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Quasicrystal (QC)-reinforced metal matrix composites fabricated by rapid solidification present promising new opportunities to develop high-strength alloys with multiple functions. In this research, specially designed Al–Fe–Cr samples possessing an Al–Fe–Cr quasicrystal-reinforced Al matrix structure were manufactured using a laser powder bed fusion (LPBF) process. Based on the optimized process parameters of laser scanning speed and hatch distance, an almost dense (99.8%) free-crack sample was obtained with the multiscaled heterogenous structure induced by the nonuniform rapid solidification in a single molten pool. The results show that nanosized Al–Fe–Cr quasicrystalline particles of different sizes are heterogeneously distributed in the α-Al columnar grain structure. In detail, the coarse flower-like and spherical QC particles can be observed at the molten pool boundary, and the fine spherical Al–Fe–Cr QC is located inside the laser fusion zone. The orientation relationship between the Al matrix and the icosahedral Al–Fe–Cr QC is as follows: Al [ ​− ​112 ] ∥ i5 with a semicoherency feature. The novel designed LPBF-processed Al–Fe–Cr alloy exhibits high mechanical strength due to the ultrafine multireinforced microstructure-induced Orowan strengthening effect. For instance, the ultimate tensile strength, yield strength and elongation of the sample processed with LPBF are 530.80 ​± ​3.19 ​MPa, 395.06 ​± ​6.44 ​MPa, and 4.16% ​± ​0.38%, respectively. The fractographic analysis shows that the fracture mechanism presents a combination of ductile‒brittle fracture. [ABSTRACT FROM AUTHOR]

Laser rapid forming (LRF) is a newly developed method of additive manufacturing that has drawn much attention owing to its outstanding advantages. However, direct formation of components with high precision and high surface quality through LRF is extremely time-consuming and expensive. To address this problem, electrochemical machining (ECM) was introduced as a subsequent finishing process. In this paper, electrochemical machining property of the laser rapid formed (LRFed) Inconel 718 alloy (both as-deposited and solution-annealed) was studied. On as-deposited LRFed sample, polarization behavior and current efficiency show isotropy, despite the anisotropy of the microstructure. After a solution annealing treatment, the polarization behavior shows no difference, but the material will be more difficult to machine. The surface topography after ECM shows anisotropy on as-deposited LRFed sample, and dendrites as a microscopic structure and layer-band (on vertical sections) as a macroscopic structure are noticeable. The height of layer bands and surface roughness (Ra) decrease with increasing current density. On solution-annealed sample, the dissolved surface was smooth and no subgrain boundaries or layer bands were observed. Finally, deep-small hole, grooves and flat surfaces were produced successfully through ECM. [ABSTRACT FROM AUTHOR]

An AlCoCrCuFeNi high-entropy alloy (HEA) coating was fabricated on a pure magnesium substrate using a two-step method, involving plasma spray processing and laser re-melting. After laser re-melting, the microporosity present in the as-sprayed coating was eliminated, and a dense surface layer was obtained. The microstructure of the laser-remelted layer exhibits an epitaxial growth of columnar dendrites, which originate from the crystals of the spray coating. The presence of a continuous epitaxial growth of columnar HEA dendrites in the laser re-melted layer was analyzed based on the critical stability condition of a planar interface. The solidification of a columnar dendrite structure of the HEA alloy in the laser-remelted layer was analyzed based on the Kurz-Giovanola-Trivedi model and Hunt's criterion, with modifications for a multi-component alloy. [ABSTRACT FROM AUTHOR]

Abstract: Alloys with composition Ti(Mn1−x Al x )2 (x Al =0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.55, 0.6, and 0.67) were studied by X-ray powder diffraction (XPD), optical microscopy, electron probe microanalysis (EPMA) and electronic density functional theory. EPMA and XPD defined an extensive solid solution of up to x Al =0.64 at 900°C. Structure determination from Rietveld refinements of X-ray powder diffraction data for Ti(Mn1−x Al x )2 (0≤ x Al ≤0.60) and from single crystal X-ray counter data for x Al =0.2 revealed a C14-MgZn2-type Laves phase, where Ti atoms fully occupy the 4f sites, whereas Mn and Al atoms share the 6h and 2a sites in various ratios. By means of density functional theory, the structural stabilities and site preferences of nine ternary compositions, Ti(Mn1−x Al x )2 (x Al =0, 0.125, 0.25, 0.375, 0.500, 0.625, 0.750, 0.875, 1.00), were further calculated for a large number of structural models. The derived Al content dependent structural stabilities, lattice parameters, and site occupations as well as enthalpies of formations are in nice agreement with experimental results. Based on the calculated data, we analyzed the occupation behaviour of Al atoms substituting for Mn atoms at the 2a and 6h sites: up to concentrations x Al <0.375 Al atoms prefer the 6h sites, whereas for 0.375< x Al <0.625 Al atoms prefer the 2a sites. The calculations furthermore revealed that the Al atoms at the 6h sites exhibit a trend of getting paired. [Copyright &y& Elsevier]

