scholarly journals Enhancement of the Hydrogenation and Dehydrogenation Characteristics of Mg by Adding Small Amounts of Nickel and Titanium

2021 ◽  
Author(s):  
Myoung Youp SONG ◽  
Young Jun KWAK
Keyword(s):  
Solid Solution ◽  
Hydrogen Absorption ◽  
Active Sites ◽  
Hydrogen Atmosphere ◽  
Solution Phase ◽  
Solid Solution Phase ◽  
Transition Elements ◽  
Hydrogenation Rate ◽  
Reactive Milling ◽  
Complex Hydrides

We compared the hydrogenation and dehydrogenation properties of Mg-based alloys to which small amounts of transition elements (Ni and Ti), halides (TaF5 and VCl3), and complex hydrides (LiBH4 and NaAlH4) were added through grinding in a hydrogen atmosphere (reactive milling). Mg-1.25Ni-1.25Ti is one of the samples compared, having a composition of 97.5 wt.% Mg + 1.25 wt.% Ni and 1.25 wt.% Ti. Even though Mg-1.25Ni-1.25Ti did not have the highest initial hydrogenation rate, it had the largest quantities of hydrogen absorbed and released for 60 min and the highest initial dehydrogenation rate. In addition, Mg-1.25Ni-1.25Ti did not show the incubation period in the dehydrogenation. We thus investigated the hydrogenation and dehydrogenation properties of Mg-1.25Ni-1.25Ti in more detail. Activated Mg-1.25Ni-1.25Ti absorbed 5.91 wt.% H in 12 bar H2 and released 5.80 wt.% H in 1.0 bar H2 at 593 K for 60 min at n = 3. For 5 wt.% hydrogen absorption by Mg-1.25Ni-1.25Ti, 18.7 min was required at 593 K in 12 bar H2 at n = 3. Although only small amounts of Ni and Ti were added, the hydrogenation and dehydrogenation properties of Mg were greatly improved. Ni and Ti-added Mg had a higher initial dehydrogenation rate and a larger Hd (60 min) than only Ni-added Mg, suggesting that the TiH1.924 and NiTi formed in Mg-1.25Ni-1.25Ti play roles in the increases in the initial dehydrogenation rate and Hd (60 min), probably acting as active sites for the nucleation of the Mg-H solid solution phase.

Transition alpha structure in beta-isomorphous Nb-Hf alloys

1987 ◽  
Vol 45 ◽  
pp. 232-233
Author(s):  
R.W. Carpenter ◽  
Changhai Li ◽  
David J. Smith
Keyword(s):  
Solid Solution ◽  
Solution Phase ◽  
Miscibility Gap ◽  
Large Strains ◽  
Solid Solution Phase ◽  
Two Phase ◽  
Diffuse Intensity ◽  
Metastable Form ◽  
The Matrix ◽  
Equilibrium Morphology

Binary Nb-Hf alloys exhibit a wide bcc solid solution phase field at temperatures above the Hfα→ß transition (2023K) and a two phase bcc+hcp field at lower temperatures. The β solvus exhibits a small slope above about 1500K, suggesting the possible existence of a miscibility gap. An earlier investigation showed that two morphological forms of precipitate occur during the bcc→hcp transformation. The equilibrium morphology is rod-type with axes along <113> bcc. The crystallographic habit of the rod precipitate follows the Burgers relations: {110}||{0001}, <112> || <1010>. The earlier metastable form, transition α, occurs as thin discs with {100} habit. The {100} discs induce large strains in the matrix. Selected area diffraction examination of regions ∼2 microns in diameter containing many disc precipitates showed that, a diffuse intensity distribution whose symmetry resembled the distribution of equilibrium α Bragg spots was associated with the disc precipitate.

Non-equilibrium Ti-Fe bulk alloys with ultra-high strength and enhanced ductility

2004 ◽  
Vol 851 ◽  
Author(s):  
Dmitri V. Louzguine-Luzgin ◽  
Larissa V. Louzguina-Luzgina ◽  
Hidemi Kato ◽  
Akihisa Inoue
Keyword(s):  
Solid Solution ◽  
Supersaturated Solid Solution ◽  
High Strength ◽  
Eutectic Structure ◽  
Solution Phase ◽  
Solid Solution Phase ◽  
Mechanical Fracture ◽  
Glassy Alloys ◽  
Fe Alloys ◽  
Bulk Alloys

ABSTRACTThe high-strength and ductile hypo-, hyper- and eutectic Ti-Fe alloys were formed in the shape of the arc-melted ingots with the dimensions of about 25–40 mm in diameter and 10–15 mm in height. The structure of the samples consists of cubic Pm 3 m TiFe and BCC Im 3 m β-Ti supersaturated solid solution phase. The arc-melted hypereutectic Ti65Fe35 alloy has a dispersed structure consisting of the primary TiFe phase and submicron-size eutectic structure. This alloy exhibits excellent mechanical properties: a Young's modulus of 149 GPa, a high mechanical fracture strength of 2.2 GPa, a 0.2 % yield strength of 1.8 GPa and 6.7 % ductility. The hard round-shaped intermetallic TiFe phase and the supersaturated β-Ti solid solution result in a high strength of the Ti65Fe35 alloy which in addition has much higher ductility compared to that of the nanostructured or glassy alloys. The reasons for the high ductility of the hypereutectic alloy are discussed.

