| With the development of the modern science and technology, especiallythe progress of aerospace and aircraft industries, more and more advancedmaterials which have excellent properties are desired. These properties such aslower density, high specifc strength and high fracture toughness are hoped, andthe probability of utilization in high temperature, high pressure, highvacuum,intense corrosion or radiation harsh environment is expected. The requirementfor light, strong and stiff materials has extended an interest in metal–matrixcomposites (MMCs) and people have paid more and more attention to thembecause of their improved strength, high elastic modulus and increased wearresistance over conventional alloys during the last 20 years. Ceramics, e.g.boron, carbon, silicon carbide and alumina which have been produced invarious forms such as continuos fibres, short or chapped fibres, whiskers andparticulates or wires have been used as reinforcement in MMCs.Among these metal matrix composites, Aluminum matrix reinforced withAl2O3 particles composites are being considered by aerospace and automotiveindustries for several engine applications such as connecting rods, pistons,gear selector torks and cylinder liners because of their high-strength-to weightratio.In this paper, we discussed the phase transformation and thephotoluminescence of mechanically milled Nano-Sized γ-alumina by XRD,TEM, DSC and PL , and we found that temperature of the phasetransformation was lowered by 210KJ/mol after ball-milling for 100h, andthere was obvious change in the PL with the ball-milling time increasing.Spectral behavior of UV luminescence suggests that the UV band cannot beassigned to F+ or Al+i center, prefer to be self-trapped exciton or bound exciton.The other bands are originated from defect center and impurity.In this paper, the development of the Al matrix composites reinforcedwith Al2O3 particles were summarized. Based on the reviews of the latestdevelopments, a new idea was brought to prepare Al matrix compositesreinforced with different ratios and sizes of Al2O3 particles. The experimentscould be divided primarily three steps: Preparation of composite powders,making green samples and sintering.The XRD and SEM methods were used to character the changes duringthe first stage of mixing composites power, and the composite powders of 5,10,20vol%Al2O3/Al were fabricated well by the high energy ball-milling. Inorder to improve the relative densities of aluminum matrix compositesreinforced with Al2O3 particles, a process of pressing in high pressure(850Mpa) and moderate temperature (230oC) was added to the conventionalpreparation method, powder metallurgy technique. Then we selected the bestmethod for sintering. After sintering, the relative densities of samples for5,10,15,20 (20nm)vol% Al2O3/Al were 99.9%,98.2%,97.2%,95%, and theyield strength was respective to 400Mpa, 503Mpa, 540Mpa and 268Mpa;for5,10,15,20vol(100nm)%Al2O3/Al, the relative densities were99.9%,99.9%,98.2%,96.5%, and the yield strength was respective to 414MPa,449MPa, 465MPa and 532MPa;for 15vol(200nm)%Al2O3/Al and15vol(500nm)%Al2O3/Al, the relative densities were 98.7% and 99.2%, andthe the yield strength was respective to 434MPa and 401MPa;for 15vol%Al2O3(2μm)/Al, the relative density was 99.6%. Dramatic enhancements instrength and hardness are for all the samples. We found that the yield strength,hardness and wear resistance were increased when the smaller size grains forthe Al2O3 were used. To be applied in some field, we regard the15vol%Al2O3p ( 100nm ) /Al as the best one. The mechanism of thereinforcement was analyzed by Hall-Petch and Orowan model.
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