Abstract: In order to improve the electrochemical cycle stability of La–Mg–Ni system (PuNi3-type) hydrogen storage alloy, a trace of Cr was added in the alloy and La2Mg(Ni0.85Co0.15)9Cr x (x =0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys were prepared by casting and rapid quenching. The effects of Cr addition on the microstructures and electrochemical performances of the as-cast and quenched alloys were investigated in detail. The obtained results show that Cr addition engenders an inappreciable influence on the phase composition of the as-cast and quenched alloys, but it changes the phase abundance of the alloys significant. The Cr addition markedly enhances the cycle stability of the as-cast and quenched alloys, but it decreases the discharge capacity. When Cr content increased from 0 to 0.4, the discharge capacity of the as-cast alloy decreased from 396.3 to 355.6mAh/g, and the cycle life prolonged from 72 to 97 cycles. For the as-quenched (30m/s) alloys, the discharge capacity reduced from 364.2 to 334.2mAh/g, and the cycle life extended from 100 to 131 cycles. [Copyright &y& Elsevier]

The rapid quenching technology was used in the preparation of the MmNi3.8Co0.4Mn0.6Al0.2Bx (x=0, 0.1, 0.2, 0.3, 0.4) electrode alloys. The microstructures and electrochemical performances of the as-cast and quenched alloys were analysed and measured. The effects of boron additive on the microstructures and electrochemical properties of as-cast and quenched alloy MmNi3.8Co0.4Mn0.6Al0.2 were investigated. The experimental results showed that the microstructure of as-cast MmNi3.8Co0.4Mn0.6Al0.2Bx (x=0, 0.1, 0.2, 0.3, 0.4) alloy is composed of CaCu5-type main phase and a small amount of CeCo4B-type secondary phase. The abundance of the secondary phase increases with the increase of the boron content x. The secondary phase in the alloys disappears when quenching rate is larger than 22 m/s. The electrochemical measurement showed that the addition of boron slightly modifies the activation performance and dramatically enhances the cycle life of the alloys, whereas it reduces the capacities of the as-cast and quenched alloys. The influence of boron additive on the electrochemical characteristics of the as-quenched alloy is much stronger than that on the as-cast alloy. It is because boron strongly promotes the formation of the amorphous phase in the as-quenched alloy. [Copyright &y& Elsevier]

In order to improve the electrochemical characteristics of AB2 Laves phase electrode alloys, the rapid quenching technology was used in the preparation of AB2 type Ti- and Ti-Zr-based electrode alloys. The effects of the rapid quenching on the electrochemical characteristics and microstructures of AB2 Laves phase electrode alloys were investigated comprehensively. The experimental results showed that the effects of the rapid quenching on the electrochemical properties and microstructures of AB2 Laves phase electrode alloys were closely relevant with the compositions of the alloys. For Ti-based alloy, the capacity of the as-quenched alloy was enhanced obviously with the increase of the quenching rate, and a maximum capacity could be obtained at a certain quenching rate. The rapid quenching had little effect on the activation capability and improved the cycle stability slightly. For Ti-Zr-based alloy, the cycle stability was exalted significantly and the capacity and activation capability were reduced dramatically with the increase of the quenching rate. The main reason why the rapid quenching can modify the electrochemical performances of AB2 Laves phase electrode alloys was that it has obviously changed the microstructures of the alloys. [Copyright &y& Elsevier]

Low Co AB5-type MmNi3.8Co0.4Mn0.6Al0.2Bx (x=0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys were prepared by cast and rapid quenching. The microstructures and electrochemical performances of the as-cast and quenched alloys were analysed and measured. The effects of boron additive and rapid quenching technique on the microstructures and electrochemical properties of as-cast and quenched alloys were investigated comprehensively. The experimental results showed that the microstructure of as-cast MmNi3.8Co0.4Mn0.6Al0.2Bx (x=0, 0.1, 0.2, 0.3, 0.4) alloys was composed of CaCu5-type main phase and a small amount of CeCo4B-type secondary phase. The abundance of the secondary phase increases with the increase of boron context x. The rapid quenching techniques were used in the preparation of the alloys. The amount of secondary phase in the alloys decreased with the increase of quenching rate. Rapid quenching made lattice constants increase slightly. The effects of rapid quenching on the electrochemical performances of the alloys are very significant. The discharge capacity of the alloys decreased obviously and the cycle stability increased dramatically with the increase of quenching rate. Rapid quenching made the activation capability of the alloys lowered. However, the activate performance and high rate discharge capability as well as discharge voltage characteristic of the alloys were modified obviously with the increase of boron content x. [Copyright &y& Elsevier]

