Maximo Pedro Victoria

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Molecular-dynamics (MD) computer simulations on three intermetallic compounds, NiAl, Ni3Al, and Cu3Au have been performed to investigate the kinetics of the disordering and amorphization processes. These systems were chosen because the embedded atom-type potentials work well for these materials and also because they have experimentally different amorphization behavior. Previous simulations of collision cascades with 5-keV Ni and Cu primary knockout atoms (PKA) have shown a complete loss of the crystalline s

The kinetics of amorphization and disordering processes in NiAl and Ni3Al induced by collision cascades have been investigated by means of molecular dynamic (MD) computer simulations, It has been shown previously (Spaczer el at. [Phys. Rev. B 52, 7171 (1995)]), that the interaction between the electron and the phonon systems of the lattice, which is simulated by removing the kinetic energy through a coupling factor, plays a key role on the evolution of the cascade. In the ordered NiAl, a 15 keV cascade lead

In order to preserve the conditions for an environmentally safe machine, at present the selection of materials fur the structural components of fusion reactors is made not only on the basis of adequate mechanical properties, behaviour under irradiation, and compatibility with other materials and cooling media, but also on their radiological properties, i.e. radioactivity, decay heat and radiotoxicity. These conditions strongly limit the number of suitable materials to a few families of alloys, generically k

Interstitial clusters in bcc-Fe and fee-Cu and vacancy clusters in fcc-Cu have been studied by computer simulation using different types of interatomic potentials such as a short-ranged empirical pair potential of Johnson type, short-ranged many-body potentials of Finnis-Sinclair type and long-ranged pair potentials obtained within the generalized pseudopotential theory. The stability of a self interstitial in bcc-Fe was found to be dependent on the range of potential but not on the type. Thus, both short-r

Titanium alloys have been identified as candidate structural materials for the first wall, the blanket and the magnetic coil structures of fusion reactors. Titanium alloys are interesting materials because of their high specific strength and low elastic modulus, their low swelling tendency and their fast induced radioactivity decay. Other attractive properties are an excellent resistance to corrosion and good weldability, even in thick sections. Furthermore titanium alloys are suitable for components expose

The differences and similarities of behaviour between fee and bcc metals after irradiation have been investigated. For this purpose, fee Cu, Pd and 304 stainless steel and bcc Fe, Mo and Mo-5% Re were irradiated with either neutrons or 590 MeV protons at temperatures below recovery stage V. It is shown that a dense population of defect clusters (up to 10(22)-10(24) m(-3)) develops, the type of cluster formed depending apparently on the stacking fault energy. In the case of stacking fault tetrahedra formed i

Intermetallic thin films of stoichiometric NiAl and Ni3Al have been deposited onto n-type silicon (100) and nickel (110) substrates using r.f.-magnetron co-sputtering. The morphology and crystal structure of the thin films have been studied by transmission electron microscopy from planar-view and cross-sectional samples. Chemical order has been assessed using nano-diffraction techniques. Superlattice reflections confirm a fully ordered structure in both intermetallics. These NiAl and Ni3Al thin films are na

The damage accumulation in Cu and W is investigated using a multiscale modeling approach. The efficiency for defect production of displacement cascades is calculated using molecular dynamics (MD). The simulation uses the recoil spectra from spallation reactions of 1.1 and 1.9 GeV protons as calculated with the Los Alamos High Energy Transport (LAHET) nuclear transport code. The total number of defects produced under these irradiation conditions is obtained both from the NRT and MID approximations. The value

Irradiated 304 and 316 stainless steel samples were investigated. The steels were neutron irradiated to 1.5 and 7.5 dpa at 550 K. Similar types of steels were irradiated at 550 K with 590 MeV protons in the PIREX facility at PSI, Switzerland. The doses reached in this case were 0.15 and 0.3 dpa. The stress-strain relationships at different temperatures were measured. The irradiation and deformation microstructures were investigated using transmission electron microscopy (TEM). Two modes of deformation were

The primary damage formation in Mo is investigated using molecular dynamics (MD) simulation with embedded-defect (ED) and embedded-atom method (EAM) interatomic potentials. The former is similar in spirit to the latter but includes an approximate treatment of bond directionality in the many-body interaction. MD simulations are used to calculate threshold displacement energy as function of crystallographic orientation and displacement cascade evolution resulting from primary knock-on atoms (PKAs) with energi

Molecular dynamics computer simulations on three intermetallic compounds, Cu,Au, Ni,AI and NiAl, have been performed to investigate the kinetics of the disordering and amorphization processes. These systems were chosen because reliable embedded atom potentials were developed for the constituent species and their alloys, and also because extended experimental results are available for them. Previous simulations of collision cascades with 5 keV Cu and Ni primary knock-out atom (PKA) showed a significant diffe

