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5. A high entropy alloy as very low melting point solder for advanced electronic packaging

Author

Liua, Yingxia, Pu, Li, Yang, Yong, He, Quanfeng, Zhou, Ziqing, Tan, Chengwen, Zhao, Xiuchen, Zhang, Qingshan, and Tu, K. N.

Subjects
Physics - Applied Physics, Condensed Matter - Materials Science
Abstract

SnBiInZn based high entropy alloy (HEA) was studied as a low reflow temperature solder with melting point around 80 oC. The wetting angle is about 52o after reflow at 100 oC for 10 min. The interfacial intermetallic compound (IMC) growth kinetics was measured to be ripening-control with a low activation energy about 18.0 kJ/mol, however, the interfacial reaction rate is very slow, leading to the formation of a very thin IMC layer. The low melting point HEA solder has potential applications in advanced electronic packaging technology, especially for bio-medical devices., Comment: 20 pages, 7 figures

Published
2020

13. Effects of High Al Content on the Phase Constituents and Thermal Properties in NiCoCrAlY Alloys.

Author

Zhang, Jin, Nie, Zhihua, Tan, Chengpeng, Mu, Rende, Li, Shilei, Ning, Xianjin, and Tan, Chengwen

Subjects
ELECTRON microscope techniques, METAL coating, PHASE equilibrium, ALLOYS, PHASE transitions, THERMAL barrier coatings, THERMAL properties
Abstract

MCrAlY (M = Ni and/or Co) metallic coatings are essential for the protection of hot-end components against thermal and corrosion damage. Increasing the Al content is considered a feasible solution to improve the high-temperature performance of MCrAlY coatings. In this paper, the effects of high Al contents (12–20 wt.%) on the phase constituents and cast microstructures in MCrAlY alloys were studied by high-energy X-ray diffraction and electron microscopy techniques combined with phase equilibria calculations. High Al content improved the stability of β, σ, and α phases. Meanwhile, an evolution of the cast microstructure morphology from a dendrite structure to an equiaxed grain structure was observed. The thermal properties were analyzed, which were closely related to the phase constituents and solid-to-solid phase transitions at evaluated temperatures. This work is instructive for developing high-Al-content MCrAlY coatings for next-generation thermal barrier applications. [ABSTRACT FROM AUTHOR]

Published
2024
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14. The Preparation of Ti–Ta Impedance-Graded Coatings with Limited Diffusion by Cold Spraying Combined with Hot Isostatic Pressing.

Author

Shen, Yaoning, Ning, Xianjin, Yu, Xiaodong, Li, Dongwei, Feng, Chengliang, and Tan, Chengwen

Subjects
ISOSTATIC pressing, DIFFUSION coatings, HOT pressing, COMPOSITE coating, SPRAYING, GRAIN refinement, SURFACE coatings, INTERFACIAL bonding
Abstract

Ti–Ta impedance-graded coatings were prepared using cold spraying combined with hot isostatic pressing. Compared to the general Ti–Ta binary diffusion couple, the interdiffusion coefficient of as-sprayed Ti–Ta can be increased by approximately 25 times at 1100 °C due to grain refinement at the interface of the cold-sprayed particles. By the control of interdiffusion, pure Ta and pure Ti regions can remain in the materials after hot isostatic pressing at 900 °C. Hot isostatic pressing with capsulate reduced the porosity of the material efficiently to less than 0.02%. The strength of the as-sprayed Ti–Ta composite coating was significantly improved to 990.1 MPa, and the fracture strain reached 11.5%. The strengthening mechanism of Ti–Ta composite coatings relies primarily on the hindrance of dislocation slip by phase interfaces between α and β. Moreover, the macroscopic interfacial bonding strength of the graded material exceeds 881 MPa, which is comparable to that of bulk materials. [ABSTRACT FROM AUTHOR]

Published
2024
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35. Dynamic mechanical properties of Ni-based medium-heavy alloy

Author

Yu Xiaodong, Zhichao Liu, Tan Chengwen, Liu Shaozun, and Wang Chunxu

Subjects
Diffraction, Materials science, Phase (matter), Failure strain, Alloy, Metallurgy, engineering, Split-Hopkinson pressure bar, Plasticity, Flow stress, engineering.material
Abstract

A Ni-based medium-heavy alloy (10.4 g/cm3) by vacuum melting with favorable dynamic mechanical properties was designed for some special applications, composed of Ni, W, Co and Ti. The X-ray diffraction (XRD) pattern illustrated that the major phase of this alloy is Ni17W3. Its critical failure strain rate exceeds 5000S−1 under Split Hopkinson Pressure Bar (SHPB) test. Meanwhile its average flow stress reached to 1948 MPa with the average plastic strain up to 0.48.

Published
2017

36. Microstructure and properties of atmospheric pressure chemical vapor deposition of tungsten carbide

Author

Huicong Zhang, Yu Xiaodong, Fang Wang, H.N. Cai, Honglei Ma, and Tan Chengwen

Subjects
Materials science, Scanning electron microscope, Inorganic chemistry, chemistry.chemical_element, Tungsten hexafluoride, Chemical vapor deposition, Tungsten, engineering.material, Electron beam physical vapor deposition, Carbide, chemistry.chemical_compound, Chemical engineering, chemistry, Coating, Tungsten carbide, engineering
Abstract

Tungsten carbide / tungsten coating is prepared from tungsten hexafluoride (WF6), hydrogen (H2) and dimethyl ether (DME) mixtures by chemical vapor deposition (CVD) under atmospheric pressure conditions. The cross-sectional structure and the surface morphology of the coating were observed using optical microscope and scanning electron microscopy. It is found that the tungsten layer is columnar and tungsten carbide / tungsten coating is fine grain lamellar structure. The preferential growth of tungsten was proposed to be effect of DME, and the {100} preferred orientation gradually disappeared by XRD. That the pre-deposition of tungsten on the substrate can improve the coverage of the tungsten carbide coating was observed. Finally, the cross section of the micrograph was measured at 28.77 GPa with a nano-indentation.

Published
2017

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