Fei-yi Hung - Academia.edu (original) (raw)

Papers by Fei-yi Hung

Materials Letters, Nov 1, 2017

A duplex surface-modification technique that combines ultrasonic-assisted etching and the fluorid... more A duplex surface-modification technique that combines ultrasonic-assisted etching and the fluorideconversion method was successively applied on the surface of a Mg alloy, and was called the MagNest surface. The results showed that the MagNest surface possessed bowl-like nest structures about 15-35 mm in diameter and 2-5 mm in depth. Electrochemical testing verified that the corrosion resistance was increased, indicating that corrosion was effectively inhibited by the surface modification. The MagNest surface also exhibited non-cytotoxicity for MG63 osteoblast-like cells, with most adhered MG63 cells rapidly extending their cell membrane and filopodia. This demonstrates the excellent cytocompatibility of this surface modification, and so constitutes a promising biodegradable material.

Metals, 2018

Post-forging heat treatment is often necessary to achieve the mechanical properties required for ... more Post-forging heat treatment is often necessary to achieve the mechanical properties required for aluminum alloy forged parts. In this study, hot-forged 6082 suspension parts are used to study the effect of rapid infrared (IR) heat treatment. The insoluble particles present in the matrix after the solutionizing process are observed. Experimental results show that using rapid IR heat treatment leads to superior solutionizing, and thus a larger critical onset strain in serrated tensile flow. The rapid IR heat treatment also had a more significant precipitation effect, which enhanced the mechanical properties of the material.

Materials, 2018

This present study applied Cu∙Zn/Al ribbon in place of a traditional Cu ribbon to a photovoltaic ... more This present study applied Cu∙Zn/Al ribbon in place of a traditional Cu ribbon to a photovoltaic (PV) ribbon. A hot-dipped and an electroplated Sn PV ribbon reflowed onto an Ag electrode on a Si solar cell and estimated the feasibility of the tested module (Ag/Solder/Cu∙Zn/Al). After bias-aging, a bias-induced thermal diffusion and an electromigration promoted the growth of intermetallic compounds (IMCs) (Cu6Sn5, Ag3Sn). To simulate a photo-generated current in the series connection of solar cells, an electron with Ag-direction (electron flows from Ag to Al) and Al-direction (electron flows from Al to Ag) was passed through the Al/Zn∙Cu/Solder/Ag structure to clarify the growth mechanism of IMCs. An increase in resistance of the Ag-direction-biased module was higher than that of the Al-direction biased one due to the intense growth of Cu6Sn5 and Ag3Sn IMCs. The coated solder of the electroplated PV ribbon was less than that of the hot-dipped one, and thus decreased the growth reacti...

Metals, 2018

This study was conducted for high temperature aging (HTA) to simultaneously reduce current treatm... more This study was conducted for high temperature aging (HTA) to simultaneously reduce current treatment time and increase the tensile ductility of 7075 aluminum alloy. Various high temperatures and different durations for artificial aging were compared. We investigated the microstructure and the tensile properties of 7075 aluminum alloy extruded rod after various HTAs, and compared them with the outcomes of full annealing (O). The total elongation (TE) of the specimen after solution heat treatment (490 °C, 1 h) and artificial aging (280 °C, 12 h) was about 25%. For full annealing, it is known as 21%. The reason for this was the formation of the η phase in the matrix, which had fewer large particles (Al-Cu phase). The hardening of HTA specimens is higher than that of O, indicating necking resistance during homogeneous plastic deformation. Thereby, HTA treatment increases the formability of 7075 aluminum alloy.

Metals, 2019

The ductility enhancement of an AA7075 aluminum alloy aided by a friction stir process (FSP) and ... more The ductility enhancement of an AA7075 aluminum alloy aided by a friction stir process (FSP) and various heat treatments was investigated and compared in terms of outcome with full annealing (O). The results indicate that a big improvement in the tensile ductility was achieved by freezing the sample at temperatures below 0 °C after the solution treatment and water quenching (W treatment), and further improvement could be acquired via a friction stir process due to grain refinement (<6 μm). Thus, the observed improvement in tensile ductility can be explained by the fact that the W treatment and friction stir processing scheme had an increased strain-hardening effect and decreased the presence of intermetallic particles that are harmful to uniform tensile deformation, consequently causing strain localization in the early stage of tensile deformation, which suggests that these treatment are a potential solution for insufficient formability. In general, the elongation to failure valu...

