Study On The In-situ Reaction Mechanism Of Al-ZrO₂-X System And Multiphase Particles Reinforced Aluminum Matrix Composites

The advancement of science and technology has greatly promoted the development of modern industry.At the same time,the requirements for the performance of engineering materials are becoming increasingly demanding,so that traditional aluminum alloy can no longer meet the requirements.Due to the dual advantages of reinforcing particles and matrix,in-situ synthesized aluminum matrix composite has become a research focus in the field of materials.However,there are few in-situ systems developed and applied in aluminum matrix composites,and the process of forming reinforced particles by in-situ reaction is often accompanied by coarse or harmful phases with special morphologies.At present,the more studied in-situ system of aluminum matrix composites is the Al-ZrO2 system,but the ZrAl3 particles produced by the reaction in system will make composite become embrittlement under stress,which limits the increase in the ceiling of the mechanical properties.In this paper,a new system Al-ZrO2-X for in-situ synthesized aluminum matrix was designed based on the Al-ZrO2 system by three ideas of controlling the morphology of the enhanced phase,designing nano-Zr compound particles and constructing a multi-phase multi-scale particle network.The reaction mechanism,mechanical properties and strengthening mechanism were also studied,which provided ideas for in-situ synthesis of new composites with comprehensive mechanical properties.The research contents of this article were as follows:(1)Multi-stage reaction mechanism of Al-ZrO2-MoSi2 and mechanical properties of compositesIt was found that the Al-ZrO2 system reacted to produce(Al2O3+ZrAl3)/Al composite after in-situ reaction at 680?,and nano-Al2O3 particles and flake-like micron ZrAl3 particles were uniformly distributed on the aluminum matrix.After introducing MoSi2 into the Al-ZrO2 system,the Al-ZrO2-MoSi2 system has undergone multi-stage in-situ reactions.When the system was heated to 573.9?,Al and ZrO2 undergone solid-solid reaction to produce Al2O3 and ZrAl3,and then Al had a liquid-solid reaction with MoSi2 to produce petal-like Al12Mo phase at a higher temperature.At the same time,the reaction was transformed flake-like ZrAl3 phase into short rod-like(Al,Zr,Si)phase,forming(Al12Mo+(Al,Zr,Si)+Al2O3)/Al composite.Due to the evolution of the reinforcing particles,the(Al12Mo+(Al,Zr,Si)+Al2O3)/Al composite had a higher hardness than the(Al2O3+ZrAl3)/Al composite.The tensile strength at room temperature was increased from 305 MPa to 330 MPa,and the tensile strength at 350? was also increased from 101 MPa to 109 MPa.(2)In-situ reaction mechanism of Al-ZrO2-B2O3 and preparation of(ZrB2+Al2O3)/Al compositeB2O3 was introduced into the Al-ZrO2 system to transform the brittle ZrAl3 phase into the ZrB2 phase.When the molar ratio of ZrO2 and B2O3 was 1:1,the system was completely reacted to synthesize(ZrB2+Al2O3)/Al composites.When the molar ratio of ZrO2 and B2O3 was 1:0.5,some micron-scale flake-like ZrAl3 particles were remained after the in-situ reaction,forming(ZrAl3+ZrB2+Al2O3)/Al composite.Through the control of the temperature of in-situ reaction,the ZrB2 and Al2O3 particles in the composite could be adjusted to have a nanometer size,and finally the nano dual-particle aluminum matrix composite was in-situ synthesized.Extrusion studies have found that the micron-sized Al matrix and ZrAl3 particles formed a preferred orientation:?-Al grains had an extruded fiber texture of<111>//ED,and the long axis of the ZrAl3 particles was parallel to the extrusion direction to form(001)ZrAl3//ED orientation.Since the introduction of B2O3 eliminated ZrAl3 particles which were prone to brittle,nano-ZrB2 and Al2O3 particles could better reduce stress concentration and hinder the dynamic softening of the aluminum matrix.Compared with(ZrAl3+ZrB2+Al2O3)/Al composite,the(ZrB2+Al2O3)/Al composite exhibited a lower thermal expansion rate and higher mechanical properties,and its tensile strength at 350? could reach 188 MPa.(3)Design and preparation of the(Al2O3+ZrB2+AlN)/Al composite with multi-phase,multi-scale and network configuration particlesA new(Al2O3+ZrB2+AlN)/Al composite was prepared by introducing N and B elements based on Al-ZrO2 system after in situ reaction at 800?.Al2O3,ZrB2 and AlN particles were micron,submicron and nanometer scale,respectively.By adjusting the content of particles,the reinforcing particles in composite could be transformed from a dispersion distribution to network distribution,forming a three-dimensional hard framework.Experiment results showed that the(Al2O3+ZrB2+AlN)/Al composite with a network configuration had better comprehensive properties.The hard particles could effectively confine the soft aluminum matrix,which made the composite have a lower thermal expansion rate and a higher elastic modulus.At the same time,the network reinforcing particles had more significant thermal mismatch strengthening and dislocation multiplication strengthening effects,so the tensile properties of(Al2O3+ZrB2+AlN)/Al composites at room temperature and high temperature could reach 504 MPa and 200 MPa.The composite has broad application prospects in the field of the advanced manufacturing industry.