Jeongho Han

Jeongho Han
Hanyang University · Division of Materials Science and Engineering (MSE)

Professor

About

56
Publications
17,325
Reads
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2,579
Citations
Introduction
Bachelor and Ph.D of materials science and engineering, Yonsei University. AvH post-doctoral fellow in MPIE (Dr. Dirk Ponge, Prof Dierk Raabe). I was working as an assistant professor from Sep. 2016 to Aug. 2019 in the department of materials science and engineering of Chungnam National University. Current position is an assistant professor in division of materials science and engineering of Hanyang University. My current focus is the Mn-bearing AHSS steels (TWIP, TRIP, and lightweight steels), superplasticity, high-performance Ti alloys, high entropy alloys, self healing alloys, and hydrogen embrittlement.
Additional affiliations
September 2019 - present
Hanyang University
Position
  • Professor (Assistant)
September 2016 - August 2019
Chungnam National University
Position
  • Professor (Assistant)
April 2016 - August 2016
Max Planck Institute for Sustainable Materials
Position
  • PostDoc Position
Education
August 2009 - August 2015
Yonsei University
Field of study
  • Metallugical engineering
March 2004 - February 2009
Yonsei University
Field of study
  • Metallurgical engineering

Publications

Publications (56)
Article
We investigated the correlation between the impact toughness and microstructures of annealed Fe-8Mn-0.2C-3Al-1.3Si (wt.%) steel to identify the key microstructural feature determining the impact toughness of medium-Mn steel. The microstructural constituents were varied by changing the hot-rolling temperature in the range of 1000–1200 °C before inte...
Article
To recover the reduced ductility of cold-worked medium-Mn steels, a novel resetting process is proposed in this study. Through a simple heat treatment, the original microstructure of the steel is restored by the re-reversion of the Mn-enriched strain-induced martensite. The ductility of the reset steel is successfully recovered, and its strength is...
Article
This work demonstrated the viability of friction stir welding for the welding of medium-Mn steels when used as cryogenic vessel materials for liquefied gas storage. We used an intercritically annealed Fe-7Mn-0.2C-3Al (wt.%) steel with a dual-phase (α′ martensite and γR retained austenite) nanolaminate structure as a base material and systematically...
Article
This study aimed to develop steels with reasonable material costs to replace Fe–9Ni (wt.%) steel, which is suitable for cryogenic applications. To this end, a newly designed Fe–2Mn–5Ni-0.1C steel was treated by quenching–tempering (QT) and quenching–lamellarizing–tempering (QLT); subsequently, the microstructural evolutions and resultant impact abs...
Article
Medium‐Mn steels have received significant attention from the steel industry as strong candidate materials for next‐generation advanced high‐strength steels. These steels can be manufactured by various routes, such as hot rolling plus annealing or cold rolling plus annealing, thereby resulting in two different microstructural morphologies: laminate...
Article
Microstructural defects and mechanical anisotropy are regarded as the main obstacles in additively manufactured, laser powder bed fusion (LPBF) IN718 superalloy, decelerating industrial development of the related components. Hot isostatic pressing (HIP) is an effective solution to overcome these challenges. In this study, standard heat treatment (H...
Article
The microstructure and hardness of Ti-6Al-4V alloys were evaluated before and after aging to investigate the effect of the cooling rate at the solution treatment stage of the solution treatment and aging (STA) process for aerospace components. The cooling rate distribution across a Ti-6Al-4V alloy sample representing practical STA process of an aer...
Article
In this study, we reveal that strain partitioning control is an essential technique to improve the mechanical response of medium-Mn steels by the micro digital image correlation analysis. An Fe-12Mn-0.06C-3Al (wt%) steel, which shows transformation-induced plasticity (TRIP) and twinning-induced plasticity (TWIP), was used as a model alloy. Two alte...
Article
Here, we investigated the effects of adding a micro-alloying element to medium-Mn steel and explored why a resulting sample containing precipitates exhibited higher strength than one without precipitates, without sacrificing ductility. The model alloys comprised steels of Fe-8Mn-0.2C-3Al-(0, 0.2)V (wt.%); they were cold-rolled and intercritically a...
Article
The microstructures and tensile properties of additively manufactured Ti-base alloys were investigated. Ti-6Al-4 V and Co-Cr-Mo alloy powders were blended and used for directed energy deposition of bulk samples containing 5 and 10 wt.% Co. The Ti-6Al-4 V and 5 wt.% Co sample exhibited an α phase at β grain boundaries, which caused a significant red...
Article
Ultrafine‐grained (UFG) dual‐phase (DP) AISI 5115 steel containing 0.12 wt% Ti is developed using thermomechanical treatment of cold rolling and intercritical annealing. The aim is to investigate the effect of intercritical annealing time on microstructural changes, mechanical properties, and fracture behavior. The results show that, with increasin...
Article
In the present study, we elucidated the possibility of improvement in H embrittlement (HE) resistance of micro-alloyed medium-Mn steels by MC carbides formation. The Fe-6Mn-0.08C (wt%) steel was used as a base material, and the different amount of Nb, Ti, and V was added to form MC carbides. All steels exhibited the nano-sized globular morphology w...
Article
The nature of melting and solidification phenomena during selective laser melting (SLM) process leads to a strong crystallographic texture in the as-built SLM components which causes mechanical anisotropy. This anisotropy is usually reduced by either optimization of the laser scanning strategy during the SLM process or high-temperature heat treatme...
Article
The effects of process temperatures for warm stamping, such as annealing (Tann), austenitizing (Taus), and stamping temperatures (Ts), on the tensile properties of Nb-bearing medium-Mn (5.9 wt pct) steel were investigated. The cold-rolled tensile specimens were first annealed at 650 °C to 750 °C, austenitized at 650 °C to 900 °C, held at Ts (500 °C...
Article
We suggest that the partial recrystallization is a novel pathway to increase the hydrogen embrittlement resistance of Fe-Mn-C twinning-induced plasticity steels. The Fe-18Mn-0.6C (wt%) cold-rolled steel was annealed for from 3 min to 30 min at 650 °C. When the annealing time was shorter than 5 min, the specimen was partially recrystallized, while w...
Article
The relationship between the cold rolling reduction ratio of medium-Mn steel before annealing, and the microstructure and tensile properties after annealing was investigated. The model alloy (Fe8Mn–0.2C3Al (wt.%) steel) was cold-rolled at different reduction ratios (between 0% and 60%) prior to intercritical annealing (IA) at 720 °C for 30 min. An...
