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No doubt friction tool which is usually called as the probe has an important role in a Friction Stir Welding (FSW) process. To obtained good joint a suitable probe should be first provided. Four difference probe designs were evaluated in this article. The application of probe no.1 shows that the probe is too long and slender. The second probe then is developed where improvement was applied based on the results obtain from the first probe application. Using the second tool, the torsion is too high due to the large shoulder of the probe. The available belt and pulley system could not provide the needed torsion and belt slip was extremely exhibited which in turn caused the Friction Stir Welding (FSW) process is stoped. In the third probe, the shoulder diameter and pin were reduced and quenching heat treatment was applied to increase the strength. Using the third probe, quiet good appearance was obtained, but was not at full pertained length which was considered as heat shortage. Intermittent slip is occasionally also takes place. In the fourth probe diameter of the body was increased and chamfer was applied to reduce the shoulder surface. Insulator was also used to prevent heat lost. Using the last probe, the quiet good result was obtained over the whole pertained length. [ABSTRACT FROM AUTHOR]

The continuous research for lightweight components for transport applications to reduce the harmful emissions drives the attention to the light alloys as in the case of Aluminium (Al) alloys, capable to combine low density with high values of the strength-to-weight ratio. Such advantages are partially counterbalanced by the poor formability at room temperature. A viable solution is to adopt a localized heat treatment by laser of the blank before the forming process to obtain a tailored distribution of material properties so that the blank can be formed at room temperature by means of conventional press machines. Such an approach has been extensively investigated for age hardenable alloys, but in the present work the attention is focused on the 5000 series; in particular, the optimization of the deep drawing process of the alloy AA5754 H32 is proposed through a numerical/experimental approach. A preliminary investigation was necessary to correctly tune the laser parameters (focus length, spot dimension) to effectively obtain the annealed state. Optimal process parameters were then obtained coupling a 2D FE model with an optimization platform managed by a multi-objective genetic algorithm. The optimal solution (i.e. able to maximize the LDR) in terms of blankholder force and extent of the annealed region was thus evaluated and validated through experimental trials. A good matching between experimental and numerical results was found. The optimal solution allowed to obtain an LDR of the locally heat treated blank larger than the one of the material either in the wrought condition (H32) either in the annealed condition (H111). [ABSTRACT FROM AUTHOR]

Sensitization of 5xxx series aluminum alloys is characterized by the gradual precipitation of the alloying element magnesium as a beta phase (Al3Mg2) along the grain boundaries after prolonged exposure to the environment. While the 5xxx alloy is corrosion resistant, these beta phases are corrosive and thus their formation increases the susceptibility of the alloy to intergranular corrosion and stress corrosion cracking. The standardized approach for measuring the degree of sensitization (DoS) is the ASTM G67 test standard. This test, however, is time consuming, difficult to perform, and destructive, as it involves measurement of a mass loss after exposing the alloy to a nitric acid solution. Given the limitations of this test standard, there is a need to develop a nondestructive evaluation (NDE) solution that is easy-to-use, non-intrusive, and faster than current inspection methods while suitable for use outside a laboratory. This paper describes the development of an NDE method for quantifying the DoS value in an alloy using ultrasonic measurements. The work builds upon prior efforts described in the literature that use electromagnetic acoustic transducers (EMATs) to quantify DoS based on velocity measurements. The prior approaches used conventional ultrasonic inspection techniques with short-duration excitation signals (less than 3 cycles) to allow identification of the echo time-of-flight and amplitude decay pattern, but their success was limited by EMAT transducer inefficiency in general, especially at higher frequencies. To overcome these challenges, this paper presents a modified ultrasonic measurement strategy using long-duration excitation signals (greater than 100 cycles), where multiple reverberations in the material overlap. By sweeping through test frequencies, it is possible to establish an acoustic resonance when the wavelength is an integer multiple of twice the material thickness. This approach allows for greatly improved signal to noise ratios as well as higher frequency operation, because the reverberations will constructively interfere at resonance. The measurement approach was evaluated on a large number of 5456-H116 aluminum alloy specimens that were sensitized to varying DoS values and compared to G67 test results. Relationships between DoS values and the ultrasonic velocity were established. [ABSTRACT FROM AUTHOR]

Cast aluminum alloy 354 is widely used for production of critical automobile components, owing to its outstanding castability and attractive combination of mechanical properties in heat-treated condition. With the engines of higher performance entering the scene, there has been a steady demand to further improve the mechanical behavior of the castings made of the alloy. Exploring improvements in processing has been one important approach in this context. The present study explores the possibility of improving tensile properties of the alloy by adopting certain non-conventional aging treatments. The treatments include aging cycles similar to T6I4 and T6I6 referred to in the published literature, artificial aging in two steps instead of in single step and artificial aging preceded by various natural aging times. The results show that none of these non-conventional treatments leads to all-round improvement of tensile properties compared to the standard T61 treatment. There is significant natural age-hardening taking place in this alloy. Changing the time of natural aging preceding artificial aging was found to have insignificant effect on tensile properties. [ABSTRACT FROM AUTHOR]

