TAN YiDalian University of Technology
,
Dalian
,
ChinaSHINODA THitachi Research Laboratory
,
Hitachi Ltd. 391-12 Hitachi
,
JapanMISHIMA YTokyo Institute of Technology
,
Nagatuta. Midori-Ku
,
Yokohama 227
,
JapanSUZUKI TDepartment of Metallurgical Engineering
,
Tokyo Institute of Technology. Ookayama
,
Meguro-Ku
,
Tokyo 152
,
Japan
金属学报(英文版)
The effects of boron addition on defect hardening at room temperature and on high temperature creep properties are investigated in the B2 NiAl intermetallic compound. It is found that boron addition is effective on increasing the room temperature hardeness on the Ni-rich side but it has no effect on the A1-rich side of stoichiometry. These observations are attributed to interstitial dissolution of boron in Ni-rich NiAl and to a lack of solubility and also due to an enrichment at grain boundaries on the A1-rich side. The similar effect is found in high temperature creep resistance of NiAl by boron addition. The high temperature creep resistance increases on the Ni-rich side but it does not affect the A1-rich side of off-stoiciometry.
关键词:
International Journal of Hydrogen Energy
Mg76T12Fe12-xNix (x = 0, 4, 8, 12) alloys were prepared by mechanical alloying and the hydrogen storage properties were investigated C systematically. In Mg76Ti12Fe12 and Mg76Ti12Ni12Ti12 alloys, the main binary alloy phase is Fe2Ti and Mg2Ni, respectively. There are same binary alloy phase structures included Fe2Ti, Mg2Ni and NiTi in Mg(76)Ti(12)Fc(8)Ni(4) and Mg76Ti12Fe4Ni8 alloys. For Mg76Ti12Fe12-xNix (x = 0, 4, 8, 12) alloys, the hydrogen storage capacity is 2.88, 3.31, 3.12 and 2.24 wt%, respectively. The hysteresis between hydrogen absorption and desorption decreases gradually with increasing the amount of substitution Ni for Fe. Mg76Ti12Fe8Ni4 shows the highest hydrogen absorption and desorption rate among Mg76Ti12Fe12-xNix (x = 0, 4, 8, 12) alloys. Fe and Ni coexistence is favorable to improve hydrogen storage properties. For Mg76Ti12Fe8Ni4 alloy, the amorphous degree increase with the milling time, and the amorphous degree increase is unfavorable to improve hydrogen storage capacity. (C) 2006 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.
关键词:
hydrogen storage alloy;thermodynamic performances;hydrogen storage;properties;mg-ni;hydriding properties;ti;atmosphere;systems;mn
Scripta Materialia
We report the nonlinear elastic deformation behaviour of Ti-30Nb-12Zr alloys containing varying amounts of oxygen and/or nitrogen. These alloys feature an electron/atom (e/a) ratio of similar to 4.19, in between the eta values of two groups of multifunctional titanium alloys reported previously (Gum Metal similar to 4.24 and Ti2448 similar to 4.15), and thus demonstrate an independence of the nonlinear elasticity on the e/a ratio. This study also found that the nonlinear elasticity persists in this type metastable beta titanium alloys regardless of the presence of a small amount of other phases such as alpha, alpha '' and omega. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
关键词:
Titanium alloys;Interstitials;Metastable phases;Elastic behavior;gum metal;biomedical applications;youngs modulus;superelasticity;mechanism;zr;sn
Solid State Communications
Accompanied by a second-order paramagnetic to ferromagnetic transition, a large reversible negative Delta S(m) above room temperature has been observed in Ni(50-x)Mn(38+x)Sb(12) alloys besides low-field magnetic entropy change Delta S(m) around/below room temperature. A -Delta S(m)(max) of 5.21 J kg(-1) K(-1) is acquired at 347 K in nominal Ni(49)Mn(39)Sb(12) alloy for a magnetic-field change from 0 to 5 T, with a refrigerant capacity of 184 J kg(-1). The large reversible Delta S(M) and the high reversible refrigerant capacity indicate that Ni(49)Mn(39)Sb(12) alloy may be a promising candidate for magnetic refrigeration above room temperature. (C) 2010 Elsevier Ltd. All rights reserved.
关键词:
Magnetically ordered materials;Thermodynamic properties;Phase;transition;induced shape recovery;room-temperature;transition
Solid State Communications
The structure and electronic transport properties have been investigated for composite PbO2-1/12Ag(2)O-xC (0 less than or equal to x less than or equal to 2) materials prepared by mechanical milling in an O-2 atmosphere. The solid-state reactions result in the occurrence of abundant phase transformations, when the graphite content increases. With the phase transformations occurring, the percolation effect is observed for the electronic transport of PbO2-1/12Ag(2)O-xC system, while its conductivity undergoes an insulator-metal transition. The percolation threshold is determined by DC conductivity measurement and analysis of X-ray diffraction patterns. (C) 2003 Elsevier Science Ltd. All rights reserved.