Metals, 2017

This study aimed to develop and evaluate the ECO-friendly Mg-5Zn-0.5Zr (ECO505) alloy for applica... more This study aimed to develop and evaluate the ECO-friendly Mg-5Zn-0.5Zr (ECO505) alloy for application in dental-guided bone regeneration (GBR). The microstructure and surface properties of biomedical Mg materials greatly influence anti-corrosion performance and biocompatibility. Accordingly, for the purpose of microstructure and surface modification, heat treatments and surface coatings were chosen to provide varied functional characteristics. We developed and integrated both an optimized solution heat-treatment condition and surface fluoride coating technique to fabricate a Mg-based regeneration membrane. The heat-treated Mg regeneration membrane (ARRm-H380) and duplex-treated regeneration membrane group (ARRm-H380-F24 h) were thoroughly investigated to characterize the mechanical properties, as well as the in vitro corrosion and in vivo degradation behaviors. Significant enhancement in ductility and corrosion resistance for the ARRm-H380 was obtained through the optimized solid-solution heat treatment; meanwhile, the corrosion resistance of ARRm-H380-F24 h showed further improvement, resulting in superior substrate integrity. In addition, the ARRm-H380 provided the proper amount of Mg-ion concentration to accelerate bone growth in the early stage (more than 80% new bone formation). From a specific biomedical application point of view, these research results point out a successful manufacturing route and suggest that the heat treatment and duplex treatment could be employed to offer custom functional regeneration membranes for different clinical patients.

Materials, 2019

The grain size of high strength 7075 hot-rolled aluminum plates was refined by a friction stir pr... more The grain size of high strength 7075 hot-rolled aluminum plates was refined by a friction stir process (FSP) to improve their mechanical properties. The results of the tensile ductility tests, which were conducted at various tool rotational speeds, in the friction stir zone indicate significant tensile ductility loss, which even resulted in a ductile-to-brittle transition (DBT). DBT depends on the tool rotational speed. Our 1450 rpm specimens showed large data fluctuation in the tensile ductility and the location of the fracture controlled the formation of friction stir induced bands (FSIB). The crack initiation site located at FSIB was due to the tool rotational speed (1670 rpm). A higher heat-input causes the formation of FSIB, which is accompanied with micro-voids. This contributes significantly to tensile cracking within the stir zone after the application of the aging treatment. This investigation aimed to determine the dominant factor causing tensile ductility loss at the stir...

Journal of Engineering, 2019

The friction stir welding process (friction stir welding/processing, FSW/FSP) has wear problems r... more The friction stir welding process (friction stir welding/processing, FSW/FSP) has wear problems related to stirring tools. In this study, the plasma transfer arc (PTA) method was used with stellite 1 powders (Co-based) to coat on the head of a SKD61 stirring tool (SKD61-ST1) in order to investigate the wear performance and phase transformation of SKD61-ST1 after FSW. Under the same experimental parameters, the wear data were compared with the high-speed steel SKH51 (tempering material SKH51-T and annealed material SKH51-A) and tungsten-carbide cobalt (TCC). Results showed the PTA coating was a γ-Co solidification matrix with M7C3 and M23C6 carbides. After FSW, the wear resistance of SKD61-ST1 was better than that of SKH51-A and SKH51-T and lower than that of TCC. The SKD61-ST1, SKH51-A, and SKH51-T stirring tools exhibited sliding wear after FSP, where the pin and shoulder of the stirring tool formed a phase transfer layer on the surface, and the peeling of the phase transfer layer ...

