Research On Mechanical Properties Of Al₂O_3p/Al Composite Prepared By Pressureless Infiltration

Alumina short fiber reinforced aluminum matrix composite materials have been successfully used in engine piston parts,but there are few reports on the application of alumina particle reinforced aluminum matrix composite materials.How to prepare different properties alumina particles reinforced aluminum matrix composite materials to expand its application range is an important topic.In this paper,3different types of Al₂O₃particle are selected and ultrasonic cleaned to prepare Al₂O_3p/Al composites by pressureless infiltration,with two being spherical and porous particles（4 different diameter ranges）and one being irregular particle.The effects of morphology and size of the Al₂O₃particles on mechanical property of the corresponding composites were investigated by means of scanning electron microscopy（SEM）,X-ray diffraction（XRD）,3-point bending test and finite element simulation.All kinds of the Al₂O₃particles are adhered by many fine alumina powder（<5μm）,which can be removed by ultrasonic cleaning method.Furthermore,many of the fine alumina particles（<10μm）can be observed in four of the nine studied Al₂O₃particle,including the porous Al₂O₃particle with average diameter（D50）being33.224μm and 51.729μm,respectively,the spherical particle with D50 being 36.960μm and the irregular particle with D50 being 38.493μm.SEM observation shows that the phenomenon of particle aggregation and the existence of the fine particles in the original Al₂O₃particles can lead to the defects in the composites.The fracture mechanism of the composite with spherical and porous alumina particles is mainly cleavage fracture of alumina particles.The fracture mechanism of composite using the irregular alumina particles is mainly interfacial debonding.XRD results show that the three types of alumina particles areα-Al₂O₃.In general,a low fraction of the interface reaction product,Mg Al₂O₄,can be formed in the composite.The elastic modulus of the composites using the spherical and porous alumina particles are higher than that of the composites using irregular alumina particle.This is because that the composite using the spherical particle possesses high density and high volume fraction of Al₂O₃.Meanwhile,the composite using the porous particles have the unique three-dimensional network configuration,which is consistent with the finite element analysis.The simulated value of the composite with porous particle（140.09 GPa）is 31.44%higher than that of the composite with irregular particle（106.58 GPa）with the same alumina volume fraction.For the spherical alumina particles reinforced aluminum matrix composites,the volume fractions of the composites,irrespective of the particle size,are about 58%.The density and elastic modulus of the composite using the finest spherical alumina particles（D50=36.690μm）are relatively low,being about 93.04%and 151.54 GPa,respectively.Meanwhile,the density and elastic modulus of the other three composites using large spherical particles being about 97%and 204 GPa,respectively.For the spherical and porous alumina particles,the bending strength of the corresponding composites increases first and then decrease as the particle size is increased.For the spherical particles,when the average particle size（D50）is 54.443μm,the composite material has the maximum bending strength,being 396.47 MPa.For the porous particles,when the average particle size（D50）is 70.936μm,the corresponding composite has the maximum bending strength,being 317.31 MPa.