Constitution of Ni3Al–Ni3Mo–Ni3W section of Ni–Al–Mo–W system

Abstract

The isothermal section of the Ni–Al–Mo–W system has been studied at 75 at.-%Ni at temperatures of 1523 and 1273 K. Constitutional data have been determined using electron probe microanalysis, X-ray diffraction, and microscopical examination. The alloys studied lay in the range 12·5–15 at.-%Al, 2·5–7·5 at.-%Mo, and 2·5–7·5 at.-% W. The phases present at 1523 K were γ, γ′, and α (based on the Mo–W continuous series of solid solutions); at 1273 K, NiMo(δ′) was also encountered. The γ/γ′ mismatch values lay in the range ?0·03 to ?0·75%. In the as-solidified state, the alloys consisted predominantly of γ-phase containing γ′-precipitates formed in the solid state.

MST/462     

Martensitic transformation behaviors of rapidly solidified Ti–Ni–Mo powders

For the fabrication of bulk near-net-shape shape memory alloys and porous metallic biomaterials, consolidation of Ti–Ni–Mo alloy powders is more useful than that of elemental powders of Ti, Ni and Mo. Ti₅₀Ni_49.9Mo_0.1 shape memory alloy powders were prepared by gas atomization, and transformation temperatures and microstructures of those powders were investigated as a function of powder size. XRD analysis showed that the B2–R–B19 martensitic transformation occurred in powders smaller than 150 μm. According to DSC analysis of the as-atomized powders, the B2–R transformation temperature (T_R) of the 25–50 μm powders was 18.4 °C. The T_R decreased with increasing powder size, however, the difference in T_R between 25–50 μm powders and 100–150 μm powders is only 1 °C. Evaluation of powder microstructures was based on SEM examination of the surface and the polished and etched powder cross sections and the typical images of the rapidly solidified powders showed cellular morphology. Porous cylindrical foams of 10 mm diameter and 1.5 mm length were fabricated by spark plasma sintering (SPS) at 800 °C and 5 MPa. Finally these porous TiNi alloy samples are heat-treated for 1 h at 850 °C, and then quenched in ice water. The bulk samples have 23% porosity and 4.6 g/cm³ density and their T_R is 17.8 °C.     

Thermophysical Properties of 75Ni–15Mo–10Re Alloy

The true heat capacity, thermal expansion, thermal conductivity, electrical resistance, and density of NMR-75 alloy (75 wt % Ni, 15 wt % Mo, and 10 wt % Re) are investigated in a temperature range of 300–1300 K. The enthalpy, mean coefficient of thermal expansion, thermal diffusivity, and Lorentz number are calculated from the obtained experimental data. The measurement results show that a reversible structural transformation occurs in the alloy in a temperature range of 750–960 K. In accordance with the phase diagram, the ternary system of the alloy consists of an a-solid molybdenum–nickel solution, which is in equilibrium with a -solid rhenium–nickel solution and a Ni₄Mo intermetallic compound. On heating the alloy in a temperature range of 750–960 K, the intermetallic compound transforms into the -solid molybdenum–nickel solution with the absorption of heat, while the ordered structure transforms into a disordered one. The thermal effect Q = 6 kJ/kg and the activation energy of alloy disordering E = 2.2 eV are estimated. The transformation proper is regarded as a second-order transition.     

Phase transitions in alloys of the Ni–Mo system

The structure of Ni–20 at.% Mo and Ni–25 at.% Mo alloys heat treated at different temperatures was studied by the method of transmission electron microscopy. X-ray photoelectron spectroscopy was used to detect the sign of the chemical interaction between Ni and Mo atoms at different temperatures. It is shown that at high temperatures the tendency toward phase separation takes place. The system of additional reflections at positions {1 ½ 0} on the electron diffraction patterns testifies that the precipitation of crystalline bcc Mo particles begins in the liquid solution. At 900 °C and below, the tendency toward ordering leads to the precipitation of the particles of the chemical compounds. A body-centered tetragonal phase Ni₄Mo (D1_a) is formed in the Ni–20 at.% Mo alloy. In the Ni–25 at.% Mo alloy, the formation of the Ni₃Mo (D0₂₂) chemical compound from the A1 solid solution has gone through the intervening stage of the Ni₄Mo (D1_a) and Ni₂Mo (Pt₂Mo) formation.     

