Effect of heat treatment on microstructure and properties of hot-extruded nickel-aluminum bronze

The effect of heat treatment on the microstructure and properties of a hot-extruded nickel-aluminum bronze was investigated. Experimental materials were heat treated through different processes, including quenching, normalizing, aging and annealing, and their microstructure, corrosion resistance and mechanical properties were characterized. It is found that quenching causes all β phase transformed into β′ phase, however, normalizing causes β phase transformed into β′, α and κ phases. When the quenched sample is aged, fine к phase is precipitated from the as-quenched microstructure of β′ phase. Annealing causes the transformation of β′ into α and к phases. The results of mechanical property tests show that quenching, normalizing and aging improve the tensile strength and hardness of the experimental material, with a corresponding fall in elongation. Annealing raises the elongation but reduces the tensile strength and hardness. Furthermore, corrosion resistance of nickel-aluminum bronze ranks from worse to better in the following order: aged, quenched, normalized, hot-extruded and annealed. However, with the exposure time of corrosion test increasing, the difference of average corrosion rate between those nickel-aluminum bronzes turns small.

Morphological evolution of γ'precipitates in a nickel-based superalloy during various solution treatments

The morphological evolution of the γ' phase in nickel-based superalloy жc6y during various solution heat treatments was investigated. The significant changes of the γ' precipitates were observed in the solution-treated samples. The coarsening and dissolution of γ' phase simulta-neously occurred at intermediate temperatures. In some areas, the primary precipitates became blunt and the adjacent ones were intercon-nected with each other via a diffuse neck, indicating a coarsening process of the primary γ' population. The coarsening was dominated by the precipitate agglomeration mechanism (PAM) rather than by the well-known Ostwald ripening mechanism. In other areas, the partial dissolu-tion of the γ' precipitates began to occur, spreading gradually from dendrite cores to interdendritic regions. In addition, a flower-like γ' struc-ture was developed during the subsolvus solution treatments. The observable long filaments composed of erraticly shaped precipitates were caused by the heterogeneous nucleation of the cooling precipitates during water quenching.

Effects of heat treatment on mechanical properties of ODS nickel-based superalloy sheets prepared by EB-PVD

A Y2O3 dispersion strengthened nickel-based superalloy sheet（0.15 mm thick） was prepared by electron beam physical vapor deposition（EB-PVD） technology.Different heat treatments were used to improve the mechanical properties of the alloy sheet.Differential thermal analysis（DTA） was used to examine the thermal stability of the as-deposited sheet.Element contents,phase composition and microstructure investigations on as-deposited and heat treated specimens were performed by X-ray fluorescence spectrometer（XRF）,X-ray diffraction（XRD） and scanning electron microscopy（SEM）.Tensile tests were conducted at room temperature on specimens as-deposited and heat treated.The results show that the as-deposited sheet is composed of equiaxed grains on the substrate side and columnar grains on the evaporation side.The as-deposited sheet shows poor ductility due to micropores between columnar grains.The strength and ductility can be improved effectively by annealing at 800°C for 3 h.For samples treated at 1100°C,the strength drops down due to the precipitates of Y3Al5O12（YAG）.

Effect of heat treatment on microstructure and high temperature tensile properties of cast nickel-base superalloy with high W, Mo and Nb contents

The microstructural features and high temperature tensile properties of M963 superalloy at as cast, as solutioned and as aged conditions were investigated in detail. The results show that the solution treatment at 1?220?℃ for 4?h, AC causes an increase in high temperature yield strength but a drastic drop in high temperature ductility due to the precipitation of both the secondary carbide M 6C along grain boundaries and at the interdendritic regions and very fine γ ′ particles in the dendrite cores. Aging treatment following the solution treatment can improve the high temperature tensile properties of M963 superalloy due to the coarsing of the γ′ precipitate. One stage aging at 850?℃ for 16?h following the solution treatment causes an increase in both strength and ductility of alloy M963, and two stage aging of 1?089?℃ / 2?h, AC plus 850?℃ / 16?h, AC following the solution treatment further increases the ductility of alloy M963 but slightly decreases its strength.

Comparison Between Electrolysis and Reduction for Treatment of Spent Electroless Nickel Plating Bath

There are lots of residual nickel and organic compounds in the spent electroless nickel plating bath. It not only wastes resource but also causes environmental pollution if the wastewater is discharged without treatment. In this paper, electrolytic method and reduction method for treating spent electroless nickel plating bath were compared. The factors studied included reaction time, pH, temperature, effectiveness and cost. It was found that the recovery rate of nickel by reduction was 99.9% under the condition ofpH 6, 50℃ for 10 min. The purity of reclaimed nickel was 66.1%. This treatment needed about 16 g NaBH4 for a liter spent solution, which cost RMB 64 Yuan. For electrolysis method, with pH 7.6, 80℃, 0.45 A （current intensity） for 2 h, the recovery rate reached 97.3%. The purity was 88.5% for the reclaimed nickel. Moreover, it was found that through electrolysis, the value of TOC （Total Organic Carbon） decreased from 114 to 3.08 g·L^-1 with removal rate of 97.3%. The main cost of electrolysis came from electric energy. It cost about 0.09 kWh （less than RMB 0.1 Yuan） per liter wastewater. Compared with reduction, electrolysis had more advantages, so the priority of selection should be given to the electrolysis method for the treatment of spent electroless nickel plating bath.

