Rongshi CHEN
,
Jianting GUO
,
Wenlong ZHOU
,
Liangyue XIONG
材料科学技术（英）
In order to understand the point defect structure in NiAl Intermetallic compound, the positron lifetime in binary Ni100-xAlx (53 greater than or equal to x greater than or equal to 45) and ternary B2 Ni50-xCoxAl50 (x=0, 5, 10, 15) intermetallic compounds as a function of composition were measured. It is shown that the positron lifetime spectra of these compounds can be consistently expressed by single-component lifetimes. The positron lifetime value in ternary Ni50-xCoxAl50 alloy is independent of Co content and equal to that detected in both stoichiometric and Al-rich NiAl. From an analysis of the present results, it is suggested that the constant lifetime of tau approximate to 180 ps should be ascribed to saturation trapping and annihilation of positron exclusively at Ni vacancy, no evidence for the presence of Al vacancy is available.
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Rongshi CHEN
,
J.J.Bl
,
in
,
M.Sue'ry
,
Qudong WANG
,
Enhou HAN
材料科学技术（英）
The effect of extrusion on grain refinement has been studied in the AZ91 cast ingots. It is found that grain size smaller than 10μm can be obtained by the extrusion processing. Vickers hardness measurements were also carried out to evaluate the effect of these processes on the room temperature mechanical properties. ...
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Magnesium alloy
,
null
Rongshi CHEN
,
Jianting GUO
,
Jiyang ZHOU
材料科学技术（英）
The microstructure of multiphase Ni-25Al-15Cr (at. pct) intermetallic alloy consists of dendritic arms (β-NiAl phase) and interdendritic regions (γ/γ´ two phases) under homogenization followed by air cooling condition. Furnace cooling following homogenization does not significantly influence its microstructure. However, the effects of aging treatment on the microstructure strongly depend on cooling rates following homogenization. A single phase g´ layer with a α-Cr `spouse' layer is observed surrounding the dendritic arms, the formation of this ‘couple’ is attributed to a four-phase invariant quasi-peritectoid, i.e: β+γ=γ´+α-Cr .
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