Cu-30Ni-xRE(x=0–0.213 wt.%) alloy was prepared by adding rare earths(RE) in melted Cu-30Ni alloy using metal mould casting method.The effects of RE on corrosion resistance of the alloy in simulated seawater were inve...Cu-30Ni-xRE(x=0–0.213 wt.%) alloy was prepared by adding rare earths(RE) in melted Cu-30Ni alloy using metal mould casting method.The effects of RE on corrosion resistance of the alloy in simulated seawater were investigated using optical microscope,scanning electronic microscope with energy-dispersive spectrometer and electrochemical measurement system.The results showed that the corrosion resistance of Cu-30Ni alloy was greatly improved by adding proper amount of RE,whereas excess addition of RE worsened ...展开更多
The crack-free Ni60 A coating was fabricated on 45 steel substrate by laser cladding and the microstructure including solidification characteristics, phases constitution and phase distribution was systematically inves...The crack-free Ni60 A coating was fabricated on 45 steel substrate by laser cladding and the microstructure including solidification characteristics, phases constitution and phase distribution was systematically investigated. The high temperature friction and wear behavior of the cladding coating and substrate sliding against GCr15 ball under different loads was systematically evaluated. It was found that the coating has homogenous and fine microstructure consisting of γ(Ni) solid solution, a considerable amount of network Ni-Ni3 B eutectics, m^23C6 with the floret-shape structure and Cr B with the dark spot-shape structure uniformly distributing in interdendritic eutectics. The microhardness of the coating is about 2.6 times as much as that of the substrate. The coating produces higher friction values than the substrate under the same load condition, but the friction process on the coating keeps relatively stable. Wear rates of the coating are about 1/6.2 of that of the substrate under the higher load(300 g). Wear mechanism of the substrate includes adhesion wear, abrasive wear, severe plastic deformation and oxidation wear, while that of the coating is merely a combination of mild abrasive wear and moderate oxidation wear.展开更多
The hot corrosion behaviors of Ni–16Cr–xAl(x=4.5%, 6.8%, 9.0%, mass fraction) based alloys in Na2SO4–25% NaCl molten salts at 600 °C were investigated. The effects of pre-oxidation and Al content on the resi...The hot corrosion behaviors of Ni–16Cr–xAl(x=4.5%, 6.8%, 9.0%, mass fraction) based alloys in Na2SO4–25% NaCl molten salts at 600 °C were investigated. The effects of pre-oxidation and Al content on the resistance to hot corrosion were examined. The hot corrosion resistance of Ni–16Cr–xAl based alloy with Al addition from 4.5% to 9.0% increases with increasing Al content. The alloy with Al content of 9.0% shows the highest hot corrosion resistance among the examined alloys because more β–NiAl phases are obtained to sustain the Al2O3 scale repaired during hot corrosion. Pre-oxidized specimens have a superior hot corrosion resistance compared with the as-cast specimens, due to a protective oxide scale formed after pre-treatment.展开更多
The effects of Ni addition on the liquid phase separation and giant magnetoresi stance (GMR) of Cu Co alloys were discussed. The results reveal that Ni additio n can partially restrain the liquid phase separation of C...The effects of Ni addition on the liquid phase separation and giant magnetoresi stance (GMR) of Cu Co alloys were discussed. The results reveal that Ni additio n can partially restrain the liquid phase separation of Cu Co alloys, resultin g in a decrease of volume fraction for the Co rich particles separated from the liquid phase and in refined microstructures. The composition analyses indicate t hat Ni is dissolved in both the Co rich and the Cu rich phases, but Ni content in the Co rich phase is much higher than that in the Cu matrix. At the same ti me, Ni addition enhance the solubility between Cu and Co, especially Cu in Co s olid solution. Ni alloying into Cu Co alloys can fully prevent the liquid phase separation during melt spinning, which is very beneficial to improve GMR of Cu Co alloys.展开更多
The isothermal oxidation behaviors of three kinds of Ni3Al-Mo based alloys at 1150 ℃ were studied.The morphology,structure and element distribution of oxide scales of the alloys were researched by scanning electron m...The isothermal oxidation behaviors of three kinds of Ni3Al-Mo based alloys at 1150 ℃ were studied.The morphology,structure and element distribution of oxide scales of the alloys were researched by scanning electron microscopy,X-ray diffraction and electron probe microanalysis.The research results show that there are three oxide layers,an outer layer of NiO,an intermediate layer mainly composed of NiO,NiAl2O4 and a small amount of NiMoO4,and an inner layer of NiAl2O4 and Al2O3.Re element was mainly distributed in the intermediate layer,which plays a role as "diffusion barrier" in the process of oxidation,and effectively reduces the diffusion rate of Al and Mo elements outward and diffusion rate of O element inward.As a result,a Al-rich oxide layer formed in the inner layer inhibits the growth of oxide layer and improves the oxidation resistance of the alloy.展开更多
This paper presents some research information on the effects of Zn, Cu and Ni on the microstructure and mechanical properties of as-cast Mg-2Dy(at.%) alloys. The Mg-2Dy alloy is composed of α-Mg and Mg24Dy5 phases. W...This paper presents some research information on the effects of Zn, Cu and Ni on the microstructure and mechanical properties of as-cast Mg-2Dy(at.%) alloys. The Mg-2Dy alloy is composed of α-Mg and Mg24Dy5 phases. With the addition of 0.5at.%Zn, 0.5at.%Cu and 0.5at.%Ni, respectively, besides α-Mg, the long period stacking order(LPSO) phases containing Zn, Cu, and Ni precipitated in the α-Mg interdentritic boundary. The addition of Ni effectively refined the dendrite arm spacing. The as-cast Mg-2Dy-0.5Ni alloy exhibited the best tensile strengths and elongation. The better mechanical properties were mainly attributed to small secondry dendrite arm spacing(SDAS) and high volume fraction of LPSO phases.展开更多
