| With the rapid development of technology,traditional materials are far from meeting the requirements and metal matrix composites with good overall performance have emerged.In particular,aluminum matrix composites have the advantages of high specific strength,high specific modulus,and high specific stiffness,which have attracted the attention of researchers from all over the world.The ternary transitional layered compound Ti3SiC2 is a new type of lubricating composition.It not only has the performance characteristics of commonly used particles,but also has comparable friction properties with graphite.In this paper,firstly,a compact,interfacially pure Ti3SiC2/Al-Mg composite block is prepared by short-time low-temperature SPS sintering process.The interfacial reaction between reinforcement particles and matrix was studied by means of isothermal heat treatment at different temperatures.The influence of interfacial reaction on the tribological properties of the material was discussed.Then,on the basis of the interface reaction temperature and the influence of the interface reaction on the properties,Al-4Mg was selected as the matrix,and 5 w.t.%Ti3SiC2 was used as the reinforcement phase.Ti3SiC2/Al-Mg composite ingots were prepared by semi-solid stirring and the composition,microstructure and performance uniformity of the ingots were evaluated.Finally,the thermal deformation ability of billet was studied by isothermal compression test,and the thermal activation energy and constitutive equation of the material were obtained.The main research work and results are as follows:(1)Low-temperature short-time SPS sintering method can obtain interfacially pure Ti3SiC2/Al-Mg composite blocks.The phase composition mainly consists of Ti3SiC2 and Al phases,with a Vickers hardness of 78.2.The isothermal heat treatment of the bulk material at 600 ? resulted in a distinct interfacial reaction between the Ti3SiC2 and the Al-Mg matrix.The interfacial reaction products were mainly Mg2Si and Al4C3.When the temperature is 550 ? and 500 ?,no obvious interface reaction characteristics are found under long-term insulation conditions.(2)The interface reaction and matrix composition have a significant effect on the tribological properties of the material.With the increase of matrix Mg content,the friction coefficient and wear amount are reduced.When the Mg content is 4 w.t.%,the friction coefficient of the composite block reaches 0.122,and the interfacial reaction significantly increases the friction coefficient and the amount of wear.(3)Semi-solid stirring casting process for preparing Ti3SiC2/Al-Mg composite ingots with uniform composition,structure,and properties.The grain shape and size of the head and tail of the ingot are basically the same,and the dimensions are all around 60 ?m.The second phase particles are mainly Ti3SiC2,Al4C3,Mg2Si and TiC phases.The distribution,size,and morphology of the particles in different positions of the ingot are similar and are mainly distributed at the grain boundaries.Some large-size particles with small size and round shape are distributed in the interior of the matrix grains.The difference in properties such as density,hardness,and conductivity is small at each position of the ingot.Compared to the Al-4Mg binary alloy,the composite hardness increased by 60.8%,the tensile strength increased by 41.7%,and the friction coefficient increased by 5.3 times.(4)Thermal simulation method was used to study the compressive deformation behavior of Ti3SiC2/Al-4Mg composites.High temperature deformation of Ti3iC2/Al-4Mg composites can be represented by hyperbolic positive selection function.The thermal activation energy of the composite can be calculated as Q=218.66 KJ/mol.The constitutive equation is as follows:(?)= 66.7798 ×[sinh(0.048)]1.9704exp(-218.66×103/8.314T)... |
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