Analysing the effect of B4C and SiC on microstructure, physical and mechanic properties of AA2024 and AA6061 matrix composites, fabricated from pressure infiltration

In this study, the effects of matrix composition and pressure value on microstructure and physical properties of AA2024 and AA6061 matrix composites reinforced with 50% of B4C and SiC particule is examined. By using B4C and SiC particules with 48μm and 37μm average grain size respectively, 50x8 mm-sized preforms are created in 50x8mm dimension steel tubes. Using pressured infiltration technique AA2024 and AA6061 aluminum matrixes are infiltrated under 7 bar and 8 bar pressure and 800 celsius degrees temperature. The microstructure analysis of composite materials is carried out by using EDS-equipped electron microscope (SEM). Porosity is calculated using a device with hooks which is placed in alcohol that is integrated to a precision scales. It is found that porosity is formed around the B4C and SiC particules. Volume of porosity is decreased by increasing the pressure. The results suggest that composites with SiC particule have higher porosity than the composites with B4C particules due to the grain size. EDS analysis also shows the formation of gray-colored intermetallics. The X-ray diffraction (XRD) is used in order to determine the structural differences which were caused by different reinforcement materials. XRD analysis shows the formation of secondary phases such as Al4C3, Al3Ti, Al3BC, Al4SiC4, Al2O3, Al4C3, Mg2Cu, Al3Cu2, MgCuAl2, CuAl2, Al6Si2O13, Al2O3 and Mg2Si. Mechanical properties are determined using hardness and compression tests. The hardness test conducted on AA2024 and AA6061 composites proves that increasing pressure on the composites with B4C and SiC results with substantial increase in hardness value. The pressing test found that increasing pressure on B4C and SiC, which were used to reinforce AA2024 or AA6061 composites, also increases its compression strength. These findings correspond to the results of the hardness test. The increase in compressive strength is the result of up to 90% decrease in porosity and of the secondary phases that occur in the structure. The comparison suggests that pressure increase improves the mechanical properties of matrix composites. According to the comparison between matrix materials, AA6061 matrix composites have better mechanical properties compared to AA2024 matrix composites. Additionally, the comparison between reinforcement materials shows that the composites reinforced with B4C have better microstructure and mechanical properties than the composites reinforced with SiC.