As a common precursor for supercritical CO_(2)(scCO_(2))deposition techniques,solubility data of organometallic complexes in scCO_(2)is crucial for the preparation of nanocomposites.Recently,metal acetylacetonates hav...As a common precursor for supercritical CO_(2)(scCO_(2))deposition techniques,solubility data of organometallic complexes in scCO_(2)is crucial for the preparation of nanocomposites.Recently,metal acetylacetonates have shown great potential for the preparation of single-atom catalytic materials.In this study,the solubilities of iron(Ⅲ)acetylacetonate(Fe(acac)3)and nickel(Ⅱ)acetylacetonate(Ni(acac)2)were measured at the temperature from 313.15 to 333.15 K and in the pressure range of 9.5–25.2 MPa to accumulate new solubility data.Solubility was measured using a static weight loss method.The semi-empirical models proposed by Chrastil and Sung et al.were used to correlate the solubility data of Fe(acac)3 and Ni(acac)2.The equations obtained can be used to predict the solubility of the same system in the experimental range.展开更多
A Ni–P alloy gradient coating consisting of multiple electroless Ni–P layers with various phosphorus contents was prepared on the aviation aluminum alloy. Several characterization and electrochemical techniques were...A Ni–P alloy gradient coating consisting of multiple electroless Ni–P layers with various phosphorus contents was prepared on the aviation aluminum alloy. Several characterization and electrochemical techniques were used to characterize the different Ni–P coatings’ morphologies, phase structures, elemental compositions, and corrosion protection. The gradient coating showed good adhesion and high corrosion and wear resistance, enabling the application of aluminum alloy in harsh environments. The results showed that the double zinc immersion was vital in obtaining excellent adhesion (81.2 N). The optimal coating was not peeled and shredded even after bending tests with angles higher than 90°and was not corroded visually after 500 h of neutral salt spray test at 35℃. The high corrosion resistance was attributed to the misaligning of these micro defects in the three different nickel alloy layers and the amorphous structure of the high P content in the outer layer. These findings guide the exploration of functional gradient coatings that meet the high application requirement of aluminum alloy parts in complicated and harsh aviation environments.展开更多
Separated preparation of prealloys and amorphous alloys results in severe solidification-remelting and beneficial element removal-readdition contradictions,which markedly increase energy consumption and emissions.This...Separated preparation of prealloys and amorphous alloys results in severe solidification-remelting and beneficial element removal-readdition contradictions,which markedly increase energy consumption and emissions.This study offered a novel strategy for the direct production of FePC amorphous soft magnetic alloys via smelting reduction of high-phosphorus iron ore(HPIO)and apatite.First,the thermodynamic conditions and equilibrium states of the carbothermal reduction reactions in HPIO were calculated,and the element content in reduced alloys was theoretically determined.The phase and structural evolutions,as well as element migration and enrichment behaviors during the smelting reduction of HPIO and Ca_(3)(PO_(4))_(2),were then experimentally verified.The addition of Ca_(3)(PO_(4))_(2)in HPIO contributes to the enrichment of the P element in reduced alloys and the subsequent development of Fe_(3)P and Fe_(2)P phases.The content of P and C elements in the range of 1.52 wt% -14.63 wt% and 0.62 wt% -2.47 wt%,respectively,can be well tailored by adding 0-50 g Ca_(3)(PO_(4))_(2)and controlling the C/O mole ratio of 0.8-1.1,which is highly consistent with the calculated results.These FePC alloys were then successfully formed into amorphous ribbons and rods.The energy consumption of the proposed strategy was estimated to be 2.00×10^(8) kJ/t,which is reduced by 30% when compared with the conventional production process.These results are critical for the comprehensive utilization of mineral resources and pave the way for the clean production of Fe-based amorphous soft magnetic alloys.展开更多
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....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.展开更多
The use of high-temperature materials is especially important in power station construction, heating systems engineering, furnace industry, chemical and petrochemical industry, waste incineration plants, coal gasifica...The use of high-temperature materials is especially important in power station construction, heating systems engineering, furnace industry, chemical and petrochemical industry, waste incineration plants, coal gasification plants and for flying gas turbines in civil and military aircrafts and helicopters. Particularly in recent years, the development of new processes and the drive to improve the economics of existing processes have increased the requirements significantly so that it is necessary to change from well-proven materials to new alloys. Hitherto, heat resistant ferritic steels sufficed in conventional power station constructions for temperatures up to 550℃ newly developed ferritic/martensitic steels provide sufficient strength up to about 600 - 620℃. In new processes, e.g. fluidized-bed combustion of coal, process temperatures up to 900℃ occur. However, this is not the upper limit, since in combustion engines, e.g. gas turbines. Material temperatures up to 1100℃ are reached locally. Similar development trends can also be identified in the petrochemical industry and in the heat treatment and furnace engineering. The advance to ever higher material temperatures now not only has the consequence of having to use materials with enhanced high-strength properties, considerable attention now also has to be given to their chemical stability in corrosive media. Therefore not only examples of the use of high-temperature alloys for practical applications will be given but also be contributed to some general rules for material selection with regard to their high-temperature strength and corrosion resistance.展开更多