关键词:
the PbO2-1/12Ag(2)O-xC system;electronic transport;percolation effect
Electrochimica Acta
Electrochemical noise technique coupled with SEM was used to study the corrosion process of LY12-T3 in the modulated EXCO test solution, and the EN data were analyzed by wavelet technique based on orthogonal db4 wavelet. The results show that, under the experimental conditions, the characteristics of energy distribution plot (EDP) obtained from wavelet analysis technique can be used as "fingerprints" of EN signal and can be used to differentiate the corrosion type. With the change of corrosion type of LY12-T3 from pitting corrosion through intergranular corrosion to exfoliation corrosion, the maximum relative energy defined in EDP will change from the region of crystal series coefficients with smaller scales through middle scales to larger scales. (C) 2005 Elsevier Ltd. All rights reserved.
关键词:
electrochemical noise;wavelet transform;localized corrosion type;impedance spectroscopy;exfoliation corrosion;aluminum;alloys
Corrosion Science
The process of the double layer rare earth metal (REM) conversion coating on aluminum alloy LY12 (2024) was introduced in this paper. The corrosion resistance of REM conversion coating was examined by electrochemical impedance spectroscopy. The results showed that the coating increased the corrosion resistance (R,) of the alloy surface, thus reducing the driving force of corrosion. The morphologies of the coating were studied by scanning electron microscope. The results revealed that the coating consisted of layers of spherical particles with different size, which grew gradually to cover the surface of aluminum alloy. The X-ray diffraction analysis revealed that the film was amorphous. The results of X-ray photoelectron spectroscopy indicated that the film consisted of cerium(III and IV) oxide and cerium(III and IV) hydroxide. (C) 2001 Elsevier Science Ltd. All rights reserved.
关键词:
rare earth metal conversion coating;corrosion resistance;morphology;amorphous;composition;film-forming inhibitors;corrosion protection;surface modification
International Journal of Fatigue
Crack closure of physical short and long cracks of LY12CZ aluminum alloy during fatigue process was investigated using acoustic emission (AE) technique. Results showed that the effective fatigue crack growth curve (da/dN vs. Delta K(eff)) of physical short and long cracks obtained by the AE technique was consistent with the effective fatigue crack growth Curve at high stress ratio (R = 0.8), which implied that the AE technique Could measure the crack closure level, especially for physical short crack. The growth rate of physical short crack was Much higher than that of long crack at the same Delta K, and the lower crack Closure level of short crack was the main reason. (C) 2008 Elsevier Ltd. All rights reserved.
关键词:
Crack Closure;Physical short crack;Acoustic emission;Aluminum alloy;LY12CZ;finite-element-analysis;threshold
Composites Science and Technology
Hydrostatic extrusion of a Zr(38)Ti(17)Co(10.5)Co(12)Be(22.5) bulk metallic glass/porous tungsten phase composite was perform ed, and the dynamic compressive deformation and fracture behavior of the as-extruded composite we. re investigated in detail at room temperature by means of the Split Hopkinson Pressure Bar (SHPB). In comparison with the as-cast composite, the as-extruded composite presented a much higher flow stress without sacrificing plasticity under dynamic compression,. exhibiting ductility increment, but evidence of work softening was observed. The specimen for the as-extruded composite failed by axial splitting with occasional shear fracture in some regions. It is suggested that the increase in flow stress and ductility of the as-extruded composite is attributed to the extrusion process which introduced hardened condition and texture in the tungsten phase as well as the 3D net structure of the porous tungsten phase. The work softening mechanism, Wears to be essentially associated with the large number of microcracks and voids under dynamic compression. (C) 2008 Elsevier Ltd. All rights reserved.
关键词:
Amorphous materials;Mechanical properties;Fractography;Extrusion;polycrystalline tungsten;mechanical-properties;fracture-toughness;glass composites;amorphous-alloys;ductility
Intermetallics
Fe(65.5)Cr(4)Mo(4)Ga(4)P(12)C(5)B(5.5) bulk amorphous rectangular bars with a cross-section of 2 x 2 mm(2) and a length of 30 mm were produced by copper mold casting. The as-cast bars as well as annealed samples were investigated by compression and Vickers hardness tests. The fracture strength for the as-cast samples sigma(f) is 2.8 GPa and the fracture strain epsilon(f) is 1.9%. Upon annealing at 715 K for 10 min, i.e. at a temperature below the calorimetric glass transition, the fracture strain drops to 1.6% and no plastic deformation is observed. The Vickers hardness HV for the as-east samples is about 885, and increases to 902 upon annealing. The fracture behavior of this Fe-based bulk glassy alloy is significantly different in comparison with the well-studied Zr-, Cu- or Ti-based good glass-formers. The fracture is not propagating along a well-defined direction and the fractured surface looks irregular. Instead of veins, the glassy alloy develops a high number of microcracks. (c) 2005 Elsevier Ltd. All rights reserved.
关键词:
glasses, metallic;fracture stress;mechanical testing;c-b alloys;magnetic-properties;amorphous-alloys;high-strength;ti