Article
A medium-Mn steel (Fe-12Mn-3Al-0.05C wt%) was designed using Thermo-Calc ® simulations to balance the fraction and stacking fault energy of reverted austenite. Intercritical annealing for 0.5, 8 and 48 h was carried out at 585 C to investigate the microstructural evolution. X-ray diffraction (XRD), electron backscatter diffraction (EBSD), 3-dimensi...
Article
In the present study, we suggest the friction stir welding (FSW) is a novel pathway for the welding technique of medium Mn steels without degradation of mechanical properties. The application of conventional fusion welding deteriorates the mechanical properties of annealed medium Mn steels because it causes the martensitic transformation at the wel...
Article
Deformation behavior and tensile properties of an austenitic Fe-24Mn-4Cr-0.5C high-manganese steel with different grain sizes were discussed in this study. Effective grain size including annealing twins and stacking fault energy increased with increasing annealing temperature from 800 °C to 1200 °C. Room-temperature tensile test results indicated t...
Conference Paper
Reversion to Ultrafine-Grained Austenite in a Medium-Mn AHSS - Volume 24 Supplement - J T Benzing, J Bentley, A Kwiatkowski da Silva, L Morsdorf, J R McBride, D Ponge, B Gault, J Han, D Raabe, J E Wittig
Article
Full-text available
The original PDF version of this Article omitted to state that "Jeongho Han and Seok-Hyeon Kang contributed equally to this work" in the affiliations section. This has now been corrected in the PDF version of the Article. The HTML version was correct from the time of publication.
Article
Full-text available
Superplastic alloys exhibit extremely high ductility (>300%) without cracks when tensile-strained at temperatures above half of their melting point. Superplasticity, which resembles the flow behavior of honey, is caused by grain boundary sliding in metals. Although several non-ferrous and ferrous superplastic alloys are reported, their practical ap...
Conference Paper
Medium-Mn steels are considered third generation advanced high strength steels (AHSS), which contain both ferrite (a) and austenite (g) and aim to balance the low cost of first generation AHSS with the outstanding mechanical properties of second generation AHSS. These steels generally exhibit an a′ martensitic microstructure after hot and cold roll...
Article
Full-text available
Recently, Fe-Mn twinning-induced plasticity steels with an austenite phase have been the course of great interest due to their excellent combination of tensile strength and ductility, which carbon steels have never been able to attain. Nevertheless, twinning-induced plasticity steels also exhibit a trade-off between strength and ductility, a longst...
Article
The effects of prior austenite (g) grain boundaries and microstructural morphology on the impact toughness of an annealed Fe-7Mn-0.1C-0.5Si medium Mn steel were investigated for two different microstructure states, namely, hot-rolled and annealed (HRA) specimens and cold-rolled and annealed (CRA) specimens. Both types of specimens had a dual-phase...
Article
The objective of the present study was to investigate the mechanism of premature tensile fracture of the gas-nitrocarburized steel. For this purpose, tempered martensitic steel specimens were nitrocarburized at 853 K (580 °C) for maximum 3.5 hours, and tensile-strained at room temperature. The prolongation of nitrocarburizing time caused the high s...
Article
The objective of the present study was to investigate the inhomogeneity of microstructure and damping capacity of a FC25 disc-brake rotor made of gray cast iron (GCI) and their interrelationship. The rotor had inhomogeneous microstructure due to different cooling rates caused by the position of inlets in a mold during casting. The volume fraction a...
Article
The objective of this study was to investigate the mechanisms of hydrogen embrittlement (HE) in intercritically annealed medium Mn steel. For this purpose, both hot-rolled and cold-rolled Fe-7Mn-0.1C-0.5Si (wt.%) steels were annealed at 640 °C for 30 min. The annealed specimens had a dual-phase microstructure of retained austenite (γR) and ferrite...
Article
The objectives of the present study were to develop the bimodal-grained microstructure in a medium Mn steel without the addition of Al only through a thermo-mechanical process, and to systematically investigate the relationship between the bimodal-grained microstructure and yielding behavior. The cold-rolled Fe-7Mn-0.05C (wt.%) steel with deformed...
Article
The stacking fault energy can play a key role in the deformation mechanism (e.g. transformation-induced plasticity and twinning-induced plasticity) of austenitic steels. Therefore, tremendous efforts have been devoted to exploring the evaluation methods and controlling parameters (e.g. alloying elements and temperature) that determine the stacking...
Article
The aim of the present study was to predict the variations in microstructure and deformation occurring during gas carburizing and quenching processes of a SCM420H planetary gear in a real production environment using the finite element method (FEM). The motivation for the present study came from the fact that previous FEM simulations have a limitat...
Article
The deformation mechanism of a medium-Mn lightweight steel with an inhomogeneously grained structure of austenite was investigated as a function of annealing temperature. All annealed specimens exhibited three different phases: γ-austenite, δ-ferrite and α′-martensite. Specimens annealed at temperatures below 1000 °C exhibited high strain-hardening...
Article
Medium Mn steels have been actively investigated due to their excellent balance between material cost and mechanical properties. The steels possess a single α′ martensite phase in hot and cold rolled states and multiphases after intercritical annealing. Many studies have focused on investigating the influences of chemical composition and annealing...
Article
The effects of the initial microstructure of α′ martensite on the microstructural evolution during intercritical annealing and the tensile properties of annealed specimens were investigated for Fe–9Mn–0.05C (wt.%) steel. The hot-rolled specimen with fully α′ martensitic microstructure showed a mixed microstructure of lath-shaped ferrite (αL) and au...
Article
Full-text available
Controlling the orientations of nanomaterials on arbitrary substrates is crucial for the development of practical applications based on such materials. The aligned epitaxial growth of single-walled carbon nanotubes (SWNTs) on specific crystallographic planes in single crystalline sapphire or quartz has been demonstrated; however, these substrates a...
Article
Both the mechanism of the reverse transformation from martensite (α′) to austenite (γ) and the stability of reverted γ were systematically investigated as a function of the heating rate using cold-rolled Fe–(5–9)Mn–0.05C (wt.%) steels. When the specimens were slowly heated at rates below 15 °C s−1, cementite formed along various boundaries, then th...

