Authors: Yong Nam Kwon, Young Seon Lee, J.H. Lee
Abstract: Thermomechanical behavior of Al-Mg-Si alloys has been studied to investigate the effect of microstructural features such as pre-existing substructure and distribution of particles on the deformation characteristics. The controlled compression tests have been carried out to get the basic information on how the alloy responds to temperature, strain amount and strain rate. Microstructural features after forging have been discussed in terms of the thermomechanical response of Al-Mg-Si alloys. As already well mentioned, we have found that the high temperature deformation of Al-Mg-Si brought the recovered structure. However, the abnormally large grains seems to occur in a certain condition as a result of deformation assisted grain growth, which means that hot forging of Al-Mg-Si alloys could lead to the undesirable microstructures and the consequent mechanical properties such as fatigue strength.
581
Authors: Z. Stokłosa, G. Badura, P. Kwapuliński, Józef Rasek, G. Haneczok, Józef Lelątko, Lucjan Pająk
Abstract: The crystallization and optimization of magnetic properties effects in FeXSiB (X=Cu, V,
Co, Zr, Nb) amorphous alloys were studied by applying X-ray diffraction methods, high resolution
transmission electron microscopy (HRTEM), resistometric and magnetic measurements. The
temperatures of the first and the second stage of crystallization, the 1h optimization annealing
temperature and the Curie temperature were determined for different amorphous alloys. Activation
energies of crystallization process were obtained by applying the Kissinger method. The influence
of alloy additions on optimization effect and crystallization processes was carefully examined.
171
Authors: Gang Wang, Wen Ru Zhao, Yan Dong Liu, Chun Yan Wang, Yan Dong Wang, Liang Zuo
Abstract: In recent years, there has been an increasing interest in magnetic shape memory alloys (MSMAs) due to their unique ability to produce very large output strains and rapid response frequency. NiMnCoIn is a new-type MSMAs in which a reversible magnetic-field-induced phase transformation is observed. The microstructural evolution in the process of dynamic recrystallization in polycrystalline Ni45Co5Mn36.7In13.3 was studied in the present paper. The experimental results showed that the high deformation temperature and slow strain rate were necessary to achieve perfect dynamic-recrystallizing microstructure in Ni45Co5Mn36.7In13.3 alloy. Precipitates with two sizes were observed. The content of Co in precipitates was higher than that in the matrix alloy, while the content of In was lower than that in the matrix alloy.
2188
Authors: Joon Sik Park, Jeong Min Kim, Young Ho Song, Byung Hwan-Hong, Ye Won Cho, Sang Wook Joo, Joong Seok-Oh
Abstract: The nature of high specific strength compared with other structural materials has led to wide application of Mg alloys. However, Mg alloys often exhibit relatively low strength and/or low surface stability, which can limit the practical application of the alloy system. In order to achieve high strength, the commercial AZ61 alloys were extruded, so that the application of the alloy system can be extended towards new structural parts for requiring the light nature of the alloy system. In this study, a high temperature extrusion has been carried out for the commercial Mg alloys (AZ61). The productivity and mechanical properties of the alloy were critically affected by the extrusion conditions such as temperature, extrusion ratio and extrusion speed. The texture development and alloy strengths with respect to the extrusion conditions have been discussed in terms of microstructural observations and phase analyses.
727
Authors: S.P. Nikanorov, B.K. Kardashev, B.N. Korchunov, V.N. Osipov
Abstract: Acoustic measurements of Young’s modulus and internal friction at frequencies of longitudinal vibrations of about 100 kHz were made in the (5×10-7 to 2×10-4) vibration strain amplitude range for Al-Si alloys. Quasi-static bending stress-strain diagrams were studied as well. The samples of the alloy were prepared using a directional crystallization by Stepanov’s method. The compositions varied from 8 to 25 wt.%Si. The micro-plastic deformation of the materials (acoustic experiments) is explained by dislocation motion in grains of α solid solution. The micro-plastic yield stress has a minimum near the eutectic composition; the flow stress of plastic bending increases smoothly when the Si content increases.
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