Ultrasonic Testing And Performance Research Of Particle Segregation Defects In Aluminum Matrix Composites

The particle-reinforced aluminum matrix composite has excellent performance,low mass production cost and simple production process,and has excellent characteristics such as high plasticity,high toughness,high hardness and high modulus.After years of development,it has become an indispensable lightweight functional material and structural material in high-tech fields such as aerospace,defense and military.However,due to the imperfect preparation process and the addition of second-phase particles,the particle-reinforced aluminum matrix composite products are prone to inhomogeneous distribution of particulates,which has a serious impact on the performance of the material and limits the particle-reinforced aluminum matrix composite Use of materials.This paper aims at the particle segregation defects that are easy to occur in particle-reinforced aluminum matrix composite materials.The characteristics of reflection,scattering and transmission of ultrasonic waves on discontinuous surfaces are used to initially establish the relationship between ultrasonic information and material organization.And the properties of the defective composites were studied.In order to explore the effect of different volume fractions of SiC on performance,pre-prepared samples of different volume fractions of SiCp/Al composites were added to 15%SiCp/2009Al and 60%SiCp/2009Al composites to Simulate SiC segregation defects.Ultrasonic nondestructive testing was performed on 15%SiCp/2009Al and 60%SiCp/2009Al composite samples containing defects prepared by powder metallurgy.At the same time,The effect of SiC segregation defects of different shapes and sizes on the performance is simulated.The 15%SiCp/2009Al and 60%SiCp/2009Al composites with defects prepared by powder metallurgy were studied by ultrasonic nondestructive testing,and it was found that the difference between the defect size and volume fraction method can be shown in the ultrasonic testing waveform.When different volume fractions of SiC are added to form defects with the same size and shape,the volume fraction of SiC is large and the peak of the defect is high;for cylinder defects of the same volume fraction,the defect size formed by the addition of SiC is large and the ultrasonic peak is high.On this basis,the defects with inhomogeneous distribution of particulates are accurately located,and then these defects are dissected out to make samples containing defects,and the tensile properties of these samples containing defects are tested.The results show that with the increase of the size of the SiC segregation defects,the tensile strength of the sample with defects decreases significantly,which is 24%lower than that of the sample without defects location.When the volume fraction increases to 60%,the tensile strength decreases by about 30%.The matrix of the normal tissue presents tough dimples,indicating that the normal tissue of the sample has undergone ductile fracture;the cleavage fracture or cracking of the SiC particles indicates that the stress can be effectively transferred from the matrix to the particles,and the role of particle reinforcement is fully exerted.When the tensile fracture is a defect structure,brittle fracture can be observed.On the basis of the above results,a fracture toughness test was performed on 15%SiCp/2009Al with inhomogeneous distribution of particulates.The fracture toughness results show that as the SiC content increases,the fracture toughness increases first and then decreases.The 15%SiCp/2009Al composites with defect has a maximum fracture toughness of 22.55 MPa·m1/2.Among the samples with a defect size of φ2mm × 4mm,the lowest value of fracture toughness was 7.68 MPa·m1/2.Compared with the standard sample without defects,the fracture toughness decreased by 64.7%.When SiC with the same shape and the same volume fraction forms a segregated region,and the volume fraction of SiC is greater than 15%,the larger the size of the segregated region,the greater the decrease in toughness.In short,through ultrasonic non-destructive testing of 15%SiCp/2009A1 and 60%SiCp/2009A1 composites with defects,we can accurately determine the equivalent size of defects for defects with a segregation area size of cp0.8mm × 1.6mm,And make a certain evaluation of the performance of the material.In the actual production process,if it is found to contain segregation defects with a size of φ1.2mm × 2.4mm or more,the tensile strength and fracture toughness of the product both decrease,and the yield strength does not change.According to the actual application scenario,it is necessary to judge whether it meets the usage requirements.