[en] Full text.Friction Stir Processing (FSP) is a new advanced material processing technique used to refine and homogenize the microstructure of sheet metals. FSP is a solid state processing technique that uses a rapidly rotating non-consumable high strength tool steel pin that extends from a cylindrical shoulder. The rotating pin is forced with a predetermined load into the work piece and moved along with the work pieces, while the rotating pin deforms and stirs the locally heated material. It is a hot working process in which a large amount of deformation is imparted to the sheet. FS processed zone is characterized by dynamic recrystallization which results in grain refinement . this promising emerging process needs further investigations to develop optimum process parameters to produce the desired microstructure. In this work, we present preliminary results on the effects of rotational and translational speeds on grain refinement of AA5052. Under certain processing conditions, sub-micron grain structure was produced using this technique

[en] This paper investigated the effects of melt thermal-rate treatment and Al-3Ti-3B-1Y grain refiner on the microstructure and mechanical properties of hypoeutectic Al-9Si-0.5Mg alloy. The results showed that the grain refining effect of the melt thermal-rate treatment was more remarkable than that of Al-3Ti-3B-1Y grain refiner. After the appropriate melt thermal-rate treatment (MTRT), the microstructure and mechanical properties of alloy were significantly optimized and the α-Al phase changed from dendritic grains to columnar grain. The MTRT technique compound with Al-3Ti-3B-1Y grain refiner could further refine the microstructure. In addition, the change of vacancy concentration induced the morphology change of α-Al phase. The mechanism of the refinement and the toxic effect of Y element were clarified, which provide a reference for developing a new type of Al-Ti-B-RE grain refiner and the melt treatment method. (paper)

[en] This research concerned the whole production of UFG materials, using Severe Plastic Deformation (SPD). These new technologies for production of semi-finished products with ultra-fine grained structure differ from conventional technologies. One of them is new type of equipment DRECE (Dual Rolling Equal Channel Extrusion), designated for obtaining UFG structure and increase of mechanical properties in strip of sheet. The main goal of the paper is a review of current achieved results obtained by processing of Cu based materials by DRECE method, the equipment of which was put in service towards the end of 2009 at the Department of mechanical technology, Faculty of mechanical engineering, VŠB - Technical University of Ostrava. Cu-based materials – technical pure Cu (99.3% purity) – is used as experimental material. Experiments with use of the formed structural material - copper was made on the forming device in order to achieve grain refinement in the strip of sheet (Cu 99,3% purity) with dimensions 58 × 2 × 1000 mm The paper describes results of determination of an influence of number of passes on resulting mechanical and micro-structural properties of the processed Cu-based materials. (paper)

[en] The experimental results, thermodynamic equilibrium and kinetic theory of the metal/gas interaction in refractory metals are reviewed. The adsorption and desorption of nitrogen, hydrogen and CO are reversible, whereas those of oxygen are irreversible, with adsorption of an oxygen atom and volatilisation of the metal oxide. Based upon this fact, a new electron beam refining technology is proposed for niobium, consisting of four points: preparation of an electrode by aluminothermic reduction; zone refining in the first melt; kinetic refining in subsequent melts and compact design of the refining plant. Experimental results from a 300 kW pilot plant were in complete agreement with the technology proposed, giving 2.4 times the productivity predicted by the conventional technology. (Author)

[en] The influence of various Fe contents on the grain refinement of commercial purity aluminum was investigated. After commercial purity aluminum melted, given amounts of Al-Fe master alloy were added into the molten in this study. Macroscopic observation indicates that the degree of grain refinement of commercial purity aluminum depends on the additions of Al-Fe master alloy. The case of 0.5 wt%Fe content was founded to be more effective in refining grain of commercial purity aluminum compared to the other Fe contents within the range studied. Basing on scanning electron microscopy analyses grain refining mechanism of Fe was discussed in this research

