Materials Science Forum Vol. 941

Abstract: The crystallographic aspects of nucleation of cube grains during annealing have been analyzed in (234)[20-28 11] - oriented aluminum single crystal. The samples were plane strain compressed in a channel-die up to logarithmic strains of 0.5 (40%) and then annealed to develop initial and final stages of primary recrystallization. The deformed and annealed samples were analyzed using scanning electron microscopy equipped with EBSD facility. Local orientation measurements reveled that significant part of the sample deforms homogeneously with only small deviation from the initial crystal orientation. The heterogeneities were thin bands of localized strain in which the crystal lattice rotate towards another variant of S orientation. After annealing the orientations identified inside deformed/recovered areas were similar to that observed in the sample just after deformation. The crystal lattice of recrystallized grains exhibit a well-defined clockwise and anticlockwise rotations around the axes grouped near all normals of the {111} planes of the deformed/recovered state. The cube grains were observed in both homogeneously and heterogeneously deformed areas despite the cube-oriented nuclei surrounded by high angle boundary were not present in the as-deformed structure.

Abstract: ince the temperature coefficient of resistance of Manganin (Cu-12Mn-2Ni) is extremely small, Manganin plate are used for resistors, especially shunts for current sensing.Generally, the melting and casting is used as a method to make an alloy such as Manganin. Further, the Manganin used as resistive material is produced by rolling after casting. Since such manufacturing processes have heating steps, long molding time is necessary and temperature control is important.In recent years, Cu-11Mn-4Ni powder has been developed. If manganin plate can be produced directly from alloy powder, simplification of the manufacturing process can be expected. A powder metallurgy is used as a method of solidifying and shaping the alloy powder. However many pores are generated in the sample because of using a binder. Therefore, the resistance value of the alloy fabricated through the method may not be stable.The Compression Shearing Method at Room Temperature (COSME-RT) is one of solutions to achieve the high density forming. In COSME-RT alloy powders are simultaneously loaded by a shearing force and a compressive stress in air at room temperature to form a plate. In the process, temperature control is unnecessary and the manufacturing time becomes shorter.In the present study, the fabrication of Cu-11Mn-4Ni plate is carried out by compression shearing method at room temperature and mechanical and electrical properties of the plate are evaluated.

Abstract: Recently, it was reported that Cu-Al alloys of low stacking fault energy (SFE) processed by severe plastic deformation show excellent tensile properties due to TWIP (Twinning induced Plasticity) phenomenon. In this study, Cu-15at% Al sheets were heavily processed by conventional multi-pass cold rolling up to 90% in reduction in thickness without annealing. In order to reveal the change in mechanical properties and the microstructure evolution, tensile test, hardness test, optical microscopy (OM) and electron backscattering diffraction (EBSD) analysis were performed. Deformation twinning due to low SFE is observed even in the case of low reduction in thickness. As the reduction increases, grains are refined by intersections of shear bands. It is found that the balance of strength and elongation of the processed sheets is comparable to those by severe plastic deformation followed by annealing in literature.

Abstract: The microstructure of Al-1.01Mg-1.11Si-0.38Cu-0.69Mn aluminum alloy plate hot-rolled from homogenization and homogenization-free ingots were investigated by optical microscopy and scanning electron microscopy assisted with energy dispersive spectroscopy (SEM/EDS). The results showed that there are 3 main kinds of constituents such as Mg₂Si, AlCuMgSi and AlFeMnSi in the as-cast Al-1.01Mg-1.11Si-0.38Cu-0.69Mn aluminum alloy ingot. After homogenization treated at 545°C for 24h, the black Mg₂Si and the white bright AlCuMgSi particles in the ingot dissolved into matrix, but the grey AlFeMnSi phase partly dissolved, contracted into sphere and become coarse, many ultrafine dispersoids appear in the dendritic arms. The constituents in the plates hot-rolled from the homogenization and homogenization-free ingots are both distributed as broken chains along the rolling direction. However, compared with the particles configuration in the plate that hot-rolled from homogenization ingot, the particles in the plate that hot-rolled from the homogenization-free ingot are finer, more numerous and more homogenous, and with insufficient recrystallization when the plates are solution treated at 545°C for 2 h and then water quenched.

