D. Ferguon
,
W. N. Chen and H. Ferguson (Dynamic Systems Inc. Poestenkill
,
NY 12140
,
USA)
金属学报(英文版)
Ultrafine grain size is often achieved by severe plastic deformation. A few techniques have been devel- oped to achieve severe plastic deformation,such as equal channel angular (ECA ) processing, torsion, and accumulative roll bonding (ARB) techmpues. This paper will introduce a moftiaxis deformation technique which can achieve essentially unlimited strain with constant deformation volume. The mul- tiaxis deformation can be fully restrained or unrestrained.The bulk volume of a multiaxis restraint compression specimen can be easily machined into mechanical testing specimens for mechanical property measurement and other studies.
关键词:
ultrafine grain
,
null
,
null
Journal of Physical Chemistry C
The Li-Mg-N-H system was prepared by reacting magnesium amide [Mg(NH(2))(2)] with lithium nitride (Li(3)N) and investigated with regard to the hydrogen storage properties. Our study shows that the present method is superior to the conventional route in enhancing the reversible dehydrogenation properties. Through optimizing the Li(3)N:Mg(NH(2))(2) ratio in the starting materials, the reversible capacity of U-Mg-N-H system increases to 4.9 wt %, 18% higher than that typically obtained from the Mg(NH(2))(2) + 2LiH mixture at 200 degrees C. Furthermore, increasing the Li(3)N:Mg(NH(2))(2) ratio is effective for mitigating the ammonia release from thus-prepared samples. Combined property/structure investigations indicate that the obtained enhancements should be ascribed to the effects of LiNH(2) and LiH that were in situ generated from the excess Li(3)N. LiNH(2) may promote the dehydrogenation reaction via seeding the reaction intermediate. The concurrently generated LiH acts as an effective ammonia trapping agent. These findings highlight the potential of "intermediate seeding" as a strategy to enhance the reversible hydrogen storage properties of metal-N-H systems.
关键词:
complex hydrides;ultrafast reaction;amide;improvement;desorption;linh2;destabilization;mechanism;mixtures;imides
材料科学技术（英文）
The dynamic tensile deformation and fracture behavior of the Zr-based metallic glass/porous W phase composite were investigated at room temperature by means of the Split Hopkinson Tension Bar (SHTB) It was found that the composite exhibited no appreciable macroscopic plastic deformation prior to catastrophic fracture and the fracture surface was perpendicular to the axial direction Substantive micro cracks were observed along the interface between W grains or the interface between the metallic glass phase and the W phase Scanning electron microscopy (SEM) observations revealed that vein-like patterns dimple-like patterns and substantive ridge-like structures were the typical fracture morphologies on the fracture surface for the metallic glass phase and the morphology of the W phase is a mixture of intergranular and transgranular fracture Based on those results referred above the dynamic tensile deformation and fracture mechanism of the Zr-based metallic glass/porous W phase composite were discussed in detail
关键词:
Metallic glasses;Porous W;Composite;Dynamic tension;Fracture;behavior;glass matrix composites;bulk amorphous-alloys;mechanical-properties;deformation-behavior;fracture-toughness;shear bands;propagation;tungsten;failure
Materials Characterization
This paper describes work performed to determine some of the properties of the electroless Ni-W-P amorphous deposits. Phosphorus contents were varied up to 32 at.%, and the amorphous structure was found to be present at phosphorus contents above 5 at.%. Irrespective of P content, all the deposits exhibited excellent adhesion to metallic substrates. The addition of even small amounts of W provided greatly increased hardness compared with the plain Ni-P deposits. The wettability properties of the Ni-W-P deposits were found to be comparable to those of Ni-P and N-B-P deposits but inferior to those of Ni-B deposits. (C) Elsevier Science Inc., 1996
关键词:
nickel
Scripta Materialia
Dynamic strain aging (DSA) in a newly developed Ni-Co superalloy, TMW-2, was examined at temperatures ranging from room temperature to 600 degrees C and strain rates between 3 x 10(-2) and 8 x 10(-5) s(-1). The alloy exhibited both normal and inverse DSA effects at the temperatures and strain rates tested. Transmission electron microscopy evidence suggests that the normal behavior is associated with conventional DSA due to dynamic dislocation-solute interaction, while the inverse behavior may be related to the occurrence of stacking faults. Crown Copyright (C) 2010 Published by Elsevier Ltd. on behalf of Acta Materialia Inc. All rights reserved.
关键词:
Forming processes-forging;Tension test;Nickel alloys;Dynamic strain;aging;alloys;behavior;flow
Materials Characterization
Dendritic coarsening of gamma' was investigated in a directionally solidified Ni-base superalloy during exposure at 1173 K for 24,000 h. Chemical homogeneity along different directions and residual internal strain in the experimental superalloy were measured by electronic probe microanalysis (EPMA) and electron back-scattered diffraction (EBSD) technique. It was indicated that the gradient of element distribution was anisotropic and the inner strain between dendrite core and interdendritic regions was different even after 24,000 h of exposure at 1173 K, which influenced the kinetics for the dendrite coarsening of gamma' phase. (C) 2010 Elsevier Inc. All rights reserved
关键词:
Superalloy;Coarsening;Exposure;Segregation;ni-base superalloy;evolution;field