Questions

Questions (2)
Question
Greeting.
I have a fundamental question about void swelling when the alloys were irradiated.
I carefully think this question is taken for granted in the fields of nuclear materials.
Generally, it is known that ferritic/martensitic steels exhibited higher resistance to void swelling than austenitic steel ( ).
That is, bcc alloys show slower void swelling.
I can`t exactly understand the reason for this phenomenon. BCC usually exhibited a faster diffusion rate compared to FCC, and thus I think BCC should show faster growth of void.
On the other hand, considering high entropy alloys ( ), FCC HEA shows a higher resistance of void swelling relative to BCC or BCC+FCC HEAs, and the authors mentioned that this result is in contrast to traditional materials (e.g., ferritic/martensite steel and austenitic stainless steel).
May I ask the reason for the higher resistance of void swelling in BCC metal rather than FCC metal?
Thank you in advance
Question
Hello.
In our department, we have a Jeol 7001F (Fe-SEM) attached with EBSD and BEI detector. During my PhD program, I always wondered about operating method for electron channeling contrast imaging (ECCI). I don`t know accurate operating method for ECCI, but slightly know the sequences (maybe this is the problem..).
I tried many times but I failed always... I prepared steel sample (Mn steel, C steel) finised with colloidal silica mixture or electro polishing. These specimens had a good enough quailty when I observed EBSD.
So my question is:
1. What is the specimen preparation method for ECCI? is there any special preparation method ?
2. Which BEI detector is needed? Specialized BEI detector is needed for ECCI? I only know both BEI (low tilt condition) and forward scatter detector (high tilt condition) are possible for ECCI.
Thank you for reading.
Best regards, Jeongho

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