Influence of Phase Composition in TiAlSiN Hard Coatings on the Evolution of Structure and Mechanical Properties

Jeong‑Han Lee,Ik‑Hyun Oh,Jun‑Ho Jang,Ju‑Hun Kim,Sung‑Kil Hong,Hyun‑Kuk Park 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.3

The aim of this study is to investigate the structural evolution and mechanical properties of TiAlSiN coatings when processedby the arc ion plating method. To form a hard coating, Ti, Al, and Si powders were mechanically alloyed by planetary ballmilling; the powders were then densely compacted during a rapid sintering process into a ternary system coating, i.e. TiAlSi. The evolution of the structural phase from a powder to a compact material is dominated considerably by phase states suchas a supersaturated solid solution or intermetallic compounds. In the case of coating layers, the factors that determine thestructural evolution are associated with the phase stability of the nano-crystalline structure that in turn is associated withthe Ti/Al composition ratio. Motivated by this, we performed experiments to investigate the distribution of microstructures;the material’s binding energy, quantitative properties, transformation of crystal structure, and distribution of amorphous/crystalline were all recorded. In particular, the relationship between the physical and chemical properties during the coatingprocess is considered to be the dominant factor controlling the orientation and morphology of that zone (1, T, and 2). TheTiAlSiN coating layer was found to have hardness above 45 GPa and an adhesion above 100 N. In other words, understandingthe evolution and structure of TiAlSin helped us to produce a material with excellent properties that can be used as a hardcoating. Specifically, these properties were induced by a grain refinement of the nano-crystalline structure that correspondsto an increase in the silicon nitride contents.

Characterization and Property Evaluation of Ti‑Based Target Materials and Their Nitride Nano‑composites Coating Layers

Jeong‑Han Lee,Hyun‑Kuk Park,장준호,Ik‑Hyun Oh 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.1

This study formed a hard TiAlSiWN coating layer using Ti, Al, Si and W raw powders that were mechanically alloyed andrefined. The TiAlSi and TiAlSiW coating targets were fabricated using a pulse current activated sintering process in a shorttime with the optimal sintering conditions. The optimized sintering condition was obtained by controlling process parameterssuch as temperature, pressure, heating rate and pulse ratio (on/off). The coating targets were successfully deposited onthe WC substrate to form the TiAlSiN and TiAlSiWN nitride nano-composite structures by an arc ion plating process andalso, their coating layers were compared according to the addition of W element. The microstructures of the nitride nanocompositecoating layer were analyzed, focusing on the distribution of the crystalline phases, amorphous phases (Si3N4),and growth orientation of the columnar crystal depending on the addition of W element. The mechanical properties of thecoating layers were exhibited a hardness of approximately 3000 kg/mm2 and adhesion of about 117.77 N in the TiAlSiN. Inparticular, the TiAlSiWN showed excellent properties with a hardness of more than 4300 kg/mm2 and an adhesion of about181.47 N, respectively.

Rapid Consolidation of WC‑ZrSiO4 Hard Materials by Spark Plasma Sintering: Microstructure, Densification, and Mechanical Properties

Jeong‑Han Lee,Ik‑Hyun Oh,Ju‑Hun Kim,Sung‑Kil Hong,Hyun‑Kuk Park 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.9

Densely consolidated WC-based hard materials with 5–20 vol% ZrSiO4was fabricated by spark plasma sintering at 1400 ℃ ata constant heating rate of 70 ℃/min−1. To achieve mechanical alloying of WC-ZrSiO4, planetary ball milling was carried outfor 12 h, during which the brittle-brittle components (WC-ZrSiO4) became fragmented and their particles became refined. Itwas observed that certain, specific, non-isothermal sintering kinetics, such as apparent activation energy, sintering exponents,and densification strain, affected the densification behavior. The evolution of phase structure from powder to compact wasfound to be related the lattice distortion and micro-strain in the basal planes of WC. By examining the mechanical propertiesof the samples, it was that the added zircon content leads to enhanced fracture toughness (12.9 MPa m1/2) owing to thepresence of WC-ZrSiO4 in the cemented carbide. In fact, the microcrack propagation of the fracture passed through zirconfrom a transgranular to a ductile component (fcc) where the crack tips could be absorbed.

Effect of Mechanical Alloying on the Microstructural Evolution of Al60Cr30Si10 Alloys Processed by Spark Plasma Sintering

Jeong‑Han Lee,Ik‑Hyun Oh,Jun‑Ho Jang,Ju‑Hun Kim,Sung‑Kil Hong,Hyun‑Kuk Park 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.5

In this study, Al, Cr and Si fine powders were alloyed by planetary ball milling to investigate their microstructural evolution,following their mechanical alloying behavior. The formation of Al(Cr) supersaturated solid solution by the Cr grainsembedded in Al-matrix, which contributed substitutional structure is discussed in relation to their structural evolution inaccordance with the distortion of a crystal lattice. The compacts of Al–Cr–Si alloys were prepared by rapid sintering withina short time by dense consolidation above the density of 99.9% as the formation of intermetallics, except in the case of thedistribution of single-phases induced by the Al-melting. The formation behavior of intermetallics was dominated by dependenceon the structures of the milled-powder and subsequent sintering temperature. To estimate the consolidated behaviorsof compacts, various approaches derived from TEM and XRD analysis were taken to obtain microstructural evidences ofthe inter-diffusion, following the presence of thermally stable intermetallics.