International Journal of Electrochemical Science, 2017

Magnesium alloy is promising new biomaterial due to its satisfactory mechanical performance, bioc... more Magnesium alloy is promising new biomaterial due to its satisfactory mechanical performance, biocompatibility and degradation of non-toxic substances. However, the dual problems of corrosion and hydrogen evolution require overcoming in order to reach a practical application level. For anticorrosion modification, fluoride conversion treatment was chosen to provide varied MgF 2 coatings on the microstructure-modified Mg-Zn-Zr alloy The aim of the present study was to investigate the influence of coating structures and their corresponding corrosion resistance. The fluoride coatings were constructed with nano-crystalline composites, which demonstrated that Mg-Zn precipitates participate in the coating-growth mechanism. In addition, the improved corrosion resistance was also systematically investigated. Compared with the pristine substrate, the F24h and F48h specimens significantly improved the anti-corrosion performance. Moreover, this report is the first report to propose a non-destructive evaluation method through simultaneous evaluation of the corrosion behavior and the establishment of a correspondence surface reflectance for fluoride conversion coatings on Mg-Zn-Zr alloy.

Journal of Nanomaterials, 2012

This study presents a successful bias crystallization mechanism (BCM) based on an indium/glass su... more This study presents a successful bias crystallization mechanism (BCM) based on an indium/glass substrate and applies it to fabrication of ZnInSnO (ZITO) transparent conductive oxide (TCO) films. The effects of bias-crystallization on electrical and structural properties of ZITO/In structure indicate that the current-induced Joule heating and interface diffusion were critical factors for low-temperature crystallization. With biases of 4 V and 0.1 A, the resistivity of the ZITO film was reduced from3.08×10−4 Ω∗cm to6.3×10−5 Ω∗cm. This reduction was attributed to the bias-induced energy, which caused indium atoms to diffuse into the ZITO matrix. This effectuated crystallizing the amorphous ZITO (a-ZITO) matrix at a lower temperature (approximately170∘C) for a short period (≤20 min) during a bias test. The low-temperature BCM developed for this study obtained an efficient conventional annealed treatment (higher temperature), possessed energy-saving and speed advantages, and can be consi...

Metals, 2016

Even though the high-temperature formability of Al alloys can be enhanced by the strain-induced m... more Even though the high-temperature formability of Al alloys can be enhanced by the strain-induced melt activation (SIMA) process, the mechanical properties of the formed alloys are necessary for estimation. In this research, a modified two-step SIMA (TS-SIMA) process that omits the cold working step of the traditional SIMA process is adopted for the 6066 Al-Mg-Si alloy to obtain globular grains with a short-duration salt bath. The high-temperature compressive resistance and mechanical properties of TS-SIMA alloys were investigated. The TS-SIMA alloys were subjected to artificial aging heat treatment to improve their mechanical properties. The results show that the TS-SIMA process can reduce compression loading by about 35%. High-temperature compressive resistance can be reduced by the TS-SIMA process. After high-temperature compression, the mechanical properties of the TS-SIMA alloys were significantly improved. Furthermore, artificial aging treatment can be used to enhance formed alloys via the TS-SIMA process. After artificial aging treatment, the mechanical properties of TS-SIMA alloys are comparable to those of general artificially-aged materials.

Journal of Nanomaterials, 2014

Cu2SnZn(S + Se)4is an excellent absorber material for solar cells. This study obtained Cu2SnZn(S ... more Cu2SnZn(S + Se)4is an excellent absorber material for solar cells. This study obtained Cu2SnZn(S + Se)4powders through solid state reaction by the ball milling and sintering processes from elemental Cu, Zn, Sn, S, and Se without using either polluting chemicals or expensive vacuum facilities. Ratios of S/S + Se in CuSnZnSSe were controlled from 0 to 1. The results showed that the 2-step sintering process (400°C for 12 hrs and then 700°C for 1 hr) was able to stabilize the composition and structure of the CuSnZnSSe powders. The crystallized intensity of the CuSnZnS matrix decreased with increasing the Se content. Raising the Se content restrained the SnS phase and reduced the resistance of the absorber layer. In addition, Raman data confirmed that Se caused a Raman shift in the CuSnZnSSe matrix and enhanced the optical properties of the CuSnZnSSe powders. For the interface of CuSnZnSSe film and Mo substrate, Mo could diffuse into CuSnZnSSe matrix after 200°C annealing. The interface ...

