THERMEC 2006

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Authors: Waldemar Alfredo Monteiro, S.J. Buso, A. Almeida Filho
Abstract: In the last decade light materials have been studied thoroughly and used in components of pieces in the automobile, naval and aerospace industries. Their application makes possible mass reduce, load capacity increase, improvement in the mechanical properties when it is possible. Aluminium-magnesium alloys present good mechanical properties at moderate mechanical efforts (400 to 700 MPa) and good corrosion resistance. The alloys in study (Al-2Mg-0.6Zr and Al-2Mg-1Nb) were made by powder metallurgy (P/M) techniques, employing hot compactation and extrusion processes followed by cold work and thermal treatments. The analysis by SEM and TEM shows an evolution in the microstructure of precipitates with the increase of the time of thermal treatment, according to literature. The distribution of the precipitates in both alloys was observed and identified by EDS microanalysis (SEM and TEM).
446
Authors: Jae Ik Cho, Xin Yan, Chang Seog Kang, Ik Hyun Oh, Jae Seol Lee, Hyeon Taek Son, Jung Chan Bae
Abstract: In this study, the microsegregation effect of copper during solidification of A356.2 aluminum casting alloy was evaluated by using solidification simulation and a series of experimental works. Electron probe micro analysis (EPMA) and the computational simulation revealed clearly that copper as a solute element segregates during solidification and it becomes more significant as the solidification approaches its completion. This microsegregation effect of copper is due to accumulated copper solute ahead of the eutectic interface during solidification. Consequently, the presence of a higher content of copper in A356.2 aluminum casting alloy causes influence on the solidification characteristics of the alloy and forms copper enriched phases at the last region to solidify in the microstructures.
452
Authors: Qiang Wang, Xue Jun Pang, Chun Jiang Wang, Tie Liu, Dong Gang Li, Ji Cheng He
Abstract: The distribution and solidified structure of alloying elements are important for the quality and the properties of alloys. In the present study, the solidification behavior of aluminum-rich alloys is studied under various high magnetic field conditions, and the influences of uniform and gradient magnetic fields with different intensity and direction on the distribution and the morphology of solute elements of Al-Cu and Al-Mg alloys are investigated. It is found that because of the differences of the electromagnetic force (Lorentz and magnetization forces) acting on Cu element and Mg element with different physical properties in the matrix, the regularities of distribution for Cu element and Mg element are opposite just in the intracrystalline and intergranular under high uniform magnetic field condition, and not only the content but the distributions of Cu and Mg elements are obviously different under high gradient magnetic field conditions as well. It can be concluded that high magnetic field has different effect on the solute distribution in alloys with different physical properties such as density, susceptibility, conductivity, etc. And the experimental results indicate that it is possible to control the terminal solubility and morphology of the solute elements in alloys by high magnetic fields.
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Authors: Dong Seok Chung, C.W. Jea, No Jin Park, J.K. Kim
Abstract: In this study, the microstructure and the texture development in Al–Zn–Mg–Cu–Zr alloys with/without 0.1%Sc has been investigated after extrusion, cold rolling, and aging treatment. After aging treatment, in Al alloy without Sc recrystallized equiaxed grains are obtained, while in Al alloy with Sc fine grains with an average size of 0.1~0.3 μm are obtained. After cold rolling, in case of the sample from the cross section (CS) to which Sc was added, texture with {112}<111>(Cu) + weak {123}<634>(S) component was developed while in case of the sample from longitudinal section (LS) to which Sc was added, texture with strong β-fiber + {110}<001>(Goss) components was developed. In case of CS and LS without Sc, texture of β-fiber was developed. After solid solution treatment and aging treatment, Al alloys (LS and CS) with Sc had rolling texture while Al alloys without Sc had random texture. The role of these differently developed textures in the plastic behavior, such as the normal anisotropy r-value (the plastic strain ratio) and planar anisotropy r-values are discussed.
463
Authors: Sang Won Han, Hyuck Mo Lee
Abstract: Permanent mold and semi-liquid die A356 cast alloys were used to examine the roles of microstructures and aging conditions on fatigue crack growth. HIP treatment to the A356 alloy generates substructure like dendritic arm boundaries as well as reduction of pores, which improves fracture elongation and fatigue fracture toughness. The similar substructure occur at primary α-Al and inter Si particles of semi-liquid die cast, too. Fracture elongation of HIPed permanent mold cast is comparable to that semi-liquid die cast, the fatigue crack growth is faster than in semi-liquid die cast. Plastic hardening occurs around fatigue crack flank, which decreases fatigue crack growth rate, and such effect appears highly in under aged alloy.
