Research On Microstructure And Mechanical Properties Of Pre-oxidized B₄C_p/Al Composites

With high hardness, low density and high fracture toughness, B4C/Al compositeshave wide potential application background in national defense industry. They also havegreat potentiality in the application of optics and precision components and inertanceinstruments. This work has done research on the oxidation behavior of B4C particles,based on which six systems of B4Cp/Al composites with50%volume fraction wereprepared by pressure infiltration. EMT-01Dynamic Modulus of Elasticity at AmbientTemperature Tester, Brinell Hardness Tester, Electronic Universal Testing Machine andTransmission Electron Microscope were used to study the basic properties, mechanicalproperties and microstructure of the composites.The oxidation behavior of B4C particles was studied. It was found that the oxydatelayer grew in a branch way, then it would melt and form amorphous state. And a cubicmodel was built to calculate the thickness of the oxydate layers. A cubic model wasbuilt to calculate the thickness of oxydate layers.Chose500℃-5min and500℃-30min pre-oxidation technologies to oxidize B4Cparticles and prepared6kinds of composites based on pure Al and2024Al matrix. Theresults showed that the density of the composites did not change a lot because of theoxydate layers were too thin. The difference of hardness came from the precipitates of2024Al.The mechanical properties and microstructure at room temperature and hightemperature indicated that oxydate layers could improve interface bonding and increaseinterface strength. Moreover, pre-oxidation could make B4C particles more mellow, soas to decrease stress concentration at corners of particles. Therefore bending strengthand ductility of the ductility of B4Cp/Al composites increased to some extent.From room temperature to300℃, with the extent of pre-oxidation increased, thecompressive strength of B4Cp/2024Al composites decreased and the compressive strainincreased. The compressive strength of B4Cp/1060Al composites did not change a lotand the compressive strain decreased a little. At400℃, the thicker the oxydate layerswere, the worse the compressive ability of B4Cp/Al composites was.