Abstract: The nanocrystalline Mg2Ni-type electrode alloys with nominal compositions of Mg20Ni10−x Cu x (x = 0, 1, 2, 3, 4) were synthesized by the melt spinning technique. The microstructures of the as-cast and spun alloys were characterized by XRD, SEM and HRTEM. The electrochemical hydrogen storage performances were tested by an automatic galvanostatic system. The results show that all the as-spun alloys hold typical nanocrystalline structure instead of an amorphous phase. The melt spinning does not modify the major phase Mg2Ni, but it leads to the formation of crystal defects such as stacking faults, dislocations, sub-grain boundary and twin-grain boundary. The melt spinning significantly improves the electrochemical hydrogen storage capacity of the alloys, whereas it slightly impairs the electrochemical cycle stability of the alloys. The substitution of Cu for Ni significantly ameliorates the electrochemical hydrogen storage performances of the alloys, involving both the electrochemical hydrogen storage capacity and the electrochemical charging and discharging stability. [Copyright &y& Elsevier]

Abstract: In order to improve the hydriding and dehydriding kinetics of the Mg2Ni-type alloys, Ni in the alloy was partially substituted by element Cu, and the nanocrystalline Mg2Ni-type Mg20Ni10−xCux (x = 0, 1, 2, 3, 4) alloys were synthesized by melt-spinning technique. The structures of the as-cast and spun alloys were studied by XRD, SEM and HRTEM. The hydrogen absorption and desorption kinetics of the alloys were measured using an automatically controlled Sieverts apparatus. The results show that the substitution of Cu for Ni does not change the major phase Mg2Ni. The hydrogen absorption capacity of the alloys first increases and then decreases with rising Cu content, but the hydrogen desorption capacity of the alloys grows with increasing Cu content. The melt spinning significantly improves the hydrogenation and dehydrogenation capacity and kinetics of the alloys. [Copyright &y& Elsevier]

Abstract: The La–Mg–Ni system PuNi3-type La0.5Ce0.2Mg0.3Co0.4Ni2.6−x Mn x (x =0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys were prepared by casting and quenching. Ni in the alloy was partially substituted by Mn in order to improve the electrochemical characteristics of the alloys. The effects of the substitution of Mn for Ni and rapid quenching on the structures and electrochemical characteristics of the alloys were investigated in detail. The results obtained by XRD, SEM and TEM show that the alloys have multiphase structures which are composed of two major phases (La, Mg)Ni3 and LaNi5 as well as a residual phase LaNi. The substitution of Mn for Ni leads to an obvious increase of the LaNi5 phase and an decrease of the (La, Mg)Ni3 in the alloys. The electrochemical measurements indicate that the discharge capacities of the as-cast and quenched alloys first increase and then decrease with growing Mn content. The substitution of Mn for Ni clearly improves the high rate discharge abilities (HRDs) and the activation capabilities of the as-cast and quenched alloys, but it slightly impairs the cycle stabilities of the alloys. The rapid quenching significantly improves the cycle stabilities of the alloys, and the discharge capacities and HRDs of the alloys have the maximum values with the variety of the quenching rate. [Copyright &y& Elsevier]

Abstract: In order to improve the cycle stability of La–Mg–Ni system (PuNi3-type) hydrogen storage alloy, Ni in the alloy was partly substituted by Fe, Mn and Al, and the electrode alloys La0.7Mg0.3Ni2.55−x Co0.45M x (M=Fe, Mn, Al; x =0, 0.1) were prepared by casting and rapid quenching. The effects of the substitution of Fe, Mn and Al for Ni and rapid quenching on the microstructures and electrochemical properties of the alloys were investigated in detail. The results obtained by XRD, SEM and TEM indicate that element substitution has no influence on the phase compositions of the alloys, but it changes the phase abundances of the alloys. Particularly, the substitution of Al and Mn obviously raises the amount of the LaNi2 phase. The substitution of Al and Fe leads to a significant refinement of the as-quenched alloy''s grains. The substitution of Al strongly restrains the formation of an amorphous in the as-quenched alloy, but the substitution of Fe is quite helpful for the formation of an amorphous phase. The effects of the substitution of Fe, Mn and Al on the cycle stabilities of the as-cast and quenched alloys are different. The positive influence of the substitution elements on the cycle stabilities of the as-cast alloys is in proper order Al>Fe>Mn, and for as-quenched alloys, the order is Fe>Al>Mn. Rapid quenching engenders an inappreciable influence on the phase composition, but it markedly enhances the cycle stabilities of the alloys. [Copyright &y& Elsevier]

