| Due to its high strength and hardness,carbide reinforced steel matrix composites have broad application prospects in mining,electric power and metallurgy.In order to improve the strength of composites,increasing the volume fraction of carbide is one of the most commonly used methods.However,with the increase of volume fraction,the strength increases continuously,while the plasticity/toughness decreases sharply.There is an inverted relationship between strength and toughness,which is of great significance to improve this inverted relationship.In this paper,titanium carbide reinforced steel base shaped composite was prepared by hot pressing sintering process.The phase composition,microstructure and mechanical properties of steel base shaped composite were investigated by XRD,SEM,EBSD,hardness tester and universal testing machine.The main conclusions are:(1)Metallurgical bonding is realized between the high strength layer(composite layer)and the high toughness layer(steel matrix layer),the reinforcement particles and the matrix of the composite material.The interface bonding is good without defects,the microstructure distribution in the high strength layer is uniform,and the obvious layered characteristic structure can be observed.The main phases of the composite material are α-Fe,Fe3C and TiC.When titanium carbide particles are introduced into the layer,the grain size presents a gradient evolution.The grain size in the outermost layer of the particle is submicron level,and the grain size becomes larger in the core of the particle,which is micron level.(2)Q235 steel,45 steel and T10 steel were used as the toughness layer of the steel based composites,and the volume fraction(20%),Size(30-50μm)and thickness(1mm)of the composite layer remained unchanged,to explore the strength and toughness matching of the composite material.When the steel layer is 45 steel and the thickness is 1 mm,the comprehensive performance of the composite is the best.In parallel direction,the maximum flexural strength of the three-layer composite is about 1902.1 MPa,and the maximum deflection is about 4.4 mm.The maximum flexural strength of the five-layer composite is about 1629.5 MPa,and the maximum deflection is about 4.7 mm.Subsequently,the influence of different thickness of steel layer(0.4 mm,0.7 mm and 1 mm)on the mechanical properties of the composites was investigated.The experimental results show that when the steel layer thickness is 1 mm,the layer thickness ratio and mechanical properties are the best.The mechanical properties of lamellar composite are better in parallel direction than in vertical direction,which fully demonstrates the advantage of lamellar structure.Compared with the original steel,the introduction of composite layer helps to improve the strength of the whole material.(3)The effect of reinforcement size on mechanical properties of composites was investigated when the particle size of reinforcement was different(0.15-0.20 μm,3-9 μm and 30-50 μm),and other parameters remained unchanged.The experimental results show that the mechanical properties of the composites are the best when the reinforcement particle size is 3-9 μm.In parallel direction,the maximum flexural strength of the five layers is 1570.0 MPa and the maximum deflection is 3.9 mm.Then,by adjusting the volume fraction of the reinforced body,the mechanical properties of the steel base composite were investigated.When the volume fraction was 20%,30%and 40%,the mechanical properties of the composite were the best.In parallel direction,the maximum flexural strength was 1678.2 MPa and the maximum deflection was 3.4mm.Finally,the interface strength between the composite layer and the steel matrix layer is investigated,and the maximum interface bonding strength is 201.7 MPa.The strengthening mechanisms of composites include heterogeneous structure effect,load transfer strengthening and dislocation strengthening.The mechanism of toughening is interlayer crack,crack deflection,crack passivation and crack bridging effect. |
PDF Full Text Request