Using direct hot-rolling approach to obtain dual-phase weathering steel Cu–P–Cr–Ni–Mo

A weathering steel Cu–P–Cr–Ni–Mo has been developed which exhibits special continuous cooling transformation characteristics which permit the desired dual-phase (DP) microstructure to be obtained by direct hot-rolling. Hot-rolling procedures to obtain DP microstructures have been designed based on the continuous cooling transformation diagram of weathering steel Cu–P–Cr–Ni–Mo. The results show that the microstructures of DP weathering steels Cu–P–Cr–Ni–Mo are characterized by an irregular distribution of island-shaped martensite–austenite in the matrix of polygonal ferrite grains. DP weathering steel Cu–P–Cr–Ni–Mo with favorable corrosion resistant property, weldability and mechanical properties, such as, high strain hardening exponent values, a lower ratio of yield to tensile strength, and higher strengths; and is obtained successfully by direct hot-rolling.     

Electroless Ni–Mo–P diffusion barriers with Pd-activated self-assembled monolayer on SiO2

Ternary Ni-based amorphous films can serve as a diffusion barrier layer for Cu interconnects in ultralarge-scale integration (ULSI) applications. In this paper, electroless Ni–Mo–P films deposited on SiO₂ layer without sputtered seed layer were prepared by using Pd-activated self-assembled monolayer (SAM). The solutions and operating conditions for pretreatment and deposition were presented, and the formation of Pd-activated SAM was demonstrated by XPS (X-ray photoelectron spectroscopy) analysis and BSE (back-scattered electron) observation. The effects of the concentration of Na₂MoO₄ added in electrolytes, pH value, and bath temperature on the surface morphology and compositions of Ni–Mo–P films were investigated. The microstructures, diffusion barrier property, electrical resistivity, and adhesion were also examined. Based on the experimental results, the Ni–Mo–P alloys produced by using Pd-activated SAM had an amorphous or amorphous-like structure, and possessed good performance as diffusion barrier layer.     

Structure and morphology of electroless Ni–P deposits

Abstract

The high-voltage electron microscope has been used to study the structure and morphology of electroless Ni–P deposits of varying phosphorus contents. Except for low (<3 wt-%) phosphorus contents the deposits are amorphous. The crystallization processes depend on a number of variables, including thickness and phosphorus content of the deposit and presence or otherwise of an iron substrate. These processes include epitaxial crystallization of Ni_2.55P, spherulitic (or dendritic) crystallization of Ni_2.55P and Ni₃P, precipitation of nickel particles, and structures arising from interdiffusion between nickel, phosphorus, and the substrate.

MST/660     

Preparation and properties of electroless Ni–Zn–P alloy films

Electroless deposition of Ni–Zn–P layers was studied on steel electrodes by varying the bath temperature (40–90°C), pH and chemical composition. The deposition parameters were optimized. Alloys containing 70–86 wt % Ni, 6–20 wt % Zn and 6–10 wt % P are obtained at 20 m h^–1 and 85°C. Corrosion measurements were performed in aerated 5% sodium chloride solution, the corrosion potential and current density are, respectively, –0.49 V/SCE and 2.6 A cm^–2.     

Effect of heat treatment on microstructure and mechanical properties of Cr–Ni–Mo–Nb steel

Abstract

The microstructure and mechanical properties of a medium carbon Cr–Ni–Mo–Nb steel in quenched and tempered conditions were investigated using transmission electron microscopy (TEM), X-ray analysis, and tensile and impact tests. Results showed that increasing austenitisation temperature gave rise to an increase in the tensile strength due to more complete dissolution of primary carbides during austenitisation at high temperatures. The austenite grains were fine when the austenitisation temperature was <1373 K owing to the pinning effect of undissolved Nb(C,N) particles. A tensile strength of 1600 MPa was kept at tempering temperatures up to 848 K, while the peak impact toughness was attained at 913 K tempering, as a result of the replacement of coarse Fe rich M₃C carbides by fine Mo rich M₂C carbides. Austenitisation at 1323 K followed by 913 K tempering could result in a combination of high strength and good toughness for the Cr–Ni–Mo–Nb steel.     