Abstract: The La0.75Mg0.25Ni2.5Co x (x =0, 0.2, 0.4, 0.6, 0.8, 1.0) hydrogen storage alloys were prepared by vacuum medium-frequency induction furnace under the argon atmosphere. The microstructures and electrochemical performances of the alloys were analyzed and measured. The effects of Co addition on the microstructures and electrochemical properties of the alloys were investigated in detail. The obtained results by X-ray diffractometer (XRD) showed that alloys were composed of the (La,Mg)Ni3, the LaNi5, LaNi2 and the La2Ni7 phases. With the increase of Co content x, the LaNi2 phase decreases, the (La,Mg)Ni3, the La2Ni7 and the LaNi5 phases increase. The results by the electrochemical measurements indicated that the maximum discharge capacity of the alloys is enhanced and activation performance is improved with the incremental change of Co content. The alloy (x =1.0) has a maximum discharge capacity of 388.7mAh/g. The addition of Co raises the high rate discharge capacity of the alloys. The cycle stability of the alloys first increases and then decreases with the growth of Co content. When Co content is 0.4, the capacity retention rate (S 100) of the alloy reaches a maximum volume of 76.9%. [Copyright &y& Elsevier]

Abstract: Mg2−x Zr x Ni (x =0, 0.15, 0.3, 0.45 and 0.6) electrode alloys were prepared by mechanical alloying (MA). The effects of substituting Mg with Zr on the microstructures and electrochemical performance of the MA alloys were investigated in detail. The results obtained by XRD and TEM show that the substitution of Zr for Mg is favorable for the formation of an amorphous phase. For a fixed milling time, the amorphous phase in the alloy increases with increasing Zr content. The electrochemical measurements indicate that the substitution of Zr can dramatically enhance the discharge capacity with preferable cycle stability, and markedly improve the discharge voltage characteristics of the alloys. The fact that Zr promotes the formation of an amorphous phase is mainly responsible for these effects. [Copyright &y& Elsevier]

Abstract: In order to investigate the influences of the stoichiometric ratios of B/A (A: gross A-site elements, B: gross B-site elements) and the substitution of Co for Ni on the structure and the electrochemical performances of the -type electrode alloys, the La–Mg–Ni–Co system (, Co; , 0.2, 0.4, 0.6, 0.8, 1.0) alloys were prepared by induction melting in a helium atmosphere. The structures and electrochemical performances of the alloys were systemically measured. The obtained results show that the structures and electrochemical performances of the alloys are closely relevant to the M content. All the alloys exhibit a multiphase structure, including , and phases, and the major phase in the alloys changes from to with the variety of M content. The electrochemical performances of the alloys, involving the discharge capacity, the high rate discharge (HRD) ability, the activation capability and the discharge potential characteristics, significantly improve with increasing M content. When M content increases from 0 to 1.0, the discharge capacity rises from 177.7 to 343.62 mAh/g for the alloy , and from 177.7 to 388.7mAh/g for the alloy . The cycle stability of the alloy first mounts up then declines with growing M content. The substitution of Co for Ni significantly ameliorates the electrochemical performances. For a fixed M content , the substitution of Co for Ni enhances the discharge capacity from 343.62 to 388.7mAh/g, and the capacity retention ratio after 100 charging–discharging cycles from 51.45% to 61.1%. [Copyright &y& Elsevier]

Abstract: The electrode alloys Mg2−x Zr x Ni (x =0, 0.15, 0.3, 0.45 and 0.6) were prepared by mechanical alloying (MA). Mg in the alloy was partially substituted with Zr in order to improve the electrochemical characteristics of the Mg2Ni-type alloy. The microstructures and the electrochemical characteristics of the experimental alloys were measured systemically. The effects of substituting Mg with Zr and MA technique on the microstructures and electrochemical performances of the alloys were investigated in detail. The results obtained by XRD, SEM and TEM show that the substitution of Zr is favourable for the formation of an amorphous phase. For a fixed milling time, the amorphous phase in the alloy grows with increasing Zr content. The electrochemical measurement indicates that the substitution of Zr can dramatically enhance the discharge capacity with preferable cycle stability, and it markedly improves the discharge voltage characteristic of the alloys. For x ≤0.3, the discharge capacity of the alloys monotonically increases with milling time. But for x >0.3, it has a maximum value with the change of milling time. [Copyright &y& Elsevier]

Abstract: The effects of the substitution of Mn for Ni on the structures and electrochemical characteristics of the as-cast and quenched (, 0.1, 0.2, 0.3, 0.4) alloys were studied systematically. The results obtained by XRD, SEM and TEM indicate that the as-cast and quenched alloys mainly consist of two major phases the and and a residual phase LaNi. With increasing Mn content in the alloys, the abundance of the phase decreases and that of the phase increases and both the lattice parameters and the cell volumes of major phases and increase. The as-quenched alloys display a nanocrystalline structure, and the grain sizes of the alloys are in a range of 20–30nm. The results by the electrochemical measurements indicate that the discharge capacities of the as-cast and quenched alloys first increase and then decrease with the variety of Mn content and obtain the maximum values for a Mn content of . The substitution of Mn for Ni clearly improves the high rate discharge abilities (HRDs) and the activation capabilities of the as-cast and quenched alloys, but it slightly impairs the cycle stabilities of the as-cast and quenched alloys. [Copyright &y& Elsevier]