469
Authors: T. Izumi, Goroh Itoh
Abstract: High-magnesium Al-Mg alloys are known to be sensitive to stress corrosion cracking involving environmental hydrogen, hydrogen invading from the corrosive environment. In this study, the behavior of the environmental hydrogen in Al-6%Mg and Al-8%Mg binary alloy sheets stretched by 10% during exposure to 3.5%NaCl solution has been investigated by means of hydrogen microprint technique. Microprint image is observed on one surface while the other surface is exposed to the solution. In both alloys, the silver particles corresponding to the sites where hydrogen atoms are emitted from the inside of the sheets are shown on the slip lines. It is shown that the hydrogen atoms are transported with moving dislocations in the alloys.
475
Authors: Dong Seok Chung, C.W. Jea, Jae Hong Yoon, J.K. Kim
Abstract: The mechanical properties of Al–5%Cu–1.3%Li–0.4%Mg–0.4%Ag–1.16%Zr alloys without Mn and with 0.3%, 0.6% and 1.2% Mn have been investigated after the aging at the temperatures of 90, 150, 180, and 230 oC. With Mn addition the alloys show a good work-hardening property, and the elongation of alloys increases. With the 0.6% Mn the best elongation can be obtained. The strength of alloys with 0.3% or 1.2% Mn is lower than that of the alloy without Mn, whereas the strength of alloy with 0.6% Mn is almost same as that of the alloy without Mn. In the alloy with 0.6% Mn aged at 180 oC for 12 hours the optimum properties – combination of tensile strength and elongation, 620 MPa and over 12 %, respectively – are obtained. These favorable effects by a proper Mn addition are considered to come mainly from the Mn-dispersoid to prevent strain localization normally associated with the shearable precipitates.
481
Authors: Vladivoj Očenášek, Bohumil Smola, Ivana Stulíková, J. Pelcová
Abstract: The present contribution deals with the effect of thermal and mechanical treatment on structure, mechanical and physical properties of as cast, cold and hot worked AlMg3 type alloy produced by conventional casting, as well as by powder metallurgy. The properties of the AlMg3 alloys with additions of Sc and Zr in the weight concentration ranges 0.14 – 0.29% and 0.05 – 0.12% respectively were studied and compared with those of the alloys without Sc and Zr additions. The anti-recrystallization effect, phase development and mechanical properties investigated in the course of isothermal as well as isochronal annealing were studied by using optical and transmission electron microscopy, electrical resistometry and hardness measurements. The parameters of technological procedure of optimum age hardening by the Al3(ScxZr1-x) phase are presented. This optimum can not be reached if the as cast alloy is exposed to temperatures higher than 350°C. Even the small additions of Sc such as 0.15 wt. % ensure the anti-recrystallization effect of Al3(ScxZr1-x) phase.
487
Authors: Ivan Saxl, Vàclav Sklenička, L. Ilucová, Milan Svoboda, Petr Král
Abstract: Considerable structural inhomogeneity and anisotropy were found even after eight ECAP passes in high purity aluminium and the creep loading of ECAP material at 473K, 15MPa resulted in scattered fracture times ~ 20-60 hours. The structure revealed by orientation imaging microscopy with different disclination bounds was analysed by stereological methods. The effect of inhomogeneity and grain orientation on the creep fracture time was assessed.
493
Authors: Eui Pak Yoon, Jung Pyung Choi, Yu Sik Seo, Tae Woon Nam
Abstract: In the casting Al alloys, Inclusions are formed by various melt treatment and the some alloying elements have a bad effect on quality of products. Generally, inclusions deteriorate mechanical properties of casting products as well as provide heterogeneous nucleation sites of hydrogen porosity. But the difficulty of removing it is the fact that the inclusions are measured generally small about 20㎛ in the melt. So, in this study, Experiments were carried out on commercial die casting aluminum alloy A383 (JIS: ADC 12). The separation system including a D.C. electric field with steady D.C. magnetic field was adopted for reduction of inclusion in molten Al alloy. Also the quantitative and qualitative analysis of inclusion in Al alloy was taken by using the PoDFA (Porous Disc Filtration Apparatus) and EPMA.
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