NiTi shape memory alloy(SMA)with nominal composition of Ni 50.8 at%and Ti 49.2 at%was additively manufactured(AM)by selective laser melting(SLM)and laser directed energy deposition(DED)for a comparison study,with emph...NiTi shape memory alloy(SMA)with nominal composition of Ni 50.8 at%and Ti 49.2 at%was additively manufactured(AM)by selective laser melting(SLM)and laser directed energy deposition(DED)for a comparison study,with emphasis on its phase composition,microstructure,mechanical property and deformation mechanism.The results show that the yield strength and ductility obtained by SLM are 100 MPa and 8%,respectively,which are remarkably different from DED result with 700 MPa and 2%.The load path of SLM sample presents shape memory effect,corresponding to martensite phase detected by XRD;while the load path of DED presents pseudo-elasticity with austenite phase.In SLM sample,fine grain and hole provide a uniform deformation during tensile test,resulting in a better elongation.Furthermore,the nonequilibrium solidification was studied by a temperature field simulation to understand the difference of the two 3D printing methods.Both temperature gradient G and growth rate R determine the microstructure and phase in the SLM sample and DED sample,which leads to similar grain morphologies because of similar G/R.While higher G×R of SLM leads to a finer grain size in SLM sample,providing enough driving force for martensite transition and subsequently changing texture compared to DED sample.展开更多
In order to improve the cyclic stability of La-Mg-Ni system (Ce2Ni7-type) alloy electrode, small amount of Co was added in La0.75Mg0.25Ni3.5 alloy. The effect of Co on electrochemical performance and microstructure ...In order to improve the cyclic stability of La-Mg-Ni system (Ce2Ni7-type) alloy electrode, small amount of Co was added in La0.75Mg0.25Ni3.5 alloy. The effect of Co on electrochemical performance and microstructure of the alloys were investigated in detail. XRD results showed that the alloys had multiphase structure composed of (La, Mg)2Ni7, LaNi5 and small amount of LaNi2 phases. The discharge capacity of the alloys first increased and then decreased with increasing Co content. At a discharge current density of 900 mA/g, the HRD of the alloy electrodes increased from 81.3% (x=0) to 89.2 % (x=0.2), and then reduced to 87.8 % (x=0.6). After 60 charge/discharge cycles, the capacity retention rate of the alloys enhanced from 52.67% to 61.32%, and the capacity decay rate of the alloys decreased from 2.60 to 2.05 mAh/g per cycle with increasing Co content. The obtained results by XPS and XRD showed that the fundamental reasons for the capacity decay of the La-Mg-Ni system (Ce2Ni7-type) alloy electrodes were corrosion and oxidation as well as passivation of Mg and Lain alkaline solution.展开更多
A statistical work has been done to collect the composition ranges of Ni-Mn-Ga alloys exhibiting different structures and martensite start temperature (M,), large magnetostrain or the co-existence of magnetic and st...A statistical work has been done to collect the composition ranges of Ni-Mn-Ga alloys exhibiting different structures and martensite start temperature (M,), large magnetostrain or the co-existence of magnetic and structural transitions. The alloys with five-layered (5M), seven-layered (7M) modulated and non-modulated (T) martensitic structures were mapped in the graph. An empirical formula has been presented to reflect the effect of elements nickel (Ni ), manganese ( Mn ) and gallium (Ga), on the martensite start temperature (M3). The martensitic structure is sensitive to the composition and the martensitic transformation temperature is most drastically affected by the Ni content. The alloys with large magnetostrain or co-existence effect of the magnetic and structural transitions were also listed in a limited area.展开更多
The NiSix based alloy typically has poor weldability due to its lower ductility. A limited amount of work has been performed on the weldability of NiSix based alloys. Therefore, the effect of heat treatment and weldin...The NiSix based alloy typically has poor weldability due to its lower ductility. A limited amount of work has been performed on the weldability of NiSix based alloys. Therefore, the effect of heat treatment and welding parameters on weldability of the alloys, and the relationship between the weldability and microstructure were studied. The results show that the as-cast Ni-Si-Nb-B alloy (Ni 76. 5%, Si 20%, Nb 3%, and B 0. 5%) could be successfully welded after preheating at 600 ℃. The welding procedure should be performed on the alloys before any heat treatment and a preheating at 600 ℃ should be used. The fusion zone is harder than the matrix due to a large amount of 7 phase and a finer microstructure. The cracks are predominantly intergranular in heat affected zone and associated with the needle-like ), phase. The heat treatment before welding increases the tendency of cracking in the fusion zone.展开更多
La Ni based alloy powders used for Ni metal hydride batteries were synthesized by mechanical alloying starting from the elements. The electrical capacity obtained was up to 320 mAh/g. In addition, the comparison in ...La Ni based alloy powders used for Ni metal hydride batteries were synthesized by mechanical alloying starting from the elements. The electrical capacity obtained was up to 320 mAh/g. In addition, the comparison in the microstructure and electrochemical properties was made between the alloy powders produced by mechanical alloying and by melting. It was shown that mechanical alloying is promising in the preparation of practical RE hydrogen storage electrode materials.展开更多