IEEE Journal of Photovoltaics, 2015

Sn-xZn (x = 9, 25, and 50 wt%) alloy solders are applied in photovoltaic (PV) ribbon and connecte... more Sn-xZn (x = 9, 25, and 50 wt%) alloy solders are applied in photovoltaic (PV) ribbon and connected with silicon solar cells. The interfacial microstructures, series resistance, and bonding strength of Sn-xZn PV modules are investigated. Cu 5 Zn 8 and AgZn 3 intermetallic compounds (IMCs) were found at the interfaces. The Zn content in the solder dominates the growth behavior of IMCs at the interface. The thickness of the Cu 5 Zn 8 and AgZn 3 IMC layer increased with increasing Zn content in the solder, and thus, the series resistance of the PV module also increased. The growth of IMCs can enhance the interfacial adhesion strength, but excess Zn overconsumes the Ag electrode, reducing the bond strength of the PV module. Applying low-Zn-content Sn-xZn solder to PV ribbon avoids overconsumption of the Ag layer and, thus, decreases the series resistance and internal stress.

Journal of Nanoparticles, 2013

This study synthesizes CuxZn1−xO powders using an aqueous solution method. The CuxZn1−xO powders ... more This study synthesizes CuxZn1−xO powders using an aqueous solution method. The CuxZn1−xO powders with different content ratios of CuO and ZnO (CuO : ZnO = 1 : 2, 1 : 1, and 2 : 1) were formed. The crystalline characteristics and electrical and magnetic properties depended primarily on the mixing effect and oxygenation. The electrical resistance of C0.5Z0.5O (1.5×105 Ω/□) powder was lower than that of CuO (5.82×105 Ω/□) powder after ZnO mixing in CuO. This reduction was attributed to the substitution of Cu+ ions at Zn2+ sites or the formation of electron trapping defect centers. The concentration ratio of Cu2O phase in CuxZn1−xO powder mainly dominated the electrical resistance. The CuxZn1−xO has a diluted ferromagnetism (DFM) and paramagnetism (PM). The electrical resistance of CuxZn1−xO decreased; the magnetic behavior increased instead. This study also analyzes the chemical binding of Cu0.5Zn0.5O powders to confirm the contribution of Cu+ ions to the electrical and magnetic proper...

MATERIALS TRANSACTIONS, 2015

An efficient and environmental-friendly method, featuring a cyanide-free plating process was esta... more An efficient and environmental-friendly method, featuring a cyanide-free plating process was established for Au-coated Ag wire (ACA). This new Ag wires can meet the reliability standards of wire bonding. The proposed ACA wire was studied to ensure compatibility with electrical properties; mechanical properties and free air ball characterization. Tensile tests showed that ACA wire was stronger than pure Ag wire. The Au coated layer has excellent an bonded interface with the Ag wire. Electrical properties at high temperature demonstrate that the ACA wire maintains outstanding electrical resistance. Further, the Au layer coating the Ag prevents wire oxidation and corrosion during the packaging process. ACA wire formed by the cyanide-free plating method can be used for IC and LED packaging processes.

MATERIALS TRANSACTIONS, 2008

In Sn-2 mass%Ag-0.5 mass%Cu solder alloy, recrystallization was induced by thermal cycles and the... more In Sn-2 mass%Ag-0.5 mass%Cu solder alloy, recrystallization was induced by thermal cycles and the homogenized effect of thermal aging promoted the vibration resistance. Due to the inner stress induced by thermal cycles, the thermal cycle specimen not only possessed a finer structure but also a large number of grain boundaries that were able to increase the vibration life. During vibration, dynamic recrystallization (DRX) was able to occur. In addition, DRX and grain growth had an obvious tendency to increase as the tensile strain rate was increased in the Sn-1 mass%Ag-0.5 mass%Cu solder alloy with a high-Sn content. Also, high temperatures and plastic deformation had a significant influence on the recrystallization of the solders.

MATERIALS TRANSACTIONS, 2011

Magnesium-carbon powders and Magnesium-lithium powders were used as the anode materials for lithi... more Magnesium-carbon powders and Magnesium-lithium powders were used as the anode materials for lithium ion batteries to investigate the structure and electrochemical behavior in room temperature. The composition of Mg-C powders contained 1 : 1 and 9 : 1. The powders and the thermal evaporated films of Mg-10Li were compared with Mg-C systems. In addition, Mg-10Li thermal evaporated film was used as the experimental materials to process the annealing treatment. The results show that Mg-C powders system had the interface effect of a Cu foil to reduce the electrochemical reaction. With increasing the carbon powder content, the charge-discharge characteristics of Mg-C powders was raised. Notably, the Mg-10Li specimen had better cycling properties than that of Mg-50C (1 : 1). After annealing at 200 C for 1 h, Mg-10Li alloy film not only increased the capacity, but also improved the charge-discharge cyclability.

