Search results for "Microstructure"
showing 10 items of 707 documents
Thermoelectric current and magnetic field interaction influence on the structure of directionally solidified Sn-10 wt.%Pb alloy
2013
International audience; In this experimental work Sn-10 wt.% Pb alloy is directionally solidified in Bridgman setup at various growth velocities (from 0.5 mu m/s to 20 mu m/s) under transverse 0.4 T magnetic field. Temperature gradient of 8 K/mm is maintained perpendicular to the solidification direction during experiments. Liquid phase convection and its influence on the structure and segregation of an alloy, caused by magnetic field and thermoelectric current interaction (thermoelectromagnetic convection or TEMC) is studied experimentally and estimated theoretically in this work. Detailed velocity order of magnitude estimation is carried out. Besides optical microscopy, component distribu…
Behaviour of advanced tritium breeder pebbles under simultaneous action of accelerated electrons and high temperature
2017
The authors greatly acknowledge the technical and experimen-tal support of O. Valtenbergs and L. Avotina (Institute of Chemical Physics, University of Latvia). The work is performed in the frames of the University of Latvia financed project No. Y9-B044-ZF-N-300, “Nano, Quantum Technologies, and Innovative Materials for Eco-nomics”.
Mechanism of Formation of TiO2-Doped Mullites from Heated Single-Phase Gels Investigated by Structural and Microstructural Parameters
2008
An analysis of the microstructure of TiO 2 -doped mullites prepared from monophasic gels thermally treated in the temperature range 900°-1600°C is reported. Two series of gels with nominal compositions 3(Al 2-x Ti x O 3 ) ·2(SiO 2 ) and 2(Al 2-x Ti x O 3 )·(SiO 2 ), in the range 0≤x≤0.15, were prepared. X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) were used to follow the structural and textural evolution from gels to the final doped mullites. The crystallite sizes and microstrains were determined by linewidth refinements of XRD patterns using the integral breadth method of Langford and the Warren-Averbach analysis. XRD patterns showed the formation of Al 2 TiO 5 and…
Synthesis of niobium aluminides using mechanically activated self-propagating high-temperature synthesis and mechanically activated annealing process
1999
The mechanically activated self-propagating high-temperature synthesis (MASHS) technique and the mechanically activated annealing process (M2AP) were used to produce NbAl3 intermetallic compound. The MASHS process results from the combination of two steps: first, a mechanical activation of the Nb 3Al powders mixture; second, a self-propagating high-temperature synthesis (SHS). The M2AP process also results from the combination of two steps: the first is the same; the second consists of the annealing of as-milled powders. Based on X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDXS), the as-milled powders, MASHS, and M2AP end-pr…
Influence of the microstructure on the corrosion behaviour of low-carbon martensitic stainless steel after tempering treatment
2014
Abstract The microstructure of grade X4CrNiMo16.5.1 stainless steel was studied at different scales. The chemical composition of the native passive film formed on the different phases was then determined at the microscale. The degree of homogeneity of the native passive film is discussed. Subsequently, the susceptibility to pitting corrosion of X4CrNiMo16.5.1 was quantified using the electrochemical microcell technique. The nature of precursor sites and the morphology of pits were investigated by combining scanning electron microscopy with Electron BackScatter Diffraction and potentiostatic pulse tests. The role of the microstructure and the cold-worked layer generated by polishing in pitti…
Corrosion behaviour of heavily deformed pearlitic and brass-coated pearlitic steels in sodium chloride solutions
2014
Abstract The influence of plastic deformation and galvanic coupling on the microstructure and corrosion behaviour of pearlitic steel and brass-coated pearlitic steel was investigated in sodium chloride solution at 25 °C. Microstructural changes were quantified using scanning electron microscopy coupled with EBSD. Chemical and electrochemical modifications were evaluated using XPS, ZRA, the electrochemical microcell technique and the weight loss method. From these experiments, the influence of microstructural changes on the electrochemical parameters and the corrosion rate was discussed.
Deposition and characterization of cold sprayed nanocrystalline NiTi
2011
International audience; Binary 50Ni–50Ti mixture was prepared by mechanical alloying from elemental powders. After 48 h of milling, the nanocrystalline B2-NiTi powder was produced. Then, this as-milled powder was deposited by cold spraying in order to produce a target which can be used to create thin films by magnetron sputtering technique. The objective is to improve the electrical characterizations of the NiTi/SiO2/Si M.O.S structures. Themorphology evolution of the powder particles, the phase identification and the alloying evolution process as function of milling time were studied using scanning electron microscopy, X-ray diffraction and transmission electron microscopy. In addition, th…
Post-sintering heat treatment effect on the coercivity of sintered (Nd,Dy)15(Fe,Co,Mo,Al)77B8 permanent magnets
2000
Abstract The effect of heat treatment on the intrinsic coercivity, iHc and microstructure were investigated for sintered (Nd,Dy)15(Fe,Co,Mo,Al)77 B8 permanent magnet. The microstructure has been investigated by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray spectroscopy and Mossbauer spectroscopy. The observed behaviour of iHc may be caused by a superposition of the following effects: (i) the distribution of the nonmagnetic phases and the ratio of the amount of hard magnetic Nd2Fe14B-phase to the amount of the residual phases; (ii) homogeneous distribution of elements in the main phases; (iii) removing the stresses in the phases; and (iv) diffusion of Al, …
Influence of reactive element oxide coatings on the high temperature cyclic oxidation of chromia-forming steels
2003
Abstract The beneficial effects of reactive element oxide coatings, Y2O3, Nd2O3 and Yb2O3, on the cyclic oxidation behaviour of a Fe–30Cr model alloy, were studied at 950 °C in air under atmospheric pressure. The oxide scale grown on uncoated samples started to spall after 2 cycles, because of its poor adherence. The coated specimens remarkably resisted to the thermal shocks, since no oxide scale spallation or cracks could be observed, even after 1000 h of cycling experiments. The surface oxide scale consisted of facetted oxide grains on the uncoated samples. On the contrary, it exhibited a fine-grained structure on the coated specimens. The reactive element beneficial effect was ascribed t…
Synthesis of bulk FeAl nanostructured materials by HVOF spray forming and Spark Plasma Sintering
2006
Abstract This paper examines the efficiency of two consolidation processing techniques: High Velocity Oxy-Fuel (HVOF) spray forming and Spark Plasma Sintering (SPS) to obtain bulk nanostructured materials from an Y 2 O 3 reinforced Fe–40Al (at.%) milled powder. The microstructures of the sintered end-products were characterized by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) in order to gain new insights in their microstructure formation mechanisms. HVOF spray forming is more effective to retain fine nanograins, in particular within retained unmelted powder particles. The drawbacks of this technique are that it inevitably leads to a high fraction of porosity…