This paper investigates the effects of substitution of Si for Ga on the martensitic transformation behaviours in Ni-Fe-Ga alloys by using optical metallographic microscope and differential scanning calorimetry (DSC)...This paper investigates the effects of substitution of Si for Ga on the martensitic transformation behaviours in Ni-Fe-Ga alloys by using optical metallographic microscope and differential scanning calorimetry (DSC) methods. The structure type of Ni55.5Fe18Ga26.5-xSix alloys is determined by x-ray diffraction (XRD), and the XRD patterns show the microstructure of Ni-Fe-Ga-Si alloys transformed from body-centred tetragonal martensite (with Si content x = 0) to body-centred cubic austenite (with x = 2) at room temperature. The martensitic transformation temperatures of the Ni55.sFelsGa26.5-xSi~ alloys decrease almost linearly with increasing Si content in the Si content range of x _~ 3. Thermal treatment also plays an important role on martensitic transformation temperatures in the Ni-Fe-Ga^Si alloy. The valence electronic concentrations, size factor, L21 degree of order and strength of parent phase influence the martensitic transformation temperatures of the Ni-Fe-Ga-Si alloys. An understanding of the relationship between martensitic transformation temperatures and Si content will be significant for designing an appropriate Ni-Fe-Ga-Si alloy for a specific application at a given temperature.展开更多
The diffusivity of hydrogen in two Ni3Al alloys (No.1 and No.2) has been measured in the temperature range of 100 degreesC to 420 degreesC using an ultrahigh vacuum gaseous permeation technique. The diffusivity data f...The diffusivity of hydrogen in two Ni3Al alloys (No.1 and No.2) has been measured in the temperature range of 100 degreesC to 420 degreesC using an ultrahigh vacuum gaseous permeation technique. The diffusivity data fall into two segments, in which the hydrogen diffusivity adheres to the Arrhenius form, respectively. From the hydrogen diffusivity, it is conjectured that the hydrogen diffusivity reflects the hydrogen transportation along the grain boundaries at lower temperature and the hydrogen transportation in the lattice at higher temperature. The intergranular fracture of Lit-type intermetallics induced by hydrogen at relative low temperature results from hydrogen transportation along the grain boundaries and not in the lattice.展开更多
The martensitic transformation,mechanical,and magnetic properties of the Ni_(2)Mn_(1.5-x)Cu_(x)Ti_(0.5) (x=0.125,0.25,0.375,0.5) and Ni_(2-y)Co_(y)Mn_(1.5-x)Cu_(x)Ti_(0.5)[(x=0.125,y=0.125,0.25,0.375,0.5) and (x=0.125...The martensitic transformation,mechanical,and magnetic properties of the Ni_(2)Mn_(1.5-x)Cu_(x)Ti_(0.5) (x=0.125,0.25,0.375,0.5) and Ni_(2-y)Co_(y)Mn_(1.5-x)Cu_(x)Ti_(0.5)[(x=0.125,y=0.125,0.25,0.375,0.5) and (x=0.125,0.25,0.375,y=0.625)]alloys were systematically studied by the first-principles calculations.For the formation energy,the martensite is smaller than the austenite,the Ni–(Co)–Mn–Cu–Ti alloys studied in this work can undergo martensitic transformation.The austenite and non-modulated (NM) martensite always present antiferromagnetic state in the Ni_(2)Mn_(1.5-x)Cu_(x)Ti_(0.5) and Ni_(2-y)Co_(y)Mn_(1.5-x)Cu_(x)Ti_(0.5) (y<0.625) alloys.When y=0.625 in the Ni_(2-y)Co_(y)Mn_(1.5-x)Cu_(x)Ti_(0.5) series,the austenite presents ferromagnetic state while the NM martensite shows antiferromagnetic state.Cu doping can decrease the thermal hysteresis and anisotropy of the Ni–(Co)–Mn–Ti alloy.Increasing Mn and decreasing Ti content can improve the shear resistance and normal stress resistance,but reduce the toughness in the Ni–Mn–Cu–Ti alloy.And the ductility of the Co–Cu co-doping alloy is inferior to that of the Ni–Mn–Cu–Ti and Ni–Co–Mn–Ti alloys.The electronic density of states was studied to reveal the essence of the mechanical and magnetic properties.展开更多
Shot peening is a surface modification technology with the metal surface nano machine(SNC),which can modify the surface microstructure and extend the fatigue life of Cu-19Ni alloy.The hardness,damage evolution and mec...Shot peening is a surface modification technology with the metal surface nano machine(SNC),which can modify the surface microstructure and extend the fatigue life of Cu-19Ni alloy.The hardness,damage evolution and mechanical properties were investigated and characterized by scanning electron microscope(SEM),laser confocal microscope(LSM)and material surface performance tester(CFT).The results showed that the surface roughness and friction coefficient of Cu-19Ni alloy decreased with the increase of shot peening duration and diameter,while the microhardness and strength increased.Moreover,with the increase in shot peening duration and diameter,SEM observation showed that the fracture dimples became smaller,meanwhile,with the increase of small cleavage planes,shear tearing ridges and the thickness of the surface nano layer,the fracture mode gradually evolved from plastic to brittle fracture.The uniaxial tensile test of shot peened Cu-19Ni alloy was carried out by MTS testing machine combined with digital image correlation technology(DIC).The evolution of Cu-19Ni surface damage was analyzed,and the evolution equations describing the damage of large deformation zone and small deformation zone were established.The effect of shot peening on the damage evolution behavior of Cu-19Ni alloy was revealed.展开更多
An investigation on the magnetostructural transformation and magnetocaloric properties of Ni48-xCo2Mn38+xSn12(x = 0, 1.0, 1.5, 2.0, and 2.5) ferromagnetic shape memory alloys is carried out. With the partial replac...An investigation on the magnetostructural transformation and magnetocaloric properties of Ni48-xCo2Mn38+xSn12(x = 0, 1.0, 1.5, 2.0, and 2.5) ferromagnetic shape memory alloys is carried out. With the partial replacement of Ni by Mn in the Ni_(48)Co2Mn38Sn12 alloy, the electron concentration decreases. As a result, the martensitic transformation temperature is decreased into the temperature window between the Curie-temperatures of austenite and martensite. Thus, the samples with x = 1.5 and 2.0 exhibit the magnetostructural transformation between the weak-magnetization martensite and ferromagnetic austenite at room temperature. The structural transformation can be induced not only by the temperature,but also by the magnetic field. Accompanied by the magnetic-field-induced magnetostructural transformation, a considerable magnetocaloric effect is observed. With the increase of x, the maximum entropy change decreases, but the effective magnetic cooling capacity increases.展开更多