It is well known that the magnetic properties such as the Curie temperature Tmag <sub>C and the mean magnetic moment β of ordered compounds have different values from those of the disordered solutions. For inst...It is well known that the magnetic properties such as the Curie temperature Tmag <sub>C and the mean magnetic moment β of ordered compounds have different values from those of the disordered solutions. For instance, both Tmag c and β of the Ni3Pt (L12) and NiPt (L10) and Tmag <sub>c of the CoPt (L10) and CoPt3 (L12) ordered compounds are strongly depressed due to the ordering compared with those of the metastable disordered Ni-Pt and Co-Pt alloys. On the other hand, the γ’-FeNi3 (L12) and the α’-FeCo (B2) ordered compounds have higher Tmag <sub>c and β values comparing with the disordered solution phases, γ (A1) and α (A2), respectively. In consequence, the stability of the ordered phase is depressed or enhanced due to the interaction between the chemical and magnetic ordering caused by the decrease or increase of Tmag <sub>c and β values. The purpose of this study is to investigate the effect of the interaction between the chemical and the magnetic ordering on the phase equilibria in the Fe-X(X=Al, Co, Ni, Rh, Si) binary systems.The Gibbs energy of the α(A2), γ(A1) and liquid phases is described by a sub-regular solution approximation. The ordering contribution to the Gibbs energy ,ΔGorder <sub>m, and deviations of magnetic properties, ΔTmag <sub>c and Δβ, of the ordered compounds, FeAl (B2), Fe3Al (D03), FeCo (B2), FeRh (B2), FeSi (B2), Fe3Si (D03) and FeNi3 (L12) is introduced by the split compound energy formalism. Effect of the interaction between the chemical ordering, B2, D03 and L12 and the magnetic ordering on the phase equilibria will be discussed according to the calculated phase diagrams of the Fe-X binary systems.展开更多
The utility of nickel/iron in the remediation of atrazine-contaminated water was investigated. The experimental results showed that nickel/iron had effective catalytic activity in dechlorinating atrazine under acidic ...The utility of nickel/iron in the remediation of atrazine-contaminated water was investigated. The experimental results showed that nickel/iron had effective catalytic activity in dechlorinating atrazine under acidic conditions. The dechlorination reaction approximately followed the first-order kinetics under the experimental conditions(nickel/iron:1.0 g/250 ml;C atrazine=20.0 mg/L), the reaction rate increased with decreasing pH value of the reaction solution and increasing the proportion of Ni:Fe within 2.95%. For condition with 2.95% nickel/iron, the reaction rate constants were 0.07518(R=0.9927), 0.06212(R=0.9846) and 0.00131 min -1(R=0.9565) at pH=2.0, 3.0 and 4.0, respectively. HPLC analysis was used to monitor the decline of atrazine concentration.展开更多
The effects of alloying elements on the as-cast microstructures and mechanical properties of heavy section ductile cast iron were investigated to develop press die material having high strength and high ductility. Mea...The effects of alloying elements on the as-cast microstructures and mechanical properties of heavy section ductile cast iron were investigated to develop press die material having high strength and high ductility. Measurements of ultimate tensile strength, 0.2% proof strength, elongation and unnotched Charpy impact energy are presented as a function of alloy amounts within 0.25 to 0.75 wt pct range. Hardness is measured on the broken tensile specimens. The small additions of Mo, Cu, Ni and Cr changed the as-cast mechanical properties owing to the different as-cast matrix microstructures. The ferrite matrix of Mo and Ni alloyed cast iron exhibits low strength and hardness as well as high elongation and impact energy. The increase in Mo and Ni contents developed some fractions of pearlite structures near the austenite eutectic cell boundaries, which caused the elongation and impact energy to drop in a small range. Adding Cu and Cr elements rapidly changed the ferrite matrix into pearlite matrix, so strength and hardness were significantly increased. As more Mo and Cr were added, the size and fraction of primary carbides in the eutectic cell boundaries increased through the segregation of these elements into the intercellular boundaries.展开更多
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 ...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).展开更多
Nickel is widely used as a bleaching element in white gold alloys, but it is a potential allergen. In this paper, a popular 18 KW gold alloy, often called "safe nickel," was chosen as the experimental material; its ...Nickel is widely used as a bleaching element in white gold alloys, but it is a potential allergen. In this paper, a popular 18 KW gold alloy, often called "safe nickel," was chosen as the experimental material; its nickel release rates under six different processing conditions were evaluated according to the EN1811 standard. The results reveal that both the surface processing method and heat treatment technology significantly affect the nickel release rate. A coarse surface releases more nickel ions than a smooth surface. The sample normalized at 700 ~C in the single region has a lower nickel release rate than the one treated at 550 ~C in the two-phase phase region, while high temperature normalizing at 800 ~C will accelerate it. All the measured nickel release rates of the experimental material under various processing conditions exceed the permitted threshold value in the Nickel Directive, which indicates that there exists the potential risk of nickel- induced allergy when it is used to make jewelries, espe- cially for piercing types.展开更多
