Study On The Microstructure And Properties Of In-Situ Al₂O₃ Particles Reinforced Al-Zn-Cu-Zr Composites

Particle-reinforced aluminum-based composite materials have attracted the attention of domestic and foreign scientific researchers due to their excellent properties such as isotropy,high strength,and low thermal expansion coefficient.Among them,Al₂O₃ is considered to be one of the ideal aluminum matrix composite reinforcements because of its high strength,high elastic modulus,wear resistance,no harmful reactions,good chemical stability,and low cost.The preparation methods of Al₂O₃ particle-reinforced aluminum matrix composites can be divided into additive method and in-situ method.Compared with the additive method,the in-situ method has the advantages of pure interface,firm bonding with the matrix,more uniform distribution,and good morphology,and has a wide range of applications prospect.In this paper,powder metallurgy technology and casting method are combined to successfully prepare Al₂O₃/Al-Zn-Cu-Zr composite materials through in-situ autogenous reaction.The Al-Zn O system is selected for the in-situ reaction system,the Al-Zn-Cu-Zr alloy is selected for the matrix materials,and the scanning electrons are equipped with an X-ray diffractometer(XRD),an energy spectrometer(EDS)and an electron backscatter diffractometer(EBSD).Microscope(SEM)and Transmission Electron Microscope(TEM)and other analytical testing methods observe and analyze the phase,crystal morphology,morphology,size distribution and crystallographic properties of the composite material.The mechanical properties of composite materials are studied.The effect of Al₂O₃ particle reinforcement on the microstructure and mechanical properties of composite materials was discussed,and the strengthening mechanism of composite materials was analyzed.The result is as follows:(1)For the Al-Zn O system,the results of EDS surface scanning show that after 4 hours of ball milling at 100r/min speed,the aluminum powder and nano-Zn O powder are uniformly mixed;XRD results show that the melt temperature is 850?and the holding time is 30 min,Zn O can be It completely reacts with the matrix in situ to generate Al₂O₃ particle reinforcement phase.(2)The microstructure observation results show that the Al₂O₃/Al-Zn-Cu-Zr composite material contains high-density,dispersed reinforcement particles.The analysis found that the reinforcement particles can be divided into two types:Al₂O₃ particle reinforcement phase and Al₂Cu precipitation phase.The distribution of Al₂O₃ particle reinforcement phase is dispersed,and the shape is mostly spherical,polygonal or ellipsoid,and the size is distributed from nanometer to micrometer.Al₂Cu precipitated phase is mostly strip or rod shape,which is easy to form and coarsen at the grain boundary.The rolling heat treatment can obviously refine the Al₂Cu precipitation phase,but has little effect on the Al₂O₃ particle reinforcement phase.Compared with the base alloy,the grain structure of the composite material after as-cast and rolling heat treatment is significantly refined.(3)The hardness test and room temperature tensile results show that the hardness of the composite materials in the as-cast,rolled and heat-treated states are 85.2HBW,105.3HBW and 124.6HBW,respectively,which are increased by 29.3%,47.9%and 54.4%compared with the base alloy;The elongation strengths of the composite materials in the as-cast,rolled and heat-treated states are 235.5MPa,306.3MPa and 398.2MPa,respectively,which are increased by 47.7%,75.9%and 101.5%compared with the base alloy.Tensile fracture studies have shown that the fracture modes of matrix alloys and composite materials are mainly plastic fracture.