Preparation Of Dense Ti 3 SiC By SPS2 /Al Composites And Their Microstructure And Properties

With the rapid development of modern industry,engineering instruments must be able to work under high temperature,corrosion,oxidation and other harsh conditions.Metal-based solid self-lubricating composite materials came into being,such materials not only has a high strength,hardness,but also has a good self-lubricating properties.Among them,the particle reinforced aluminum matrix composites materials cost is relatively low,rich raw material resources,the preparation process is simple,has attracted wide attention of the various disciplines of materials.The combination of suitable reinforcing particles and aluminum matrix can be used to prepare composite materials with excellent performance,which has great potential and application prospect.In this paper,pure Al as the matrix,the choice of both metal and ceramic properties of the typical MAX phase-Ti₃SiC₂ as an external solid lubricating components.Ti₃SiC₂/Al composites were fabricated by spark plasma sintering technique.The properties of the composites were evaluated by testing the density,hardness,dry friction coefficient and wear of the samples.The microstructures of the composites were investigated by XRD phase analysis,metallographic observation,scanning electron microscopy and energy dispersive spectroscopy.The main contents and main results are as follows:?1?The effect of SPS process parameters on the microstructure and properties of Ti₃SiC₂/Al composites was studied.At the sintering temperature of 480-600 ?,sintering time 5-15 min,sintering pressure 20-40 MPa under the experimental conditions,the main phase composition of Ti₃SiC₂ and Al phase,Ti₃SiC₂ distribution in the grain boundary,no significant characteristics of the interface reaction.With the increase of sintering temperature and sintering pressure,the density and hardness of the material gradually increase,and the friction coefficient and wear amount decrease gradually.With the extension of sintering time,the density and hardness increase first and then decrease,and the friction coefficient and wear amount decrease first and then increase.While the sintering temperature is 600?,the time is 10 min and the pressure is 40 MPa,the sintered sample with good grain size,uniform composition,low porosity,good density,high hardness and good tribological properties can be obtained.?2?The effect of Ti₃SiC₂ contents on the microstructure and properties of the composites was studied.With the Ti₃SiC₂ mass fraction increased from 0 to 50%,the main phase of the composite material is Ti₃SiC₂,Al and a small amount of impurity TiC phase.While Ti₃SiC₂ content is low,the matrix of the composites is Al phase,Ti₃SiC₂ is mainly distributed in grain boundary.While the Ti₃SiC₂ content exceeds25 wt.%,the Al phase gradually loses the microstructure of the mesh connection,and a large amount of Ti₃SiC₂ phase accumulates between the Al grains.With the increase of Ti3 Si C2 content,the density of composites increased first and then decreased,and the hardness increased gradually.While the content of Ti₃SiC₂ was 10 wt.%,the composites could obtain high hardness and density.?3?The effect of Ti₃SiC₂ content on the friction and wear behavior of the composites was studied.With the increase of Ti₃SiC₂ content,the friction coefficient and wear amount of the composites decreased first and then increased.When the content of Ti₃SiC₂ is 10 wt.%,the composites can obtain lower friction coefficient and wear amount at the same time.The mechanism of friction and wear at the initial stage of the sintered samples was mainly attributed to the mixed wear mechanism of adhesive wear and abrasive wear;With the continuous action of the friction,the adhesive wear to the main change to abrasive wear-based mixed wear mechanism.After the long time friction test,the enhanced phase Ti₃SiC₂ was easily decomposed and oxidized by the high temperature friction,and the oxidation products were TiO2,SiO2 and so on.?4?The interfacial reaction characteristics of 10 wt.% Ti₃SiC₂/Al sintered samples were incubated at 500-700? for 1-10 h respectively.In the 500? conditions,even after a long period of time has not yet obvious significant interface reaction;The temperature began to 600 ? long time under the conditions of insulation,the interface began to occur,Al3 Ti phase gradually formed;The temperature is further increased to 700?,the degree of interfacial reaction is obviously aggravated,and the Al3 Ti phase with large strip of stripes appears in the composite structure.