MATERIALS TRANSACTIONS, 2011

The Zn-In-Sn-O (ZITO) transparent conductive oxide (TCO) films were deposited onto indium/glass s... more The Zn-In-Sn-O (ZITO) transparent conductive oxide (TCO) films were deposited onto indium/glass substrate by co-sputtering system. The bias-crystallization mechanism (BCM) was used to promote the quality of ZITO films. After biasing treatment (biased at 4 V for 20 min), the resistivity of ZITO film reduced from 3:08 Â 10 À4 Ãcm to 6:3 Â 10 À5 Ãcm. This reduction was attributed to the indium ions diffused into ZITO film using BCM. According to the Joule's law and Ohm's law, the required energy of biasing treatment was only 480 Joule. Comparing with traditional annealed treatment (annealing at 500 C for 20 min in vacuum required 9:8 Â 10 6 Joule), BCM had improved the conductivity of ZITO film in a short time at room temperature and possessed an excellent competitiveness of cost.

MATERIALS TRANSACTIONS, 2006

Compared with gold wire, copper wire is cheaper and possesses lower cost, greater strength and be... more Compared with gold wire, copper wire is cheaper and possesses lower cost, greater strength and better electrical conductivity, and therefore is becoming more commonly used. But the lower ductility and oxidation undermine the reliability of copper wire bonding, making the wire susceptible to breaking. In the present study, the annealed effect (at 150-250 C for 1 hour) on the tensile mechanical properties of copper wires with ¼ 25 mm (1 mil) was investigated. In addition, the microstructural characteristics and the mechanical properties before and after an electric flame-off (EFO) process were also studied. Experimental results indicate that with annealing temperatures of more than 200 C, the copper wires possessed a fully annealed structure, the tensile strength and the hardness decreased, and the elongation was raised significantly. Through recrystallization, the matrix structure transferred from long, thin grains to equiaxed grains and a few annealed twins. The microstructures of the free air ball (FAB) of the variation annealing wires after an EFO process were column-like grains. The column-like grains grew from the heat-affected zone (HAZ) to the Cu ball, and the preferred orientation was h100i. Under the thermal effect of EFO, the necks of the Cu balls underwent recrystallization and the grain growth was induced. Additionally, the decreased hardness and the strength of the HAZ resulted in the breakage sites of the EFO wires being in the HAZ near the Cu balls.

MATERIALS TRANSACTIONS, 2006

The effect of electrical current on the microstructure, the tensile properties and vibration defo... more The effect of electrical current on the microstructure, the tensile properties and vibration deformation mechanisms of the Sn-9Zn-1Cu leadfree solder were examined in this study. Results showed that Zn-rich phase, Sn-Zn eutectic, Cu 5 Zn 8 intermetallic compounds and proeutectic Sn-rich phase existed in the matrix of a Sn-9Zn-1Cu specimen. An electrical current flowing for a short duration was able to improve the tensile strength of the solder alloy. But prolonging the duration more than 7 hours led to a deterioration in the tensile mechanical properties and vibration resistance. Under both constant force and initial-deflection conditions, the electrical current caused the vibration life of the specimens to deteriorate. Lamellar-deformed structures (LDS) decreased and Cu 5 Zn 8 fractured easily, which in turn decreased the crack propagation resistance.

Materials Letters, Nov 1, 2017

Metals, 2018

Materials, 2018

Metals, 2018

Metals, 2019

Metals, 2017

Materials, 2019

Journal of Engineering, 2019

International Journal of Electrochemical Science, 2017

Journal of Nanomaterials, 2012

Metals, 2016

Journal of Nanomaterials, 2014

IEEE Journal of Photovoltaics, 2015

Journal of Nanoparticles, 2013

MATERIALS TRANSACTIONS, 2015

MATERIALS TRANSACTIONS, 2008

MATERIALS TRANSACTIONS, 2011

MATERIALS TRANSACTIONS, 2006