Effects of Cr Content on the Microstructure and Properties of 26Cr–3.5Mo–2Ni and 29Cr–3.5Mo–2Ni Super Ferritic Stainless Steels

By using scanning electron microscopy,energy-dispersive spectrometry,X-ray diffraction,strength and hardness measurements,the microstructure,precipitation,mechanical properties,and corrosion resistance have been investigated for two super ferritic stainless steels,26Cr–3.5Mo–2Ni and 29Cr–3.5Mo–2Ni,with the aim to consider the effect of Cr content.The results showed that with the addition of Cr content,the recrystallization temperature was increased;the precipitation of Laves and Sigma(σ)phases was promoted and the mechanical properties of super ferritic stainless steel were modified.Furthermore,the pitting corrosion resistance and corrosion resistance to H_2SO_4 of the two super ferritic stainless steels were improved.In addition,suitable annealing processing is a key factor to maintain integrated performance by optimizing microstructure and removing detrimental precipitation phases.     

Preparation and electromagnetic characteristics of silica coated Fe–Ni–Mo alloy flakes

The Fe–Ni–Mo alloy flakes were firstly prepared from water atomized powders. Subsequently, by a facile sol–gel technique using tetraethylorthosilicate (Si(OC₂H₅)₄) as a precursor, we successfully synthesized silica coated Fe–Ni–Mo alloy flakes. These products were characterized by Scanning Electron Microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Furthermore, their electromagnetic parameters, complex permittivity and complex permeability within 2–12 GHz were measured. The results show that both and values of the silica coated flakes substantially decrease with the increase of coating times. Meanwhile, the μ′ values of silica coated samples are larger than those of the as-milled sample at the high frequencies. However, the maximum μ′ exhibits a decline while resonance frequency shifts to high values with the increase of coating times. The calculated reflection loss (RL) curve reveals that a proper thickness of coating can redound to improve the absorbing performances of silica coated Fe–Ni–Mo alloy flakes in high frequency range.     

Prediction of the temperature dependence of fracture toughness of 12Cr–2Ni–Mo refractory steel

We study the influence of temperature and the size of the specimens on the characteristics of static crack resistance of 12Cr–2Ni–Mo refractory steel. It is shown that, in the temperature range 20–450°C, the increase in the thickness of specimens leads to an insignificant increase in fracture toughness obtained along a 5% secant line according to the standards of evaluation of the characteristics of crack resistance. The evaluation of the characteristics of crack resistance of 12Cr–2Ni–Mo steel with regard for the scale effect according to an earlier developed numerical-experimental model reveals the existence of satisfactory agreement with the experimental data in the entire investigated temperature range. Translated from Problemy Prochnosti, No. 4, pp. 78–88, July–August, 2009.     

On the glass-forming ability of Ni–P binary alloys

The composition dependence of glass-forming ability (GFA) of Ni–P binary alloys was systematically examined by fabricating ribbons of different thicknesses, and the microhardness of the glassy ribbon was measured. The eutectic alloy Ni_80.4P_19.6 has the best GFA and the highest microhardness in glassy state. As the alloy composition is deviated from the eutectic composition, both GFA and microhardness decrease, accompanied with an increasing full width at half maximum of the main broad peak in the X-ray diffraction spectrum of the glassy ribbon. All these results indicate a close correlation among microstructure, GFA and microhardness for the metallic glass.     

化学沉积Ni—Mo—P合金

研究了溶液的组分及操作条件对Ｎｉ－Ｍｏ－Ｐ合金形成的影响，以得到合适的沉积工艺。试验结果表明，ＰＨ＝５．６，ｔ＝９０℃，溶液中的Ｎｉ＾２＋／ＭｏＯ４＾２－＝１３．９－１６．７；ｐＨ＝９．０，ｔ＝８５℃，Ｎｉ＾２＋／ＭｏＯ４＾２－＝２３．４－２８．５，有利于获得良好的Ｎｉ－Ｍｏ－Ｐ的合金层。     

Magnetic susceptibility of electroless Ni84P16 and Ni84P16–B4C

X-ray amorphous and crystallised NiP alloys possess structural inhomogeneities with nano-scale sizes, linked to the existence of a distribution of excess free volumes. The way the observed magnetic inhomogeneities are related to structural ones is not yet fully understood. In particular the dispersion of ceramic particles in a NiP-matrix composite adds further, uninvestigated structural peculiarities. In this work we focus our attention on the possibility of antiferromagnetic exchange between nickel atoms in the relevant materials. The magnetic susceptibility was investigated by the Faraday method in the temperature range 290–770 K with magnetic fields B=0.4–1.2 Tl. Amorphous pure-matrix and composite samples show one and two spin-glass transitions, respectively. Crystallised pure-matrix material shows field-independent susceptibility and ferromagnetic behaviour. Crystallised composites show field-dependent susceptibility, but are superparamagnetic.     

