| Silicon carbide particles(SiCp)reinforced aluminium matrix composites are high quality structural materials with wear and high temperature resistance and have been widely used in aerospace and other fields.This paper investigates the preparation process,plastic deformation processing,toughness heat treatment and tissue properties of 7.5vol%vol 1μm SiCp and 2.5%vol 100nm SiCp hybrid reinforced 7000 series（Al-8.85Zn-2.05Mg-0.439Cu-0.0241Ti-0.0032Zr-0.383Si-0.57Fe-0.379Mn）aluminium matrix composites.The work carried out and the research results obtained are as follows:（1）The preparation process of nano-micron SiCphybrid reinforced 7000 series aluminum matrix composites was studied,including the preparation of composite powder,initial ingot preparation of the composite material,and subsequent plastic deformation processing（primary extrusion,secondary extrusion）.The results show that after high energy ball mills,the uniformity of the reinforcement distribution in the aluminum matrix composite is effectively improved.After plastic deformation processing,the dislocation density is greatly improved,and the distribution of reinforcement is more uniform.Compared with primary extrusion,the microstructure of aluminum matrix composites produced by secondary extrusion is denser and the grains are finer.（2）The microstructure and properties of nano-micron SiCp hybrid reinforced 7000series aluminum matrix composites after solid solution treatment were studied.The results indicate that G2（450℃×2h+475℃×2h+500℃×2h）solid solution process has the best effect,and the second phase has the best degree of resorption.The hardness reached its maximum value of 201.18HV and the conductivity was 20.74%IACS.The contribution of dislocations to strength also reached a maximum of 104.04MPa.The tensile strength also reached 551MPa,with an elongation after fracture of 1.5%.（3）The organisation and properties of nano-micron SiCp hybrid reinforced 7000-series aluminium matrix composites were investigated by ageing.The results show that the T4（natural ageing）,T6 and T6I4 ageing were carried out on the basis of the optimum solid solution effect G2.TEM observations revealed that only the GP zone was present in the crystal and relatively enriched under T4 ageing,while the ageing precipitated phases of the T6 and T6I4 ageing aluminium matrix composites were in the coarsening phase of theηphase and the transition to theη’phase respectively.The enrichment of Mg elements near the reinforcement reduces the ageing precipitated phase in the matrix.The hardness at T4 aging was 201.18HV,the electrical conductivity was 20.74%IACS,the tensile strength was 551MPa and the elongation after break was1.5%.At T6 aging the hardness is 216.48HV,the electrical conductivity is 20.18%IACS,the tensile strength is 519MPa and the elongation after break is 2.7%.The hardness of the composite at T6I4 aging was 204.20HV,the electrical conductivity was20.37%IACS,the tensile strength was 518MPa and the elongation after break was 3.0%.（4）The grain boundary characteristics and corrosion resistance（intergranular corrosion resistance,spalling corrosion resistance,electrochemical corrosion resistance）of nano-micron SiCp hybrid reinforced 7000 series aluminium matrix composites were investigated.Under T6 aging,there is a certain amount of precipitated phaseηdistribution at the grain boundarie.Under T6I4 aging,the grain boundaries are also clean and tidy.The experimental results show that the maximum depth of intergranular corrosion resistance of the composites under the three aging regimes of T4,T6 and T6I4is 180.63μm,232.86μm and 223.79μm respectively,and the excellent degree of intergranular corrosion resistance is T4>T6I4>T6;the grades of spalling corrosion resistance are EA,EC and EB respectively,and the excellent degree is T4>T6I4>T6,and the highest grade of spalling corrosion resistance is EA.In the electrochemical corrosion experiments,the corrosion potential is T6>T6I4>T4,and the corrosion current density is T6>T4>T6I4,with a minimum corrosion current density of 7.373×10-8A·cm-2.In conclusion,nano-micron SiCphybrid reinforced 7000 series aluminum matrix composites with tensile strength of 551MPa,plasticity of 1.5%,intergranular corrosion resistance of 180.63μm,spallation corrosion resistance of EA and corrosion current density of 9.8892×10-8 A·cm-2 were successfully prepared in this experiment.The important technological parameters,such as preparation,secondary processing and element design,provided an important reference for the subsequent research of aluminum matrix composites. |
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