Dong-Hyun Lee

Jung-A Lee

Yakai Zhao

Moo-Young Seok

In-Chul Choi

Yong-Jae Kim

Byung-Gil Yoo

A-Hyun Jeon

Jeong-Min Park

Woo-Jin Kim

Hoon-Seop Kim

Jun-Hak Oh

Byoung-Wook Choi

Ji-Young Lee

June-Hyung Kim

Tae-Kyung Lee

The Nano/ Micro Mechanical Behavior Laboratory has developed both experimental and theoretical approaches towards the better understanding of the small scale (especially micro- or nano-level) mechanical behaviors of materials. Our group has developed a variety of new applications for the instrumented micro / nano indentation technique, and has also investigated nano-scale deformation, phase transformation and cracking of semiconductoturs, metals, ceramics, polymers, glasses, etc.

나노/마이크로 역학 거동 연구실은 재료의 작은 규모(특히 마이크로 또는 나노 수준)에서의 기계적 거동을 더 잘 이해하기 위한 실험적 및 이론적 접근 방식을 모두 개발했습니다. 우리 그룹은 계측된 마이크로/나노 압입 기술을 위한 다양한 새로운 응용 분야를 개발했으며, 또한 반도체, 금속, 세라믹, 고분자, 유리 등의 나노 스케일 변형, 상 변태 및 균열을 연구했습니다.

A novel specimen geometry for an improved estimation of hydrogen effects on the tensile behavior of face-centered cubic alloys

Substrate-field-modulated remote-van der Waals hybrid epitaxy in transition metal dichalcogenide heterostructures

This study introduces a novel multi-material design strategy termed spatial metastability control (SMC) for enhancing the transformation-induced plasticity (TRIP) behaviors in ferrous medium-entropy alloys (MEAs). The approach utilizes a compositional heterostructure by integrating pure Fe into a metastable MEA, establishing a gradual phase stability across the MEA/Fe interface. This gradient forms a distinct transition region characterized by refined grain size, thermal martensite formation, and moderate solid solution strengthening. The engineered spatial distribution of metastability facilitates efficient strain accommodation and promotes sequential TRIP activation. As a result, the SMC-designed alloys demonstrate exceptional strength-ductility synergies at both room and cryogenic temperatures. The SMC30 sample exhibits extensive martensitic transformation (~95 vol%), validating the effectiveness of spatially engineered phase metastability in enhancing TRIP behavior. This design framework offers a versatile pathway for developing next-generation structural alloys with tunable mechanical performance through spatial control of phase stability across a broad temperature range.

Spatial metastability control via compositional heterostructures for enhanced TRIP behavior in ferrous medium-entropy alloys

High-strength gradient Ti-Ni-Cu-Pd ribbon with large recoverable strain and high cyclic stability under load

Direct and scalable edge-induced alloying of Mo1-xWxS2 via patterned MoS2 templates

Manipulating grain boundary migration to fabricate integral core–shell structure with enhanced strain hardening in Ni-based high-entropy alloy

Role of Ni in high elastic modulus Al-Si-Ni alloys: Solidification and microstructure evolution

Multimodality of critical strength for incipient plasticity in L12-precipitated (CoCrNi)94Al3Ti3 medium-entropy alloy: coherent interface-facilitated dislocation nucleation

Thermomechanical behavior and microstructural evolution in nodes and struts of face-centered cubic lattice structures during laser powder bed fusion processing

Microstructural refinement in a high elastic modulus Al-18Si-8Ni casting alloy

Integrated experimental and computational study on the effect of hydrogen in mechanical responses of pure tungsten

Stochastic nature of incipient plasticity in a body-centered cubic medium-entropy alloy

Severe plastic deformation for producing superfunctional ultrafine-grained and heterostructured materials: An interdisciplinary review

Heterostructuring of BN-CoCrFeMnNi high-entropy alloy via severe plastic deformation

Shear deformation behavior of heterostructured materials: Experimental and numerical analyses

Hydrogen trapping and micromechanical behavior in additively manufactured CoCrFeNi high-entropy alloy in as-built and pre-strained conditions

On the superelastic behavior during spherical nanoindentation of a Ni-Ti shape memory alloy

Supreme tensile properties in precipitation-hardened 316L stainless steel fabricated through powder cold-consolidation and annealing

Impact of uneven distribution of grain characteristics on yield strength and martensite transformation of as-hot-rolled medium-entropy alloys

