Bin ZHAO
,
Kuiwei GENG
,
Fei ZENG
,
Feng PAN
材料科学技术（英文）
The Ni80Nb20 films were prepared by ion beam assisted deposition (IBAD) with various Ar+ ion energies. A phase evolution of fcc→amorphous→Ni+Nb→Ni+hcp was observed with the increasing of ion beam energy from 2 keV to 8 keV. When bombarded by Ar+ ions of 8 keV during deposition, a new crystalline phase with hcp structure was obtained, of which the lattice parameters are a=0.286 nm and c=0.483 nm, different from those of the similar A3B-type hcp phase previously reported. The experimental results were discussed in terms of thermodynamics and restricted kinetic conditions in the far-from-equilibrium process of IBAD. The formation of hcp phase may also be related to the valence electron effect.
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Hcp phase
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Bin ZHAO
,
Jiansheng WU
,
Zhonghou LI
,
Xiaoping LIU
,
Zhong XU
材料科学技术（英文）
Due to the slow cooling rate in the alloying furnace, large amount of brittle precipitates appear in the alloyed layers which are formed by the DGPSA (Double Glow Plasma Surface Alloying) with tungsten-molybdenum. It causes the mechanical properties of the samples to be seriously degraded. Qualitative phase analysis reveals that they are mainly composed of the p-phase, and a small amount of carbide, M6C. In this paper the microstructure and thermodynamic factors of the precipitates are exhaustively investigated. There are two transformation noses in the isothermal transformation (IT) diagram of the precipitates. As a major object of this work, an effective measure is offered to depress the deposition of the precipitates.
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