The structures and electrochemical properties of the Ti1.4V0.6Ni ribbon before and after heat treatment are investigated systematically. The structure of the sample is characterized by X-ray powder diffraction analysi...The structures and electrochemical properties of the Ti1.4V0.6Ni ribbon before and after heat treatment are investigated systematically. The structure of the sample is characterized by X-ray powder diffraction analysis. Electrochemical properties including the discharge capacity, the cyclic stability and the high-rate discharge ability are tested. X-ray powder diffraction analysis shows that after heat treatment at 590 °C for 30 min, all samples mainly consist of the icosahedral quasicrystal phase (I-phase), Ti2Ni phase (FCC), V-based solid solution phase (BCC) and C14 Laves phase (hexagonal). Electrochemical measurements show that the maximum discharge capacity of the alloy electrode after heat treatment is 330.9 mA?h/g under the conditions that the discharge current density is 30 mA/g and the temperature is 30 °C. The result indicates that the cyclic stability and the high-rate discharge ability are all improved. In addition, the electrochemical kinetics of the alloy electrode is also studied by electrochemical impedance spectroscopy (EIS) and hydrogen diffusion coefficient (D).展开更多
The effects of the addition of 5.0 wt.%Ni to an Al−6wt.%Cu alloy on the solidification cooling rate(T),growth rate(V_(L)),length scale of the representative phase of the microstructure,morphology/distribution of inter...The effects of the addition of 5.0 wt.%Ni to an Al−6wt.%Cu alloy on the solidification cooling rate(T),growth rate(V_(L)),length scale of the representative phase of the microstructure,morphology/distribution of intermetallic compounds(IMCs)and on the resulting properties were investigated.Corrosion and tensile properties were determined on samples solidified under a wide range of T along the length of a directionally solidified Al−6wt.%Cu−5.0wt.%Ni alloy casting.Experimental growth laws were derived relating the evolution of primary(λ_(1))and secondary(λ_(2))dendritic spacings with T and V_(L).The elongation to fracture(δ)and the ultimate tensile strength(σ_(U))were correlated with the inverse of the square root of λ_(1) along the length of the casting by Hall−Petch type experimental equations.The reinforcing effect provided by the addition of Ni in the alloy composition is shown to surpass that provided by the refinement of the dendritic microstructure.The highest corrosion resistance is associated with a microstructure formed by thin IMCs evenly distributed in the interdendritic regions,typical of samples that are solidified under higher T.展开更多
Correlation between site occupation evolution of alloying elements in L12 phase and growth of DO22 phase in Ni75Al7.5V17.5 was studied using microscopic phase field model. The results demonstrate that the growing proc...Correlation between site occupation evolution of alloying elements in L12 phase and growth of DO22 phase in Ni75Al7.5V17.5 was studied using microscopic phase field model. The results demonstrate that the growing process of DO22 phase can be divided into two stages. At the early stage, composition in the centre part of L12 phase almost remains unchanged, and the nucleation and growth of DO22 phase is controlled by the decrease of interface between L12 phases. At the late stage, part of V for growth of DO22 phase is supplied from the centre part of L12 phase and mainly comes from Al sublattice, the excess Ni spared from the decreasing L12 phase migrates into the centre part of L12 phase and occupies the Ni sublattices exclusively, while the excess Al mainly occupies the Al sublattice. At the late stage, the growth of DO22 phase is controlled by the evolution of antisite atoms and ternary additions in the centre part of L12 phase.展开更多
Based on the microscopic phase-field model, the correlation between site occupation evolution of alloying elements in Ni3V-DO22 phase and growth of Ni3Al-L12 phase was studied during the phase transformation of Ni75Al...Based on the microscopic phase-field model, the correlation between site occupation evolution of alloying elements in Ni3V-DO22 phase and growth of Ni3Al-L12 phase was studied during the phase transformation of Ni75Al4.2V20.8. The results demonstrate that the growth of L12 phase can be divided into two stages: at the early stage, the composition of alloying elements in DO22 phase almost remains unchanged; at the late stage, the compositions of Ni and Al decrease while V increases in DO22 phase. Part of alloying elements for L12 phase growth are supplied from the site occupation evolution of alloying elements on three kinds of sublattices in DO22 phase. Ni is mainly supplied from V sublattice, and part of Al is supplied from NiⅠ and V sites at the centre of DO22 phase. The excessive V from the decreasing DO22 phase migrates into the centre of DO22 phase and mainly occupies V and NiII sites. It is the site occupation evolution of antisite atoms and ternary additions in DO22 phase that controls the growth rate of L12 phase at the late stage.展开更多
基金Project Financially supported by Major State Basic Research Development Program of China (2007CB616903)
文摘Cu-30Ni-xRE(x=0–0.213 wt.%) alloy was prepared by adding rare earths(RE) in melted Cu-30Ni alloy using metal mould casting method.The effects of RE on corrosion resistance of the alloy in simulated seawater were investigated using optical microscope,scanning electronic microscope with energy-dispersive spectrometer and electrochemical measurement system.The results showed that the corrosion resistance of Cu-30Ni alloy was greatly improved by adding proper amount of RE,whereas excess addition of RE worsened ...