Abstract: A new La–Mg–Ni system (PuNi3-type) La0.7Mg0.3Co0.45Ni2.55−x M x (M=Cu, Al, Mn; x =0, 0.1, 0.2, 0.3, 0.4) electrode alloys were prepared by casting and rapid quenching. The effects of element substitution and rapid quenching on the microstructures and electrochemical performances of the alloys were investigated. The results obtained by XRD, SEM and TEM show that the alloys have a multiphase structure, including the (La, Mg)Ni3, the LaNi5 and the LaNi2 phases. The substitution of Cu for Ni promotes the formation of an amorphous phase in the as-quenched alloy, and a reversal result produced by the substitution of Al for Ni. The electrochemical measurement indicates that the element substitution decreases the discharge capacity of the alloys, whereas it obviously improved the cycle stability of the alloys. The positive influence of three kinds of substitution elements on the cycle life of the alloys is in the sequence Al>Cu>Mn, and the negative influence on the discharge capacity in the sequence Al>Mn>Cu. [Copyright &y& Elsevier]

The electrode alloys were prepared by mechanical alloying (MA). Mg in the alloy was partially substituted with Zr in order to improve the electrochemical characteristics of the -type alloy. The microstructures and the electrochemical characteristics of the experimental alloys were measured systemically. The effects of substituting Mg with Zr as well as the relevant MA technique on the microstructures and electrochemical performances of the alloys were investigated in detail. The results show that the substitution of Zr is favourable for the formation of an amorphous phase. The electrochemical measurement indicated that the substitution of Zr can dramatically enhance the discharge capacity and cycle stability, and it markedly improves the discharge voltage characteristic of the alloys. For a fixed alloy, the electrochemical performances, including the cycle stability, the discharge voltage characteristic and discharge capacity, of the alloys were significantly improved with the increase of the ball-milling duration. [Copyright &y& Elsevier]

Abstract: In order to improve the cycle stability of La–Mg–Ni system (PuNi3-type) hydrogen storage alloy, Ni in the alloy was partially substituted by Al, and La0.7Mg0.3Ni2.55−x Co0.45Al x (x =0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys were prepared by casting and rapid quenching. The effects of substituting Ni with Al on the microstructures and electrochemical performances of the as-cast and quenched alloys were investigated in detail. The results obtained by XRD show that the as-cast and quenched alloys have a multiphase structure, including the (La, Mg)Ni3, the LaNi5 and the LaNi2 phases. The substitution of Al for Ni increases the amount of the LaNi2 phase in the as-cast alloys, but it has an inappreciable influence on the abundance of the LaNi2 phase in the as-quenched alloy. The results obtained by SEM and TEM indicate that the substitution of Al for Ni leads to the grains of the as-quenched alloys coarsen and restrain an amorphous phase formed in the as-quenched alloys. The results of the electrochemical measurement indicate that the capacities of the as-cast and quenched alloys monotonously decrease and their cycle stabilities significantly increase with the increase of Al content. When the amount of substitution Al for Ni increased from 0 to 0.4, the cycle life of the as-cast alloys increased from 72 to 132 cycles, and that of the as-quenched (20ms−1) alloys from 86 to 134 cycles. [Copyright &y& Elsevier]

Abstract: A new type of hydrogen storage alloy La0.7Mg0.3Ni2.55−x Co0.45Al x (x =0, 0.1, 0.2, 0.3, 0.4) with a PuNi3-type structure (R−3m) were prepared by casting and rapid quenching. The effects of the rapid quenching on the microstructures and electrochemical performances of the specimen alloys were investigated in detail. The results obtained by XRD, SEM and TEM show that the as-cast and quenched alloys have a multiphase structure, including the (La, Mg)Ni3 phase, the LaNi5 phase and the LaNi2 phase. The rapid quenching had an inappreciable influence on the phase composition of the alloys, but it obviously changed the phase abundance of the alloys. The rapid quenching can significantly improve the compositional homogeneity and markedly decrease the grain size of the alloys. The results obtained by the electrochemical measurements indicate that the rapid quenching obviously enhanced the cyclic stability of the alloys, but it decreased the discharge capacity and activation capability of the alloys. [Copyright &y& Elsevier]