Abstract: Recycling Mg alloys has been demanded as the demand of Mg alloys has been increased. It is difficult to separate Mg with Al because the properties are similar except for the density. In this study, gravity sorting by vibrating particulate bed ajusted the density to intermediate between Mg and Al was applied for Mg separation with Al. The relationship the vibrating condition and the sorting accuracy was investigated by applying different vibration acceleration and by applying the vertical and horizontal vibration. Turbulent flow was observed and the recovery rate was improved when vertical vibration with high acceleration was applied to the bed. Higher recovery rate was achieved when horizontal vibration was applied to the bed. This result suggested that the horizontal movement of particle affected the behavior of sorting materials and high recovery ratio was achieved by optimizing vibrational condition such as vibration acceleration and the direction of vibration.

Abstract: Cold spray processing appears to be a highly promising manufacturing process for coils for high field magnet. Dense and sizable material can be obtained characterized by high mechanical properties and high electrical conductivity thanks to the chamber of deposition under helium atmosphere. A low oxygen content material is obtained and the tensile and conductivity tests highlight the significance of the thermal treatment for the manufacturing process optimization.

Abstract: Solidification of alloys in a thermal gradient usually involves the generation of flows by thermal or thermosolutal convection. We experimentally study their effects on the dynamics of a solidification interface by inducing a controlled sweeping flow in a directional solidification device. Flow is induced in the sample from an external thermosiphon. Downstream inclination of microstructures and downstream sidebranch development are observed. However, the major outcome is the evidence of large scale travelling waves on the solidification interface. They are induced by the coupling between solidification and flow and yield repetitive striations of the solid phase. Two waves are observed and characterized.

Abstract: Recent research findings on the mechanical behavior of metal foams are summarized in this work. Thanks to their properties in compressive tests, a wide range of foamed materials has been considered for energy-absorption applications such as Al, Fe, Ti, Ni and its alloys. The main parameters affecting energy absorption are focused and presented: cell size, relative density, strain rate, hybrid foam (Al-Cu, Al-Ni), base metal, and composites structures (Al-foam filled tube and sandwich). Metal foam response, impact resistance and failure are discussed in many configurations and test conditions. The results of finite elements modelling and its validation by means of mechanical tests are discussed too.

Abstract: The development of explosion welding (EXW) technology underwent a stop as soon as it was introduced, however, in the recent years an increasing interest was found due to the wide range of materials which can be welded, similar and especially dissimilar ones. In addition to the high quality, such welded joints show a good compromise among the involved materials properties. Literature does not provide a comprehensive understanding of the whole mechanism and occurring phenomena but is mostly limited to analyse just some process parameters, like the investigations on joint properties that can be achieved if process takes place under vacuum or open air. In this work some key points are discussed to describe the evolution step of the process and the innovations introduced like the MIL (metallic-intermetallic laminate) composites for aerospace industry. Process parameters are analyzed to highlight the positive and negative aspects, the experiments in the laboratory will be described to confine the explosion to the joint and in particular to minimize the explosion energy and to improve the efficiency of the technique. At last some significant applications where this technique is widely used are showed.

Abstract: Titanium and its alloys possess high specific strength, excellent corrosion resistance and good biocompatibility [1] [2]. Since oxygen is an unavoidable impurity in such materials, it has been adopted as an alloying element in the development of low-cost titanium alloys. Therefore, it is important to investigate the role of oxygen in these alloys, especially in β-type alloys. In the present study, the effects of oxygen on the electrical resistivity, Vickers hardness and heat treatment behavior of a Ti-20mass%V alloy which is the lowest concentration for which the fully retained β phase is obtained were assessed. The electrical resistivity and Vickers hardness of solution-treated and quenched specimens increased with increasing oxygen content, due to the dissolution of oxygen into the β phase and solid solution hardening, respectively. Upon isothermal aging at 673 K, the addition of O accelerated a-phase precipitation. The addition of O was found to suppress the appearance of the athermal ω phase in the solution-treated and quenched state.