基金Project(2012AA040210)supported by the National High-Tech Research and Development Program of ChinaProject(510-C10293)supported by the Central Finance Special Fund to Support the Local University,ChinaProject(2010A090200048)supported by the Key Project of Industry,Education,Research of Guangdong Province and Ministry of Education,China
文摘The crack-free Ni60 A coating was fabricated on 45 steel substrate by laser cladding and the microstructure including solidification characteristics, phases constitution and phase distribution was systematically investigated. The high temperature friction and wear behavior of the cladding coating and substrate sliding against GCr15 ball under different loads was systematically evaluated. It was found that the coating has homogenous and fine microstructure consisting of γ(Ni) solid solution, a considerable amount of network Ni-Ni3 B eutectics, m^23C6 with the floret-shape structure and Cr B with the dark spot-shape structure uniformly distributing in interdendritic eutectics. The microhardness of the coating is about 2.6 times as much as that of the substrate. The coating produces higher friction values than the substrate under the same load condition, but the friction process on the coating keeps relatively stable. Wear rates of the coating are about 1/6.2 of that of the substrate under the higher load(300 g). Wear mechanism of the substrate includes adhesion wear, abrasive wear, severe plastic deformation and oxidation wear, while that of the coating is merely a combination of mild abrasive wear and moderate oxidation wear.
基金Project (2009AA032601) supported by the National High-tech Research and Development Program of China
文摘The hot corrosion behaviors of Ni–16Cr–xAl(x=4.5%, 6.8%, 9.0%, mass fraction) based alloys in Na2SO4–25% NaCl molten salts at 600 °C were investigated. The effects of pre-oxidation and Al content on the resistance to hot corrosion were examined. The hot corrosion resistance of Ni–16Cr–xAl based alloy with Al addition from 4.5% to 9.0% increases with increasing Al content. The alloy with Al content of 9.0% shows the highest hot corrosion resistance among the examined alloys because more β–NiAl phases are obtained to sustain the Al2O3 scale repaired during hot corrosion. Pre-oxidized specimens have a superior hot corrosion resistance compared with the as-cast specimens, due to a protective oxide scale formed after pre-treatment.
文摘The effects of Ni addition on the liquid phase separation and giant magnetoresi stance (GMR) of Cu Co alloys were discussed. The results reveal that Ni additio n can partially restrain the liquid phase separation of Cu Co alloys, resultin g in a decrease of volume fraction for the Co rich particles separated from the liquid phase and in refined microstructures. The composition analyses indicate t hat Ni is dissolved in both the Co rich and the Cu rich phases, but Ni content in the Co rich phase is much higher than that in the Cu matrix. At the same ti me, Ni addition enhance the solubility between Cu and Co, especially Cu in Co s olid solution. Ni alloying into Cu Co alloys can fully prevent the liquid phase separation during melt spinning, which is very beneficial to improve GMR of Cu Co alloys.
基金Project(50971012) supported by the National Natural Science Foundation of China
文摘The isothermal oxidation behaviors of three kinds of Ni3Al-Mo based alloys at 1150 ℃ were studied.The morphology,structure and element distribution of oxide scales of the alloys were researched by scanning electron microscopy,X-ray diffraction and electron probe microanalysis.The research results show that there are three oxide layers,an outer layer of NiO,an intermediate layer mainly composed of NiO,NiAl2O4 and a small amount of NiMoO4,and an inner layer of NiAl2O4 and Al2O3.Re element was mainly distributed in the intermediate layer,which plays a role as "diffusion barrier" in the process of oxidation,and effectively reduces the diffusion rate of Al and Mo elements outward and diffusion rate of O element inward.As a result,a Al-rich oxide layer formed in the inner layer inhibits the growth of oxide layer and improves the oxidation resistance of the alloy.
基金supported by the National Natural Science Foundation of China(51301082 and 51464031)College students’ innovative entrepreneurial training plane of Lanzhou University of Technology(DC2015005)
文摘This paper presents some research information on the effects of Zn, Cu and Ni on the microstructure and mechanical properties of as-cast Mg-2Dy(at.%) alloys. The Mg-2Dy alloy is composed of α-Mg and Mg24Dy5 phases. With the addition of 0.5at.%Zn, 0.5at.%Cu and 0.5at.%Ni, respectively, besides α-Mg, the long period stacking order(LPSO) phases containing Zn, Cu, and Ni precipitated in the α-Mg interdentritic boundary. The addition of Ni effectively refined the dendrite arm spacing. The as-cast Mg-2Dy-0.5Ni alloy exhibited the best tensile strengths and elongation. The better mechanical properties were mainly attributed to small secondry dendrite arm spacing(SDAS) and high volume fraction of LPSO phases.
