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Effect of Particle Size on the Damping Property of SiC_p/Al Composites

Author: ShiHongXia
Tutor: LiAiBin
School: Harbin Institute of Technology
Course: Materials Science
Keywords: Aluminum matrix composites Particle size Powder Metallurgy Damping properties Damping mechanism
CLC: TB331
Type: Master's thesis
Year: 2009
Downloads: 76
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Abstract

In order to clarify the particle size of the aluminum matrix composite microstructure, mechanical properties and damping properties of the impact of the law, this article uses 10% of the nanoscale prepared by powder metallurgy, submicron and micron (40nm, 500nm, 1μm, 5μm and 10 μm) the SiCp / Al composites. Focus on the preparation of nanoscale composite milling process, as well as the preparation of micron composite milling and mechanical mixing flour two processes. SEM and TEM to study the microstructure of composite materials with different particle size, test the corresponding tensile properties at room temperature, and particle size on the microstructure and mechanical properties of material. The dynamic mechanical analyzer (DMA) to test the low frequency damping properties of composite materials with strain and temperature variations damping performance on the law of particle size on the damping properties of composite materials and damping mechanisms. Through the study of the impact of nano-SiC and Al milling process of milling time and stearic acid powder mixed effect, determine the optimal milling process parameters: 15h of milling time, process control agent content 2wt%. And successfully prepared a comprehensive performance nano and submicron composite tensile strength of 395 and 365MPa, respectively 259% and 232%, respectively, compared to the pure Al; elongation decreased, respectively, 12.51% and 11.4 still %. After annealing performance declined marginally. Both processes were used milling and mechanical powder mixed micron (1μm, 5μm and 10μm) composites were prepared. Ball Milling composite tensile strength of 305 ~ 316MPa, the plasticity is only 4.0 to 7.2%; while the tensile strength of the composite prepared by mechanical mixing powder only 133 to 142MPa plasticity reach 17.3 to 26.3%. The study showed that the milling process than mechanical powder mixing process easier substantial increase in the tensile strength of the composite material, at the same time while filling plastic sharp decline. The mixed powder preparation for the high-energy ball milling of different particle size of SiCp / Al composites, tensile strength, yield strength than pure Al significantly improved elongation decreased. With the reduction in the size of the SiC particles, the tensile strength of the composite material is extruded, the yield strength and elongation, is gradually increased; After annealing, the strength and ductility of the composite material than extruded slightly reduced. TEM analysis showed that the particle size of 40nm and 500nm squeezed state SiCp / Al composite thermal mismatch dislocations near the interface, matrix deformation dislocation caused by hot extrusion composite fine grain . Annealing eliminates deformation bit wrong, composite recrystallization, nano SiC impede dislocation movement inhibit grain growth, recrystallized grains are very small. SiCp / Al composites of extruded micron level at the interface and the matrix has a large number of dislocations, annealing to eliminate part of the deformation dislocation composite recrystallization. Dynamic mechanical analyzer composite damping. Room temperature damping - the strain amplitude curve studies have shown that both nano and submicron and micron the level composite materials at room temperature are shown typical dislocation mechanisms. With the reduction in the size of the SiC particles, the damping performance is gradually increasing. After annealing, with the increase in the size of the SiC particles, the damping performance is gradually increased. And found that the the nanoscale composite damping performance significantly higher than other size materials; After annealing, the damping performance becomes minimum. Damping - temperature spectra of the test results showed that the particle size significantly affected the internal friction peak appears. Nm, submicron and micron composite discovered the existence of the dislocation internal friction peak and shift as the particle size increases, the internal friction peak. Grain boundary damping peak in the nano and submicron composites can be significantly observed, is not evident in the micron level composite material.

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