Analysis on mechanical properties of nickel-iron steel after post-weld heat treatment

X-ray diffraction was utilized to measure the residual stress of 45 mm UNS N08810 plates after post-weld heat treatment at temperatures of 680℃ and 900℃, which showed reductions of 86.9% and 71.6% in the residual stress, respectively. This indicates that post-weld heat treatment can play a significant role in reducing residual stress, while no significant effects on tensile stress and micro-hardness of the welding joint were observed after treatment.

Microstructure Evolution of a Single Crystal Nickel-Base Superalloy During Heat Treatment and Creep

Microstructure evolution of a single crystal nickel-base superalloy during heat treatment and tensile creep at 1010°C and 248 MPa for 30h was observed and analyzed. Internal stresses because of lattice mismatch between and / phase provided the driving force for / shape evolution during heat treatment. More than 65 vol. % distorted cubic phase keeping coherency with the y matrix precipitated after solution at 1295°C for 32h. The shape of phase was perfectly cubic with increasing precipitate size during the two-step aging treatment. Due to the applied stress and internal stress field the continuous y1/ lamellar structure perpendicular to the applied stress was formed after 30h tensile creep.

Effect of solution treatment on microstructure of Inconel 601 nickel-based superalloy weld seam

The microstructure of lneonel 601 nickel-based superalloy after gas tungsten arc welding and its transformation at different solution temperatures are studied. The results show that the original microstructure of weld seam is characterized coarsened austenitic granular crystal, there are a large amount of dispersed carbide and γ＇ phase with carbide as the core in the boundary of grains. Grain of heat-affected zone grows up severely with very little precipitated carbide. The carbide and γ＇ phase are gradually solved into the austenite matrix with the increase of solution treatment temperature. Especicdly solution treated at 1 150 ℃, the carbide and γ＇ phase are completely solved into the austenite matrix, the coarsened equiaxed anstenite grain sizes are refined.

Recovery of valuable metals from a low-grade nickel ore using an ammonium sulfate roasting-leaching process

Metal leaching from a low-grade nickel ore was investigated using an ammonium sulfate roasting-water leaching process. The nickel ore was mixed with ammonium sulfate, followed by roasting and finally leaching with water. During the process the effects of the amotmt of ammonium sulfate, roasting temperature, and roasting time on the leaching recovery of metal elements were analyzed. The optimum technological parameters were determined as follows： ammonium sulfate/ore ratio, 0.8 g/g; roasting temperature, 400℃; and roasting time, 2 h. Under the optimum condition the leaching recoveries ofNi, Cu, Fe, and Mg were 83.48%, 76.24%, 56.43%, and 62.15%, respectively. Furthermore, the dissolution kinetics of Ni and Mg from the nickel ore was studied. The apparent activation energies for the leaching reaction of Ni and Mg were 18.782 and 10.038 kJ.mo1-1, which were consistent with the values of diffusion control reactions. Therefore, the results demonstrated that the leaching recoveries of Ni and Mg were controlled by diffusion.

Immobilized chitosan as a selective absorbent for the nickel removal in water sample

Method for preparation of chitosan immobilized on silica gel(CTS silica) was described. The CTS silica was used as absorbent for the absorption of nickel in water. The results showed that this absorbent had relatively high selectivity and strong affinity to nickel. The maximum absorption capacity for nickel can reach 667 mg/g of chitosan. Factors that affect the absorption capacity, such as pH, ion strength and the presence of calcium, EDTA and the mechanism of absorption were discussed in detail. The absorbent can be regenerated with acid and reused for several times. The recovery rate for nickel can reach 99 99%. This absorbent filled in a column can be used in nickel removal from wastewater and drinking water.

Removal of nickel from spent electroless nickel-plating bath with nickel foam cathode

The electrochemical method was used to remove nickel ion from spent electroless nickel plating bath (pH=5 3). An electrolytic cell was composed of a porous nickel foam cathode and an inert RuO 2/Ti anode. Nickel ions were reduced and deposited on the surface of the nickel foam cathode. The effect of current density (i), linear velocity of wastewater(v), gap between cathode and anode(d C/A) and reaction time(t) on nickel removal rate and current efficiency were studied. As reaction time prolonged, nickel removal rate increased while current efficiency decreased. And larger v and smaller d C/A can enhance nickel removal rate and increase current efficiency by promoting mass transfer and dropping concentration polarization. The effect of current density on nickel removal by electrochemistry was related to other parameters. After three hours’ electrolysis with i=1 0 A/dm2, v=18 5 cm/min and d C/A=0 5 cm, nickel removal rate and current efficiency reached 85 6% and 29 1%, respectively.