The low-energy, multi-impact fracture resistance and the abrasiveness of the cross-rolled low alloy white cast iron grinding balls were studied after heat treatments at residual rolling temperature. Moreover, the mean...The low-energy, multi-impact fracture resistance and the abrasiveness of the cross-rolled low alloy white cast iron grinding balls were studied after heat treatments at residual rolling temperature. Moreover, the means by which they are damaged and characters of the wear surface were analyzed. The results show that high resistance to impact fracture and high abrasiveness can be achieved after appropriate heat treatment at residual rolling temperature. This kind of heat treatment technology has several advantages under low impact and hard abrasive. These results are very useful for determining the optimized heat treatment technology at residual rolling temperatures.展开更多
To quantify the nonuniform micromechanical performance of welded joint,the load-displacement curves by nanoindentation test were introduced to examine different zones including base metal,coarse grained heat affected ...To quantify the nonuniform micromechanical performance of welded joint,the load-displacement curves by nanoindentation test were introduced to examine different zones including base metal,coarse grained heat affected zone,partially melted zone,weld metal near the fusion boundary and weld metal center.The results showed that the strengthening effect of weld metal was more obvious than that of heat affected zone for nickel based welded joint and especially in coarse grained heat affected zone,the hardening resulted from overheating was not apparent.Nickel based weld metal with high content of alloying elements which were often segregated at interdendritic regions or precipitated in grain interior under nonequilibrium solidification contributed to the characteristics that differ from conventional low alloy steel welded joint.展开更多
Dissimilar joints comprised of copper–nickel and steel alloys are a challenge for manufacturers in modern industries, as these metals are not thermomechanically or chemically well matched. The present study investiga...Dissimilar joints comprised of copper–nickel and steel alloys are a challenge for manufacturers in modern industries, as these metals are not thermomechanically or chemically well matched. The present study investigated the effects of tool rotational speed and linear speed on the microstructure and mechanical properties of friction stir-welded C71000 copper–nickel and 340 stainless steel alloys using a tungsten carbide tool with a cylindrical pin. The results indicated that a rotational-to-linear speed ratio of 12.5 r/mm did not cause any macro defects, whereas some tunneling defects and longitudinal cracks were found at other ratios that were lower and higher. Furthermore, chromium carbide was formed on the grain boundaries of the 304 stainless steel near the shoulder zone and inside the joint zone, directing carbon and chromium penetration toward the grain boundaries. Tensile strength and elongation percentages were 84% and 65% of the corresponding values in the copper–nickel base metal, respectively.展开更多
Surface preparation is potentially important to the corrosion and biomedical properties of NiTi shape memory alloys. The effect of surface preparation on corrosion properties and nickel release of a Ti-56 wt.%Ni alloy...Surface preparation is potentially important to the corrosion and biomedical properties of NiTi shape memory alloys. The effect of surface preparation on corrosion properties and nickel release of a Ti-56 wt.%Ni alloy has been studied. Surface of the NiTi coupons were prepared by four methods, namely, chemical etching, electropolishing, mechanical polishing and oxidizing, and then examined by corrosion test system. Furthermore, the Ni ion releases from NiTi samples with different surface preparations dipped in 1% HCl solution were analysed. Compared with the surface after chemical treatment, mechanical polishing and thermal oxidation, electropolished surface has better corrosion resistance and less nickel release for not only its lower surface roughness, but also the composition and property of its surface film.展开更多
Numerous studies have demonstrated that Na2SO4 can significantly inhibit the reduction of iron oxide in the selective reduction process of laterite nickel ore. FeS generated in the process plays an important role in s...Numerous studies have demonstrated that Na2SO4 can significantly inhibit the reduction of iron oxide in the selective reduction process of laterite nickel ore. FeS generated in the process plays an important role in selective reduction, but the generation process of FeS and its inhibition mechanism on iron reduction are not clear. To figure this out, X-ray diffraction and scanning electron microscopy analyses were conducted to study the roasted ore. The results show that when Na2SO4 is added in the roasting, the FeO content in the roasted ore increases accompanied by the emergence of FeS phase. Further analysis indicates that NaeS formed by the reaction of Na2SO4 with CO reacts with SiO2 at the FeO surface to generate FeS and Na2Si2Os. As a result, a thin film forms on the surface of FeO, hindering the contact between reducing gas and FeO. Therefore, the reduction of iron is depressed, and the FeO content in the roasted ore increases.展开更多