Abstract: In order to improve the cycle stability of La–Mg–Ni system (PuNi3-type) hydrogen storage alloy, Ni in the alloy was partly substituted by Cu, Cr and Al, respectively. La–Mg–Ni system hydrogen storage electrode alloys La0.7Mg0.3Ni2.55−x Co0.45M x (M=Cu, Cr, Al; x =0, 0.1, 0.2, 0.3, 0.4) were prepared by casting and rapid quenching. The microstructures of the as-cast and quenched alloys were systematically determined by XRD, SEM and TEM. The obtained results show that the as-cast and quenched alloys are composed of the (La, Mg)Ni3 phase and the LaNi5 phase as well as the LaNi2 phase. The element substitution and rapid quenching have an inappreciable influence on the phase composition of the alloys, but both change the phase abundance of the alloys obviously. The results obtained by the electrochemical measurement indicated that the substitution decreased the discharge capacities of the as-cast and quenched alloys, whereas it improved the cycle stability, and the effect of three kinds of substitution elements on the cycle life of the alloys increased in the sequence Al>Cr>Cu. The rapid quenching significantly enhanced the cycle stability of the alloys, but it notably decreased the discharge capacity of the alloys. [Copyright &y& Elsevier]

Abstract: A trace of Cr was added in La–Mg–Ni based (PuNi3-type) electrode alloy and rapid quenching technique was used in order to improve its cycle stability. The electrode alloys La2Mg(Ni0.85Co0.15)9Cr x (x =0, 0.1, 0.2, 0.3, 0.4) were prepared by casting and rapid quenching, and the effects of Cr addition on the microstructures and electrochemical performances of the as-cast and quenched alloys were investigated in detail. The results obtained by XRD, SEM and TEM show that the as-cast and quenched alloys have a multiphase structure, including two main phases of (La, Mg)Ni3 and LaNi5, a residual phase of LaNi2. The Cr addition has an inappreciable influence on the phase compositions of the alloys, whereas it changes the phase abundance of the alloys. The results obtained by the electrochemical measurement indicate that the Cr addition obviously enhances the cycle stability of the as-cast and quenched alloys and leads to a different extent decrease of the discharge capacity of the alloys. When the amount of Cr addition changes incrementally from 0 to 0.4, the discharge capacity of the as-cast alloy decreases from 396.5 to 355.6mAh/g, and the cycle life increases from 72 to 97 cycles. For the as-quenched (30m/s) alloys, the discharge capacity decreases from 364.6 to 334.2mAh/g, and the cycle life increases from 100 to 131 cycles. The Cr addition improves the discharge voltage characteristic and activation capability of the as-cast alloys, but it slightly decreases the activation capability of the as-quenched alloys. [Copyright &y& Elsevier]

In order to improve the electrochemical performances of La–Mg–Ni system (PuNi3-type) hydrogen storage alloy, a trace of B was added in La2Mg(Ni0. 85Co0. 15)9 alloy. La2Mg(Ni0. 85Co0. 15)9B () hydrogen storage alloys were prepared by casting and rapid quenching. The electrochemical charging-discharging cycling lives and microstructures of the as-cast and quenched alloys were measured and analyzed. The effects of B additive on the microstructures and cycling lives of as-cast and quenched alloys were investigated in detail. The results show that the as-cast and quenched alloys are composed of the (La, Mg)Ni3 phase (PuNi3 structure), the LaNi5 phase and the LaNi2 phase. A trace of the Ni2B phase exists in the as-cast alloys containing B. The Ni2B phase in the alloys containing B nearly disappears after rapid quenching and the relative ratio of each phase in the alloys changes with the variety of the quenching rate. The addition of B obviously enhances the charging-discharging cycling stabilities of the as-cast and quenched alloys. When B content increases from 0 to 0. 2, the cycling lives of the as-cast and quenched at 20m/s alloys were increased from 72 to 94 cycles and from 86 to 104 cycles, respectively. [Copyright &y& Elsevier]

Abstract: In order to improve the cycle stability of the La–Mg–Ni system (PuNi3-type) hydrogen storage alloy, Ni in the alloy was partly substituted by Cu. Hydrogen storage alloys La0.7Mg0.3Ni2.55−x Co0.45Cu x (x =0, 0.1, 0.2, 0.3, 0.4) were prepared by casting and rapid quenching. The effects of substituting Ni with Cu and the quenching rate on the microstructures and the cycle stability of the as-cast and quenched alloys were investigated in detail. The results obtained by X-ray diffraction show that the as-cast and quenched alloys have a multiphase structure, including the (La, Mg)Ni3 phase, the LaNi5 phase and the LaNi2 phase, and the amount of the LaNi2 phase increased with the increase of the Cu content. The substitution and rapid quenching have an inappreciable influence on the phase compositions of the alloys, but both obviously changed the phase abundances of the alloys. The results derived by transmission electron microscopy confirm that the substitution of Cu for Ni is favourable for the formation of an amorphous phase in the as-quenched alloys. The results obtained by the electrochemical measurement indicate that substituting Ni with Cu improved the cycle stability. When the Cu content increases from 0 to 0.4, the cycle lives of the as-cast and rapidly solidified alloys increased from 72 cycles to 88 cycles and from 100 cycles to 122 cycles, respectively. [Copyright &y& Elsevier]