Predicting microstructure evolution of metals under irradiation requires an in depth understanding of the production and properties of point defects and their clusters. Although, analytical descriptions based on the production bias model have recently been applied successfully to explain the behaviour of metals under different irradiation conditions, they still lack an important ingredient, namely that of the diffusion mechanism of the defects produced. In the present investigation, a hierarchical computer

The visibility of conventional transmission electron microscopy (CTEM) images of small crystalline defects generated by molecular dynamics (MD) simulation is investigated. Faulted interstitial dislocation loops in Al smaller than 2 nm in diameter and stacking fault tetrahedra (SFT) in Cu smaller than 4 nm in side are assessed. A recent approach allowing to simulate the CTEM images of computer generated samples described by their atomic positions is applied to obtain bright field and weak beam images. For th

Total reflection X-ray fluorescence spectroscopy (TXRF) has been used in combination with synchrotron radiation in order to determine detection limits and lowest limits of concentration of trace elements in metal matrices. Two applications on irradiated material are described, where the TXRF method has some advantages, as compared to other detection methods, because only a few micrograms of material is needed for the measurements. The first application is devoted to radiation damage studies on first wall ma

F82H low-activation martensitic steel was irradiated in the Swiss Spallation Neutron Source (SINQ) Target-III to irradiation doses of 10-12 dpa in a temperature range of 140-360 degreesC. Transmission electron microscope observations have been performed to study the radiation effects on the microstructure at different irradiation temperatures. The results show: (1) High-density helium bubbles of size greater than or equal to 1 nm are observed in the samples irradiated at temperatures greater than or equal t

Leading long term considerations for choices in the European Long Term Technology programme are the high temperature mechanical- and compatibility properties of structural materials under neutron irradiation. The degrees of fabrication process freedom are closely investigated to allow the construction of complex shapes. Another important consideration is the activation behaviour of the structural material. The ideal solution is the recycling of the structural materials after a relatively short 'cooling' per

Nanostructured materials should present a good resistance to irradiation because the large volume fraction of grain boundaries can be an important sink for radiation-induced defects. The objective of the present study is to experimentally investigate the irradiation impact on the microstructure in nanostructured materials. Nickel and Cu-0.5A(2)O(3) specimens were synthesized by electro deposition (ED) and severe plastic deformation (SPD). 590 MeV proton irradiation was conducted in the Proton IRradiation EX

The irradiation of metals by energetic particles causes significant degradation of the mechanical properties(1,2), most notably an increased yield stress and decreased ductility, often accompanied by plastic flow localization. Such effects limit the lifetime of pressure vessels in nuclear power plants(3), and constrain the choice of materials for fusion-based alternative energy sources(4). Although these phenomena have been known for many years(1), the underlying fundamental mechanisms and their relation to

The microstructure and tensile behavior of pure single crystalline Ni irradiated to low doses at room temperature with 590 MeV protons are investigated. Tensile tests performed at room temperature show radiation induced hardening, which increases with increasing dose. The microstructure of irradiation induced defects observed under transmission electron microscopy consists of about 50% stacking fault tetrahedra, 30-40% dislocation loops and 10% of unidentified features. In addition, the irradiated and defor

Maximo Pedro Victoria

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Evidence of Amorphization in Molecular-Dynamics Simulations on Irradiated Intermetallic Nial

Cascade overlap induced amorphization and disordering in irradiated intermetallics NiAl and Ni3Al: A molecular dynamic study

Structural materials for fusion reactors

Computer simulation of vacancy and interstitial clusters in bcc and fcc metals

Tensile and fatigue properties of two titanium alloys as candidate materials for fusion reactors

The microstructure and associated tensile properties of irradiated fcc and bcc metals

Microstructure and growth modes of stoichiometric NiAl and Ni3Al thin films deposited by r.f.-magnetron sputtering

Multiscale modeling of radiation damage: applications to damage production by GeV proton irradiation of Cu and W, and pulsed irradiation effects in Cu and Fe

The effects of irradiation and testing temperature on tensile behaviour of stainless steels

Primary damage formation in molybdenum: a computer simulation study

Computer simulations of disordering and amorphization kinetics in intermetallic compounds

Defect production and damage evolution in Al: a molecular dynamics and Monte Carlo computer simulation

Quantitative analysis of CTEM images of small dislocation loops in Al and stacking fault tetrahedra in Cu generated by molecular dynamics simulation

Effects of irradiation on the microstructure and mechanical properties of nanostructured materials

Measurement of trace element concentration in a metal matrix using total reflection X-ray fluorescence spectrometry

The impact of irradiation temperature on the microstructure of F82H martensitic/ferritic steel irradiated in a proton and neutron mixed spectrum

European structural materials development for fusion applications

Impact of irradiation on the microstructure of nanocrystalline materials

Multiscale modelling of plastic flow localization in irradiated materials

Irradiation induced behavior of pure Ni single crystal irradiated with high energy protons