반음절기반의 한국어 연속숫자음인식과 그 후처리에 대한 연구

정재부,정훈,정익주 한국음성과학회 2001 음성과학 Vol.8 No.4

This paper describes the effect of new recognition unit, a unit based on semi-syllable, and its post processing method. A recognition unit based on semi-syllable expresses Korean connected digit's coarticulation effect. An existing method using semi-syllable limits next models, derived from current recognized models, to make complete connected digit sequence. However, this paper uses a new method to make complete connected digit sequence. The new post-processing method recognizes isolated digit words which include digits sequence from the digit combinations being able to occur from current recognized semi-syllable sequence. This method gives an improved accuracy rate than that of existing method. This new post processing provides two advantages. 1) It corrects current rnis-recognized semi-syllable unit. 2) When people say each digit, they say it without regard to saying duration.

GIS를 이용한 교통량 및 오염물질 배출량의 산정

정태섭,임익현 全北大學校 附設 都市및環境硏究所 1998 都市 및 環境硏究 Vol.13 No.1

The results of this study are summarized as follows' The traffic of link and emission of air pollutant described using GIS. And thus, it enables to analysis transport and air pollution system more powerfully in terms of graphics and data management. Applying graphic ability in GIS to analysis and describe, the results are expressed graphically easily understood. This study was carried on traffic system of Daejeon. First, network of road constructed in Daejeon using roads data. And then, network was inputed data of traffic and emission of air pollutants in links. The results of a test study on realistic network and emission shows various ways of representation of output data. Therefore, it is essy to traffic management and pollutants anlysis.

소음·진동의 측정, 분석에 있어서 퍼스컴의 활용에 관한 연구

정명진,이익형 서울보건대학 1995 서울보건대학 부설 한국보건과학연구소 논문집 Vol.1 No.1

The measurement system of the noise and vibration is consisted of personal computer, AID converter, interfacing sound level and vibration meters. The experiment is performed in a dynamic system by this system, and some information which are necessary for the noise and vibration analysis can be obtained through the processing of the data that are stored in the computer. These are sound pressure level, RMS level, peak value, p-p value, frequencies, displacement, velocity, acceleration. With this experimental system, it will be considered that more easy way of sound and vibration data pick-up and processing is possible.

마이크로 엔드밀링에서 음향방출 신호를 이용한 상태감시

정연식,강익수,김전하,강명창,김정석,안중환 한국공작기계학회 2004 한국공작기계학회 추계학술대회논문집 Vol.2004 No.-

Ultraprecision machining and MEMS technology have been taken more and more important position in machining of microparts. Micro endmilling is one of the prominent technology that has wide spectrum of application field ranging from macro parts to micro products. Also, the method of micro-grooving using micro endmilling is used widely owing to many merit, but has problems of precision and quality of products due to tool wear and tool fracture. This investigation deals with state monitoring using acoustic emission(AE) signal in the micro-grooving. Characteristic evaluation of AE raw signal, AE hit and frequency analysis for state monitoring is also presented in the paper.

총체적 언어교육 접근법이 학습장애아동의 읽기 및 쓰기 능력에 미치는 효과

정익권,전병운 公州大學校 特殊敎育硏究所 2003 특수교육논집 Vol.7 No.-

The purpose of this study was to examine the effect of the elementary Korean curricula for grade 1, which was reconstructed on the basis of whole language learning approach, on the reading and writing skills of children with learning disability. It’s specially meant to determine its impact on the reading fluency, reading comprehension and writing of educationally retarded children. The subjects in this study were 10 children in their third and fourth years. Out of them, five children in the experimental group were selected from among children with learning disability in an elementary school, and the other students were selected from five other elementary schools in the same region, who were all allocated into a control group. The experimental group received whole language learning approach in 30 sessions for eight weeks. To find out the effect of whole language learning approach, intergroup t-test was implemented, and how much that was effective for individual children was analyzed. The brief findings of this study were as below: 1. The whole language learning approach didn’t give a notable impact on the reading fluency of the children with learning disability. 2. The whole language learning approach served to increase the reading comprehension of the children with learning disability(p<.05). Compared to the children who received regular instruction, the children exposed to the whole language learning approach made a remarkable progress in reading comprehension. 3. The whole language learning approach improved the writing skills of the children with learning disability(p<.05). The children who underwent the whole language learning approach observed the writing rules better than the others who didn’t, and the former group excelled the latter in expressing themselves in a written form. The above-mentioned findings suggested that the whole language learning approach had a favorable effect on enhancing the reading and writing skills of the children with learning disability.

SM570, POSTEN60 및 80 강재의 피로균열성장특성

정영화,김익겸,강성립,남왕현,김은성 江原大學校 産業技術硏究所 2001 産業技術硏究 Vol.21 No.A

In this study, a series of fatigue tests are carried out in order to estimate quantitatively the characteristics of fatigue crack growth rate for high strength steels of SM570, POSTEN60, and POSTEN80 steel, that is, the influence on fatigue crack growth rate according to the welding line, the characteristics of fatigue crack growth according to the welding method and the kinds of steel, and the characteristics of fatigue crack growth for base metal, heat affected zone and weld metal. From the test results, in case that the notch if parallel to welding line, it knows that the retardations of fatigue crack growth ramie in crack tip at early stage increase remarkably than in case that the notch is perpendicular to welding line due to compressive residual stress. And the characteristics of fatigue crack growth rate according to welding method are that the dispersion of fatigue crack growth rate in case of FCAW method is smaller than that of SAW method. Also, it knows that the fatigue crack growth rate converges in high stress intensity factor range.