Abstract: In order to improve the cycle stability of La–Mg–Ni system (PuNi3-type) hydrogen storage alloy, Ni in the alloy was partly substituted by Al, and La0.7Mg0.3Ni2.55−x Co0.45Al x (x =0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys were prepared by casting and rapid quenching. The effects of substituting Ni with Al and rapid quenching on the microstructures and electrochemical performances of the as-cast and quenched alloys were investigated in detail. The results obtained by XRD show that the as-cast and quenched alloys have a multiphase structure, including the (La, Mg)Ni3 phase, the LaNi5 phase and the LaNi2 phase. The substitution of Al for Ni increases the amount of the LaNi2 phase in the as-cast alloys, but it has an inappreciable influence on the abundance of the LaNi2 phase in the as-quenched alloy. The results obtained by the electrochemical measurement indicate that the capacities of the as-cast and quenched alloys monotonously decrease and their cycle stabilities significantly increase with the increase of Al content. Rapid quenching leads to the decrease of the capacity and an obvious improvement of the cycle stability of the alloys. [Copyright &y& Elsevier]

Abstract: The La–Mg–Ni-based (PuNi3-type) La2Mg(Ni0.85Co0.15)9 (, Cr, Ti; ) hydrogen storage electrode alloys were prepared by casting and rapid quenching. The microstructures and electrochemical performances of the as-cast and quenched alloys were analyzed and measured. The effects of B, Cr, Ti and rapid quenching on the microstructures and electrochemical properties of the alloys were investigated in detail. The obtained results show that the as-cast and quenched alloys are composed of the (La, Mg)Ni3 phase (PuNi3-type structure) and the LaNi5 phase as well as the small amount of the LaNi2 phase. A trace of the Ni2B phase exists in the as-cast alloy containing boron, and the Ni2B phase in the alloy nearly disappears after rapid quenching. The relative amount of each phase in the alloys depends on the composition of the alloys and the quenching rate. The addition of B, Cr enhances the cycle stability of the as-cast alloys, while the addition of Ti reduces the cycle stability of the as-cast alloy. The addition of B, Cr, Ti decreases the discharge capacities of the alloys. Rapid quenching increase the cycle lives of the alloys, but the effect of rapid quenching on the discharge capacity of the alloys is different. Except the alloy containing boron, the capacities of the alloys decrease monotonously with the increase of the quenching rate. The capacity of the alloy containing boron has a maximum value with the increase of the quenching rate. The as-cast and quenched alloys have an excellent activation performance. [Copyright &y& Elsevier]

Abstract: The rare-earth-based AB5-type Mm(NiMnSiAl)4.3Co0.6−x Fe x (x =0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) hydrogen storage alloys were prepared by casting and rapid quenching. The microstructures of the as-cast and quenched alloys were analysed by XRD, SEM and TEM, and electrochemical cycle stabilities of the alloys were measured. The effects of substituting Co with Fe on microstructures and cycle stabilities of the as-cast and quenched alloys were investigated in detail. The obtained results show that the effects of substituting Co with Fe on the phase structures of the as-cast and quenched alloys are imperceptible, but its effects on cycle stabilities of the alloys are notable. Substituting Co with Fe improves slightly the cycle stabilities of the as-cast alloys, but it can significantly enhance the cycle lives of the as-quenched alloys, which is mainly attributed to the grain refinement of the alloys caused by substituting Co with Fe. [Copyright &y& Elsevier]

Abstract: The PuNi3-type La2Mg (Ni0.85Co0.15)9M x (M=B, Cr, Ti; x =0, 0.1) hydrogen storage electrode alloys were prepared by casting and rapid quenching. The electrochemical cycle stabilities and microstructures of the as-cast and quenched alloys were measured and determined. The effects of B, Cr, Ti and rapid quenching on the microstructures and electrochemical properties of the alloys were investigated in detail. The obtained results show that the as-cast alloys are composed of the (La, Mg)Ni3 phase (PuNi3-type) and the LaNi5 phase as well as a small amount of the LaNi2 phase. A trace of the Ni2B phase exists in the as-cast alloy containing boron, and the Ni2B phase in the alloy nearly disappears after rapid quenching. The relative amount of each phase in the alloys changes with varying quenching rate. The addition of B, Cr enhances the cycle stabilities of the alloys, whereas the addition of Ti reduces the cycle stabilities of the alloys. Rapid quenching increases the cycle stabilities of the alloys, the cycle stabilities of the alloys increase monotonously with the increase of the quenching rate. [Copyright &y& Elsevier]