Hierarchically heterogeneous microstructure and mechanical behavior of the multi-materials prepared by powder severe plastic deformation

A statistical analysis of the second ‘pop-in’ behaviour of the spherical-tip nanoindentation of Zr-based bulk metallic glasses

A review of recent research on nanoindentation of high-entropy alloys processed by high-pressure torsion

Enhanced mechanical properties and homogeneous T5 age-hardening behavior of Al-Si-Cu-Mg casting alloys

Crucial role of Ce particles during initial hydrogen absorption of AB-type hydrogen storage alloys

A study on the interaction between a Sr modifier and an Al-5Ti-1B grain refiner in an Al-7Si-0.35Mg casting alloy

Microstructure and shear strength of Au-20wt%Sn solder joints fabricated by thermos-compression bonding for LED packages

Rate-dependent mechanical behavior of single-, bi-, twinned, and poly-crystals of CoCrFeNi high-entropy alloy

Decoupling the roles of constituent phases in the strengthening of hydrogenated nanocrystalline dual-phase high-entropy alloys

Nanomechanical and microstructural characterization on the synergetic strengthening in selectively laser melted austenitic stainless steel

Small-scale analysis of brittle-to-ductile transition behavior in pure tungsten

Titanium iron (TiFe) alloy is a room-temperature hydrogen-storage material, and it absorbs hydrogen via a two-step process to form TiFeH and then TiFeH2. The effect of V addition in TiFe alloy was recently elucidated. The V substitution for Ti sublattice lowers P2/P1 ratio, where P1 and P2 are the equilibrium plateau pressure for TiFe/TiFeH and TiFeH/TiFeH2, respectively, and thus restricts the two-step hydrogenation within a narrow pressure range. The focus of the present investigation was to optimize the V content such that maximum usable storage capacity can be achieved for the target pressure range: 1 MPa for absorption and 0.1 MPa for desorption. The effect of V substitution at selective Ti or Fe sublattices was closely analyzed, and the alloy composition Ti46Fe47.5V6.5 displayed the best performance with ca. 1.5 wt.% of usable capacity within the target pressure range. At the same time, another issue in TiFe-based alloys, which is a difficulty in activation at room temperature, was solved by Ce addition. It was shown that 3 wt.% Ce dispersion in TiFe alloy imparted to it easy room-temperature (RT) activation properties.

Design of V-substituted TiFe-based alloy for target pressure range and easy activation

Corrosion and oxidation resistance behaviors of Ta-containing low alloying zirconium

Indentation of glasses

Exploring the hydrogen absorption and strengthening behavior in nanocrystalline face-centered cubic high-entropy alloys

Hierarchical refinement of primary phases in a multicomponent Al-14Si-CuNiMg casting alloy by ultrasonic melt treatment

Oxidation-resistant coating of FeCrAl on Zr-alloy tubes using 3D printing direct energy deposition

Significance of grain refinement on micro-mechanical properties and structures of additively-manufactured CoCrFeNi high-entropy alloy

Hydrogen uptake and its influence in selective laser melted austenitic stainless steel: A nanoindentation study

Bimodality of incipient plastic strength in face-centered cubic high-entropy alloys

The mechanical bonding of dissimilar metals though the application of high‐pressure torsion (HPT) processing is developed recently for introducing unique ultrafine‐grained alloy systems involving microstructural heterogeneity leading to excellent mechanical properties. Considering further developments of the processing approach and the produced hybrid materials, the size effect on microstructural evolution and micromechanical responses of the mechanically bonded Al–Mg systems is evaluated. In practice, processing by HPT is conducted at room temperature on the separate Al and Mg disks having 25 mm diameter under 1.0 GPa at 0.4 rpm, and the results are compared with the mechanically bonded Al–Mg system having 10 mm diameter. The Al–Mg disks having 25 mm diameter show a general hardness distribution where low hardness appears around the disk centers, and it increases at the disk peripheries. Nanoindentation measurements demonstrate that there is excellent plasticity at the edges of the Al–Mg system with 25 mm diameter. The Al–Mg system with both 10 and 25 mm diameters show a consistent trend of hardness evolution outlining an exponential increase of hardness with increasing equivalent strain. The results are anticipated to provide a conceptual framework for the development and scale‐up of the HPT‐induced mechanical bonding technique.

Size effect on microstructural evolution and micromechanical responses of mechanically bonded aluminum and magnesium by high-pressure torsion

A rational route to create wrinkling patterns with individually controllable location and direction in thin polymer films.

