Erwin Huang | National Chiao Tung University (original) (raw)

Papers by Erwin Huang

Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications

Al–Si alloys, with excellent properties such as low weight, low thermal expansion coefficient, an... more Al–Si alloys, with excellent properties such as low weight, low thermal expansion coefficient, and high wear-resistance, are ideal materials for the automobile and aerospace industries. However, their applications have been hampered by the coarsening of the primary-Si particles in Al–Si alloys. In this study, the rolling-and-T6-treatments effect on A6061/Al2O3 metal-matrix composites is investigated. The A6061/Al2O3 metal-matrix composites with different amounts of reinforcing Al2O3 particles are examined in the aspects of wear resistance and hardness. Upon the T6 treatment, the hardness is enhanced in all cases and is summarized. The results suggest that the increase of Al2O3 particles reduce the wear rate. The possible reinforce mechanisms and the environmental temperature effects are discussed. This improvement in wear resistance is due to the particle size refinement of silicon at a high percentage-roll-reduction.

Fatigue & Fracture of Engineering Materials & Structures

In-situ neutron-diffraction and temperature measurements were simultaneously applied to investiga... more In-situ neutron-diffraction and temperature measurements were simultaneously applied to investigate low-cycle-fatigue behaviour of a nano-precipitate strengthened nickel-based superalloy. Two transitions in the temperature-evolution are observed subjected to cyclic loading. Two models are compared with the measured temperature evolution. One is based on bulk stress, and the other is based on lattice-strain evolution. The calculated thermoelastic responses in both models qualitatively agree with the measured bulk-temperature evolution for the first transition. The in-situ neutron-diffraction results reveal that the first transition is associated with the cyclic hardening/softening dislocation-structural transformation. However, the second transition, which is observed at larger number of fatigue cycles during the steady cycles, does not correlate with the dislocation evolution. A phenomenological model is applied to describe the second temperature-transition stages. The energy dissipation evolutions in the second fatigue stage indicate the initiation and the growth activities of fatigue microcrack. The data reported here may be useful for cohesive zone model.

Acta Materialia, 2016

Abstract Insights into the phase transformation kinetics and lattice dynamics associated with the... more Abstract Insights into the phase transformation kinetics and lattice dynamics associated with the newly discovered confined martensitic transformation are of great significance to the in-depth understanding of the phase transformation behavior responsible for the rich new physical phenomena in shape memory alloys and could shed light on the design of novel multifunctional properties through tuning the confined martensitic transformation. Here, we employ in-situ elastic and inelastic neutron scattering techniques to reveal the characteristics of transformation kinetics and lattice dynamics in two Ni 55-x Co x Fe 18 Ga 27 magnetic shape memory alloys with x = 5.5 and 6.5. With a remarkable difference in transformation temperature, these two alloys show similar vibrational properties. Phonon softening of the TA 2 [ξξ0] phonon branch, manifested as a dip at ξ ∼ 0.33 on the phonon dispersion curves, was disclosed by inelastic neutron scattering experiments; but this phonon softening is much less pronounced than that observed in stoichiometric Ni 2 MnGa or near-stoichiometric Ni–Fe–Ga Heusler alloys. The dispersion curves for the TA 2 [ξξ0] phonon branch are only weakly dependent on temperature. The less pronounced phonon softening and very weak temperature dependence of the phonon dispersion curves could be attributed to the martensitic transformation which is confined by local inhomogeneities. This confined martensitic transformation shows a sluggish nature and occurs in a broad temperature range. The sluggish transformation was evidenced by the existence of residual austenite at low temperatures far below the martensitic transformation start temperature.

$Research paper thumbnail of Fatigue Crack-Tip Stress Mapping Using Neutron Diffraction$

Korean Journal of Materials Research, 2015

Fatigue crack growth experiments were carried out on a 304 L stainless steel compact-tension(CT) ... more Fatigue crack growth experiments were carried out on a 304 L stainless steel compact-tension(CT) specimen under load control mode. Neutron diffraction was employed to quantitatively measure the residual strains/stresses and the evolution of stress fields in the vicinity of a propagating fatigue-crack tip. Three principal stress components (i.e. crack growth, crack opening, and through-thickness direction stresses) were examined in-situ under loading as a function of distance from the crack tip along the crack-propagation path. The stress/strain fields, measured both at the mid-thickness and near the surface of the CT specimen, were compared. The results show that much higher compressive residual stress fields developed in front of the crack tip near the surface than developed at the mid-thickness area. The change of the stresses ahead of the crack tip under loading is more significant at the mid-thickness area than it is near the surface.