Nanocrystalline Ni-30wt%Fe Supersaturated Solid Solution Synthesized by Mechanical Alloying

2014 ◽  
Vol 490-491 ◽  
pp. 38-42
Author(s):  
Yu Chen ◽  
Yang Yu ◽  
Wen Cong Zhan ◽  
Er De Wang
Keyword(s):  
Solid Solution ◽  
Crystallite Size ◽  
Powder Mixture ◽  
Supersaturated Solid Solution ◽  
Average Crystallite Size ◽  
Solution Phase ◽  
Elemental Powder ◽  
Solid Solution Alloy ◽  
Solid Solution Phase ◽  
Elemental Powder Mixture

Ni-30wt%Fe elemental power mixture was mechanically milled under argon atmosphere for variuos times up to 25h.The evolution of Ni-Fe alloying during milling and the microstructure of the as-milled powders were characterized by XRD, EPMA (electron probe microanalysis), SEM and TEM, respectively. The results show that nanocrystalline Ni (Fe) supersaturated solid solution alloy powders with 30wt. % Fe in composition can be synthesized by mechanical milling of the elemental powder mixture. Both the content of Fe dissolved and the microstrain developed in the as-synthesized Ni (Fe) solid solution phase increase, while the crystallite size decreases, steadily with increasing milling time. In particular, the Ni-30wt%Fe alloy powders obtained by 25h milling consist of a single Ni (Fe) supersaturated solid solution phase with average crystallite size of about 15nm and accumulated microstrain as high as 1.12%. DSC tests show that the nanocrystalline Ni-30wt%Fe alloy powders have a lower melting temperature than the elemental powder mixture, attributed to the unique Ni (Fe) solid solution phase structure, the nanocrystallization, and the high strain energy.

Interaction between Two Ni-Base Alloys and Ceramic Moulds

2013 ◽  
Vol 747-748 ◽  
pp. 765-771 ◽  
Author(s):  
Jian Sheng Yao ◽  
Ding Zhong Tang ◽  
Xiao Guang Liu ◽  
Cheng Bo Xiao ◽  
Xin Li ◽  
...  
Keyword(s):  
Solid Solution ◽  
Interface Reaction ◽  
Vapour Phase ◽  
Optical Microscope ◽  
Solution Phase ◽  
Solid Solution Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Scanning Electron ◽  
Reaction Surfaces

The interfacial reactions between ceramic moulds and DZ417G and DZ125 superalloys were investigated. The microstructure and composition of the interface region were observed by optical microscope, X-ray diffraction and scanning electron microscope with energy dispersive spectroscopy. The results showed that (Al1-xCrx)2O3solid solution phase with pink color was formed from the dissolution of Cr2O3and Al2O3and vapour phase, which was transferred to the reaction surfaces. The reaction layer thicknesses of DZ417G and DZ125 alloys were about in the range of 40-50μm. The interface reaction product between DZ417G alloy and ceramic mould was TiO2and the product between DZ125 alloy and ceramic mould was HfO2.

Discovery of a thermally persistent h.c.p. solid-solution phase in the Ni-W system

2014 ◽  
Vol 116 (8) ◽  
pp. 083515 ◽  
Author(s):  
S. J. B. Kurz ◽  
S. B. Maisel ◽  
A. Leineweber ◽  
M. Höfler ◽  
S. Müller ◽  
...  
Keyword(s):  
Solid Solution ◽  
Solution Phase ◽  
Solid Solution Phase

High Temperature Compression Properties of Ni3(Si,Ti) Based Intermetallic Compounds

2014 ◽  
Vol 783-786 ◽  
pp. 1129-1135
Author(s):  
Takehito Hagisawa ◽  
Hirokazu Madarame ◽  
Shinji Tanaka ◽  
Yasuyuki Kaneno ◽  
Takayuki Takasugi
Keyword(s):  
Heat Treatment ◽  
Solid Solution ◽  
High Temperature ◽  
Strain Rate ◽  
Volume Fraction ◽  
Solution Phase ◽  
Solid Solution Phase ◽  
Ti Alloy ◽  
Compression Properties ◽  
Ti Alloys

High temperature compression properties of Al-, Cr-or Nb-added Ni3(Si,Ti) based intermetallic compounds were investigated by uni-axial compression test and microstructural observation. The Al-or Cr-added Ni3(Si,Ti) alloys after homogenization heat treatment exhibited a two-phase microstructure consisting of L12and Ni-solid solution phases. The Nb-added Ni3(Si,Ti) alloy after homogenization heat treatment exhibited a triple-phase microstructure consisting of G-phase with D8a structure and Ni-solid solution phase in the L12matrix. The volume fraction of Ni-solid solution phase increased in order of Cr-, Nb-and Al-added Ni3(Si,Ti) alloys. The Cr-added Ni3(Si,Ti) alloy was deformable at high strain rate, while the Nb-added one was deformable at low strain rate. It can be considered that the deformability of Ni3(Si,Ti) at high temperature is closely correlated with volume fraction of Ni-solid solution phase and recrystallization behavior.

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