A Study of the Magnetoelastic Effect of Metal Textured Ni–5 at % W Tapes

In the temperature range of 50–360 K, the effect of the plane mechanical deformations on the magnetic susceptibility χ_ac(T) of metal biaxially textured Ni–5.0 at % W tapes has been investigated. To create the state of plane stress, the temperature cycling of thin tapes cemented to thick substrates of Si, Mo, Ti, and D16T aluminum alloy has been performed. It has been shown that the main features of the magnetic susceptibility behavior can be explained by magnetoorientation transitions and the appearance of internal stresses σ(T) exceeding the yield strength of the tape material.     

Microstructure and Its Influence on the Mechanical Properties of Ni–28W–6Cr-Based Alloy-Welded Joints by GTAW

Microstructure and mechanical properties of Ni–28W–6Cr alloy-welded joints produced by gas tungsten arc welding were investigated in this work.Results showed that original fine-grain base metal near fusion line totally transformed into coarse heat affected zone after welding.Carbides with different shapes were found in the weld metal and base metal, which all were determined as M6C carbides.In comparison with carbides in base metal, M6C carbides in weld metal are rich in Si and Cr but deficient in W.Moreover, M6C carbides are extremely scarce and hard to be detected in weld metal.Mechanical tests show that the hardness value of weld metal is only about 60% of base metal; the yield strength and tensile strength of welded joint are much lower than those of base metal due to the absence of carbides in weld metal.     

Influence of Fe on Microstructure and Mechanical Properties in Pdoped Ni–Cr–Fe Alloys

The influence of Fe on the microstructure and mechanical properties of P-doped Ni–Cr–Fe alloys has been investigated.Results showed that increasing Fe content refined the dendrite microstructure and enhanced the solubility of P in as-cast alloys. The change of microhardness in different dendrite regions was attributed to the segregation of P atoms in solid solution state, which had strengthening effects. Increasing Fe contents from 15.2 to 60.7 wt% reduced the yield strength and tensile strength but had little influence on the elongation of alloys. The stress rupture life of alloys after heat treatment decreased with the increment of Fe contents, and the failure fracture modes transferred from transgranular to intergranular fracture mode. The change of fracture modes was due to the weakness of grain boundaries caused by the increment of Fe.In addition, the precipitation of M_(23)C_6 was believed to be related to the segregation of P toward grain boundaries, which led to the fluctuation of carbon and chromium atoms near the grain boundaries in alloys with low Fe contents. Consequently, the increment of Fe decreased the strength of matrix and changed the existence of P atoms and the precipitates at grain boundaries.     

Effect of Surface Layer Structural-Phase Modification on Tribological and Strength Properties of a TiC–(Ni–Cr) Metal Ceramic Alloy

This paper reports TiC–(Ni–Cr) metal ceramic alloy(ratio of components 50:50) with nanoscaled components formed in the surface layer and smoothly transformed into the initial inner structure throughout the material under pulsed electron irradiation of the alloy surface. Principal changes in the surface layer are ascribed to the formation of gradient structure leading to the increase in wear resistance of the surface layer, drop of friction coefficient and improvement of specimen bending resistance when stressing on the irradiated surface side. The above changes of tribological and strength properties in the surface layer under pulsed electron irradiation become more apparent with increasing atomic mass of a plasma-forming inert gas.     

The Influence of Co Concentration on the Properties of Conventionally Electrodeposited Ni–Co–Al2O3–SiC Nanocomposite Coatings

Protection of Metals and Physical Chemistry of Surfaces - In this study, Ni–Co–Al2O3–SiC nanocomposite coatings with varying concentrations of Co were electrodeposited in a...     

Study of the Properties of a High-Temperature 50Ti–40Pd–10Ni Shape Memory Alloy

Combined studies of the properties of the 50Ti–40Pd–10Ni alloy with a high-temperature shape memory effect have been carried out. The elemental and phase compositions and its mechanical and thermomechanical characteristics have been determined. Samples cut from the strip with a thickness of 2.04 mm have been studied. The phase transformations are in the range of M_f = 371.3°С to A_f = 436.9°С. These are acceptable values. The maximum values of the shape memory effect ε_SME and of the degree of shape recovery η_SME are 3.9 and 49%, respectively. These values are insufficient to create workable safety devices. These characteristics can be improved via optimal changes in the elemental composition of the shape memory alloy and by an adequate choice of the regimes of heat treatment and of the regimes of providing strain in the investigated objects. The results of these studies are necessary in order to develop different devices used in nuclear power plants.     

Influence of Physical and Mechanical Properties of the Substrate on the Behavior of Zr–Si–B Coatings under Sliding Friction and Cyclic Impact-Dynamic Loading

Protection of Metals and Physical Chemistry of Surfaces - The method of magnetron sputtering of a ZrB2–20% Si target was used to obtain coatings on substrates of molybdenum, chromium, and...     

