix composites were prepared by melting and casting methods,and the alloy was subjected to extrusion deformation treatment to obtain 6082 aluminum alloy bars reinforced with nano phase.Microstructure of the alloy was characterized by scanning electron microscope（SEM）,transmission electron microscope（TEM）and electron backscattering diffraction（EBSD）,and the mechanical properties and corrosion resistance of the alloy were tested.With the addition of nano-phase,the microstructure of as-cast 6082 aluminum alloy gradually changed from coarse dendrites to equiaxed crystals,and the non equilibrium eutectic phase at the alloy grain boundary was refined,reducing element segregation during solidification process.The average grain size of 6082,Er+Zr/6082 aluminum alloys and Gr/6082 aluminum matrix composites are 134.9μm,111.2μm and 132.6μm.After homogenization at 560℃/8h,the chain-likeβ-Al（Fe,Mn）Si phase at the grain boundary of6082 aluminum alloy broke up and dissolved,transforming into sphericalα-Al（Fe,Mn）Si phase particles.The Er and Zr were precipitated from the matrix again,profusely forming secondary Al₃（Er,Zr）spherical particles.With more Gr,the diffusion and re-dissolution of elements during homogenization annealing were promoted,dissolving more Al（Fe,Mn）Si phases,and promoted the diffusion and re-nucleation of non equilibrium eutectic phases.The addition of Er and Zr effectively inhibited the recrystallization of 6082 aluminum alloy.The microstructure after extrusion was mainly composed of elongated deformed grains positioned along the extrusion direction,with some recrystallized grains at the grain boundaries.The addition of Er and Zr cut down the proportion of recrystallization in 6082 aluminum alloy from 11.6%（6082 aluminum alloy）to 4.7%,inhibiting the nucleation and growth behavior of recrystallized grains during solution aging,and the proportion of recrystallized grains（10%）decreased by 7.0%compared to 6082 aluminum alloy（17.1%）.The large-size Al（Fe,Mn）Si phase in Er+Zr/6082 aluminum alloy was more finely dispersed,which weakened the PSN effect caused by the pinning dislocation of large-size impurity particles.The fine dispersed Al₃（Er,Zr）particles increased the Zener force and inhibited the growth of recrystallized grains.The nanophase graphene was uniformly dispersed at the matrix and grain boundaries after addition,firmly bonding with the matrix interface and hindering dislocation migration between adjacent grains,which resulted in higher dislocation density in Gr/6082 aluminum matrix composite.During tensile deformation of composite materials,graphene was deformed by interfacial tensile stress and impedes dislocation transfer,which played a role in strengthening load transfer and improving the strength and plasticity of the composite material.With the addition of Er and Zr,the strength of 6082 aluminum alloy was improved while maintaining a high elongation.The addition of graphene improved the strength and elongation of aluminum matrix composites simultaneously.After T6 heat treatment,the tensile strength（UTS）,yield strength（YS）and elongation of the three materials were 308 MPa,352 MPa and317 MPa,269 MPa,324 MPa and 272 MPa,18.5%,18.5%and 20.5%respectively.With the addition of Er and Zr,the strength of 6082 aluminum alloy was improved mainly through fine grain strengthening,Orowan strengthening and coherent strengthening.The addition of graphene mainly improved the strength and plasticity of Gr/6082 aluminum matrix composites through fine grain strengthening and load transfer strengthening.