[en] A process on how to apply new aluminium alloys by thermal spray coating is discussed. Aluminium-based high alloying compositions were selected as coating materials to protect soft substrates against friction, abrasion and others. The beneficial properties of these new alloys are its high hardness and low friction coefficient. The atomic structures of the alloys are either quasi-crystalline and/or crystalline, and in the latter case the structures obtained have a close structural relation with quasi-crystals

[en] Fatigue tests subjected to constant amplitude under the environments of dry air were performed on 5A06-O aluminum alloy, 7A05-T6 aluminum alloy and 5A06-O/7A05-T6 dissimilar aluminum alloy ring welded joints in a new type sandwich high-pressure shell. The fatigue behaviors were analyzed and compared based on the experimental data, and the mechanisms of welding defect impacts on fatigue properties of the welded joints were deduced from fractographic analysis. It is showed that welding defect has a detrimental influence on fatigue properties of the welded joints. The lower stress level can cause the more obvious decrease of fatigue life of the welded joints. Fatigue cracks of aluminum alloys base metal usually initiated at the surface defects such as two-phase particles and inclusions, and however, welding defect of welded joints are more likely to cause stress concentration and lead to the early initiation of fatigue cracks, which is dominated in decreasing of fatigue life of the welded joints. (paper)

No abstract available

[en] Short communication

[en] Continuous and interrupted torsion tests have been conducted in the temperature range of 320-520 deg C at constant strain rates of 1.26-5.71 x 10^-3 sec^-1 on an Al-Cu-Mg alloy. During the continuous deformation, dynamic recrystallization was observed above 370 deg C and the nucleation of the recrystallization at dislocation clusters or adjacent to second phase particle. The presence of deformation substructure in the recrystallized grain provided a direct evidence that recrystallization had occurred during the deformation. In the interrupted tests, duration of the interruptions were 10,20, or 40 sec at equal strain intervals of either 0.4 or 0.6. During the interrupted deformation, the major softening mechanism was static recovery and partially static recrystallization above 370 deg C. The degree of softening was augmented by increase in the temperature, the interruption strain, and the interruption time. (Author)

[en] The Moessbauer spectroscopy was applied to study radiation damage in Al-0.09 m% Fe alloys (having Al₁₃Fe₄ and solid solution phases) irradiated with 225 MeV Ar ions at room temperature. In the Moessbauer spectra of irradiated samples a dose dependent increase of the intensity of line representing iron atoms in solid solution was observed. Simultaneously, the intensity of lines belonging to the iron atoms in Al₁₃Fe₄ phase decreased with increasing fluences. The depth dependence of the irradiation induced phase transformation shows a qualitative agreement with the elastic collision energy transferred to the matrix by the heavy ion. (author) 12 refs., 3 figs

[en] Short communication

[en] Three methods available in the literature to estimate the axial S-N curve from the rotating bending fatigue performance were summarized. Axial and rotating bending fatigue tests were conducted at various alternating stresses on specimens excised from A356 aluminum alloy castings in the high cycle fatigue range. These data were used to assess the effectiveness of the models. Among the three models, the one developed by Manson and Muralidharan did not provide good estimates of the axial fatigue performance from rotating bending data. The geometric correction factor proposed by Philipp yielded the best fit, however, did not alter the Basquin exponent whereas the one proposed by Halford and Manson provided a poor estimate. Only the model proposed by Esin provided accurate estimates of fatigue performance as well as the Basquin exponent.

[en] The friction-stir process (FSW) developed by England's TWI in the last decade is a new concept in solid phase friction welding that is particularly appropriate for soldering aluminum and its alloys. It offers interesting aspects and can advantageously replace the usual arch processes. It is an automatic process that solders together long pieces by butt or lap welding and, therefore, overcomes the greater limitation of the conventional friction process that can be applied only to pieces with revolution symmetry. FSW is based essentially on the use of a cylindrical tool with a special profile, which is inserted between the surfaces where the materials meet to join them together at a certain rotation speed and under a specific force. The pieces must be rigidly butt bonded or overlapped to prevent movement when the tool moves forward along the joint producing the dispersion of oxides, local plastisizing of the material and the weld. Since its creation FSW has been the subject of many international publications, but until the present work there was no technologically relevant data about tools and procedures. For this reason, when its promising and novel nature was noticed, the CNEA began its own development project in 1997. The main characteristics of the tool are reviewed here and the results of tests carried out to evaluate the influence of the feed velocity on the mechanical properties of the butt joining of a 6.25 mm thick AA6061 T6 plate. Different accumulated aspects of the experience are discussed as well (cw)

[en] The mixing of two dissimilar aluminum alloys in friction stir welding (FSW) was investigated using etching. The results show that the materials from the retreating side mixed into the advancing side in rather narrow and elongated bands whereas the materials from the advancing side mixed into the retreating side in the form of thick bands and lobes. A computational method using smoothed particle hydrodynamics (SPH) is introduced as a way to properly describe the complex mixing behavior in FSW