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 Posted: Mon 18:04, 10 Jan 2011 Post subject: stivali ugg Particle reinforced composites SiCp-60 |
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Particle reinforced composite solder joints SiCp/6061Al and tensile fracture behavior
butionofhardnessofweldedjointalongverticaldirection metal area. After the weld wire melting is rapid cooling of the crystal structure, and its nature depends on the chemical composition of the alloy wire and crystallization process. SiCp/6061 weld aluminum matrix composites, mostly form the final crystalline columnar dendrite and equiaxed weld center. There are unevenly distributed in the weld of the dispersion and segregation of SiC particles. The cast loose structure, strength, low hardness, plasticity poor. The lowest hardness at the weld center, and the tensile test breaks in the weld area in the center shows where the weakest for the welded joints at the J. In helium and argon gas mixture under the protection of the AC TIG welding, the filler material with high Si 4047 wire, welded on both sides to get a good weld joints. SiC particle reinforced aluminum matrix composites is the main problem when welding weld and weld pool in the metallurgical reaction. The reinforcement of the existence of the welding bath in the melting process and the physical and chemical processes undergone great changes, SiC Although Al does not occur in any solid-state reaction, but in the liquid with the activity of Al is able to react with liquid Al. According to the literature [6], the reaction is as follows: 3SiC (solid) +4 A1 (fluid) - Al4C3 (solid) +3 Si (solid) △ G / j-mol ~ = 113900-12.06TLnT +8.92 × 10 a +7.53 × 10 for a T ~ +21.5 T +3 RTlna where 1 is the Si in liquid Al in the activity. Al4C3 (solid) flaky precipitation,[link widoczny dla zalogowanych], Si (solid) showed a massive precipitation. The reaction not only consumes the SiC reinforcement, and the resulting brittle flakes AlC, so that the fracture toughness decreased. In addition, AlC in moist air or water in the environment can react to produce acetylene leaving soon weld corrosion. Welding process for the inhibition of SiC and liquid Al reaction, from process considerations, the use of TIG welding in the welding,[link widoczny dla zalogowanych], because of its low and controllable heat input will help reduce the pool heat, reduce the pool there is time; At the same time with good mobility with high Si4047 wire as filling material, to improve the pool of liquidity, reduce viscosity, reduce porosity, incomplete fusion and incomplete penetration defects such as sensitivity. In the liquid metal solidification process, the lack of fusion of reinforcement SiC particles can not play the central role of crystallization, but by advancing solidification exclusion, leading to the enrichment and enhancement phase segregation. But in the joint microstructure is not found brittle flakes AlC, generation, indicating that silicon-rich wires with better welding process inhibits the reaction of SiC and AI. 5 Conclusions 1) SiCp/6061 aluminum matrix composite mechanical properties of welded joints is lower than the mechanical properties of the matrix material, the tensile fracture of welded joints in the weld seam is the weakest part of welded joints, brittle cleavage fracture fracture. 2) The mechanical properties of the weld than the main reasons for the existence of low porosity, defects such as osteoporosis,[link widoczny dla zalogowanych], but also reinforced phase SiC particles is unevenly distributed. 3) considerations from the process, TIG welding and high-Si filler material with the application, the weld can inhibit the reaction SiC and liquid Al, to avoid the formation of brittle sheets AlC phase. References [1] Niu Ji-tai, LIU Li-ming,[link widoczny dla zalogowanych], Han Hong. Welding of aluminum matrix composites Status and Prospects [J]. Harbin Institute of Technology University ,1999.31:130-132. [2] T Ⅳ Klein, PJ Withers. Introduction to Metal Matrix Composites [M]. Beijing: Metallurgical Industry Press, 1996. [3] Wu Renjie. Metal Matrix Composites Present and Future [J], Materials Science, 1997,33 (1) :78-84, [4] Li Hui in the TRANSACTIONS OF Chenming An so on, 2519 aluminum alloy welded joint microstructure and properties [J], China Nonferrous Metals, 2004,[link widoczny dla zalogowanych],14 (6) :956-960, [5] Ma rain, Li Zhi, Liu Chang-sheng. Solution heating temperature on microstructure and properties of 2A70 aluminum alloy effects [J] Light Alloy Fabrication Technology, 2003,31 (5) :43-46, [6] EllisM, B. D. , GittosM. F,, ThreadgillP, L. JointingofAlumi-numBasedMetalMatrixComposites [J], InternationalMaterialsReviews, 1996,41 (2): 4l a 58, ∞ Canada: Come ∞ ∞ ∞ O> = / s8 port Lan 2u a pI
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