Effects of electric-field treatment on a Ni-base superalloy

The effects of electric-field treatment on the microstructure and deformation behavior of a nickel-base superalloy were summarized.The results show that the electric-field treatment increases the ductility of the superalloy but has no evident influence on its static strength at both room and elevated temperatures,while,the strength increases but elongation changes weekly with the increasing tensile strain rate.It is found that the direction of microcrack propagation can be changed by the presence of the annealing twins during the tensile deformation,and it causes the increasing of the plastic deformation energy and delay of the fracture,which is considered as the reason for the increasing the ductility.

Influence of solution treatment on microstructure, corrosion resistance, and oxidation behavior of cast G-NiCr28W alloy

G-NiCr28W is a nickel-based cast alloy. Its microstructure consists of nickel-rich matrix phase and chromium-rich eutectic carbides. The solution treatment process can provide homogenous microstructure and desired mechanical/thermal properties for G-NiCr28W alloy. However, the solution treatment process affects the corrosion resistance of the alloy and it causes metal loss due to the occurrence of oxidation at atmospheric conditions. Therefore, determining the changes in the properties of the G-NiCr28W is important. For this purpose, G-NiCr28W specimens were solution treated at 1,040 ℃, 1,100 ℃ and 1,160 ℃ for 1 h and 8 h, respectively. The microstructures of the solution-treated samples were characterized by optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction analysis. Moreover, hardness, corrosion resistance and oxidation behaviors of the solution-treated samples were examined. The solution treatment process applied at 1,160 ℃ led to the formation of Fe_2W_2C blocky carbides, and hardness of the sample increased with the existence of blocky carbides, while corrosion resistance decreased. Furthermore, excessive metal loss occurred depending on oxidation due to the high process temperature at 1,160 ℃.

Nickel solvent extraction from cold purification filter cakes of Angouran mine concentrate using LIX984N

Cold purification filter cakes generated in the hydrometallurgical processing of Angouran mine zinc concentrate commonly contain significant amounts of Zn, Cd, and Ni ions and thus are valuable resources for metal recovery. In this research, a nickel containing solution that was obtained from sulfuric acid leaching of the filter cake following cadmium and zinc removal was subjected to solvent extraction experiments using 10vol%LIX984N diluted in kerosene. Under optimum experimental conditions （pH 5.3, volume ratio of organic/aqueous （O：A） = 2：1, and contact time -5 min）, more than 97.1% of nickel was extracted. Nickel was stripped from the loaded organic by contacting with a 200 g/L sulfuric acid solution, from which 77.7% of nickel was recovered in a single contact at the optimum conditions （pH 1-1.5, O：A =5：1, and contact time =15 min）.

Effect of oxygen content and heat treatment on carbide precipitation behavior in PM Ni-base superalloys

The influence of oxygen content and heat treatment on the evolution of carbides in a powder metallurgy （PM） Ni-base superalloy was characterized. The results reveal that oxygen content has little influence on the precipitation of carbides inside the particles. However, under the consolidated state, stable Ti oxides on the particle surface act as nuclei for the precipitation of prior particle boundaries （PPB）. Also, oxygen can diffuse internally along grain boundaries under compressive stress, which favors the precipitation of carbides inside the particles. Therefore, a higher amount of carbides will appear with more oxygen content in the case of consolidated alloys. It is also observed that PPB can be disrupted into discontinuous particles at 1200℃, but this carbide network is hard to be eliminated completely. The combined MC-M23C6 morphology approves the nucleation and growth mechanism of carbide evolution.

Corrosion Behavior of Heat Treated Nickel-Aluminum Bronze Alloy in Artificial Seawater

The effect of microstructure of nickel-aluminum bronze alloy (NAB) on the corrosion behavior in artificial seawater is studied using linear polarization, impedance and electrochemical noise tests. The alloy was heat treated in different heating cycles including quenching, normalizing and annealing. Microstructure of the specimens was characterized before and after heat treatment by optical microscopy and scanning electron microscopy. Results showed that the value of pearlite phase in the normalized alloy is much more than other specimens, leading to higher corrosion resistance. Polarization test showed that starting point of passivation in the polarization of the normalized alloy is lower than other specimens. The dissolution of Mn and Fe rich phases increased the Mn and Fe contents in solid solution, and this enhanced the passivation power of the surface of the alloy. The effect of the alloying elements was seen by a lower corrosion potential and an inflexion at around 280 mV (SCE) in the polarization curve, indicating the preferential dissolution of some elements beyond that potential. The polarization curve showed that the anodic polarization behavior of the alloy in the solution was essentially controlled by the intermetallic phases, mainly containing Cu. Two types of corrosion, pitting and selective corrosion, were observed in the specimens after being exposed to artificial seawater.

