Microstructure & Mechanical Properties Investigation Of Al Matrix Composite Reinforced With In Situ Regulated Al/Cu Intermetallic Compound Particles

Metal matrix composites have been widely used in the fields of aerospace industry,national defense and so on for their good comprehensive mechanical properties.Meanwhile,as a kind of large plastic deformation technology,accumulative roll bonding?ARB?with advantages of easy operating,lower cost and multi-component combination choices is viewed an ideal metal matrix composites preparation method.Also,composites reinforced with particles like SiC?Al₂O₃ and B₄C have been a hot topic for the blocked dislocation movements during plastic deformation with the existence of those hard particles.Also,intermetallic compound with considerable hardness is used as the reinforced particles though related reports are limited.As a result,the idea of fabricating Al matrix composite reinforced with in situ formed intermetallic compound particles is put forward in this study.Then,factors including the particle size,shape,distribution in matrix,phase component together with their effects on the microstructure and mechanical properties of composite we obtained were investigated.In this thesis,the microstructure evolution,interface bonding,mechanical properties and fracture mechanism of the Al/Cu composite sheet were studied in depth by optical microscope?OM?,hardness tester,scanning electron microscope?SEM?,transmission electron microscope?TEM?,X-ray diffractometer?XRD?and universal tensile testing machine.Results show that:it is effective to achieve not only good interface bonding but also the continuously formation and fracture of Al/Cu intermetallic compound layer via ARB?250??and various annealing time?350??.In this process,the matrix grains are refined gradually with increasing ARB cycles;Production of the intermetallic compound layer which contains Al₂Cu,AlCu and Al₄Cu₉ can be mainly attributed to the diffusion of Cu atoms to Al side.Particles with core-shell structure in composite with eight cycles are nearly consisted of Al₂Cu.Besides,parameters including anneal temperature,time,numbers of ARB cycles,and initial thickness of Cu layer are worth considered to achieve ideal distribution and finer size of the particles;After one ARB cycle,emergence of fresh Al/Cu interface during rolling provides diffusion channels for the formation of more intermetallic compound in subsequent anneal.Meanwhile,the increased solution of Cu atoms in Al matrix is also helpful to the strength of composite;Strength of the composite?eight cycles?reaches a highest value of 181MPa which is 1.8 times of that for annealed 1060 while the composite?five cycles?owes the best comprehensive mechanical properties?161.3MPa,4.1%?.Better interface bonding inside composite is achieved with the increase of ARB cycles and the fracture analysis indicates a typical ductile fracture for Al layer,on that the equiaxed dimples are gradually transformed into shearing like ones.Typical brittle intergranular fracture is observed on the position of Al/Cu intermetallic compound particles;In situ tensile curves of the composite samples can be divided into three parts:elastic stage,plastic stage and failure stage.For the absence of brittle intermetallic compound particles,tensile curve of the composite sample?eight cycles?is dominated by plastic deformation stage comparing with that of the primary sandwich.In addition,the initiation and propagation process of the main crack is realized through the joint action of micro cracks?nearly along normal direction?connection inside particles,the generation of voids at the edge of particles and the horizontal local delamination along previous Al/Al interfaces.