This paper aims to investigate if the dental restoration of nickel-chromium based alloy(Ni-Cr) leads to the enhanced excretions of Ni and Cr in urine.Seven hundred and ninety-five patients in a dental hospital had sin...This paper aims to investigate if the dental restoration of nickel-chromium based alloy(Ni-Cr) leads to the enhanced excretions of Ni and Cr in urine.Seven hundred and ninety-five patients in a dental hospital had single or multiple Ni-Cr alloy restoration recently and 198 controls were recruited to collect information on dental restoration by questionnaire and clinical examination.Urinary concentrations of Ni and Cr from each subject were measure by graphite furnace atomic absorption spectrometry.Compared to the control group,the urinary level of Ni was significantly higher in the patient group of < 1 month of the restoration duration,among which higher Ni excretions were found in those with either a higher number of teeth replaced by dental alloys or a higher index of metal crown not covered with the porcelain.Urinary levels of Cr were significantly higher in the three patient groups of <1,1 to <3 and 3 to <6 months,especially in those with a higher metal crown exposure index.Linear curve estimations showed better relationships between urinary Ni and Cr in patients within 6-month groups.Our data suggested significant increased excretions of urinary Ni and Cr after dental restoration.Potential short- and long-term effects of Ni-Cr alloy restoration need to be investigated.展开更多
Iron nickel oxide catalysts were prepared using co-precipitation procedure and studied for the conversion of synthesis gas to light olefins.In particular,the effects of a range of preparation variables such as Fe/Ni m...Iron nickel oxide catalysts were prepared using co-precipitation procedure and studied for the conversion of synthesis gas to light olefins.In particular,the effects of a range of preparation variables such as Fe/Ni molar ratios of the precipitation solution,precipitate aging times,calcination conditions,different supports and loading of optimum support on the structure of catalysts and their catalytic performance for the tested reaction were investigated.It was found that the catalyst containing 40%Fe/60%Ni/40wt%Al 2O3 ,which was aged for 180 min and calcined at 600 ℃ for 6 h was the optimum modified catalyst.The catalytic performance of optimal catalyst has been studied in different operation conditions such as reaction temperatures,H2 /CO molar feed ratios and reaction total pressure.Characterization of both precursors and calcined catalysts was carried out by powder X-ray diffraction(XRD),scanning electron microscopy(SEM),Brunauer-Emmett-Teller(BET) surface area measurements,thermal analysis methods such as thermal gravimetric analysis(TGA) and differential scanning calorimetry(DSC).展开更多
This paper provides an investigation of the phase transition and spalling characteristic induced during shock loading and unloading in the pure iron and the FeMnNi alloy. The impact for the pure iron is symmetric and ...This paper provides an investigation of the phase transition and spalling characteristic induced during shock loading and unloading in the pure iron and the FeMnNi alloy. The impact for the pure iron is symmetric and with the same-thickness for both the flyer and the target plate. It is found that an abnormal multiple spalling happens in the pure iron sample as the pressure exceeds the α- ε transition threshold of 13 GPa. In the symmetric and same-thickness impact and reverse impact experiments of the FeMnNi alloy, two abnormal tension regions occur when the pressure exceeds the α - ε transition threshold of 6.3 GPa, and the reverse phase transition s - ~ begins below 4.2 GP. The experimental process is simulated successfully from the non-equilibrium mixture phase and Boettger's model. Such abnormal spalling phenomena are believed to relate to the shocked α - ε phase transition. The possible reasons for the abnormal multiple spalling, which occurs during the symmetric and same-thickness impact experiments of pure iron and FeMnNi alloy, are discussed.展开更多
An FeMo-alloy-doped β-SiA1ON (FeMo/β-SiA1ON) composite was fabricated via a reaction-bonding method using raw materials of Si, Al2O3, A1N, FeMo, and Sm2O3. The effects of FeMo on the microstructure and mechanical ...An FeMo-alloy-doped β-SiA1ON (FeMo/β-SiA1ON) composite was fabricated via a reaction-bonding method using raw materials of Si, Al2O3, A1N, FeMo, and Sm2O3. The effects of FeMo on the microstructure and mechanical properties of the composite were investi- gated. Some properties of the composite, including its bending strength at 700℃ and after oxidization at 700℃ for 24 h in air, thermal shock resistance and corrosion resistance to molten aluminum, were also evaluated. The results show that the density, toughness, bending strength, and thermal shock resistance of the composite are obviously improved with the addition of an FeMo alloy. In addition, other properties of the composite such as its high-temperature strength and oxidized strength are also improved by the addition of FeMo alloy, and its corrosion re- sistance to molten aluminum is maintained. These findings indicate that the developed FeMo/β-SiA1ON composite exhibits strong potential for application to molten aluminum environments.展开更多
The effect of rare earth(RE) elements on carbide of high NiCr alloy cast iron was investigated. Meanwhile, the continuous cooling transformation(CCT) curves of cast iron with and without RE addition were determined. T...The effect of rare earth(RE) elements on carbide of high NiCr alloy cast iron was investigated. Meanwhile, the continuous cooling transformation(CCT) curves of cast iron with and without RE addition were determined. The results show that the carbides in high NiCr cast iron can be refined and changed from network and long strip structures into island and block ones. The phase transformation temperature was raised and incubation period of bainite transformation was shortened by adding RE element in high NiCr alloy cast iron.展开更多
基金financial support from the National Key Research and Development Program of China(2020YFA0710202)the National Natural Science Foundation of China(21978043,U1662130)+1 种基金Inner Mongolia University of Technology Scientific Research Initial Funding(DC2300001240)Talent Introduction Support Project of Inner Mongolia(DC2300001426).
