Effects Of The Combination Variation Of Matrix And Particle On The Damage Evolution And The Mechanical Properties Of Particle Reinforce Aluminum Matrix Composite

Effects of the combination variation of particle and matrix on mechanical properties and the effective strengthening matching range of particle and matrix in particle reinforced aluminum matrix composite were studied.Eighteen composites combine of particles with size of 4?m?8?m?12?m?15?m?20?m?30?m and Al-Cu-Mg alloy matrices with yield strength of 90 MPa?292 MPa?378 MPa were manufactured by powder metallurgy process.Their yield strength,ultimate strength and elongation range from 90 MPa to 379 MPa,131 MPa to 561 MPa and 18%to 31%,respectively.The feature of damage evolution from loading to failure of these composites were counted and analyzed using in situ tensile testing.Based on the analysis,the link between the damage evolution and mechanical properties of composite was built.Effects of combination variation of matrix and particle on damage evolution and mechanical properties of composite were obtained.The effective strengthening matching range of particle and matrix were established.The research shows that during deformation of the composite,two major damage would occur,particle cracking and matrix slippage.These two damages were accumulating with the deformation process of composites.Based on the statistical data of these two major damages,the damage evolution was divided into three stages,the elastic stage in which no damage occurs,the transition stage in which the most of the particle cracking accumulates and the plastic deformation stage in which particle cracking almost remains constant and slippage density continues increasing.The relative ratio of the particle cracking and the slippage density is decided by the combination of matrix and particle.The variation of this ratio leads to different failure mechanisms.A composite with a relatively high strength matrix or a large size particle will fracture with large quantity of particle induced damage and have a low value of the ratio.When the value of this ratio is high,the matrix of the composite will sustain more damage and failure with the void coalescence.When compared the damage evolution and the mechanical properties of the composite,the effective strengthening matching range of particle and matrix was found.In this matching range,the composite strength increases with the increasing matrix strength and decreasing particle size.When the particle and matrix achieve an improper match,the composite strength can be lower than that of its matrix.As for the strengthening of the composite yield strength,when the particle bears a stress exceeding its strength in the elastic stage,the particle cracking will happen before the yielding of the composite.With a relatively high strength matrix or a large size particle is used in composite,the early fracture of the particle would happen and cause the lowering of the composite's yield strength under its matrix's yield strength.As for the ultimate strength of the composite,when too much damage occurs in the process of composite deformation,this composite will fracture with large quantity of particle induced damage and has an ultimate strength of composite lower than that of its matrix.As for the ductility,the elongation of the composite increase with the increasing particle size when the particle size is smaller than the critical size.The main factor in this stage is the resistance of the particle to the matrix deformation.When particle size is larger than the critical size,the composite elongation decreases with the increasing particle size due to the early fracture caused by particle cracking.Based on the changing rules of the mechanical properties of the composite,effective strengthening matching range of particle and matrix was defined as a function of the particle size and the matrix strength using polynomial fitting.When the particle size D and matrix yield strength a satisfy the numerical relation:2.03+2.90×10-2D+2.68×10-3?+2.69×10-5D2-2.06x10-6?+2.18×10-5D??1,the composite is in effective strengthening state.And in this rang,a higher elongation can be obtained when the particle size chosed is closed to 12?m.When the particle size D and matrix ultimate strength a only satisfy the numerical relation 1.48+1.17×10-2 D+2.09×10-3?+4.28×10-5D2-2.40×10-6?2+2.19×10-5D??1,the composite is in limited strengthening state,and only ultimate strength can be strengthened.When a composite is designed mainly for a structure part,the combination of particle and matrix should satisfy the effective strengthening relation to achieve better performance.