[en] Highlights: • Formation mechanism of even-distributed δ phase during aging is revealed. • Competition relationship between SRX nucleation and breakage of δ phase during annealing is found. • Initial deformed microstructure state for refining deformed mixed grain during annealing is obtained The effect of initial mixed grain microstructure state of deformed Ni-based superalloy on its refinement behavior during two-stage annealing treatment was investigated. Firstly, the deformed specimens with different initial mixed grain microstructure states were obtained by different hot compression experiments. Then, two-stage heat treatment experiments including aging treatments (AT) for precipitating δ phase and subsequent recrystallization annealing treatments (RT) to refine mixed grains were carried out. The results show that the deformation energy and dynamic recrystallization (DRX) degree are the main initial microstructure factors that affect the refinement behavior of deformed mixed grains. The deformation energy was estimated by the area under the stress-strain curve (S) due to the proportional relationship between them. When S is high, the recrystallization rate during the RT is high, and the final annealed grain is uniform and fine. When S is medium, the recrystallization rate is determined by DRX degree. The recrystallization rate is low and the final annealed grain is nonuniform when DRX degree is high. However, when DRX degree is low, the recrystallization rate is quick and final annealed grains are coarse but uniform. Besides, it is found that besides deformation energy, the competition relationship between static recrystallization (SRX) nucleation and breakage of δ phase affects the dissolution of δ phase during the RT. When the SRX nuclei form at δ phase boundary, the corresponding δ phase is protected.

[en] Summer Lecture Series 2006: Andy Sessler, Berkeley Lab director from 1973 to 1980, sheds light on the Lab's nearly eight-decade history of inventing and refining particle accelerators, which continue to illuminate the nature of the universe.

[en] Highlights: • Combined addition of Al-5Ti-1B ribbon and Zr element achieves a very efficient refining effect on ZA22 alloy. • The refining mechanisms of the grains of ZA22 alloy are discussed in detail. • With the decrease of grain size, the tensile strength, elongation and hardness of ZA22 alloy increase. • With the decrease of grain size, the damping of ZA22 alloy shows different variation patterns at different temperatures. A novel Al-5Ti-1B ribbon was prepared and used as inoculant to refine the grains of Zn-Al eutectoid (ZA22) alloy with the aim to significantly enhance the mechanical properties while remaining the high damping capacity. It was found that compared with the commercial Al-5Ti-1B rod the present ribbon had better refining effect on the ZA22 alloy due to its finer and more uniformly distributed TiB₂ and L1₂-Al₃Ti particles formed during rapid cooling process. It has been confirmed that both of the two kinds of particles could act as effective heterogeneous nucleation sites of α-Al phase, and then led to the refinement of α-Al grains. The combined addition of Al-5Ti-1B ribbon and Zr element could achieve the best refining effect because Zr could further promote the heterogeneous nucleation and hinder the growth of α-Al grains. Properties tests illustrated that with the decrease of average grain size, the tensile strength, elongation and hardness of the ZA22 alloy increased obviously because of the fine-grain strengthening and dispersion strengthening effects, while the damping showed different variation patterns within different temperature regions, which has been ascribed to the synthetic effect of two opposite influencing factors.

[en] High-intensity ultrasonic treatment (UT) for grain refinement of magnesium alloys has been investigated using a novel theoretical approach in order to better understand its grain-refining potential and the mechanism of nucleation. The process demonstrated significantly superior grain-refining potency to carbon inoculation for Al-containing magnesium alloys but inferior potency to zirconium for Al-free alloys. Details revealed by applying the theoretical approach to ultrasonic grain refinement provide new clues to understanding the mechanism of grain nucleation by UT

[en] The grain size of as-cast Ti-6Al-4V is reduced by about an order of magnitude from 1700 to 200 μm with an addition of 0.1 wt.% boron. A much weaker dependence of reduction in grain size is obtained for boron additions from >0.1% to 1.0%. Similar trends were observed in boron-modified as-cast Ti-6Al-2Sn-4Zr-2Mo-0.1Si