Study On Aging Behavior Of Low Volume Fraction B₄C/6061Al Composites

In this paper,3vol.%,6vol.%,9vol.%and 12 vol.%B₄C/6061 Al composites were prepared by pressure sintering.The aging behavior of four kinds of composites was studied by hardness tester,DSC differential scanning analysis,SEM,TEM and universal electronic test machine.The diffusion behavior of Mg and Si elements in B₄C/6061 Al was revealed by introducing the number of different interfaces and adjusting the spacing of particles,and the mechanism of aging microstructure and its influence on mechanical properties were clarified by adjusting the aging temperature and time.The DSC test results of composite materials show that when the volume fraction of B₄C increases,the reaction peak representing the precipitated phase in the DSC curve is passivated and the precipitation behavior of the metastable phase is suppressed in varying degrees.The results of hardness test of composites show that with the increase of the volume fraction of B₄C,the time of the composite material to reach the peak hardness is shortened,and the aging hardening rate?peak aging of the same temperature?is on the rise.This indicates that B₄C can accelerate the aging kinetics of composites and increase the age hardening rate of composites.At the same time,when the aging temperature of the composites increases,the time to reach the peak hardness decreases,and the peak hardness decreases.The study of the peak aging structure of B₄C/6061 Al composite shows that B₄C does not change the aging order of the composite,but the number density,the average cross section area,the average needle length and the volume fr action of the precipitated phase change.When the content of B₄C particles in the composite increases,the interface area in the matrix increases and the Mg element will be segregated at the interface,which reduces the Mg element in the matrix,thus reduc ing the volume fraction of the composites.At the same time,the dislocation density in the composite increases with the increase of the volume fraction of the B₄C,causing the Mg and Si elements to be biased.It is beneficial to precipitate the phase nucl eation and increase the number density;the increase of the B₄C content is accompanied by the decrease of the particle spacing,which is not conducive to the diffusion of the elements,inhibits the growth of the precipitate phase and reduces the average cr oss section area of the precipitate phase.The effects of B₄C volume fraction and peak aging temperature on tensile properties of B₄C/6061 Al composites were studied.With the increase of B₄C volume fraction,the elastic modulus,tensile strength and yield strength of the composites increase.The composites with low volume fraction have good plasticity.The tensile strength of 9vol.%B₄C/6061 Al composites at 160?is 470 MPa,the elongation is7.9%,and the modulus of elasticity is 95 GPa.The fracture analysis shows that the four volume fraction composite exhibits plastic fracture characteristics.With the increase of B₄C volume fraction,the number of dimples increases,but the depth becomes shallow.At the same time,the fracture phenomenon of large size B₄C particles is observed in the dimple of the composite material.