Direct nanofluidic channels via hardening and wrinkling of thin polymer films

Mechanical properties and structural stability of a bulk nanostructured metastable aluminum-magnesium system

Statistical nature of the incipient plasticity in amorphous alloys

An overview of the mechanical bonding of dissimilar bulk engineering metals through high‐pressure torsion (HPT) processing at room temperature is described in this Review. A recently developed procedure of mechanical bonding involves the application of conventional HPT processing to alternately stacked two or more disks of dissimilar metals. A macroscale microstructural evolution involves the concept of making tribomaterials and, for some dissimilar metal combinations, microscale microstructural changes demonstrate the synthesis of metal matrix nanocomposites (MMNCs) through the nucleation of nanoscale intermetallic compounds within the nanostructured metal matrix. Further straining by HPT during mechanical bonding provides an opportunity to introduce limited amorphous phases and a bulk metastable state. The mechanically bonded nanostructured hybrid alloys exhibit an exceptionally high specific strength and an enhanced plasticity. These experimental findings suggest a potential for using mechanical bonding for simply and expeditiously fabricating a wide range of new alloy systems by HPT processing.

Synthesis of hybrid nanocrystalline alloys by mechanical bonding through high-pressure torsion

Effect of grain size on the strain rate sensitivity of CoCrFeNi high-entropy alloy

Wallpapering-inspired spreading and wrinkling of atomically-thin material

A new Zr-rich intermetallic phase in an Al-14Si-3Cu-4.5Ni casting alloy with trace additions of Zr

The present study demonstrates an innovative approach of utilizing high‐pressure torsion (HPT) processing for the mechanical bonding of dissimilar metals during the microstructural refinement process. This processing approach has been developed recently for introducing unique alloy systems with improving physical and mechanical properties. Accordingly, the present study focuses specifically on the microstructural evolution and development in micro‐mechanical responses in the mechanically bonded Al‐Mg and Al‐Cu hybrid alloy systems when synthesized by HPT processing for very high number of turns up to 60 under 6.0 GPa at room temperature. The microstructural and hardness evaluations confirm the capability of the HPT procedure for the formation of heterostructures with extreme hardness at the disk peripheries and with low hardness at the disk centers in these processed alloy systems. Nanoindentation measurements demonstrate that both hybrid alloy systems exhibit excellent plasticity at the disk edges, where the hardness is the highest. There is a considerable potential for applying the solid‐state reaction through the HPT process for the bonding of dissimilar metals as a manufacturing technique and for the development of hybrid alloy systems.

Mechanical bonding of aluminum hybrid alloy systems through high-pressure torsion

A survey of nanoindentation studies on HPT-processed materials

Bulk-state reactions and improving the mechanical properties of metals through high-pressure torsion

Influences of hydrogen charging method on the hydogen distribution and nanomechanical properties of face-centered cubic high-entropy alloy: A comparative study

Nano-graining a particle-strengthened high-entropy alloy

Influence of hydrogen on incipient plasticity in CoCrFeMnNi high-entropy alloy

High‐pressure torsion (HPT) is used to investigate the formation of a new metal system by the direct bonding of separate disks of Al and Cu by processing at room temperature under a compressive pressure of 6.0 GPa and with increasing numbers of HPT turns up to 60. A detailed examination of the microstructure and a phase analysis reveal the presence of three intermetallic compounds, Al2Cu, AlCu, and Al4Cu9, in the nanostructured Al matrix with a grain size of ≈30 nm. Processing by HPT leads to the formation of a metal–matrix nanocomposite with extreme hardness near the edge of the Al–Cu disks after 60 HPT turns. Experiments show that the estimated wear rates exhibit an improvement in wear resistance while maintaining low wear rates for high applied loads up to ≈40–50 N under dry sliding conditions. The results confirm that there is a significant potential for using HPT processing in the joining and bonding of dissimilar metals at room temperature and in the expeditious fabrication of a wide range of new metal systems having enhanced mechanical and functional properties.