文摘As a common precursor for supercritical CO_(2)(scCO_(2))deposition techniques,solubility data of organometallic complexes in scCO_(2)is crucial for the preparation of nanocomposites.Recently,metal acetylacetonates have shown great potential for the preparation of single-atom catalytic materials.In this study,the solubilities of iron(Ⅲ)acetylacetonate(Fe(acac)3)and nickel(Ⅱ)acetylacetonate(Ni(acac)2)were measured at the temperature from 313.15 to 333.15 K and in the pressure range of 9.5–25.2 MPa to accumulate new solubility data.Solubility was measured using a static weight loss method.The semi-empirical models proposed by Chrastil and Sung et al.were used to correlate the solubility data of Fe(acac)3 and Ni(acac)2.The equations obtained can be used to predict the solubility of the same system in the experimental range.
基金financially supported by the National Natural Science Foundation of China (No.52271073)。
文摘A Ni–P alloy gradient coating consisting of multiple electroless Ni–P layers with various phosphorus contents was prepared on the aviation aluminum alloy. Several characterization and electrochemical techniques were used to characterize the different Ni–P coatings’ morphologies, phase structures, elemental compositions, and corrosion protection. The gradient coating showed good adhesion and high corrosion and wear resistance, enabling the application of aluminum alloy in harsh environments. The results showed that the double zinc immersion was vital in obtaining excellent adhesion (81.2 N). The optimal coating was not peeled and shredded even after bending tests with angles higher than 90°and was not corroded visually after 500 h of neutral salt spray test at 35℃. The high corrosion resistance was attributed to the misaligning of these micro defects in the three different nickel alloy layers and the amorphous structure of the high P content in the outer layer. These findings guide the exploration of functional gradient coatings that meet the high application requirement of aluminum alloy parts in complicated and harsh aviation environments.
基金financially supported by the National Natural Science Foundation of China(Nos.52174217 and 52304354)the China Postdoctoral Science Foundation(No.2020M682495)。
文摘Separated preparation of prealloys and amorphous alloys results in severe solidification-remelting and beneficial element removal-readdition contradictions,which markedly increase energy consumption and emissions.This study offered a novel strategy for the direct production of FePC amorphous soft magnetic alloys via smelting reduction of high-phosphorus iron ore(HPIO)and apatite.First,the thermodynamic conditions and equilibrium states of the carbothermal reduction reactions in HPIO were calculated,and the element content in reduced alloys was theoretically determined.The phase and structural evolutions,as well as element migration and enrichment behaviors during the smelting reduction of HPIO and Ca_(3)(PO_(4))_(2),were then experimentally verified.The addition of Ca_(3)(PO_(4))_(2)in HPIO contributes to the enrichment of the P element in reduced alloys and the subsequent development of Fe_(3)P and Fe_(2)P phases.The content of P and C elements in the range of 1.52 wt% -14.63 wt% and 0.62 wt% -2.47 wt%,respectively,can be well tailored by adding 0-50 g Ca_(3)(PO_(4))_(2)and controlling the C/O mole ratio of 0.8-1.1,which is highly consistent with the calculated results.These FePC alloys were then successfully formed into amorphous ribbons and rods.The energy consumption of the proposed strategy was estimated to be 2.00×10^(8) kJ/t,which is reduced by 30% when compared with the conventional production process.These results are critical for the comprehensive utilization of mineral resources and pave the way for the clean production of Fe-based amorphous soft magnetic alloys.
文摘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.
