Alloy

About: Alloy is a research topic. Over the lifetime, 171884 publications have been published within this topic receiving 1719420 citations. The topic is also known as: alloys.

Solvothermal Synthesis of Platinum Alloy Nanoparticles for Oxygen Reduction Electrocatalysis

Abstract: Platinum alloy nanoparticles show great promise as electrocatalysts for the oxygen reduction reaction (ORR) in fuel cell cathodes. We report here on the use of N,N-dimethylformamide (DMF) as both solvent and reductant in the solvothermal synthesis of Pt alloy nanoparticles (NPs), with a particular focus on Pt–Ni alloys. Well-faceted alloy nanocrystals were generated with this method, including predominantly cubic and cuboctahedral nanocrystals of Pt3Ni, and octahedral and truncated octahedral nanocrystals of PtNi. X-ray diffraction (XRD) and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), coupled with energy dispersive spectroscopy (EDS), were used to characterize crystallite morphology and composition. ORR activities of the alloy nanoparticles were measured with a rotating disk electrode (RDE) technique. While some Pt3Ni alloy nanoparticle catalysts showed specific activities greater than 1000 μA/cm2Pt, alloy catalysts prepared with a nominal composition of PtNi disp...

Microstructural Effects on the Tensile and Fracture Behavior of Aluminum Casting Alloys A356/357

Abstract: The tensile properties and fracture behavior of cast aluminum alloys A356 and A357 strongly depend on secondary dendrite arm spacing (SDAS), Mg content, and, in particular, the size and shape of eutectic silicon particles and Fe-rich intermetallics. In the unmodified alloys, increasing the cooling rate during solidification refines both the dendrites and eutectic particles and increases ductility. Strontium modification reduces the size and aspect ratio of the eutectic silicon particles, leading to a fairly constant particle size and aspect ratio over the range of SDAS studied. In comparison with the unmodified alloys, the Sr-modified alloys show higher ductility, particularly the A356 alloy, but slightly lower yield strength. In the microstructures with large SDAS (>50 µm), the ductility of the Sr-modified alloys does not continuously decrease with SDAS as it does in the unmodified alloy. Increasing Mg content increases both the matrix strength and eutectic particle size. This decreases ductility in both the Sr-modified and unmodified alloys. The A356/357 alloys with large and elongated particles show higher strain hardening and, thus, have a higher damage accumulation rate by particle cracking. Compared to A356, the increased volume fraction and size of the Fe-rich intermetallics (π phase) in the A357 alloy are responsible for the lower ductility, especially in the Sr-modified alloy. In alloys with large SDAS (>50 µm), final fracture occurs along the cell boundaries, and the fracture mode is transgranular. In the small SDAS (<30 µm) alloys, final fracture tends to concentrate along grain boundaries. The transition from transgranular to intergranular fracture mode is accompanied by an increase in the ductility of the alloys.

Nickel-base alloys

Abstract: : A novel alloy composition consisting essentially of 10 from about 50% to about 70% nickel by weight and correspondingly from about 50% to about 30% titanium by weight is described. The said alloy has the structure of a TiNi phase in combination with a TiNi3 phase dispersed in a TiNi matrix within a temperature range of from about 500 C to about -75 C and having the properties of being paramagnetic, of retaining hardness throughout said temperature range and of being corrosion resistant. A novel alloy composition consisting essentially of 20 from 52% to about 56% nickel by weight and correspondingly from about 48% to about 44% titanium by weight is described. The said alloy having the structure of a substantially TiNi phase within a temperature range of from about 500 C to about -75 C and having the properties of being paramagnetic, of being highly vibration damping at about room temperature and having the capability of being plastically deformed at about room temperature and retaining the deformed shape until heated to a higher temperature whereupon the prior nondeformed condition will be reassumed. A novel alloy composition consisting essentially of from about 56% to about 64% nickel by weight and correspondingly from about 44% to about 36% titanium by weight is described. The said alloy having the structure of a substantially TiNi3 phase dispersed in a TiNi matrix within a temperature range of from about 450 C to about -75 C and having the properties of being paramagnetic, of high hardness upon heat treatment, of being abrasion and corrosion resistant and capable of being hot wrought into useable shapes prior to hardening. (Author)