Research On Corrosion Behavior Of B₄C/6061 Al Composites

B₄C/Al composites are widely used in the aerospace field due to their performance such as high specific strength,low density,good thermal neutron absorption capacity.However,the composites cannot avoid contact with the external environment during use.The corrosion problem has become the main reason for restricting the application of the composites.At present,the research is focused on mechanical properties of composites,and the corrosion behavior and mechanism of composites need to be further developed.Three volume fractions of 5%,10% and 15% B₄C/6061 composites were prepared by hot-press sintering.The composites were treated in different aging.And the effects of aging and reinforcement content on the corrosion behavior of composites were analyzed.The corrosion of composites was carried out in a salt spray box and an electrochemical workstation,respectively.The corrosion morphology of the composites was analyzed by SEM and TEM,and the width of the corrosion pits was counted.The morphology and height changes of the composites after corrosion was characterized by laser confocal Finally,the size relationship of the corrosion resistance of the composites is evaluated by the analysis of weightlessness and electrochemical parameters.The results show that the composite structure is denser and the reinforcements are more evenly distributed with the increase of B4 C content.With the volume fraction of B4 C increasing,the tensile strength,yield strength and elastic modulus of the composites increase.The fracture mechanism of the composites is the ductile fracture of the matrix and the cleavage fracture of the reinforcement.In the salt spray environment,the mass loss of the composites were increased with the extension of the corrosion time and B4 C content.The results of electrochemical tests show that the corrosion current density of the composites increases and the corrosion potential decreases with the B4 C content increases.Both the salt spray environment and the electrochemical corrosion results show that the corrosion sensitivity of the three volume fraction composites is 15 vo.l%>10vol.%>5vol.%.Similarly,the effect of aging on its performance was studied.The peak-aging composites have the highest hardness and the under-aging composites have the lowest hardness,which is closely related to the composite matrix precipitates.The results of TEM characterization show that the precipitates of the composites in the peak aging is the ?? phase,and the precipitates of the composite material in the over-aging is the ?? phase.Corrosion in a salt spray environment,the quality loss of the composites and the change in corrosion pit width indicate that the composite.The relationship between the corrosion rate of the material is over-aging>peak-aging>under-aging.The rules obtained by the electrochemical test are consistent with the corrosion laws of the composites in the salt spray environment.Compared with the effect of the reinforcement content,the effect of the aging on the corrosion behavior of the composite material smaller.The corrosion mechanism of B₄C/6061 Al composite is as follows.On the one hand,the addition of B4 C prevents the formation of a continuous oxide film on the surface of the composites,and the interface position becomes a corrosion-sensitive area.The interface position was corroded preferentially by Cl-,and then the Al matrix formed corrosion pits.On the other hand,the main precipitates of the B₄C/6061 Al composites were anodic dissolved firstly.That was coupled with the Al galvanic couple,Al was corroded.With the extension of B4 C content and aging time,the number of internal interfaces and precipitated phases of the composites increase.The active sites of corrosion increase,and the degree of corrosion increases.Due to the small size of the precipitates,the effect of changes in the aging on the corrosion behavior of the composites is less than the effect of changes in the B4 C content.