文摘The use of high-temperature materials is especially important in power station construction, heating systems engineering, furnace industry, chemical and petrochemical industry, waste incineration plants, coal gasification plants and for flying gas turbines in civil and military aircrafts and helicopters. Particularly in recent years, the development of new processes and the drive to improve the economics of existing processes have increased the requirements significantly so that it is necessary to change from well-proven materials to new alloys. Hitherto, heat resistant ferritic steels sufficed in conventional power station constructions for temperatures up to 550℃ newly developed ferritic/martensitic steels provide sufficient strength up to about 600 - 620℃. In new processes, e.g. fluidized-bed combustion of coal, process temperatures up to 900℃ occur. However, this is not the upper limit, since in combustion engines, e.g. gas turbines. Material temperatures up to 1100℃ are reached locally. Similar development trends can also be identified in the petrochemical industry and in the heat treatment and furnace engineering. The advance to ever higher material temperatures now not only has the consequence of having to use materials with enhanced high-strength properties, considerable attention now also has to be given to their chemical stability in corrosive media. Therefore not only examples of the use of high-temperature alloys for practical applications will be given but also be contributed to some general rules for material selection with regard to their high-temperature strength and corrosion resistance.
文摘It is well known that the magnetic properties such as the Curie temperature Tmag <sub>C and the mean magnetic moment β of ordered compounds have different values from those of the disordered solutions. For instance, both Tmag c and β of the Ni3Pt (L12) and NiPt (L10) and Tmag <sub>c of the CoPt (L10) and CoPt3 (L12) ordered compounds are strongly depressed due to the ordering compared with those of the metastable disordered Ni-Pt and Co-Pt alloys. On the other hand, the γ’-FeNi3 (L12) and the α’-FeCo (B2) ordered compounds have higher Tmag <sub>c and β values comparing with the disordered solution phases, γ (A1) and α (A2), respectively. In consequence, the stability of the ordered phase is depressed or enhanced due to the interaction between the chemical and magnetic ordering caused by the decrease or increase of Tmag <sub>c and β values. The purpose of this study is to investigate the effect of the interaction between the chemical and the magnetic ordering on the phase equilibria in the Fe-X(X=Al, Co, Ni, Rh, Si) binary systems.The Gibbs energy of the α(A2), γ(A1) and liquid phases is described by a sub-regular solution approximation. The ordering contribution to the Gibbs energy ,ΔGorder <sub>m, and deviations of magnetic properties, ΔTmag <sub>c and Δβ, of the ordered compounds, FeAl (B2), Fe3Al (D03), FeCo (B2), FeRh (B2), FeSi (B2), Fe3Si (D03) and FeNi3 (L12) is introduced by the split compound energy formalism. Effect of the interaction between the chemical ordering, B2, D03 and L12 and the magnetic ordering on the phase equilibria will be discussed according to the calculated phase diagrams of the Fe-X binary systems.
文摘The utility of nickel/iron in the remediation of atrazine-contaminated water was investigated. The experimental results showed that nickel/iron had effective catalytic activity in dechlorinating atrazine under acidic conditions. The dechlorination reaction approximately followed the first-order kinetics under the experimental conditions(nickel/iron:1.0 g/250 ml;C atrazine=20.0 mg/L), the reaction rate increased with decreasing pH value of the reaction solution and increasing the proportion of Ni:Fe within 2.95%. For condition with 2.95% nickel/iron, the reaction rate constants were 0.07518(R=0.9927), 0.06212(R=0.9846) and 0.00131 min -1(R=0.9565) at pH=2.0, 3.0 and 4.0, respectively. HPLC analysis was used to monitor the decline of atrazine concentration.
文摘The effects of alloying elements on the as-cast microstructures and mechanical properties of heavy section ductile cast iron were investigated to develop press die material having high strength and high ductility. Measurements of ultimate tensile strength, 0.2% proof strength, elongation and unnotched Charpy impact energy are presented as a function of alloy amounts within 0.25 to 0.75 wt pct range. Hardness is measured on the broken tensile specimens. The small additions of Mo, Cu, Ni and Cr changed the as-cast mechanical properties owing to the different as-cast matrix microstructures. The ferrite matrix of Mo and Ni alloyed cast iron exhibits low strength and hardness as well as high elongation and impact energy. The increase in Mo and Ni contents developed some fractions of pearlite structures near the austenite eutectic cell boundaries, which caused the elongation and impact energy to drop in a small range. Adding Cu and Cr elements rapidly changed the ferrite matrix into pearlite matrix, so strength and hardness were significantly increased. As more Mo and Cr were added, the size and fraction of primary carbides in the eutectic cell boundaries increased through the segregation of these elements into the intercellular boundaries.
文摘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).
