Browsing by Author "Jang, Jason S. C."

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Development of Novel Lightweight Dual-Phase Al-Ti-Cr-Mn-V Medium-Entropy Alloys with High Strength and Ductility
(2020-01-01)
Liao, Yu-Chin
;
Chen, Po-Sung
;
Li, Chao-Hsiu
;
Tsai, Pei-Hua
;
Jang, Jason S. C.
A novel lightweight Al-Ti-Cr-Mn-V medium-entropy alloy (MEA) system was developed using a nonequiatiomic approach and alloys were produced through arc melting and drop casting. These alloys comprised a body-centered cubic (BCC) and face-centered cubic (FCC) dual phase with a density of approximately 4.5 g/cm(3). However, the fraction of the BCC phase and morphology of the FCC phase can be controlled by incorporating other elements. The results of compression tests indicated that these Al-Ti-Cr-Mn-V alloys exhibited a prominent compression strength (1940 MPa) and ductility (30%). Moreover, homogenized samples maintained a high compression strength of 1900 MPa and similar ductility (30%). Due to the high specific compressive strength (0.433 GPag/cm(3)) and excellent combination of strength and ductility, the cast lightweight Al-Ti-Cr-Mn-V MEAs are a promising alloy system for application in transportation and energy industries.
Structural and nanomechanical properties of a-plane ZnO thin films deposited under different oxygen partial pressures
(2012-05-01)
Jian, Sheng-Rui
;
Chen, Hou-Guang
;
Chen, Guo-Ju
;
Jang, Jason S. C.
;
Juang, Jenh-Yih
The effects of O-2 partial pressure during RF magnetron sputtering on the structural and nanomechanical properties of a-plane ZnO thin films were investigated by using X-ray diffraction (XRD) and nanoindentation techniques. The XRD and the transmission electron microscopy (TEM) selected area diffraction results indicate that the epitaxial relationship between ZnO thin films and Al2O3 substrates is ZnO (11 (2) over bar0)//Al2O3 (1 (1) over bar 02). The average values of the hardness and Young's modulus of the a-plane ZnO films were found to decrease with increasing oxygen partial pressure. The cross-sectional TEM revealing the localized plastic deformation of ZnO thin films beneath the Berkovich indenter, indicating the prominent role played by the threading dislocations in the film deformation behavior. At higher indentation loadings, the sapphire substrate exhibits extensive deformation with narrow slip bands appearing on {0001} plane. However, no evidence of pressure-induced phase transformation, as well as cracking and/or delamination phenomena at the film-substrate interface was observed. (C) 2011 Elsevier B.V. All rights reserved.