Shape memory effect in γ⇄ϵ transformation in Fe-30Mn-1Si alloy single crystals

A new approach to achieve coalescence and sintering of metallic nanoparticles at room temperature is presented. It was discovered that silver nanoparticles behave as soft particles when they come into contact with oppositely charged polyelectrolytes and undergo a spontaneous coalescence process, even without heating. Utilizing this finding in printing conductive patterns, which are composed of silver nanoparticles, enables achieving high conductivities even at room temperature. Due to the sintering of nanoparticles at room temperature, the formation of conductive patterns on plastic substrates and even on paper is made possible. The resulting high conductivity, 20% of that for bulk silver, enabled fabrication of various devices as demonstrated by inkjet printing of a plastic electroluminescent device.

Triggering the sintering of silver nanoparticles at room temperature.

This report gives results of a study of the bulk mechanical properties of samples of nanocrystalline Cu and Pd consolidated from powders prepared by inert gas condensation. Fourier analysis x-ray diffraction techniques, used to determine average grain size and mean lattice strains of the as-consolidated samples, show grain sizes in the range of 3–50 nm and lattice strains ranging from 0.02–3%. Sample densities range from 97–72% of the density of a coarse-grained standard. Microhardness of the nanocrystalline samples exceeds that of annealed, coarse-grained samples by a factor of 2–5, despite indications that sample porosity reduces hardness values below the ultimate value. Uniaxial tensile strength of the nanocrystalline samples is similarly elevated above the value of the coarse-grained standard samples. Restrictions on dislocation generation and mobility imposed by ultrafine grain size are believed to be the dominant factor in raising strength. Residual stress may also play a role. Room temperature diffusional creep, predicted to be appreciable in nanocrystalline samples, was not found. Instead, samples appear to show logarithmic creep that is much smaller than the predicted Coble creep.

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Mechanical behavior of nanocrystalline Cu and Pd

A TRIP-assisted dual-phase high-entropy alloy: Grain size and phase fraction effects on deformation behavior

An Fe–35 wt-%Mn alloy, aimed to be used as a metallic degradable biomaterial for stent applications, was prepared via a powder metallurgy route. The effects of processing conditions on the microstructure, mechanical properties, magnetic susceptibility and corrosion behaviour were investigated and the results were compared to those of the SS316L alloy, a gold standard for stent applications. The Fe35Mn alloy was found to be essentially austenitic with fine MnO particles aligned along the rolling direction. The alloy is ductile with a strength approaching that of wrought SS316L. It exhibits antiferromagnetic behaviour and its magnetic susceptibility is not altered by plastic deformation, providing an excellent MRI compatibility. Its corrosion rate was evaluated in a modified Hank's solution, and found superior to that of pure iron (slow in vivo degradation rate). In conclusion, the mechanical, magnetic and corrosion characteristics of the Fe35Mn alloy are considered suitable for further development ...

Iron–manganese: new class of metallic degradable biomaterials prepared by powder metallurgy

This paper is a detailed and updated review of the properties and specifics of METGLAS amorphous brazing foil (MBF) and a review of the positive qualities it has brought to many applications in the last two decades. The major emphasis is to provide practical guidance for intelligent use that will contain, in the first part, a description of these materials in the virgin as cast state. This state has a unique combination of physical properties. The metallurgical background will also be given in this part to the existing range of available chemical compositions and their potential compatibility with various base metals. The amorphous alloy mechanical properties and thermal stability, wettability over various metals and its dependence on the brazing atmosphere and preform preparation will also be described. The second part presents the properties of MBF joints manufactured from various classes of base metals and obtained under optimised brazing conditions for each class of base metals. Particular at...

Brazing with (NiCoCr)-B-Si amorphous brazing filler metals: alloys, processing, joint structure, properties, applications

A palladium-based alloy is disclosed having a composition consisting essentially of nickel in the range of about 3 to about 30 atom percent, silicon in the range of about 15 to about 20 atom percent, the balance being palladium plus incidental impurities The alloys of the present invention are particularly suited for joining stainless steels employed in orthodontic devices at brazing temperatures less than about 900° C The alloys are typically produced in the form of a foil having a thickness of at least about 150 μm

Low melting nickel-palladium-silicon brazing alloys

Crystallography and a model of the α → ω phase transformation in zirconium

State of the art of titanium-based brazing filler metals

TiPd (ASTM grade 7) and Ti-6Al-4V alloys (where the composition is in approximate weight per cent) were brazed in a vacuum furnace, each to itself, by using a new rapidly solidified amorphous 25Ti-25Zr-50Cu brazing foil. The joint tensile strength, fatigue resistance and microstructure were determined, the latter by X-ray diffraction analysis, scanning electron microscopy-energy-dispersive spectroscopy and scanning microscopy. The joint tensile strength is close to that of each base metal. The fatigue properties of TiPd (grade 7) joints do not differ from those of this base metal. The microstructure and mechanical properties of the brazed joints depend on the brazing cycle conditions: a fine lamellar eutectic joint microstructure consisting of α-Ti and γ-[Ti(Zr)]2Cu (tetragonal MoSi2-type) phase is observed after brazing of Ti-6Al-4V alloy at 900 °C for 10 min, followed by fast cooling. This brazing operation results is high strength joints. Brazing at temperatures higher than 900 °C and/or with a relatively low cooling rate results in a coarse dendritic microstructure consisting of γ-[Ti(Zr)]2Cu and hexagonal λ Laves Cu2TiZr phases. Fine precipitations of γ-tetragonal phase in the α-Ti matrix were also observed in the transition area between the base metal and joint in this case. Joints with such microstructures are brittle and have a low strength. It is shown that fast cooling suppresses formation of the λ Laves brittle phase, thus resulting in high mechanical properties of the brazed joint.

Anatol Rabinkin

Papers

Brazing with (NiCoCr)-B-Si amorphous brazing filler metals: alloys, processing, joint structure, properties, applications

Low melting nickel-palladium-silicon brazing alloys

Crystallography and a model of the α → ω phase transformation in zirconium

State of the art of titanium-based brazing filler metals

Brazing of titanium-based alloys with amorphous 25wt.%Ti-25wt.%Zr-50wt.%Cu filler metal