Synthesis and Characterization of Ni-Zn Ferrite Nanoparticles (Ni_0.25Zn_0.75Fe₂O₄) by Thermal Treatment Method

Cubic structured nickel-zinc ferrite nanoparticles (Ni0.25Zn0.75Fe2O4) have been synthesized by thermal treatment method. In this procedure, an aqueous solution containing metal nitrates as precursors, polyvinyl pyrrolidone as a capping agent, and deionized water as a solvent were thoroughly stirred, dried at 353 K for 24 h, and crushed into powder before calcination to remove organic matters and crystallize the particles. The structure and particle size were characterized by X-ray powder diffraction and transmission electron microscopy. The average particle size increased from 7 to 25 nm with increase of calcination temperature from 723 to 873 K respectively. The magnetic properties were determined by vibrating sample magnetometer and electron paramagnetic resonance electron paramagnetic resonance at room temperature. By increasing the calcinations temperatures from 723 to 873 K it showed an increase of the magnetization saturation from 11 to 26 emu/g and the g-factor from 2.0670 to 2.1220. The Fourier transform infrared spectroscopy was used to confirm the presence of metal oxide bands at all temperatures and the removal of organic matters at 873 K.

CO_2 selective hydrogenation to synthetic natural gas(SNG) over four nano-sized Ni/ZrO_2 samples:ZrO_2 crystalline phase & treatment impact

Two type zirconia (monoclinic and tetragonal phase ZrO2) carriers were synthesized via hydrothermal route, and nano-sized zirconia supported nickel catalysts were prepared by incipient impregnation then followed thermal treatment at 300 °C to 500 °C, for the CO2selective hydrogenation to synthetic natural gas (SNG). The catalysts were characterized by XRD, CO2-TPD-MS, XPS, TPSR (CH4, CO2) techniques. For comparison, the catalyst NZ-W-400 (monoclinic) synthesized in water solvent exhibited a better catalytic activity than the catalyst NZ-M-400 (tetragonal) prepared in methanol solvent. The catalyst NZ-W-400 displayed more H2absorbed sites, more basic sites and a lower temperature of initial CO2activation. Then, the thermal treatment of monoclinic ZrO2supported nickel precursor was manufactured at three temperature of 350, 400, 500 °C. The TPSR experiments displayed that there were the lower temperature for CO2activation and initial conversion (185 °C) as well as the lower peak temperature of CH4generation (318 °C), for the catalyst calcined at 500 °C. This sample contained the more basic sites and the higher catalytic activity, evidenced byCO2-TPD-MS and performance measurement. As for the NZ-W-350 sample, which exhibited the less basic sites and the lower catalytic activity, its initial temperature for CO2activation and conversion was higher (214 °C) as well as the higher peak temperature of CH4formation (382 °C). © 2016 Science Press

Leaching of nickel laterite ore assisted by microwave technique

The application of microwave technique in the hydrometallurgy of nickel laterite ores was described.The mixture of nickel laterite ores and sulfuric acid was pre-treated by microwave irradiation.The dissolving of nickel was conducted in hot water at the atmospheric pressure.The effects of factors,such as microwave power,microwave irradiation time,and sulfuric acid dosage, were investigated.In microwave field,the migration of ionic species and/or rotation of dipolar species promote the liquid?solid reaction process due to the increased contact area of reactants and leaching reaction rate constant.Thanks to the strengthening action of microwave,the microwave-assisted leaching process has its advantages,such as higher extracting rate than conventional atmospheric leaching,and no need for high-pressure operation as high pressure acid leaching(HPAL).The ferric iron in leaching solution could be effectively removed by sodium jarosite process with a little loss of nickel in the jarosite precipitate.

Wear Evaluation of Copper-Nickel-Aluminum Alloys under Extreme Conditions

Cu-Ni-Al alloys at different concentrations were obtained using a high frequency induction melting unit, keeping a balance in the nominal compositions. Light alloys are important to be used in industrial applications. Aluminum additions result in a positive hardness increment of the ternary alloys in comparison with the binary Cu-Ni alloys. Generalized wear mechanisms of the alloys with low aluminum content are basically type abrasive, while samples with 5 and 10 at.% Al present an oxidative-adhesive wear mechanism. Wear results have indicated that aluminum addition affects positively the wear resistance, mainly in samples with high aluminum content product of the creation during the test of different oxides corresponding to the elements present in the alloys.