Study On The Properties Of Aluminum Matrix Composites With Different Particulate Reinforcement

Particles Reinforced Aluminum Matrix Composites (AMCs) have been widely used in the field of aerospace, electronic packaging, automobiles and daily life. At present, SiCp reinforced ACMs which have been most extensively applied are mostly fabricated by directly adding methods. These composites do not achieve favorable effects of reinforcement due to large-sized particles and poor wet ability between particles and matrix. Therefore, people began to look for better reinforced particles and fabricating methods. Scientists find that TiB2 particles have outstanding mechanical and other physical properties, and moreover they are able to be synthesized directly in the aluminum matrix through chemical reactions. This kind of in-situ ACMs, has small and fine particles and better bond of interfaces. So the purpose of this research is to compare the microstructures and mechanical, damping and wear performances of the ACMs at similar particle contents fabricated by these two different methods and discuss the advantages of in-situ fabricating process.7wt%TiB2 reinforced A356 alloys are successfully fabricated by mixing salts method. In-situ TiB2 particles of which the average size is 300nm mostly have the shape of hexahedral prism and are well distributed within the matrix alloy. Theα-Al grains appear mostly as equal axial and the grain size is much finer than that in the base alloys. SiCp/A356 as compared material fabricated by stir casting has particles has particles of 15μm and also well distributed, but majority of SiC particles have pointed edges and corners. The tensil strength andmodulus of elasticity of 7%TiB2/A356 have reached to 362.5MPa and 81.2GPa respectively, with the increace of 12.4% and 21.6%, but the plasticity has fallen off.The damping-temperature curves of 7%TiB2/A356 and 8%SiCp/A356 are investigated in this research, and conclusions can be drawed as follows: the damping capacity of both two composites increases with the rise of temperature, and high damping capacity are more likely to emerged in low frequency; the sequence of damping capacity of composites and base alloy is: 7%TiB2/A356>8%SiCp/A356>A356. The reason why these two composites have higher damping capacity is the dislocations generated while fabricating and which become a source of damping. That 7%TiB2/A356 has higer damping capacity can be ascribed to much more interfaces and grain boundaries result from small TiB2 particles.The dry wear performances of 7%TiB2/A356 and 8%SiCp/A356 are also studied, 8%SiCp/A356 is better than 7%TiB2/A356 in wear performance. Both compostes have lower wear rate than base alloy and 40Cr, and with rise of sliding speed, the wear rate of 8%SiCp/A356 has slightly decreased and that of 7%TiB2/A356 has increased. The wear mechanism of 8%SiCp/A356 at low load is mainly adhesive wear, and abrasion wear and adhesive wear at high load. A mechanical mixed layer is able to form on the wear surface so as to prevent from abrasing, and this layer is more inclined to emerge in higer siding speed. The wear mechanism of 7%TiB2/A356 is mainly adhesive wear at low load and adhesive wear and delamination wear at high load. With sliding speed increases, oxidation wear ought to be taken into consideration.