Abstract: In order to improve the electrochemical cycle stability of La–Mg–Ni system (PuNi3-type) hydrogen storage alloy, a trace of Cr was added and rapid quenching techniques were employed. The electrochemical performances and microstructures of the as-cast and -quenched alloys were determined and measured. The effects of Cr content and quenching rate on the microstructures and electrochemical properties of the alloys were investigated in detail. The obtained results show that the as-cast and -quenched alloys are composed of the (La, Mg)Ni3 phase (PuNi3-type structure) and the LaNi5 phase as well as the LaNi2 phase. The amount of the LaNi2 phase increases with the increase of Cr content. The addition of Cr enhances the cycle stability of the as-cast and -quenched alloys, but decreases the discharge capacities of the alloys. The cycle lives of the alloys increase with the increase of the quenching rate. The as-cast and -quenched alloys have an excellent activation performance. [Copyright &y& Elsevier]

Abstract: The microstructures of the rare-earth-based AB5-type Mm(NiMnSiAl)4.3Co0.6-xFex (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6) hydrogen storage alloys were analysed by XRD, SEM and TEM, and electrochemical characteristics of the as-cast and quenched alloys were measured. The effects of substituting Co with Fe on microstructures and electrochemical characteristics of the as-cast and quenched alloys were investigated in detail. The obtained results show that the effects of substituting Co with Fe on the phase structures of the as-cast and quenched alloys are imperceptible, but its effects on electrochemical characteristics of the alloys are notable. The discharge capacities decrease, but the cycle lives of the alloys were improved with the increase of the amount of Fe substitution. Especially, substituting Co with Fe can significantly enhance the cycle lives of the as-quenched alloys, which is mainly attributed to the grain refinement caused by substituting Co with Fe. [Copyright &y& Elsevier]

In order to improve the electrochemical performance of rare-earth-based AB5-type electrode alloy, the AB5-type Mm(NiMnSiAl)4.3Co0.6-xFex (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) electrode alloys were quenched by melt-spinning. The phase structures and microstructure morphologies of the as-cast and quenched alloys were analyzed by XRD, SEM and TEM. The effects of the rapid quenching on the microstructures and electrochemical performances of the alloys were investigated in detail. The obtained results show that the as-quenched alloys have an excellent activation performance and can be completely activated through two to five charge–discharge cycles. The effect of the rapid quenching on the capacities of the alloys with Fe content x ≤ 0.2 is minor, and the capacities and high rate discharge abilities of the alloys with Fe content x > 0.2 decrease significantly with the increase of quenching rate. The cycle lives of the alloys increase greatly with the increase of the quenching rate. [Copyright &y& Elsevier]

The rare-earth Mg-based La2Mg(Ni0.85Co0.15)9Bx (x=0–0.2) hydrogen storage electrode alloys were prepared by casting and rapid quenching. The microstructures and electrochemical performances of the as-cast and quenched alloys were determined and measured systematically. The effects of boron content and quenching rate on the microstructures and electrochemical properties of the alloys were investigated in detail. The obtained results show that the as-cast and quenched alloys are composed of the (La, Mg)Ni3 phase (PuNi3-type structure), the LaNi5 phase as well as of the LaNi2 phase. A trace of the Ni2B phase exists in the as-cast alloys containing boron, and when the quenching rate is larger than 15 m/s, the Ni2B phase in the alloys nearly disappears. The relative amount of each phase in the alloys depends on the composition of the alloys and the quenching rate. The addition of boron enhances the cycle stability of the as-cast and quenching alloys, but decreases the discharge capacity of the alloys. The capacity of the alloys without boron monotonously decreases with increasing quenching rate, but for the alloys containing boron, the capacities have a maximum value when varying the quenching rate. The cycle lives of the as-quenched alloys increase with increasing quenching rate. The as-cast and quenched alloys have an excellent activation performance. [Copyright &y& Elsevier]

In order to modify the electrochemical characteristics of low-Co AB5-type electrode alloy, the low-Co AB5-type Mm(NiCoMnAl)5Bx (x=0, 0.1, 0.2, 0.3, 0.4) electrode alloys were quenched by melt-spinning. The phase structure and microstructure morphologies of the as-cast and quenched alloys were analysed and examined by XRD and SEM. The effects of rapid quenching on the microstructures and the electrochemical characteristics of low-Co AB5-type electrode alloys were investigated in detail. The obtained results showed that the as-quenched alloys have an excellent activation performance and can be activated through 2–5 charge–discharge cycles. Rapid quenching can enhance the discharge capacity of the alloys in a certain range of quenching rate. The discharge capacity of the as-quenched alloy was lower than that of the as-cast alloy when the quenching rate is higher than some critical value. The critical quenching rate depends on the compositions of the alloys. The cycle life of the alloys monotonously increased with increasing of quenching rate. [Copyright &y& Elsevier]