Interatomic potential to predict the glass-forming ability of Ni–Nb–Mo ternary alloys

With the recently proposed formulation, an interatomic n-body potential was first constructed for the Ni–Nb–Mo metal system, and then applied to atomistic simulations to investigate the glass formation of the Ni–Nb–Mo ternary alloys. The simulations not only clarify the atomistic process of the metallic glass formation but also predict for the ternary system of a quantitative composition region within which metallic glass formation is energetically favored. In addition, the energy difference between crystalline solid solution and disordered phase i.e., the driving force for a supersaturated solid solution to amorphize could be considered as an indicator of the glass-forming ability (GFA) for a specific alloy. The GFAs of a series of Ni–Nb–Mo alloys were derived from the simulations, leading to pinpoint the Ni₅₅Nb₃₀Mo₁₅ alloy with superior GFA in this ternary metal system. The Ni₅₅Nb₃₀Mo₁₅ alloy can be considered as the optimized ternary metallic glass for thermal stability and manufacturability.     

Formation kinetics of Ni–15% Fe–5% Mo during ball milling

Systematic study on Ni–15% Fe–5% Mo by high energy ball milling of elemental Mo powder and pre-alloyed intermetallic FeNi₃ has been done to understand the formation kinetics during ball milling. X-ray powder diffraction (XRPD) has been employed to study the structure evolution. Mo atoms were found to dissolve into FeNi₃ within 40 h of milling. The speed of the diffusion of Mo atoms into FeNi₃ alloy was very slow as analyzed using the Johnson–Mehl–Avrami (JMA) equation. The substitution process destroyed the long-range FeNi₃ and NiMo bonds were formed. This change caused a decrease in magnetization.     

Crystal Structure of (Ti,Mo)12P7and Refined Phase Equilibria in the Ti–Mo–P System

A new ternary compound of composition Ti_3.8Mo_8.2P_7.0 was identified, and its structure was determined by single-crystal x-ray diffraction: sp. gr. P6¯, a= 1.67821(6) nm, c= 0.33196(2) nm; R _F = 0.073 and R _w = 0.078 for 1359 independent reflections with F _hkl > 4(F _hkl). The phase equilibria in the Ti–Mo–P system were refined in the region 0–25 mol % Ti and 33–40 mol % P.     

Effect of multicomponent modifier on microstructure and mechanical properties of high Ni–Cr–Mo cast iron

Abstract

The microstructure and mechanical properties of high Ni–Cr–Mo indefinite chilled cast iron with the addition of a newly developed multicomponent modifier consisting of mixed rare earths, Si–Ca alloy and Bi–Sb alloy have been investigated through optical microscopy, X-ray diffraction and scanning electron microscopy, along with hardness, impact toughness and wear resistance measurements. After the addition of the modifier, the grain sizes of the primary austenite and eutectic carbides are found to be greatly refined, and the typically highly continuous net-like carbides become less interconnected but rather appear more blocky shaped. Such microstructure changes lead to mechanical property improvement in the cast specimen, with its hardness increased from 43 to 50 HRC, impact toughness from 6·3 to 7·8 J cm^?2 and ?20% increase in abrasive wear resistance.     

Process and properties of electroless Ni–Cu–P–ZrO2 nanocomposite coatings

Electroless Ni–Cu–P–ZrO₂ composite coating was successfully obtained on low carbon steel matrix by electroless plating technique. Coatings with different compositions were obtained by varying copper as ternary metal and nano sized zirconium oxide particles so as to obtain elevated corrosion resistant Ni–P coating. Microstructure, crystal structure and composition of deposits were analyzed by SEM, EDX and XRD techniques. The corrosion behavior of the deposits was studied by anodic polarization, Tafel plots and electrochemical impedance spectroscopy (EIS) in 3.5% sodium chloride solution. The ZrO₂ incorporated Ni–P coating showed higher corrosion resistance than plain Ni–P. The introduction of copper metal into Ni–P–ZrO₂ enhanced the protection ability against corrosion. The influence of copper metal and nanoparticles on microhardness of coatings was evaluated.