In this work the effect of the anodizing process on the surface properties of SSR components was investigated. EN AC-46500 aluminium alloy components were formed using a 700 Ton high pressure machine and an Idra Semi Solid Rheocasting Station (SSR). The samples were heat treated with the aim of modifying the form and distribution of the eutectic silicon phase and after the heat treatment they were shotpeened in different conditions to obtain different surface roughness. Finally, the components were anodized with the purpose of improving the tribological properties and corrosion resistance. Surface modifications were investigated as they might have beneficial effects on the wear and corrosion behaviour. Experiments using a tribometer (ball on disc configuration) were performed in order to evaluate the tribological properties of the material and salt spray corrosion tests were used to study the corrosion resistance. These studies were carried out before and after the anodizing process. The anodized components show a significant improvement of the corrosion and wear resistance under the tested conditions, in spite of the high percentage of intermetallics compounds present in the AC-46500 alloy. [ABSTRACT FROM AUTHOR]

Friction stir welding is a solid state joining process with relatively low welding temperatures. Nevertheless, the mechanical properties of friction stir welded blanks are degraded after welding. Indeed, both strength and ductility of the welds are decreased after welding. Often, the resulting friction stir welded blanks need to be formed to their final structural shape. Therefore, the formability of friction stir welded blanks is of primary importance in the manufacturing of structural parts. This paper studies how the mechanical properties and particularly formability of friction stir welded blanks can be improved by applying a post weld heat treatment. Two aluminum alloys from 2000 and 7000 series, namely 2024-T3 and 7075-T6, are selected for the study. The sheet thickness of both materials is 2,0 mm. The selected alloys are welded in three configurations: 2024-T3 and 2024-T3, 7075-T6 and 7075-T6, and 2024-T3 and 7075-T6. The resulting welds are naturally aged for a few months. Three sets of standard dog bone shape tensile test specimens are then machined from the welds. The first set of the specimens is tested without any heat treatment. The second set of the specimens is solution heat treated and quenched before testing. The third set of the specimens is solution heat treated, quenched, and naturally aged for a week before testing. The mechanical properties of the three different sets of specimens are compared with each other. It is shown that careful selection of post weld heat-treatment can greatly improve the formability of friction stir welded blanks. [ABSTRACT FROM AUTHOR]

Abstract.In this paper, the microscopic morphology of a semi solid Al5Cu alloy by strain induced melt activated (SIMA) process were investigated, and the effects of predeformation, microstructural evolution, aging response and hardness changes were determined. The microstructural observation shows that while the grain boundaries started to appear after 620° C, globular grains surrounded wet boundaries needed for SSP were obtained at 650° C. The grain sizes exhibited ununiformity from the outer surface to the center of the sample because of ununiform predeformation. Although isothermal heat treatments reduced hardness, age hardening gave back the hardness loss. [ABSTRACT FROM AUTHOR]

γ-alumina nanoparticles were annealed sequentially at 800°C, 950°C and 1100°C and structural transitions as a function of heat treatment were studied by X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC) and 27Al Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR) methods.. XRD studies found that γ-Al2O3 is stable upto a temperature of at least 950°C and transforms to the thermodynamically stable α-phase after annealing at 1100°C. MAS-NMR revealed that γ-alumina contains AlO4 and AlO6 structural units in the ratio 1: 2, while α-phase contains only AlO6 units. DSC confirmed that γ → α transition initiates at 1060°C. [ABSTRACT FROM AUTHOR]

A series of shock loading experiments have been performed on two heat-treated states of the aluminium alloy, 6061; T0, a solution treated condition, and T6, a solution treated and fully aged state. Lateral stress measurements indicate the T6 condition is stronger than T0, as would be expected. Results also indicate that the rate of hardening behind the shock front is somewhat greater in T0 than T6, indicating a shift in deformation from one based upon the generation of, and storage of, dislocations, to one where the presence of intermetallic precipitates appears to inhibit dislocation generation and storage processes. [ABSTRACT FROM AUTHOR]

In this work, synthesis of copper matrix composite powder reinforced by in situ niobium carbide particle was prepared by mechanical alloying of elemental powder and subsequent heat treatment. Elemental powders of Cu-Nb-C correspond to Cu-40wt%Nb-10%wtC composition was milled for 54 hours at room temperature in a planetary ball mill. The effect of heat treatment temperature on the formation of niobium carbide was analyzed. Characterization by X-ray diffraction was done on the milled powder and heat-treated powder in order to investigate NbC formation. Results indicate that NbC began to precipitate after mechanical alloying for about 54h with heat treatment temperature of 900 °C and 1000 °C. [ABSTRACT FROM AUTHOR]

