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Shenzhen, China

Sheng L.Y.,PKU HKUST Shenzhen Hong Kong Institution | Sheng L.Y.,Peking University | Yang F.,Shenzhen Airlines | Xi T.F.,Peking University | And 2 more authors.
Intermetallics | Year: 2012

The NiAl-Cr(Nb)/Dy alloy was fabricated by conventionally casting and rapid solidification and treated by hot isostatic pressing treatment (HIP). The results reveal that Cr 2Nb phase contains much of Ni and Al elements and retains the C14 crystal structure at room temperature. The rapid solidification refines the NiAl phase, Cr 2Nb phase and needle-like Cr 2Nb precipitates in NiAl matrix. Moreover the rapid solidification increases α-Cr phase and results in the formation of Cr 7Ni 3 phase with stacking faults and microtwins inside. The HIP treatment transforms the needle-like Cr 2Nb precipitate in the NiAl phase into sphere shape and blunts the tip of the Cr 2Nb phases along the NiAl phase boundary. In addition, the HIP treatment leads to some moveable dislocations in the alloy, which is beneficial to the compressive ductility. The mechanical test shows the rapidly solidified alloy with HIP treatment has the best mechanical properties, whose compressive ductility is more than ten times that of the as cast alloy. © 2012 Elsevier Ltd. All rights reserved. Source


Sheng L.-Y.,Peking University | Yang F.,Shenzhen Airlines | Guo J.-T.,CAS Shenyang Institute of Metal Research | Xi T.-F.,Peking University
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2014

A nickel-based superalloy with good corrosion resistance was fabricated by directional solidification, and its microstructure and tensile properties at elevated temperatures were investigated. Microstructure observations reveal that the γ′ precipitates are arrayed in the γ matrix regularly with some MC, Ni5Hf and M3B2 particles distributed along the grain boundary. The tensile tests exhibit that the tensile properties depend on temperature significantly and demonstrate obvious anomalous yield and intermediate-temperature brittleness (ITB) behavior. Below 650 °C, the yield strength decreases slightly but the ultimate tensile strength almost has no change. When the temperature is between 650 °C and 750 °C, the yield and ultimate tensile strengths rise rapidly, and after then they both decrease gradually with temperature increasing further. The elongation has its minimum value at about 700 °C. The TEM examination exhibits that sharing of the γ′ by dislocation is almost the main deformation mechanism at low temperatures, but the γ′ by-pass dominates the deformation at high temperatures. The transition temperature from shearing to by-pass should be around 800 °C. The anomalous yield and intermediate-temperature brittleness behaviors should be attributed to the high content of γ′. In addition, the carbides and eutectic structure also contribute some to the ITB behaviors of the alloy. © 2014 The Nonferrous Metals Society of China. Source


Sheng L.Y.,Peking University | Sheng L.Y.,PKU HKUST Shenzhen Hong Kong Institution | Yang F.,Shenzhen Airlines | Xi T.F.,Peking University | And 2 more authors.
Composites Part B: Engineering | Year: 2011

A copper/aluminum/copper sandwich clad sheet was fabricated by means of cold rolling process and heat treated with different temperature and time. The Al/Cu interface and its bond strength were investigated by SEM, TEM and peeling test. The results reveal that low temperature heat treatment can improve the morphology of Al/Cu interface and increase its bond strength. However high temperature and long time result in the formation of Al2Cu intermetallic compound layer, which is detrimental to the bond strength, and moreover, small Al2O3 particles precipitate along the Al2Cu and Al interface. When the interlayer along Al/Cu interface grows to a certain thickness, the effect of heat treatment temperature and time become weak. For the present study, the reasonable heat treatment may be 423 K and 20 h. © 2011 Elsevier Ltd. All rights reserved. Source


Sheng L.Y.,Peking University | Yang F.,Shenzhen Airlines | Xi T.F.,Peking University | Guo J.T.,CAS Shenyang Institute of Metal Research
Journal of Alloys and Compounds | Year: 2013

NiAl-TiC-Al2O3 composite was fabricated by self-propagation high-temperature synthesis with extrusion technique. Its microstructure, compressive properties and wear behavior at 873, 973, 1073 and 1173 K were investigated. The results reveal that the NiAl-TiC-Al 2O3 composite exhibits self-lubricating behavior and excellent wear resistance properties at 973 K, which should be ascribed to the lubricant film formed on the surfaces of the NiAl-TiC-Al2O 3 composite and SiC friction pair during the sliding wear test. TEM observation shows that the lubricant film is composed of amorphous and NiO and Al2O3 nanoparticles, while the matrix adjacent to the lubricant film mainly contains NiAl and Ni3Al nanocrystalline. While at 873, 1073 and 1173 K, lubricant film on the composite surface is spalled partly or greatly, which results in the increase of the friction coefficient and the wear rate. In summary, the NiAl-TiC-Al2O3 composite could form the lubricant film at high temperature and possess good wear resistance. © 2012 Elsevier B.V. All rights reserved. Source


Sheng L.Y.,Peking University | Yang F.,Shenzhen Airlines | Xi T.F.,Peking University | Lai C.,Peking University | Guo J.T.,CAS Shenyang Institute of Metal Research
Materials Research Innovations | Year: 2013

In this paper, a nickel based superalloy with good corrosion resistance is fabricated by directional solidification, and its microstructure and tensile properties were investigated. Microstructure observations reveal that besides the γ′ precipitates and γ matrix, some MC, Ni5Hf and M3B2 particles precipitate along the grain boundary. Tensile tests exhibit that the alloy has obvious anomalous yield and intermediate temperature brittleness (ITB) behaviour. The tensile properties depend on temperature significantly. Below 650°C, the yield strength decreases slightly but rises rapidly between 650 and 750°C, and after then, it decreases gradually with temperature increasing further. Examination by TEM exhibits that sharing of the γ′ by dislocation is almost the main deformation mechanism at low temperature, but the γ′ bypass dominates the deformation at high temperature and the transition temperature should be ~800°C. In addition, the carbides and eutectic structure contribute partly to the ITB behaviours. © W. S. Maney & Son Ltd. 2013. Source

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