| Particle reinforced aluminium matrix composites possess low cost,high specific modulus,high specific strength,good resistance to abrasion and so on,and thus they are widely used in aerospace,aviation,automotive and other fields.The in situ methods are widely concerned because of its clean interface between reinforced phase and matrix,combining with the advantages of small particle size and the good distribution of ceramic particle.In recent years,some research about nano-sized ceramic particles reinforced metal matrix composite materials has been well known,since nano-sized ceramic particles can improve the strength of the matrix without sacrificing the ductility.However,it is difficult to disperse nano-sized particle uniformly in matrix due to the large surface area of nano-sized ceramic particles,which may often lead to nano-particles reunion and has largely limited the applications and the strengthening effect of nano-particles.The study has found that particles reinforced aluminum matrix composites with surplus strength may be gotten by the method of introducing nano-sized and micro-sized ceramic particles in the metal matrix at the same time.This method can take advantage of the synergy among different scale particles,realizing the improvement of material performance.At present,in situ synthesized nano/micron-sized hybrid ceramic particles reinforced aluminum matrix is very lack,thus it is necessary to reveal and explore this materials.In this paper,nano/micro-sized Ti Cx reinforced Al/Al-Cu matrix composites were fabricated by combustion synthesis combined with hot pressing,and combustion synthesis combined with hot pressing and hot extrusion method.This paper mainly analyzes the flowing aspects: the influence of different ratios between carbon black and CNTs,the accretion of alloy elements(Zn,Cu,Mg and Si)and the content of Ti Cx on the microstructure,mechanical properties and wear behavior(abrasive wear and friction wear)of nano-sized Ti Cx reinforced Al/Al-Cu composites at room and elevated temperature.The strengthening mechanisms and wear resistance mechanisms of nano-sized Ti Cx reinforced Al/Al-Cu composites are revealed.In this paper,several main points are shown by thefollowing:(1)It reveals that the different ratio between carbon black and CNTs have largely effects on the microstructure,the size of Ti Cx ceramic particle and the compression properties of Ti Cx/Al composites.And the strengthening mechanisms of Ti Cx reinforced Al composites are also researched.1)It reveals that the size of endogenous Ti Cx particles can be gradually refined as the rates of CNTs increased in Al-Ti-C system.The size of Ti Cx ceramic particles would be 3.44mm and 265.31 nm when pure carbon black is used to fabricated Ti Cx/Al composite;the size of Ti Cx ceramic particles would be 1.94mm and 240.86 nm when50 wt.% CNTs is used to fabricated Ti Cx/Al composite;the size of Ti Cx ceramic particles would be 175.25 nm when pure CNTs is used to fabricated Ti Cx/Al composite.2)It reveals that compression strength of composites gradually increased as the rates of CNTs increased in Al-Ti-C system,while the fracture strain reflects a trend of increase after decrease first.The ?0.2 and ?UCS of Ti Cx/Al composite fabricated by pure CNTs as carbon source are the highest,417.5MPa and 538.3MPa,respectively;the compression comprehensive performance of Ti Cx/Al composite fabricated by 50 wt.% CNTs as carbon source materials is the best,whose ?0.2,?UCS and ?f are332.3MPa,505.6MPa and 28.1%,respectively.3)It reveals the strengthening mechanisms of nano/micro Ti Cx/Al matrix composites.On the one hand,nano-sized Ti Cx ceramic particles have a pinning effect on ?-Al grain boundary.Under the effect of stress,the dislocation motion is hindered by intracrystalline Ti Cx ceramic particles and the grain boundary sliding is hindered by Ti Cx ceramic particles existed in grain boundary,thus the strength of composites are enhanced.On the other hand,a large number of dislocation and other defects appear in the composite,since the different elastic modulus and thermal expansion coefficient exist between micro-sized particles and the aluminum matrix.Under the effect of stress,dislocation become intersection and entanglement,and matrix become strain hardening,which have reinforced composite materials.