This work has been performed along two main directions. First of all we present the experimental results and effects obtained by backward extrusion tests on semi-solid aluminum alloy at three different forming temperatures and different holding times in isothermal conditions. The semi-solid billets were fabricated by the re-melting heat treatment method. Semi-solid extrusion tests were carried out to investigate the load-displacement curves and the deformation behaviour at different temperatures. The load level clearly decreases with increasing temperature and increasing holding time. Numerical simulations of semi-solid extrusion has been made too, using Forge 2005,. Experimental and simulated results are compared and discussed. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

Germanium nanoparticles in a thin SiO2 film on Si have been formed by negative ion implantation for the development of very low power consumption electron devices using nanoparticles. Their electrical properties of 25-nm-SiO2/Si films including Ge nanoparticles were investigated with CV method after subsequent annealing at various temperatures. Ge atoms were implanted at 10 keV with fluencies of 1×1015 and 5×1015 ions/cm2. Samples were annealed at 300, 500, 700 and 900°C for 1 h. Depth profiles of implanted Ge atoms in the SiO2 films were measured by using a high-resolution RBS technique. The formed Ge nanoparticles were studied by cross-sectional TEM observation. After annealing at less than 700°C, Ge nanoparticles were confirmed in the film. After 300°C-annealing, a CV curve had so small hysteresis that could not be applied to memory devices. After 500°C-annealing, both samples with 1×1015 ions/cm2 and with 5×1015 ions/cm2 had obvious hysteresis curves. Calculations of charge and nanoparticle intensity from flat band shift and implanted Ge dose lead about one electron in one nanoparticle with 3nm diameter. These results suggest that thin SiO2 films including Ge nanoparticles formed with negative ion implantation can applied with memory devices. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Since the introduction of the cable-in-conduit conductor (CICC) concept, a variety of alloys have been proposed for fabricating the jacket. The jacket provides primary containment of the liquid helium coolant and is typically also the primary structural component for the magnet coils. These functions create requirements for strength, toughness, fatigue crack resistance, and fabricability. When the CICC uses Nb3Sn superconductor, the conduit alloy must retain good mechanical properties after exposure to the superconductor’s reaction heat treatment. Here we present data from cryogenic fracture toughness and fatigue crack growth rate tests on 316LN and a Cr-Mo-Ni base super-alloy (Haynes 242) at 4 K before and after the exposure to the heat treatment. These alloys are presently being considered as candidates for use in the next-generation series connected hybrid magnet for the NHMFL. Both of the alloys are found to have adequate fatigue and fracture properties for the CICC application while the superalloy has distinctly better elastic properties of modulus and thermal expansion. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Austenitic stainless steels are considered to be the candidate materials for liquid hydrogen vessels and the related equipments, and those welding parts that require high toughness at cryogenic temperature. The authors have found that the weld metal of Type 316L stainless steel processed by reduced pressure electron beam (RPEB) welding has high toughness at cryogenic temperature, which is considered to be due to the single-pass welding process without reheating effect accompanied by multi-pass welding process. In this work, the effect of heat treatment on low temperature toughness of the RPEB weld metal of Type 316L was investigated by Charpy impact test at 77K. The absorbed energy decreased with higher temperature and longer holding time of heat treatment. The remarkable drop in the absorbed energy was found with heat treatment at 1073K for 2 hours, which is as low as that of conventional multi-pass weld metal such as tungsten inert gas welding. The observations of fracture surface and microstructure revealed that the decrease in the absorbed energy with heat treatment resulted from the precipitation of intermetallic compounds near delta-ferrite phase. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Samples of an aluminium-zinc-magnesium alloy, typical of high strength weldable aluminium alloys, have been heat treated to produce two different microstructural conditions, these being peak-aged and under-aged. Mechanical tests have been performed, both at quasi-static strain rates and under shock loading conditions to determine how the mechanical properties change with heat treatment. Results indicate that the material has its highest strength when peak aged. Properties are discussed in relation to observed features within the microstructure, as recorded by optical and scanning electron microscopy. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

The response of U and Ti alloys has been studied in planar and ballistic impact experiments performed with a 25 mm light-gas gun. Free surface velocities were monitored by VISAR. The velocity profiles and the damage maps were simulated using 2D AUTODYN™ finite differences code. A modified Steinberg-Cochran-Guinan constitutive model was calibrated by simulating planar impact experiments. Bauschinger effect and a single-parameter spall model were added to describe the unloading and the tensile paths. The ballistic experiments were simulated by using the calibrated model. Softly recovered samples revealed different degrees of spall fracture (planar impact) and of adiabatic shear bands (ballistic experiments). The results demonstrate a possibility to combine experimental and numerical techniques, VISAR and AUTODYN, to calibrate constitutive models of solids in a wide range of shock-induced strain. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

The article presents a study which examines the structure and properties of aluminums alloys after treatments by the concentrated flows of energy. Researchers studied the aluminum compound, which were deposited by a high-rate plasma jet to a substance of tough pitch copper. It notes that Rutherford and back ion scattering (RBS and BS), nuclear reactions, scanning election microscopy with microanalysis, measurements of microhardness and adhesion were used as the methods of analysis.