Influence of Annealing on the Properties of Explosively Welded Titanium Grade 1—AW7075 Aluminum Alloy Bimetals

Explosive welding of titanium Grade 1 to AW7075 aluminum alloy arranged in parallel setup was performed. The annealing of produced bimetals at the temperatures of 450, 500 and 550 °C for times ranging from 20 to 100 h was carried out after explosive welding. The produced bimetal was characteristic by its wavy interface typical for that bonding process. Increase in the microhardness at the interface was recorded due to work hardening. Delamination of titanium Grade 1 flyer sheet was firstly observed when annealing temperature of 500 °C for 40 h was carried out. Annealing at 550 °C also resulted in delamination of upper sheet. The intermetallic compound (IMC) layer was observed at the interface after annealing of bimetals. The higher the annealing temperature and time, the higher the thickness of continuous IMC layer. The maximum measured thickness of IMC layer averaged 13 µm. Energy dispersive x-ray spectroscopy (EDS) and x-ray diffraction (XRD) analyses revealed that the interface layer is consisted of Al₁₈Ti₂Mg₃ IMC. Microhardness at the interface increased dramatically up to 439 HV0.1 after annealing of bimetal due to the presence of above-mentioned IMC.     

Influence of Cr and Ni content in stainless steel on the degradation mechanisms in PbO–CaO–SiO2 slag

Degradation of stainless steel in contact with PbO–CaO–SiO₂ slag at 1200 °C is experimentally investigated. The contact between steel and slag leads to the reduction of PbO from the slag to liquid Pb, and concurrent oxidation of the steel. The degradation mechanisms can be divided into liquid slag and liquid metal corrosion and oxidation. High Cr content is beneficial as it promotes the formation of a Cr₂O₃ scale which shields the steel from the slag and liquid Pb. The high solubility of Ni in liquid Pb is responsible for the increasing dissolution rate with increasing Ni content of the steel.     

Influence of Alloying Element Addition on Cu–Al–Ni High-Temperature Shape Memory Alloy without Second Phase Formation

In this study,the effects of rare earth Gd and Fe elements on the microstructure,the mechanical properties and the shape memory effect of Cu–11.9Al–3.8Ni high-temperature shape memory alloy were investigated by optical microscopy,scanning electron microscopy,X-ray diffraction and compression test.The microstructure observation results showed that both Cu–11.9Al–3.8Ni–0.2Gd and Cu–11.9Al–3.8Ni–2.0Fe–0.2Gd alloys displayed the fine grain and singlephase b01martensite,and their grain size was about several hundred microns,one order of the magnitude smaller than that of Cu–11.9Al–3.8Ni alloy.The compression test results proved that the mechanical properties of Cu–11.9Al–3.8Ni alloy were dramatically improved by alloying element additions due to grain refinement and solid solution strengthening,and the compressive fracture strains of Cu–11.9Al–3.8Ni–0.2Gd and Cu–11.9Al–3.8Ni–2.0Fe–0.2Gd were 12.0%and 17.8%,respectively.When the pre-strain was 10%,the reversible strains of 5.4%and 5.9%were obtained for Cu–11.9Al–3.8Ni–0.2Gd and Cu–11.9Al–3.8Ni–2.0Fe–0.2Gd alloys after being heated to 500°C for 1 min,and the obvious two-way shape memory effect was also observed.     

High-Temperature Structural Stabilities of Ni-Based SingleCrystal Superalloys Ni–Co–Cr–Mo–W–Al–Ti–Ta with Varying Co Contents

It has been recently pointed out that the compositions of industrial alloys are originated from cluster-plus-glueatom structure units in solid solutions. Specifically for Ni-based superalloys, after properly grouping the alloying elements into Al, Ni-like(■), r-forming Cr-like(■) and c-forming Cr-like(■), the optimal formula for single-crystal superalloys is established [Al–Ni_(12)](Al_1■~_(0:5) ■_(1:5)). The Co substitutions for Ni at the shell sites are conducted on the basis of the first-generation single-crystal superalloy AM3, formulated as [Al–■_(12)Co_x](Al_1Ti_(0.25)Ta_(0.25)Cr_1W_(0.25)Mo_(0.25)), with x = 1.5, 1.75, 2 and 2.5(the corresponding weight percents of Co are 9.43, 11.0, 12.57 and 15.71, respectively). The900 ℃ long-term aging follows the Lifshitz–Slyozov–Wagner theory(LSW theory), and the Co content does not have noticeable influence on the coarsening rate of c0. The microstructure and creep behavior of the four(001) single-crystal alloys are investigated. The creep rupture lifetime is reduced as Co increases. The alloy with the lowest Co(9.43 Co) shows the longest lifetime of about 350 h at 1050 ℃/120 MPa, and all the samples show N-type rafting after creep tests.     

Effects of Temperature on the Properties of Ni–Co–BN (h) Nanocomposite Coating in Jet Electrodeposition

Protection of Metals and Physical Chemistry of Surfaces - Ni–Co–BN (h) nanocomposite coating was prepared by jet electrodeposition (JED) under different temperatures. The surface...     