(2)It reveals that different alloy elements(Zn,Cu,Mg and Si)have effected on the microstructure,Ti Cx ceramic particle size and compression performance of Ti Cx/Al composite materials.And the strengthening mechanism of Ti Cx/Al composite reinforced by alloy elements is also researched.1)As the addition of Zn,Cu,Mg and Si,the reaction temperature of Al-Ti-C system reduce and Ti Cx particle size decrease under a lower temperature.The average sizeof Ti Cx ceramic particle reduce from a of mixed scale(1.94 mm and 240.86nm)to 94 nm,200nm,96 nm and 98 nm,accordingly.2)Alloy elements refine Ti Cx particles and increase the strength of composite.The strengthening effect in order is: Mg>Cu>Si>Zn.It reveals that alloy elements significantly cause Ti Cx particles refinement and the solid solution strengthening of matrix.The composite with 5 wt.% Mg addition have the highest ?0.2 and ?UCS,which are 612.3MPa and 782.9MPa,respectively.(3)It reveals that different ceramic content and different ratio between carbon black and CNTs have affected the microstructure,the size of Ti Cx ceramic particle,compression properties and wear behaviors of Ti Cx/2014 Al composites.And the strengthening mechanisms and wear resistance mechanisms of Ti Cx reinforced 2014 Al matrix are revealed.1)It reveals that endogenous Ti Cx particles are gradually refined with the rising rates of CNTs in Al-Ti-C system,while decrease with the volume fraction of endogenous ceramic particles increase.The 30 vol.% Ti Cx/2014 Al composite fabricated with 50 wt.% CNTs as carbon source possess the best compression comprehensive performance,which Ti Cx particle have a smaller size and an optimum dispersion.The ?0.2??UCS and ?f would be 411.2MPa?711.8MPa and 17.2%,respectively.It reveals that the reinforcement mechanism of Ti Cx/2014 Al fabricated with 50 wt.%CNTs as carbon source: nano-sized particles has hindered the dislocation motion and grain boundary sliding,while micron-sized particles has caused thermal mismatch.2)It reveals that the volume wear rate of Ti Cx/2014 Al composites increase and the surface furrows are deepen and widen when load applied and sliding speed increases.It reveals the friction wear mechanism of composites are mainly adhesive wear and abrasive wear,combining with some oxidation wear.In the process of friction,Ti Cx particles not only undertake the effect of squeezing and plough cut,but also beard scroll effect,which produce plough cut between particles and matrix interface.(4)It was reveals that different ceramic content and different ratio between carbon black and CNTs have affected the microstructure,Ti Cx particles distribution,tensile properties and wear behaviors of hot extrusion Ti Cx/2014 Al composites.And the strengthening mechanisms at room,high temperature and resistance to abrasive wear mechanisms of Ti Cx reinforced 2014 Al matrix are revealed.1)The 30 vol.% Ti Cx/2014 Al composite fabricated with 50 wt.% CNTs as carbon source possess the best tension performance,which Ti Cx particle have a smaller size and an optimum dispersion.The ?0.2(466.1MPa)and ?UTS(656.2MPa)would be thelargest,comparing with 2014 Al,which have increased by 67.8% and 34.0%.493 K,the?0.2(197.8MPa)and ?UTS(318.0MPa)of 20 vol.% Ti Cx/2014 Al composite fabricated with 50 wt.% CNTs as carbon source are relatively high,comparing with 2014 Al which had increased by 64.4% and 74.7%.2)It reveals the strengthening mechanisms of nano-sized Ti Cx/2014 Al composites: the grain boundary sliding and dislocation movement can be hindered by the well dispersed nano-sized Ti Cx ceramic particles,which has raised the strength of composites at room temperature and high temperature.3)It reveals that the volume wear rate of Ti Cx/2014 Al composites increased and the surface furrow was deepen and widen when load applied,abrasive size increase and endogenous Ti Cx ceramic particles volume fraction decrease.Composites have better resistance to abrasive wear than 2014 Al.The 30 vol.% Ti Cx/2014 Al composite fabricated with 50 wt.% CNTs as carbon source has increased its resistance to abrasion by 180%,comparing with 2014 Al.4)It reveals the abrasive wear mechanism of Ti Cx reinforced 2014 Al matrix: Ti Cx ceramic particles has a high hardness than Al2O3 abrasive,which on the one hand help hinder abrasive cut into material,on the other hand make abrasive passivation.The wear resistance is also due to the dispersion of nano-sized particles,since nano-sized particles can effectively transmit load,reduce internal stress and work as a block between composites and abrasive. |
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