基金financially supported by the united foundation of the National Natural Science Foundation of China and Guangdong province (No. U1034002)
文摘Nickel is widely used as a bleaching element in white gold alloys, but it is a potential allergen. In this paper, a popular 18 KW gold alloy, often called "safe nickel," was chosen as the experimental material; its nickel release rates under six different processing conditions were evaluated according to the EN1811 standard. The results reveal that both the surface processing method and heat treatment technology significantly affect the nickel release rate. A coarse surface releases more nickel ions than a smooth surface. The sample normalized at 700 ~C in the single region has a lower nickel release rate than the one treated at 550 ~C in the two-phase phase region, while high temperature normalizing at 800 ~C will accelerate it. All the measured nickel release rates of the experimental material under various processing conditions exceed the permitted threshold value in the Nickel Directive, which indicates that there exists the potential risk of nickel- induced allergy when it is used to make jewelries, espe- cially for piercing types.
基金Item Sponsored by Guiding Program of Science and Technology Research of Jilin Province of China (20000513)
文摘The low-energy, multi-impact fracture resistance and the abrasiveness of the cross-rolled low alloy white cast iron grinding balls were studied after heat treatments at residual rolling temperature. Moreover, the means by which they are damaged and characters of the wear surface were analyzed. The results show that high resistance to impact fracture and high abrasiveness can be achieved after appropriate heat treatment at residual rolling temperature. This kind of heat treatment technology has several advantages under low impact and hard abrasive. These results are very useful for determining the optimized heat treatment technology at residual rolling temperatures.
基金supported by the Primary Research&Developement Plan of Jiangsu Province(BE2017168)
文摘To quantify the nonuniform micromechanical performance of welded joint,the load-displacement curves by nanoindentation test were introduced to examine different zones including base metal,coarse grained heat affected zone,partially melted zone,weld metal near the fusion boundary and weld metal center.The results showed that the strengthening effect of weld metal was more obvious than that of heat affected zone for nickel based welded joint and especially in coarse grained heat affected zone,the hardening resulted from overheating was not apparent.Nickel based weld metal with high content of alloying elements which were often segregated at interdendritic regions or precipitated in grain interior under nonequilibrium solidification contributed to the characteristics that differ from conventional low alloy steel welded joint.
基金the funding support of Babol Noshirvani University of Technology (No. BNUT/370167/97)
文摘Dissimilar joints comprised of copper–nickel and steel alloys are a challenge for manufacturers in modern industries, as these metals are not thermomechanically or chemically well matched. The present study investigated the effects of tool rotational speed and linear speed on the microstructure and mechanical properties of friction stir-welded C71000 copper–nickel and 340 stainless steel alloys using a tungsten carbide tool with a cylindrical pin. The results indicated that a rotational-to-linear speed ratio of 12.5 r/mm did not cause any macro defects, whereas some tunneling defects and longitudinal cracks were found at other ratios that were lower and higher. Furthermore, chromium carbide was formed on the grain boundaries of the 304 stainless steel near the shoulder zone and inside the joint zone, directing carbon and chromium penetration toward the grain boundaries. Tensile strength and elongation percentages were 84% and 65% of the corresponding values in the copper–nickel base metal, respectively.
文摘Surface preparation is potentially important to the corrosion and biomedical properties of NiTi shape memory alloys. The effect of surface preparation on corrosion properties and nickel release of a Ti-56 wt.%Ni alloy has been studied. Surface of the NiTi coupons were prepared by four methods, namely, chemical etching, electropolishing, mechanical polishing and oxidizing, and then examined by corrosion test system. Furthermore, the Ni ion releases from NiTi samples with different surface preparations dipped in 1% HCl solution were analysed. Compared with the surface after chemical treatment, mechanical polishing and thermal oxidation, electropolished surface has better corrosion resistance and less nickel release for not only its lower surface roughness, but also the composition and property of its surface film.
基金the Specialized Research Fund for the Doctoral Program of Higher Education of China (No.20130006110017) for the financial support for this research
文摘Numerous studies have demonstrated that Na2SO4 can significantly inhibit the reduction of iron oxide in the selective reduction process of laterite nickel ore. FeS generated in the process plays an important role in selective reduction, but the generation process of FeS and its inhibition mechanism on iron reduction are not clear. To figure this out, X-ray diffraction and scanning electron microscopy analyses were conducted to study the roasted ore. The results show that when Na2SO4 is added in the roasting, the FeO content in the roasted ore increases accompanied by the emergence of FeS phase. Further analysis indicates that NaeS formed by the reaction of Na2SO4 with CO reacts with SiO2 at the FeO surface to generate FeS and Na2Si2Os. As a result, a thin film forms on the surface of FeO, hindering the contact between reducing gas and FeO. Therefore, the reduction of iron is depressed, and the FeO content in the roasted ore increases.
