Hu Wangyu

Properties of electroless Ni-W-P amorphous alloys

This paper describes work performed to determine some of the properties of the electroless Ni-W-P amorphous deposits. Phosphorus contents were varied up to 32 at.%, and the amorphous structure was found to be present at phosphorus contents above 5 at.%. Irrespective of P content, all the deposits exhibited excellent adhesion to metallic substrates. The addition of even small amounts of W provided greatly increased hardness compared with the plain Ni-P deposits. The wettability properties of the Ni-W-P deposits were found to be comparable to those of Ni-P and N-B-P deposits but inferior to those of Ni-B deposits

Structure and crystallization of amorphous Fe-B alloys obtained by chemical plating

Abstract Fe100-xBx (x = 2.2–27.4 at%) alloys are prepared by chemical plating. It is found that when the boron content is 18 at% or more, the structure is amorphous. A two-step process of crystallization is observed for the amorphous specimens. The kinetics of the crystallization is discussed; it is analogous to that for samples prepared by rapid quenching. The activation energy of crystallization for the present samples ranges from 184.5 to 129.1 kJ/mol as the boron content varies from 18 to 27.4 at%; this is lower than that for the same composition alloys produced by rapid quenching.

Electroless deposition of iron-boron alloys

Iron-boron deposits on a copper substrate were obtained by electroless plating. The films were prepared on the substrate which was immersed in a bath containingferrous sulphate, sodium potassium tartrate, sodium hydroxide and potassium borohydride and contacted with an aluminium strip. The plating mechanism is a combination of galvanic and chemical deposition due to reduction of the Fe cation by BH 4 - accompanied by boron codeposition. The effects of the concentration of ligand and reducing agent, pH value and temperature on the deposition rate and boron content were studied

Structure and crystallization of amorphous FeMoB alloys obtained by electroless plating

Abstract FeMoB alloys are prepared by electroless plating. It is found that when the boron content ranges from 10.1–30.00 at.%, the structure is amorphous. A two-step process of crystallization is observed for the amorphous Fe 63.4 Mo 13.3 B 23.3 , Fe 58.7 Mo 11.3 B 30.0 , Fe 73.6 Mo 16.3 B 10.1 and Fe 74.7 Mo 18.9 B 6.4 alloys. The crystallization temperature ranges from 745 to 771 K for a B content ranging from 6.4–30.0 at.% of the amorphous samples, which is higher than the range for the FeB amorphous films.

Magnetic properties of crystalline and amorphous Fe-B alloys prepared by electroless plating

Abstract Amorphous samples of Fe 100− x B x ( x =18, 24, 27.4) and crystalline samples of Fe 100− x B x ( x =2.2, 10.6) have be en prepared by electroless plating. Their magnetic properties have been studied. The Curie temperature T C increases upon increasing the boron concentration for the amorphous alloys from 613 K ( x =18) to 776 K ( x =27.4). However, the saturation magnetization and magnetic moment decrease with increasing boron concentration for both the crystalline and amorphous alloys. The data have been analyzed and discussed using the molecular-field theory and the rigid-band theory and the charge transfer of sp electrons from the metalloids to the d-band of the transition metals. The dependence of the magnetic properties of the amorphous alloys on heat treatment has also been studied.

Molecular dynamics simulations of point defects in plutonium grain boundaries

A modified analytic embedded atom method (MAEAM) potential is constructed for fcc δ-Pu. Molecular dynamics (MD) simulations with the potential are performed to investigate the interactions between two symmetrical tilt grain boundaries (GBs) and point defects such as He atom, vacancy and self-interstitial atom (SIA) in Pu. The calculated results show that point defect formation energies are on average lower than those in the lattice but variations from site to site along the GBs are very remarkable. Both substitutional and interstitial He atoms are trapped at GBs. Interstitial He atom is more strongly bound at the GB core than the substitutional He atom. The binding energy of SIA at GB core is higher than those of He atom and vacancy. GB core can bind many He atoms and SIAs due mainly to the fact that it contains many vacancies. Compared with He atom and SIA, the vacancy far from GB core is difficult to diffuse into the core. The GBs can act as sinks and sources of He atoms and SIAs, which may be a reason for the swelling of Pu after a period of self-irradiation because of the higher concentration of vacancy in the bulk.

Molecular dynamics simulation of surface melting behaviours of the V(110) plane

The modified analytic embedded-atom method and molecular dynamics simulations are applied to the investigation of the surface premelting and melting behaviours of the V(110) plane by calculating the interlayer relaxation, the layer structure factor and atomic snapshots in this paper. The results obtained indicate that the premelting phenomenon occurs on the V(110) surface at about 1800K and then a liquid-like layer, which approximately keeps the same thickness up to 2020K, emerges on it. We discover that the temperature 2020K the V(110) surface starts to melt and is in a completely disordered state at the temperature of 2140K under the melting point for the bulk vanadium.

Monte Carlo simulation of hydrogen adsorption on Ni surfaces

In the present paper the adsorption kinetics of the hydrogen molecule on the (111) and (100) surfaces have been studied with the model proposed by Panczyk and the grand canonical Monte Carlo simulation method. The equilibrium adsorption isotherms are calculated at five different temperatures ranging from 314 K to 376 K and compared with the experimental equilibrium adsorption isotherms. The effects of temperature and pressure on coverage are also analyzed.

A TEM study on the crystallization of amorphous Fe73Si3B24 alloys

The crystallization of Fe73Si3B24 amorphous alloys has been studied by transmission electron microscopy (TEM). A metastable phase P has been found and determined by a double tilting method in TEM. This phase belongs to a primitive tetragonal lattice with a = 0.62 nm and c = 1.43 nm. Its probable space group is P4nc or P4/mnc. In the Fe2B phase, we found threefold twins which are rotated 120° around the [1 1 0] axis. The crystallization process of this alloy is suggested to be Amorphous→Amorphous + α-Fe(Si) + Fe3B + P → α-Fe(Si) + Fe3B + Fe2B → α-Fe(Si) + Fe2B.

THE CRYSTALLINE PHASES IN RAPIDLY SOLIDIFIED AL65CU20FE15 ALLOY POWDERS

An Al{sub 65}Cu{sub 20}Fe{sub 15} alloy with the composition of Al-65at%, Cu-20at% and Fe-15at% was prepared from 99.5% pure starting materials. Alloy powders were then produced with a rapidly solidified (RS) device developed by Chen et al. The powders obtained have an average particle size of about 15{mu}m and their cooling rates are estimated to be 10{sup 5}--10{sup 7} K/S. The powders were uniformly sprinkled on to microgrids for observation by transmission electron microscope (H-800 transmission electron microscope equipped with an EDAX SW9100 composition analysis system).