The Fabrication Of B₄C/Aluminum Composites By Vacuum Hot-pressing Sintering

Particles reinforced aluminum composite materials were widely applied to aviation aerospace field and civil field. B4C particles reinforced aluminum composites are the developing one. Study on particles reinforced aluminum composite materials have important practical significance and value, now being pay close attention by more and more scientific research institutions and scholars. Preparation technology of vacuum hot-pressing sintering was explored.Successfully prepare B4C reinforced6061aluminum composites with different B4C contents of10wt%,20wt%,30wt%,40wt%by vacuum hot-pressing sintering method. The preparation technology, microstructure, mechanical properties, corrosion resistance and rolling board performance of the composite material have been studied.Technology research shows that the best process for vacuum hot-pressing method:B4C powder was cleaned by alcohol or acetone in advance, then preoxidated at420℃one hour after the powder was dry. Heat temperature was preserved at500℃for30minutes in the process of heating. Sintering process parameters were:sintering time of60min. sintering temperature of650℃, sintering pressure of120MPa.Microstructure research shows that, in the composite material prepared by the method of hot pressing, B4C particles distribute uniformly, material forming quality is good. No new phase appear during the hot-pressing sintering process. With the rise of content of B4C, the sizes of the particles in the composite materials decrease because of the particles break during the preparation. The interface between the two phases have obvious element diffusion phenomenon. The physical and mechanical properties research shows that, the consistency of composite materials was high and with the increase of the content of B4C reduced. Materials with the content of B4C hardness increases, when the B4C content was10wt%,20wt%,30wt%,40wt%, the average hardness of B4C particles reinforced6061aluminum composites was91.08,102.1,123.6,139.2HV, matrix was increased by12.8%,26.5%,53.2%,72.5%. When the content of B4C was30wt%, the microscopic Vickers hardness of the region around the particles increased by51.4%compared with the matrix.Corrosion test show that, different contents of B4C did not significantly change the electrochemical corrosion properties of composite materials, along with the increase of the content of B4C, corrosion potential Ecorr of material have not changed much, corrosion current icorr present the trend of increased after the first decreases, the corrosion current icorr was4.772×10-6A·cm-2,2.803×10-6A·cm-2,2.526×10-6A·cm-2,7.597×10-6A·cm-2. The polarization characteristics of pure aluminum matrix composites and6061aluminum matrix composites have a little difference. When contain the same content of B4C, the corrosion resistance of pure aluminum composite material below the6061aluminum matrix composites and the corrosion current icorr eight times of that for the latter. Corrosion resistance test through weight-loss method had the same conclusion as the above results.Composite material performance study of rolling plate suggests that, the density and hardness had increased greatly with hot pressing state materials, the tensile properties of composite material decreased with the increase of the content of B4C. When the B4C content is30wt%, the tensile strength is only82%of6061aluminum alloy matrix. B4C/Al composite materials fracture mode is brittle fracture, the fracture appeared toughening nest and matrix crack.