基金supported by Open Fund of State Key Laboratory of Oral Diseases,Sichun University
文摘This paper aims to investigate if the dental restoration of nickel-chromium based alloy(Ni-Cr) leads to the enhanced excretions of Ni and Cr in urine.Seven hundred and ninety-five patients in a dental hospital had single or multiple Ni-Cr alloy restoration recently and 198 controls were recruited to collect information on dental restoration by questionnaire and clinical examination.Urinary concentrations of Ni and Cr from each subject were measure by graphite furnace atomic absorption spectrometry.Compared to the control group,the urinary level of Ni was significantly higher in the patient group of < 1 month of the restoration duration,among which higher Ni excretions were found in those with either a higher number of teeth replaced by dental alloys or a higher index of metal crown not covered with the porcelain.Urinary levels of Cr were significantly higher in the three patient groups of <1,1 to <3 and 3 to <6 months,especially in those with a higher metal crown exposure index.Linear curve estimations showed better relationships between urinary Ni and Cr in patients within 6-month groups.Our data suggested significant increased excretions of urinary Ni and Cr after dental restoration.Potential short- and long-term effects of Ni-Cr alloy restoration need to be investigated.
文摘Iron nickel oxide catalysts were prepared using co-precipitation procedure and studied for the conversion of synthesis gas to light olefins.In particular,the effects of a range of preparation variables such as Fe/Ni molar ratios of the precipitation solution,precipitate aging times,calcination conditions,different supports and loading of optimum support on the structure of catalysts and their catalytic performance for the tested reaction were investigated.It was found that the catalyst containing 40%Fe/60%Ni/40wt%Al 2O3 ,which was aged for 180 min and calcined at 600 ℃ for 6 h was the optimum modified catalyst.The catalytic performance of optimal catalyst has been studied in different operation conditions such as reaction temperatures,H2 /CO molar feed ratios and reaction total pressure.Characterization of both precursors and calcined catalysts was carried out by powder X-ray diffraction(XRD),scanning electron microscopy(SEM),Brunauer-Emmett-Teller(BET) surface area measurements,thermal analysis methods such as thermal gravimetric analysis(TGA) and differential scanning calorimetry(DSC).
基金Project supported by the National Science Foundations of China (Grant Nos. 10776032 and 10902102)Science Foundation of China Academy of Engineering Physics (Grant Nos. 20060104 and 2009B0201014)
文摘This paper provides an investigation of the phase transition and spalling characteristic induced during shock loading and unloading in the pure iron and the FeMnNi alloy. The impact for the pure iron is symmetric and with the same-thickness for both the flyer and the target plate. It is found that an abnormal multiple spalling happens in the pure iron sample as the pressure exceeds the α- ε transition threshold of 13 GPa. In the symmetric and same-thickness impact and reverse impact experiments of the FeMnNi alloy, two abnormal tension regions occur when the pressure exceeds the α - ε transition threshold of 6.3 GPa, and the reverse phase transition s - ~ begins below 4.2 GP. The experimental process is simulated successfully from the non-equilibrium mixture phase and Boettger's model. Such abnormal spalling phenomena are believed to relate to the shocked α - ε phase transition. The possible reasons for the abnormal multiple spalling, which occurs during the symmetric and same-thickness impact experiments of pure iron and FeMnNi alloy, are discussed.
基金financially supported by the National Natural Science Foundation of China (No. 51272208)the Program for New Century Excellent Talents in University (NCET–12–0454)the Program for Young Excellent Talents in Shaanxi Province, China (2013KJXX–50)
文摘An FeMo-alloy-doped β-SiA1ON (FeMo/β-SiA1ON) composite was fabricated via a reaction-bonding method using raw materials of Si, Al2O3, A1N, FeMo, and Sm2O3. The effects of FeMo on the microstructure and mechanical properties of the composite were investi- gated. Some properties of the composite, including its bending strength at 700℃ and after oxidization at 700℃ for 24 h in air, thermal shock resistance and corrosion resistance to molten aluminum, were also evaluated. The results show that the density, toughness, bending strength, and thermal shock resistance of the composite are obviously improved with the addition of an FeMo alloy. In addition, other properties of the composite such as its high-temperature strength and oxidized strength are also improved by the addition of FeMo alloy, and its corrosion re- sistance to molten aluminum is maintained. These findings indicate that the developed FeMo/β-SiA1ON composite exhibits strong potential for application to molten aluminum environments.
文摘The effect of rare earth(RE) elements on carbide of high NiCr alloy cast iron was investigated. Meanwhile, the continuous cooling transformation(CCT) curves of cast iron with and without RE addition were determined. The results show that the carbides in high NiCr cast iron can be refined and changed from network and long strip structures into island and block ones. The phase transformation temperature was raised and incubation period of bainite transformation was shortened by adding RE element in high NiCr alloy cast iron.