Metals, 2015

We investigated the evolution of the strain fields around a fatigued crack tip between the steady... more We investigated the evolution of the strain fields around a fatigued crack tip between the steady-and overloaded-fatigue conditions using a nondestructive neutron diffraction technique. The two fatigued compact-tension specimens, with a different fatigue history but an identical applied stress intensity factor range, were used for the direct comparison of the crack tip stress/strain distributions during in situ loading. While strains behind the crack tip in the steady-fatigued specimen are irrelevant to increasing applied load, the strains behind the crack tip in the overloaded-fatigued specimen evolve significantly under loading, leading to a lower driving force of fatigue crack growth. The results reveal the overload retardation mechanism and the correlation between crack tip stress distribution and fatigue crack growth rate.

Advanced Materials, 2015

In situ synchrotron X-ray diffraction is used to investigate a three-way piezo-phototronic soft m... more In situ synchrotron X-ray diffraction is used to investigate a three-way piezo-phototronic soft material. This new system is composed of a semi-crystalline poly(vinylidene fluoride-co-trifluoro-ethylene) piezoelectric polymer and titanium oxide nanoparticles. Under light illumination, photon-induced piezoelectric responses are nearly two times higher at both the lattice-structure and macroscopic level than under conditions without light illumination. A mechanistic model is proposed.

Scripta Materialia, 2015

An equal-molar CoCrFeMnNi, face-centered-cubic high-entropy alloy system and a face-centered-cubi... more An equal-molar CoCrFeMnNi, face-centered-cubic high-entropy alloy system and a face-centered-cubic stainless steel described as a medium-entropy system, are measured by in-situ neutron-diffraction experiments subjected to continuous tension at room and several elevated temperatures, respectively. With spallation neutron, the evolution of multiple diffraction peaks are collected simultaneously for lattice-elasticity study. Temperature variation of elastic stiffness of a single face-centered-cubic-phase Ni and a single face-centered-cubic-phase Fe are compared as low-entropy metals. The CoCrFeMnNi high-entropy alloy show distinct lattice anisotropy.

$Research paper thumbnail of In-situ neutron diffraction studies on high-temperature deformation behavior in a CoCrFeMnNi high entropy alloy$

Intermetallics, 2015

ABSTRACT An equiatomic, face-centered-cubic, CoCrFeMnNi high-entropy alloy was tensile tested at ... more ABSTRACT An equiatomic, face-centered-cubic, CoCrFeMnNi high-entropy alloy was tensile tested at 800 K and 1,000 K with a nominal strain rate of 6.7 Â 10 À6 s À1. In addition to the macroscopic (bulk) behavior, mesoscopic (lattice) phenomena during the pseudo-creep deformation were investigated simultaneously using in-situ neutron diffraction. The evolutions of lattice strains, peak widths, and intensities of several hkl reflections suggest that the dominant deformation mode is the dislocation glide at 800 K and diffusion-controlled dislocation creep at 1,000 K.

Langmuir : the ACS journal of surfaces and colloids, Jan 30, 2014

The structures of C- and N-terminally monoPEGylated human parathyroid hormone fragment hPTH(1-34)... more The structures of C- and N-terminally monoPEGylated human parathyroid hormone fragment hPTH(1-34) as well as their unmodified counterparts, poly(ethylene glycol) (PEG) and hPTH(1-34), have been studied by small-angle neutron scattering (SANS). The scattering results show that free hPTH(1-34) in 100 mM phosphate buffer (pH 7.4) aggregates into clusters. After conjugation with PEG, the PEG-peptide conjugates self-assemble into a supramolecular core-shell structure with a cylindrical shape. The PEG chains form a shell around the hPTH(1-34) core to shield hPTH(1-34) from the solvent. The detailed structural information on the self-assembled structures is extracted from SANS using a model of the cylindrical core with a shell of Gaussian chains attached to the core surface. On the basis of the data, because of the charge-dipole interactions between the conjugated PEG chain and the peptide, the conjugated PEG chain forms a more collapsed conformation compared to free PEG. Moreover, the siz...