基金Project(2020JJ2046)supported by the Science Fund for Hunan Distinguished Young Scholars,ChinaProject(S2020GXKJGG0416)supported by the Special Project for Hunan Innovative Province Construction,China+1 种基金Project(2018RS3007)supported by the Huxiang Young Talents,ChinaProject(GuikeAB19050002)supported by the Science Project of Guangxi,China。
文摘NiTi shape memory alloy(SMA)with nominal composition of Ni 50.8 at%and Ti 49.2 at%was additively manufactured(AM)by selective laser melting(SLM)and laser directed energy deposition(DED)for a comparison study,with emphasis on its phase composition,microstructure,mechanical property and deformation mechanism.The results show that the yield strength and ductility obtained by SLM are 100 MPa and 8%,respectively,which are remarkably different from DED result with 700 MPa and 2%.The load path of SLM sample presents shape memory effect,corresponding to martensite phase detected by XRD;while the load path of DED presents pseudo-elasticity with austenite phase.In SLM sample,fine grain and hole provide a uniform deformation during tensile test,resulting in a better elongation.Furthermore,the nonequilibrium solidification was studied by a temperature field simulation to understand the difference of the two 3D printing methods.Both temperature gradient G and growth rate R determine the microstructure and phase in the SLM sample and DED sample,which leads to similar grain morphologies because of similar G/R.While higher G×R of SLM leads to a finer grain size in SLM sample,providing enough driving force for martensite transition and subsequently changing texture compared to DED sample.
基金the National Natural Science Foundation of China (50701011)Natural Science Foundation of Inner Mongolia, China (200711020703)Science and Technology Planned Project of Inner Mongolia, China (20050205)
文摘In order to improve the cyclic stability of La-Mg-Ni system (Ce2Ni7-type) alloy electrode, small amount of Co was added in La0.75Mg0.25Ni3.5 alloy. The effect of Co on electrochemical performance and microstructure of the alloys were investigated in detail. XRD results showed that the alloys had multiphase structure composed of (La, Mg)2Ni7, LaNi5 and small amount of LaNi2 phases. The discharge capacity of the alloys first increased and then decreased with increasing Co content. At a discharge current density of 900 mA/g, the HRD of the alloy electrodes increased from 81.3% (x=0) to 89.2 % (x=0.2), and then reduced to 87.8 % (x=0.6). After 60 charge/discharge cycles, the capacity retention rate of the alloys enhanced from 52.67% to 61.32%, and the capacity decay rate of the alloys decreased from 2.60 to 2.05 mAh/g per cycle with increasing Co content. The obtained results by XPS and XRD showed that the fundamental reasons for the capacity decay of the La-Mg-Ni system (Ce2Ni7-type) alloy electrodes were corrosion and oxidation as well as passivation of Mg and Lain alkaline solution.
基金the National Natural Science Foundation of China (No. 50271002) New Century Program for Excellent Talents of Ministry of Education of China (No. 04-0165).
文摘A statistical work has been done to collect the composition ranges of Ni-Mn-Ga alloys exhibiting different structures and martensite start temperature (M,), large magnetostrain or the co-existence of magnetic and structural transitions. The alloys with five-layered (5M), seven-layered (7M) modulated and non-modulated (T) martensitic structures were mapped in the graph. An empirical formula has been presented to reflect the effect of elements nickel (Ni ), manganese ( Mn ) and gallium (Ga), on the martensite start temperature (M3). The martensitic structure is sensitive to the composition and the martensitic transformation temperature is most drastically affected by the Ni content. The alloys with large magnetostrain or co-existence effect of the magnetic and structural transitions were also listed in a limited area.
基金Item Sponsored by State Key Lab of Mechanical Transmissions,Chongqing University
文摘The NiSix based alloy typically has poor weldability due to its lower ductility. A limited amount of work has been performed on the weldability of NiSix based alloys. Therefore, the effect of heat treatment and welding parameters on weldability of the alloys, and the relationship between the weldability and microstructure were studied. The results show that the as-cast Ni-Si-Nb-B alloy (Ni 76. 5%, Si 20%, Nb 3%, and B 0. 5%) could be successfully welded after preheating at 600 ℃. The welding procedure should be performed on the alloys before any heat treatment and a preheating at 600 ℃ should be used. The fusion zone is harder than the matrix due to a large amount of 7 phase and a finer microstructure. The cracks are predominantly intergranular in heat affected zone and associated with the needle-like ), phase. The heat treatment before welding increases the tendency of cracking in the fusion zone.
文摘La Ni based alloy powders used for Ni metal hydride batteries were synthesized by mechanical alloying starting from the elements. The electrical capacity obtained was up to 320 mAh/g. In addition, the comparison in the microstructure and electrochemical properties was made between the alloy powders produced by mechanical alloying and by melting. It was shown that mechanical alloying is promising in the preparation of practical RE hydrogen storage electrode materials.
基金supported by the National Natural Science Foundation of China (Grant No. 10976007)the Fundamental Research Funds for the Central Universities (Grant Nos. ZYGX2009J046 and ZYGX2009X007)Royal Academy of Engineering-Research Exchanges with China and India Awards in UK
文摘This paper investigates the effects of substitution of Si for Ga on the martensitic transformation behaviours in Ni-Fe-Ga alloys by using optical metallographic microscope and differential scanning calorimetry (DSC) methods. The structure type of Ni55.5Fe18Ga26.5-xSix alloys is determined by x-ray diffraction (XRD), and the XRD patterns show the microstructure of Ni-Fe-Ga-Si alloys transformed from body-centred tetragonal martensite (with Si content x = 0) to body-centred cubic austenite (with x = 2) at room temperature. The martensitic transformation temperatures of the Ni55.sFelsGa26.5-xSi~ alloys decrease almost linearly with increasing Si content in the Si content range of x _~ 3. Thermal treatment also plays an important role on martensitic transformation temperatures in the Ni-Fe-Ga^Si alloy. The valence electronic concentrations, size factor, L21 degree of order and strength of parent phase influence the martensitic transformation temperatures of the Ni-Fe-Ga-Si alloys. An understanding of the relationship between martensitic transformation temperatures and Si content will be significant for designing an appropriate Ni-Fe-Ga-Si alloy for a specific application at a given temperature.
