Study On Mechanical Properties And Dry Friction Wear Behavior Of TiB₂ Particle Reinforced Iron Matrix Composite

Under the development background of energy conservation,lightweight of metal material has been an important growing trendency.Owing to the advantages of low cost,excellent mechanical properties and broad application prospects,iron-based composite has been a focused area in material research.Relative study shows,a novel composite Fe-TiB₂ can be obtained through adding low density and high strength TiB2 particle into iron-base.This paper was designed to prepare iron-based composites reinforced with different volume fraction of 15%,20%and 25%of TiB₂ obtained by in-situ synthesis method,the effects of TiB₂ content on tensile properties and dry friction and wear behaviours were investigated by experiment research and numerical simulation.The main research conclusion are as follows:?1?Fe-TiB₂ composites were consist of?-Fe and TiB₂.A few TiB₂ were hexagonal and most of them were quadrilateral in 3-4?m².With the increase of TiB₂ content,density of composite decreased and the micro hardness showed an upward trend.Fe-25%TiB₂ composite had lowest density of 7.12g/cm³ and highest micro hardness of368.3Hv0.1.?2?Yield and tensile strength of Fe-TiB₂ increased with TiB₂ content,but the total enlongation sharply decreased.The tensile strength of Fe-TiB₂ containing different TiB₂content were 531MPa,632MPa and 659MPa,corresponding enlongation were 22.0%,15.4%and 7.9%,respectively.Fracture morphology of Fe-TiB₂ composites indicated that the increase of TiB₂ content caused a transformation in fracture mechanism from ductile fracture to brittle fracture.?3?The nano indentation test showed that with the increase of TiB₂ content,the modulus of?-Fe increased and the ability of deformation resistance was stronger.Besides,the modulus of Fe-TiB₂ increased with TiB₂ content,which were 215.5GPa,222.5GPa and 247.0GPa,moreover,the variation of composites hardness shows the same trend with 6.43GPa,9.56GPa and 14.51GPa.?4?The monotonic tensile behavior was simulated by 2-D multi-particle random distruibution representative volume element model generated by Python script.True stress-strain curve simulation results agreed well with measured value in elastic stage,however in plastic stage the simulated value was higher.The microscopic stress and strain distruibution showed the particle remained obvious stress concentration.In the load direction,?-Fe in both sides of TiB₂ also remained high stress with distinct strain,which resulted in the 45°plastic shear bands in the whole model.?5?The behavior under uniaxial pressure load was simulated by axisymmetric unit cell model.Simulation results showed more particles in the composite contuibuted more to overall stiffness increase,therefore,the deformation resistnace ability enhanced as wll.Stress distuibution revealed the particle hold much more load than?-Fe,and stress decreased form press location to the edge through particle,a sharp decrease happened in the Fe/TiB₂ interface.?6?Friction wear under dry condition tests were conducted in different rotation speeds and loads.Research showed when the roatation speed was 100r/min,the increase of load in the range of 50-100N lead to the incease of friction coefficient and volume loss of the composites,the same trend was found when the rotation speed increased from100r/min to 300r/min under a load of 100N.Importantly,the increase in volume loss decreased with TiB₂ particle content.The volume loss of Fe-25%TiB₂ was less than the traditional wear-resistant cast steel?24CrNiMo?under the same wear condition.?7?Dry Friction and wear of Fe-TiB₂ composites material could be divided into 3stages,which were mild wear stage,transition stage and severe wear stage.The surface morphology during mild wear stage was microcutting,the main wear mechanism was abrasive wear.In transition stage,element migration occurred and a mechanical mixed layer was formed on the sample surface.Finally,in severe wear stage the mechanical mixed layer begain to peel off and micro cracks appeared in the sample surface duing to accumulated plastic deformation,so in this stage delamination wear and adhesive wear were the main mechanism.Moreover,oxidative wear happened through all stages.As for Fe-TiB₂ composites,wear resistance increased with volume fraction of TiB₂ so as to delay the arrival of severe wear stage.