Intermetallic Compounds Research Papers - Academia.edu (original) (raw)

The exoskeleton of the lobster Homarus americanus is a multiphase biological composite material which consists of an organic matrix (crystalline α-chitin fibers and various types of non-crystalline proteins) and minerals (mainly calcite). In this study we discuss experimental data about the mesoscopic structure and the crystallographic texture (orientation distribution) of the α-chitin–protein fiber network in this material. The synchrotron measurements reveal very strong crystallographic textures of the α-chitin. According to these data, a large fraction of the α-chitin lattice cells is arranged with their longest axis parallel to the normal of the surface of the exoskeleton. Additionally, a smaller fraction of the α-chitin cells is oriented with their longest axis perpendicular to the cuticle surface. These structural investigations reveal the pronounced role of crystallographic orientation distributions in mineralized biological composite materials which may be of relevance for an improved understanding of biological and bio-inspired nano-composites.

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- Materials Engineering, Mechanical Engineering, Materials Science, Crystallography
- by Robert Dowding
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- Electron Microscopy, Composite Materials, Strain Rate, Grain Boundaries
- by Hermann Riedel
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- Materials Engineering, Mechanical Engineering, Thermodynamics, Kinetics
- by Radovan Kovacevic
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- Materials Science, Microstructure, Electronic Materials, Composite Materials
- by Geoff Scamans
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- Materials Engineering, Mechanical Engineering, Civil Engineering, Materials Science
- by Muhammad Abbasi
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- Materials Engineering, Condensed Matter Physics, SEM, Friction Welding
- by Sean McDeavitt
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- Materials Engineering, Mechanical Engineering, Materials Science, Microstructure
- by Dierk Raabe
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- Materials Engineering, Mechanical Engineering, Materials Science, Crystallography
- by alfredo cruz
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- Engineering, Materials Engineering, Chemical Engineering, Condensed Matter Physics
- by mariyam ghazali
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- Casting, Sliding wear, Materials Design, Microhardness
- by 俊苏
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- Thermodynamics, Modelling, Crystal structure, Metals

In this study, dissimilar sheets of commercially available pure aluminium and copper, were butt joined by friction stir welding (FSW) with a thickness of 3mm to explore the effect of tool rotational speeds on microstructures and mechanical properties experimentally. Three rotational speeds of 1000, 1750 and 2000 rpm were applied. The transverse speed and the axial force were kept constant at 30 mm/min and 7.5 KN, respectively. The cylindrical shoulder and conical pin tool was used to produce the joints. Macrostructures, microstructures, X-ray diffraction (XRD), Vickers microhardness and tensile strength were investigated at these different rotational speeds. The joint welded at 1750 rpm was compared with their counterparts and observed significantly better. The formation of relatively hard brittle intermetallic compounds (Al2Cu and Al4Cu9) were observed with the joint fabricated at rotational speed of 2000 rpm. The results of microhardness (HV) at the nugget zone (NZ) were superior ...

- by Radovan Kovacevic
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- Mechanical Engineering, Feasibility Study, Friction Welding, Porosity
- by Tomi Laurila and +1
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- Engineering, Thermodynamics, Microstructure, Kinetics
- by Vincenzo Buscaglia
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- Materials Engineering, Mechanical Engineering, Microstructure, Kinetics
- by Pradeep Lall
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- Crack propagation, Printed Circuit Board, Manufacturing Engineering, Reliability
- by Zeev Porat and +1
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- Materials Engineering, Condensed Matter Physics, Nanoparticles, Reduction

As solder joints become increasingly miniaturized to meet the severe demands of future electronic packaging, it is vitally important to consider whether the solder joint size and geometry could become reliability issues and thereby affect implementation of the Pb-free solders. In this study, three bumping techniques, i.e., solder dipping, stencil printing followed by solder reflow, and electroplating of solders with subsequent reflow, were used to investigate the interfacial interactions of molten Sn-3.5Ag, Sn-3.8Ag-0.7Cu, and pure Sn solders on a copper pad at 240°C. The resultant interfacial microstructures, coming from a variety of Cu pads, with sizes ranging from 1 mm to 25 µm, and representing different solder bump geometries, have been investigated. In addition, a two-dimensional thermodynamic/kinetic model has been developed to assist the understanding of the kinetics of interdiffusion and the formation of interfacial intermetallic compounds. Experimental results and theoretical predictions both suggest that the solder bump size and geometry can influence the as-soldered microstructure; therefore, this factor should be taken into consideration for the design of future reliable ultrafine Pb-free solder joints.

- by Paul P Conway
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- Thermodynamics, Kinetics, Electronic Materials, Copper
- by Rada Novakovic
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- Materials Engineering, Condensed Matter Physics, Thermodynamics, Phase Diagrams
- by Timothy Dyer
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- Chemical Engineering, Materials Science, Thermodynamics, Kinetics
- by Sikander Azam and +1
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- Materials Engineering, Condensed Matter Physics, Quantum Physics, Computational Materials Science
- by Eduardo Donoso
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- Microcalorimetry, Magnesium, Differential scanning calorimetry, Copper

First-principles calculations are used to address the problem of phonon anomalies in non-magnetic and magnetic Heusler alloys. Phonon dispersions of the cubic L21 structure were obtained along the [110] direction. We consider compounds that exhibit phonon instabilities and compare them with their stable counterparts. The analysis of the electronic structure allows us to identify the characteristic features leading to structural instabilities. The phonon dispersions of the unstable structures show that, while the acoustic modes tend to soften, the optical modes disperse in a way that is significantly different from that of the stable structures. In an external field the affected optical modes are Raman active, which is considered as an indication of a stronger covalent interaction in the case of unstable systems. This covalent interaction changes the usual metallic behaviour of some Heusler alloys leading to the possibility of localization of vibrational modes and a possible relationship to similar features observed in perovskites.