On Diagnostics of Double Electric Layer in the Zone of Metal–Polymer Adhesion Contact Using the Positron-Annihilation-Probe Method

Protection of Metals and Physical Chemistry of Surfaces - Application of the positron-annihilation-probe technique for nondestructive diagnostics of the double electric layer (DEL) at the...     

Sliding wear of nanocrystalline Ni–W: Structural evolution and the apparent breakdown of Archard scaling

Sliding wear of nanocrystalline Ni–W alloys with grain sizes of 3–47 nm, a range which spans the transition in deformation mechanisms from intra- to inter-granular, has been studied through pin-on-disk wear testing. The extreme conditions produced during sliding wear are found to result in structural evolution and a deviation from Archard scaling for the finest grain sizes; in the finest nanocrystalline materials wear resistance is higher than would be expected based on hardness alone. The repetitive sliding load is found to lead to a modest amount of grain growth and grain boundary relaxation, which in turn leads to local hardening in the wear track. Analysis of the dynamic microstructure suggests that it is produced primarily as a result of local plasticity and is not principally due to frictional heating.     

Effect of Surfactants on the Anticorrosive and Mechanical Performance of Ni–W–MWCNTs Nanocomposites Coating

Protection of Metals and Physical Chemistry of Surfaces - In the nickel–tungsten plating bath with MWCNTs, the influence of surfactants cetyltrimethyl- ammonium bromide (CTAB), sodium dodecyl...     

Influence of the Oxygen Partial Pressure on the High Temperature Corrosion of 38Ni–34Fe–25Cr Alloy in Presence of NaCl Deposit

In biomass gasification processes, some molten salts formed during the process can promite high temperature corrosion. In this study the chromia-forming austenitic alloy Haynes^® HR-120 was oxidized with a deposit of sodium chloride for 96 h at 825 and 900 °C. Two different atmospheres were selected; one with a high oxygen partial pressure (Ar/O₂ 90/10 %vol.) and one, named syngas, with a low oxygen partial pressure (CO/H₂/CO₂ 45/45/10 %vol.). While at 900 °C the behaviour of the alloy in presence of sodium chloride was catastrophic in high oxidizing conditions, the impact of sodium chloride was insignificant in the syngas atmosphere. When exposed to the Ar/O₂ mixture, the catastrophic oxidation was attributed to the setting up of an active oxidation. At 900 °C under the syngas atmosphere, the protective behaviour of the alloy seems linked to the association of a faster evaporation of the salt and a very low oxygen partial pressure. At 825 °C a catastrophic behaviour is observed under the syngas atmosphere as the NaCl evaporation rate is much slower.     

Depletion and Voids Formation in the Substrate During High Temperature Oxidation of Ni–Cr Alloys

A numerical model to treat the kinetics of vacancy annihilation at the metal/oxide interface but also in the bulk metal has been implemented. This was done using EKINOX, which is a mesoscopic scale 1D-code that simulates oxide growth kinetics with explicit calculation of vacancy fluxes. Calculations were performed for high temperature Ni–Cr alloys oxidation forming a single chromia scale. The kinetic parameters used to describe the diffusion in the alloy were directly derived from an atomistic model. Our results showed that the Cr depletion profile can be strongly affected by the cold work state of the alloy. In fact, the oversaturation of vacancies is directly linked to the efficiency of the sinks which is proportional to the density of dislocations. The resulting vacancy profile highlights a supersaturation of vacancy within the metal. Based on the classical nucleation theory, the possibility and the rate of void formation are discussed.     

Effects of Annealing Temperature on the Structural,Optical,and Electrical Properties of ZnO Thin Films Grown on n-Si<100>Substrates by the Sol–Gel Spin Coating Method

The effects of annealing temperature on the sol–gel-derived ZnO thin films deposited on n-Sh100 i substrates by sol–gel spin coating method have been studied in this paper.The structural,optical,and electrical properties of ZnO thin films annealed at 450,550,and 650 °C in the Ar gas atmosphere have been investigated in a systematic way.The XRD analysis shows a polycrystalline nature of the films at all three annealing temperatures.Further,the crystallite size is observed to be increased with the annealing temperature,whereas the positions of various peaks in the XRD spectra are found to be red-shifted with the temperature.The surface morphology studied through the scanning electron microscopy measurements shows a uniform distribution of ZnO nanoparticles over the entire Si substrates of enhanced grain sizes with the annealing temperature.Optical properties investigated by photoluminescence spectroscopy shows an optical band gap varying in the range of 3.28–3.15 eV as annealing temperature is increased from 450 to 650 °C,respectively.The fourpoint probe measurement shows a decrease in resistivity from 2:1 10 2to 8:1 10 4X cm with the increased temperature from 450 to 650 °C.The study could be useful for studying the sol–gel-derived ZnO thin film-based devices for various electronic,optoelectronic,and gas sensing applications.