文摘The diffusivity of hydrogen in two Ni3Al alloys (No.1 and No.2) has been measured in the temperature range of 100 degreesC to 420 degreesC using an ultrahigh vacuum gaseous permeation technique. The diffusivity data fall into two segments, in which the hydrogen diffusivity adheres to the Arrhenius form, respectively. From the hydrogen diffusivity, it is conjectured that the hydrogen diffusivity reflects the hydrogen transportation along the grain boundaries at lower temperature and the hydrogen transportation in the lattice at higher temperature. The intergranular fracture of Lit-type intermetallics induced by hydrogen at relative low temperature results from hydrogen transportation along the grain boundaries and not in the lattice.
基金financially supported by the National Natural Science Foundation of China(No.51771044)the Natural Science Foundation of Hebei Province(No.E2019501061)+3 种基金the Performance subsidy fund for Key Laboratory of Dielectric and Electrolyte Functional Material Hebei Province(No.22567627H)the Fundamental Research Funds for the Central Universities(No.N2223025)the State Key Lab of Advanced Metals and Materials(No.2022-Z02)Programme of Introducing Talents of Discipline Innovation to Universities 2.0(the 111 Project of China 2.0,No.BP0719037)。
文摘The martensitic transformation,mechanical,and magnetic properties of the Ni_(2)Mn_(1.5-x)Cu_(x)Ti_(0.5) (x=0.125,0.25,0.375,0.5) and Ni_(2-y)Co_(y)Mn_(1.5-x)Cu_(x)Ti_(0.5)[(x=0.125,y=0.125,0.25,0.375,0.5) and (x=0.125,0.25,0.375,y=0.625)]alloys were systematically studied by the first-principles calculations.For the formation energy,the martensite is smaller than the austenite,the Ni–(Co)–Mn–Cu–Ti alloys studied in this work can undergo martensitic transformation.The austenite and non-modulated (NM) martensite always present antiferromagnetic state in the Ni_(2)Mn_(1.5-x)Cu_(x)Ti_(0.5) and Ni_(2-y)Co_(y)Mn_(1.5-x)Cu_(x)Ti_(0.5) (y<0.625) alloys.When y=0.625 in the Ni_(2-y)Co_(y)Mn_(1.5-x)Cu_(x)Ti_(0.5) series,the austenite presents ferromagnetic state while the NM martensite shows antiferromagnetic state.Cu doping can decrease the thermal hysteresis and anisotropy of the Ni–(Co)–Mn–Ti alloy.Increasing Mn and decreasing Ti content can improve the shear resistance and normal stress resistance,but reduce the toughness in the Ni–Mn–Cu–Ti alloy.And the ductility of the Co–Cu co-doping alloy is inferior to that of the Ni–Mn–Cu–Ti and Ni–Co–Mn–Ti alloys.The electronic density of states was studied to reveal the essence of the mechanical and magnetic properties.
基金Funded by Natural Science Foundation of the Inner Mongolia(Nos.2019MS01015,2019MS01017)National Natural Science Foundation of China(No.11002065)。
文摘Shot peening is a surface modification technology with the metal surface nano machine(SNC),which can modify the surface microstructure and extend the fatigue life of Cu-19Ni alloy.The hardness,damage evolution and mechanical properties were investigated and characterized by scanning electron microscope(SEM),laser confocal microscope(LSM)and material surface performance tester(CFT).The results showed that the surface roughness and friction coefficient of Cu-19Ni alloy decreased with the increase of shot peening duration and diameter,while the microhardness and strength increased.Moreover,with the increase in shot peening duration and diameter,SEM observation showed that the fracture dimples became smaller,meanwhile,with the increase of small cleavage planes,shear tearing ridges and the thickness of the surface nano layer,the fracture mode gradually evolved from plastic to brittle fracture.The uniaxial tensile test of shot peened Cu-19Ni alloy was carried out by MTS testing machine combined with digital image correlation technology(DIC).The evolution of Cu-19Ni surface damage was analyzed,and the evolution equations describing the damage of large deformation zone and small deformation zone were established.The effect of shot peening on the damage evolution behavior of Cu-19Ni alloy was revealed.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51601092,51571121,and 11604148)the Fundamental Research Funds for the Central Universities,China(Grant Nos.30916011344 and 30916011345)+5 种基金Jiangsu Natural Science Foundation for Distinguished Young Scholars,China(Grant No.BK20140035)China Postdoctoral Science Foundation(Grant No.2016M591851)the Natural Science Foundation of Jiangsu Province,China(Grant Nos.BK20160833 and BK20160829)Qing Lan Project of Jiangsu Province,ChinaPriority Academic Program Development of Jiangsu Higher Education Institutions,ChinaNMG–NJUST Joint Scholarship Program for Ishfaq Ahmad Shah(Student ID:914116020118)
文摘An investigation on the magnetostructural transformation and magnetocaloric properties of Ni48-xCo2Mn38+xSn12(x = 0, 1.0, 1.5, 2.0, and 2.5) ferromagnetic shape memory alloys is carried out. With the partial replacement of Ni by Mn in the Ni_(48)Co2Mn38Sn12 alloy, the electron concentration decreases. As a result, the martensitic transformation temperature is decreased into the temperature window between the Curie-temperatures of austenite and martensite. Thus, the samples with x = 1.5 and 2.0 exhibit the magnetostructural transformation between the weak-magnetization martensite and ferromagnetic austenite at room temperature. The structural transformation can be induced not only by the temperature,but also by the magnetic field. Accompanied by the magnetic-field-induced magnetostructural transformation, a considerable magnetocaloric effect is observed. With the increase of x, the maximum entropy change decreases, but the effective magnetic cooling capacity increases.
