Microstructures And Properties Of Cylindrical Parts Of SiCp Reinforced Al Matrix Leaping Functionally Graded Materials Manufactured By Centrifugal Casting

Due to special properties, functional graded materials (FGMs) has becoming one direction of new materials investigation. However, the production still remains in an experimental stage, mainly because of a lack of the fundamental theory research. Focusing on reducing cost and bulk production, the fabrication and centrifugal casting forming of particle-reinforced Al matrix composites was investigated. So as to properties.Based on experiment data, the paper simulated segregation of SiC particles of three different sizes under centrifugal field, firstly. The results showed that most particles distributed in the outer wall and relative thickness of particle-rich region was larger than that containing one size particles. Sedimentation did existed in gravitational field without machine whisk, attributed to density difference between particles and Al melt. The process of depositing sediment was also computed in 5 minutes, resulting in composition diversity vary with axes. And it was observed that bigger particles have faster sediment speed.More than 30kg, composites was fabricated, in which ZL104 alloy and ZL109 alloy were matrix, respectively, and volume fraction of SiC particles was 20% , whose diameter were 15μm,30μm and 59μm. Particles and matrix would react in high temperature, and resultant would weaken whole properties of composites. Oxygenation was a effective method to prevent react and promote wettability. Machine whisk at semi-solid temperature, dispersing particles, was expounded. With centrifugal casting, two cylinders were manufactured at 766℃and 820℃, respectively. Increasing machine whisk time and casting temperature, bubble and oxidation were decreased notablely. A particle-rich region and a particle-free region were seperated by a interface obviously, standing for the particles dispersed leapingly. Relative thickness was close to simulation, but volume fraction of SiC particles was less. It was observed that particles and matrix were connected with mechanical interlocking and atomic diffusion, and there were alloy and silicon elements segregation around interface.Hardness and wear behaviour were detected before and after heat treatment. Results showed that: heat treatment enhanced hardness of composites and it was a way to increase hardness of metal matrix composites reinforced by particles, while the degree of enhancement in particle-rich region was bigger than that in particle-free region; aging cuttd down composites wear ability; peak hardness was advanced to 3h or 4h, because particles accelerated nucleation dynamic of precipitation during aging in matrix. The diversity between experimental result and simulation was analysed: solidification and variational viscosity had great effect on particles distribution, substitute for solidification should take into account to make simulation result close to the experimental.Finally, a thin-wall cylinder with 2.5mm thickness and 80mm high was manufactured by turning. Compared with nomal materials, composites weared cutting tool severely, while generating large quantity of heat, and surface quality was hard to control.