$Research paper thumbnail of Residual Strain Distribution around a Fatigue-Crack Tip Determined by Neutron Diffraction$

An analysis of residual stress, one of the contributory factors to the crack tip driving force, i... more An analysis of residual stress, one of the contributory factors to the crack tip driving force, is extremely important to probe the fatigue crack growth mechanism and to further develop the life prediction methodology. Since fatigue crack growth is governed by crack-tip plasticity and crack closure in the wake of the crack tip, the investigation of residual stain/stress field in both behind and in front of the crack tip is crucial. In the current work, a 304L stainless steel compact-tension specimen is pre-cracked under constant-amplitude cyclic loading. Neutron diffraction is employed to directly measure the three orthogonal residual strain fields with 1-mm spatial resolution as a function of distance from the crack tip. The mapping results show that the three orthogonal residual-strain distributions around the crack tip depend on the stress multiaxiality, not following a single Poisson relationship to each axis.

Materials Science Forum, 2014

Carbon-carbon composites are deemed as candidate materials for application in very high temperatu... more Carbon-carbon composites are deemed as candidate materials for application in very high temperature reactors. In a very high temperature reactor, carbon-carbon composite materials would experience severe environmental impacts from high temperatures. As a result, we applied non-destructive ex-situ diffraction experiments to investigate the microstructure changes of the carbon-carbon composite materials experiencing different temperatures. In this study, the samples were prepared in a format of a three-dimensional pitch-based carbon-carbon composite. The samples were heated to 500 (°C), 700 (°C), and 900 (°C) for 2 minutes, respectively. In order to understand the temperature effect on carbon-carbon composite, we facilitated the high penetration of the synchrotron X-ray diffraction at National Synchrotron Radiation Research Center to examine the evolution of microstructures subjected to heat treatment. The results show that the lattice parameters of a-axis and c-axis evolve upon heati...

Procedia Engineering, 2012

We simulate the Wigner Effect of the nuclear-grade graphite for the High Temperature Gas-cooled R... more We simulate the Wigner Effect of the nuclear-grade graphite for the High Temperature Gas-cooled Reactor (HTGR) operation environment. The graphite was artificially irradiated with 3MeV C 2+ ion to mimic the fast neutron-radiation damage of the HTGR core environment. In a high vacuum environment of 10-7 torr, the irradiation temperatures were controlled in the range of 600 to 900. Due to the high-dosages radiation, enormous amounts of Frenkel pairs are created, and these defects induce the swelling of lattice spacing. Those vacancies and interstitials form new strain fields and store energy in the distorted crystalline structure. We quantify the structural integrity of the graphite with/without irradiation via synchrotron X-ray diffraction experiments. The synchrotron X-ray diffraction experimental results, gauged from bulk specimens, reveal the texture reorientation and microstructure development subjected to the combination of the irradiation and high temperature effects. A correlation between lattice strain and irradiation effect is developed. The deformation mechanisms are revealed.

Philosophical Magazine Letters, 2011

An experimental investigation, combining synchrotron X-ray powder diffraction, small-angle neutro... more An experimental investigation, combining synchrotron X-ray powder diffraction, small-angle neutron scattering and transmission electron microscopy, has been undertaken to study the microstructure of nanoprecipitates in a nickel-based superalloy. Upon increasing the ageing time during a heat-treatment process, the average size of the precipitates first decreases before changing to a monotonically growth stage. Possible reasons for this observed structural evolution, which is predicted thermodynamically, are suggested.

Metallurgical and Materials Transactions A, 2012

International. This e-offprint is for personal use only and shall not be self-archived in electro... more International. This e-offprint is for personal use only and shall not be self-archived in electronic repositories. If you wish to selfarchive your work, please use the accepted author's version for posting to your own website or your institution's repository. You may further deposit the accepted author's version on a funder's repository at a funder's request, provided it is not made publicly available until 12 months after publication.

$Research paper thumbnail of Three-Orthogonal-Direction Stress Mapping around a Fatigue-Crack Tip Using Neutron Diffraction$