基金Project (20112216120001) supported by the Doctoral Program of Tertiary Education of the Ministry of Education of ChinaProject(21215141) supported by the Natural Science Foundation of Jilin Province, China+3 种基金Project (20921002) supported by the Foundation for Innovative Research Groups of the National Natural Science Foundation of ChinaProjects (21073179, 61106050) supported by the National Natural Science Foundation of ChinaProject (BE2012047) supported by Scientific and Technological Supporting Program of Jiangsu Province of China and GS Yuasa Corporation of JapanProject (11KZ38) supported by and Scientific and Technological Pillar Project of Changchun, China
文摘The structures and electrochemical properties of the Ti1.4V0.6Ni ribbon before and after heat treatment are investigated systematically. The structure of the sample is characterized by X-ray powder diffraction analysis. Electrochemical properties including the discharge capacity, the cyclic stability and the high-rate discharge ability are tested. X-ray powder diffraction analysis shows that after heat treatment at 590 °C for 30 min, all samples mainly consist of the icosahedral quasicrystal phase (I-phase), Ti2Ni phase (FCC), V-based solid solution phase (BCC) and C14 Laves phase (hexagonal). Electrochemical measurements show that the maximum discharge capacity of the alloy electrode after heat treatment is 330.9 mA?h/g under the conditions that the discharge current density is 30 mA/g and the temperature is 30 °C. The result indicates that the cyclic stability and the high-rate discharge ability are all improved. In addition, the electrochemical kinetics of the alloy electrode is also studied by electrochemical impedance spectroscopy (EIS) and hydrogen diffusion coefficient (D).
基金CNPq-National Council for Scientific and Technological Development(Grant:407871/2018-7)CAPES-Coordenação de Aperfeiçoamento de Pessoal de Nível Superior,Brazil,for the financial support。
文摘The effects of the addition of 5.0 wt.%Ni to an Al−6wt.%Cu alloy on the solidification cooling rate(T),growth rate(V_(L)),length scale of the representative phase of the microstructure,morphology/distribution of intermetallic compounds(IMCs)and on the resulting properties were investigated.Corrosion and tensile properties were determined on samples solidified under a wide range of T along the length of a directionally solidified Al−6wt.%Cu−5.0wt.%Ni alloy casting.Experimental growth laws were derived relating the evolution of primary(λ_(1))and secondary(λ_(2))dendritic spacings with T and V_(L).The elongation to fracture(δ)and the ultimate tensile strength(σ_(U))were correlated with the inverse of the square root of λ_(1) along the length of the casting by Hall−Petch type experimental equations.The reinforcing effect provided by the addition of Ni in the alloy composition is shown to surpass that provided by the refinement of the dendritic microstructure.The highest corrosion resistance is associated with a microstructure formed by thin IMCs evenly distributed in the interdendritic regions,typical of samples that are solidified under higher T.
基金Projects (50941020, 10902086, 50875217, 20903075) supported by the National Natural Science Foundation of ChinaProjects (SJ08-ZT05, SJ08-B14) supported by the Natural Science Foundation of Shaanxi Province, China
文摘Correlation between site occupation evolution of alloying elements in L12 phase and growth of DO22 phase in Ni75Al7.5V17.5 was studied using microscopic phase field model. The results demonstrate that the growing process of DO22 phase can be divided into two stages. At the early stage, composition in the centre part of L12 phase almost remains unchanged, and the nucleation and growth of DO22 phase is controlled by the decrease of interface between L12 phases. At the late stage, part of V for growth of DO22 phase is supplied from the centre part of L12 phase and mainly comes from Al sublattice, the excess Ni spared from the decreasing L12 phase migrates into the centre part of L12 phase and occupies the Ni sublattices exclusively, while the excess Al mainly occupies the Al sublattice. At the late stage, the growth of DO22 phase is controlled by the evolution of antisite atoms and ternary additions in the centre part of L12 phase.
基金Projects(51174168,51274167)supported by the National Natural Science Foundation of ChinaProject(2013M532082)supported by Postdoctoral Science Foundation of ChinaProjects(13R21421700,13R21421800)supported by the Postdoctoral Science Foundation of Shanghai,China
文摘Based on the microscopic phase-field model, the correlation between site occupation evolution of alloying elements in Ni3V-DO22 phase and growth of Ni3Al-L12 phase was studied during the phase transformation of Ni75Al4.2V20.8. The results demonstrate that the growth of L12 phase can be divided into two stages: at the early stage, the composition of alloying elements in DO22 phase almost remains unchanged; at the late stage, the compositions of Ni and Al decrease while V increases in DO22 phase. Part of alloying elements for L12 phase growth are supplied from the site occupation evolution of alloying elements on three kinds of sublattices in DO22 phase. Ni is mainly supplied from V sublattice, and part of Al is supplied from NiⅠ and V sites at the centre of DO22 phase. The excessive V from the decreasing DO22 phase migrates into the centre of DO22 phase and mainly occupies V and NiII sites. It is the site occupation evolution of antisite atoms and ternary additions in DO22 phase that controls the growth rate of L12 phase at the late stage.