- by Mehmet Acet
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- Low Frequency, Physical sciences, Low Energy Buildngs, Electronic Structure
- by Srdjan Milenkovic
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- Microstructure, Crystal Growth, Kinetics, Scanning Electron Microscopy
- by Martin Blaber
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- Materials Engineering, Physics, Condensed Matter Physics, Plasmonics
- by John Evans
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- Packaging, Design of Experiments, Response Surface Methodology, Sensitivity Analysis
- by Pradeep Lall
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- Assembly, Lead, Reliability, Intermetallic Compounds

The coloured intermetallic compounds AuAl 2 and PtAl 2 are attractive and unique, with AuAl 2 being deep purple and PtAl 2 golden yellow. These phases are formed in a very narrow range within the Al-Au or Al-Pt phase diagrams and, for this reason, it is challenging to manufacture pure samples of them. Here we show that physical vapour deposition (PVD) can be used to form pure, thin film coatings by co-sputtering of the elements. The chemical compositions, X-ray diffraction patterns, microstructures and reflectance spectra of the nanoscale films are compared to those of bulk samples that had been produced by vacuum arc furnace melting. A range of colours can be obtained if the thickness of the films is varied. Simulated and measured reflectance and transmittance data of coloured nanoscale films are compared and the CIE chromaticity indices (a* and b*) of films of various thicknesses determined.

- by Supitcha Supansomboon
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- Intermetallic Compounds
- by Steven Son
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- Chemical Engineering, Intermetallic Compounds, Impact Test

Previous work on the stability of the solid solution phases in the high entropy alloys is inconclusive. We used a series of thermo-mechanical treatments to study the stability of the solid solution phases in a high-entropy Al0.5CoCrCuFeNi alloy. The solid solution phases were found to be stable, against the intermetallic compounds, at high temperatures >850 °C and at low temperatures <300 °C. At intermediate temperatures, however, the intermetallic σ-phase co-existed with the solid solution phases. The experimental observations were verified by the thermodynamic calculation results. The mechanisms for the phase stability, both at equilibrium and after quenching-equivalent annealing treatments, were discussed, and the roles of high entropy and slow diffusion kinetics were highlighted.

- by Luca Lutterotti
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- Materials Engineering, Mechanical Engineering, Materials Science, Microstructure
- by Tomi Laurila
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- Materials Engineering, Mechanical Engineering, Crystal structure, Superconductors

- by Dr. Uday M. Basheer and +1
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- Materials Engineering, Materials Science and Engineering, Friction Stir Welding, Rotational speed
- by Emmanuel Isaac
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- Mechanical Engineering, Composites, Aluminum, Reinforcement
- by Marianne Balat-Pichelin
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- Intermetallics, Multidisciplinary, Intermetallic Compounds, Oxidation
- by Sankum Nusen
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- Hydrometallurgy, Intermetallic Compounds

In the present study, an attempt has been made to prepare and characterize Al-Al3Ti metal matrix composites with varying percentage of in-situ Al3Ti (3, 5 and 7%). The composites were prepared by the reaction commercial purity aluminum 99.7% and K2TiF6 salt at a reaction temperature of 800 °C. The prepared samples were characterized by optical microscopy. The wear tests were conducted on all the prepared samples by varying parameters like wt. % of Al3Ti particles, normal pressures, sliding speeds. Mechanical properties were assessed using computerized universal testing machine, Brinell hardness tester, Surface roughness tester and micro hardness tester. The worn surfaces were examined by optical microscopy after wear test.Al-3Ti, Al-5Ti and Al-7Ti alloys were prepared and effect of Ti content on hardness, tensile strength, volumetric wear rate and surface roughness were examined. Experimental alloys were fabricated by salt route method. Volumetric wear rate of the reinforced Al-3Ti, Al-5Ti and Al-7Ti alloys at room temperature were measured. The present results suggest that the wear resistance of Al-Al3Ti composites increases with increase in percentage of Al3Ti particles compared to pure aluminum. In addition, the improvement in mechanical properties of the composite was observed in Al-5Ti composite when compared to Al-3Ti and Al-7Ti and to the pure Al. Better tribological properties of these alloys can be achieved at Al-5Ti.

An imperfectly B2 ordered Fe3Al aggregate was cast, thermomechanically hot rolled and finally annealed at 870 K. Subsequently, the specimen was rolled at 800–830 K to a strain ε of 80%. The microstructure and the crystallographic texture of the rolled polycrystalline sample was investigated within the range ε=20–80%. The microstructure consisted of flat, elongated grains. In numerous grains straight slip lines were detected. Even after ε=80% recrystallization was not observed. The rolling texture of Fe3Al considerably deviates from that of non-ordered body centered cubic (b.c.c.) alloys and pure b.c.c. metals. The {111}〈uvw〉 texture fibre (7-fibre) was very pronounced, while the {hkl}〈110〉 fibre (α-fibre) was very weak. The {112}〈110〉 orientation which represents the strongest texture component in non-ordered b.c.c. alloys did not occur at all. The textures are discussed in terms of the {110}〈111〉, {112}〈111〉, {112}〈111〉 and {123}〈111〉 slip systems. The contribution of crystallographic slip of the various types of potential slip systems was simulated by means of the Taylor theory.

- by Dierk Raabe
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- Intermetallics, Crystallographic Texture, Grain size, Grain Size Measurement
- by Melania Oana
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- Condensed Matter Physics, Quantum Physics, Surface Science, Chemisorption