Direct bonding of aluminum-copper metals through high-pressure torsion processing

Fabrication of nanocomposite through diffusion bonding under high-pressure torsion

Activation energy for plastic flow in nanocrystalline CoCrFeMnNi high-entropy alloy: A high temperature nanoindentation study

Effects of interfacial layer-by-layer nanolayers on the stability of the Cu TSV: Diffusion barrier, adhesion, conformal coating, and mechanical property

The influence of chemical heterogeneities on the local mechanical behavior of a high-entropy alloy: A micropillar compression study

Unusual flow behavior of Fe-based soft magnetic amorphous ribbons under high temperature tensile loading

Influence of pre-strain on the gaseous hydrogen embrittlement resistance of a high-entropy alloy

Indentation size effect for spherical nanoindentation on nanoporous gold

Annealing effect on plastic flow in nanocrystalline CoCrFeMnNi high-entropy alloy: A nanomechanical analysis

Indentation size effect in nanoporous gold

Significant strengthening of nanocrystalline Ni sub-micron pillar by cyclic loading in elastic regime

Critical bending radius of thin single-crystalline silicon with dome and pyramid surface texturing

AbstractWe fabricate nanotubular ZnO with wall thickness of 45, 92, 123 nm using nanoporous gold (np-Au) with ligament diameter at necks of 1.43 μm as sacrificial template. Through micro-tensile and micro-compressive testing of nanotubular ZnO structures, we find that the exponent m in $$\bar{\sigma }\propto {\bar{\rho }}^{m}$$
                      
                        σ
                        ¯
                      
                      ∝
                      
                        
                          
                            ρ
                            ¯
                          
                        
                        m
                      
                    , where $$\bar{\sigma }$$
                      
                        σ
                        ¯
                      
                     is the relative strength and $$\bar{\rho }$$
                      
                        ρ
                        ¯
                      
                     is the relative density, for tension is 1.09 and for compression is 0.63. Both exponents are lower than the value of 1.5 in the Gibson-Ashby model that describes the relation between relative strength and relative density where the strength of constituent material is independent of external size, which indicates that strength of constituent ZnO increases as wall thickness decreases. We find, based on hole-nanoindentation and glazing incidence X-ray diffraction, that this wall-thickness-dependent strength of nanotubular ZnO is not caused by strengthening of constituent ZnO by size reduction at the nanoscale. Finite element analysis suggests that the wall-thickness-dependent strength of nanotubular ZnO originates from nanotubular structures formed on ligaments of np-Au.

Wall-thickness-dependent strength of nanotubular ZnO

This paper summarizes recent efforts to evaluate the potential for the formation of a metal matrix nanocomposite (MMNC) by processing two commercial bulk metals of aluminum and magnesium alloy through high-pressure torsion (HPT) at room temperature. After significant evolutions in microstructures, successful fabrication of an Al-Mg hybrid system was demonstrated by observing unique microstructures consisting of a multi-layered structure and MMNC. Moreover, the evolution of small-scale mechanical properties was examined through the novel technique of nanoindentation and the improvement in plasticity was estimated by calculating the strain rate sensitivity of the Al-Mg hybrid system after HPT. The present paper demonstrates that, in addition to conventional tensile testing, the nanoindentation technique is exceptionally promising for ultrafine-grained materials processed by HPT, where the samples may have small overall dimensions and include heterogeneity in the microstructure.

Micro-mechanical response of an Al-Mg hybrid system synthesized by high-pressure torsion

The Nano/ Micro Mechanical Behavior Laboratory

교수님 소개

장재일

연구실 소개

연구실 키워드

알럼나이가 간 회사

연구실 지원 방법

대우 조건

연도별 논문 인용수

저널 & 학회 논문 출판 수

연구실 논문 목록

High-strength gradient Ti-Ni-Cu-Pd ribbon with large recoverable strain and high cyclic stability under load

Direct and scalable edge-induced alloying of Mo1-xWxS2 via patterned MoS2 templates

Manipulating grain boundary migration to fabricate integral core–shell structure with enhanced strain hardening in Ni-based high-entropy alloy

연구실 보유 특허

대학별 입시끈

우리 연구실 모집

교수님 소개

장재일

연구실 키워드

알럼나이가 간 회사

연구실 지원 방법

대우 조건

연도별 논문 인용수

저널 & 학회 논문 출판 수

연구실 논문 목록

High-strength gradient Ti-Ni-Cu-Pd ribbon with large recoverable strain and high cyclic stability under load

Direct and scalable edge-induced alloying of Mo1-xWxS2 via patterned MoS2 templates

Manipulating grain boundary migration to fabricate integral core–shell structure with enhanced strain hardening in Ni-based high-entropy alloy

연구실 보유 특허

최근 3년간 연구실적 높은 연구실

대학별 입시끈

우리 연구실 모집