전자 후방 산란 분석기술과 결정소성 유한요소법을 이용한 전해 도금 구리 박막의 결정 방위에 따른 소성 변형 거동 해석

박현,신한균,김정한,이효종 한국마이크로전자및패키징학회 2024 마이크로전자 및 패키징학회지 Vol.31 No.2

구리 전해 도금 기술은 반도체 패키징 및 반도체, 이차 전지 등 다양한 마이크로 전자 산업 분야에서 구리 박막 또는 배선의 제조를 위해 사용되고 있으며, 각 응용처에서 요구하는 특성을 획득하기 위해 이들 구리 박막 또는 배선의 미세조직을 제어하고자 광범위한 연구가 이루어지고 있다. 본 연구에서는 기계적 물성이 우수한 이차 전지용 구리 박막을 제조하기 위해, 이차 전지 제조 공정 중 기계적 또는 열적 하중에 의한 박막의 소성 변형 시 박막을 구성하는 결정립들의 결정학적 이방성의 영향성을 조사하였다. 이를 위해, 상이한 집합조직이 발달한 2 종류의 10 μm 두께 전해 도금구리 박막에 대해 전자 후방 산란 (electron backscattering diffraction or EBSD) 기술을 이용하여 표면 또는 단면의 결정방위 지도를 측정하였고, 이들을 초기 입력 정보로 한 결정소성 유한요소해석을 통해 1축 인장 변형에 따른 박막 내부의국부적 변형 거동을 분석하였다. 이를 통해, 인장 변형률의 증가에 따른 박막 내 소성 변형 불균질성과 집합조직의 변화를 추적하였고, 불균질한 소성 변형을 일으키는 결정립의 결정 방위를 확인하였다. Copper electrodeposition technology is essential for producing copper films and interconnects in the microelectronics industries including semiconductor packaging, semiconductors and secondary battery, and there are extensive efforts to control the microstructure of these films and interconnects. In this study, we investigated the influence of crystallographic orientation on the local plastic deformation of copper films for secondary batteries deformed by uniaxial tensile load. Crystallographic orientation maps of two electrodeposited copper films with different textures were measured using an electron backscatter diffraction (EBSD) system and then used as initial conditions for crystal plasticity finite element analysis to predict the local plastic deformation behavior within the films during uniaxial tension deformation. Through these processes, the changes of the local plastic deformation behavior and texture of the films were traced according to the tensile strain, and the crystal orientations leading to the inhomogeneous plastic deformation were identified.

Performance evaluation of soil-embedded plastic optical fiber sensors for geotechnical monitoring

Cheng-Cheng Zhang,Hong-Hu Zhu,Bin Shi,Jun-Kuan She,Dan Zhang 국제구조공학회 2016 Smart Structures and Systems, An International Jou Vol.17 No.2

Based on the distributed fiber optic sensing (DFOS) technique, plastic optical fibers (POFs) are attractive candidates to measure deformations of geotechnical structures because they can withstand large strains before rupture. Understanding the mechanical interaction between an embedded POF and the surrounding soil or rock is a necessary step towards establishing an effective POF-based sensing system for geotechnical monitoring. This paper describes a first attempt to evaluate the feasibility of POF-based soil deformation monitoring considering the POF–soil interfacial properties. A series of pullout tests were performed under various confining pressures (CPs) on a jacketed polymethyl methacrylate (PMMA) POF embedded in soil specimens. The test results were interpreted using a fiber–soil interaction model, and were compared with previous test data of silica optical fibers (SOFs). The results showed that the range of CP in this study did not induce plastic deformation of the POF; therefore, the POF–soil and the SOF–soil interfaces had similar behavior. CP was found to play an important role in controlling the fiber–soil interfacial bond and the fiber measurement range. Moreover, an expression was formulated to determine whether a POF would undergo plastic deformation when measuring soil deformation. The plasticity of POF may influence the reliability of measurements, especially for monitored geo-structures whose deformation would alternately increase and decrease. Taken together, these results indicate that in terms of the interfacial parameters studied here the POF is feasible for monitoring soil deformation as long as the plastic deformation issue is carefully addressed.

열차 반복하중에 의한 철도 노반의 소성침하량 예측

원상수(Sang-Soo Won),정영훈(Young-Hoon Jung),이진욱(Jin-Wook Lee),이성혁(Seong-Hyeok Lee) 한국철도학회 2013 한국철도학회 학술발표대회논문집 Vol.2013 No.5

반복하중에 의한 노반의 변형은 회복변형과 영구변형으로 나눌 수 있으며, 그 중 영구변형은 회복이 불가능한 소성변형을 뜻한다. 노반의 주된 소성변형 거동은 연직방향의 침하로서 과다 발생시 궤도 구조체의 안정성과 유지보수에 영향을 준다. 따라서 반복적인 열차하중에 의한 소성침하 거동의 예측과 검토가 필요하다. 본 논문에서는 콘크리트 궤도를 대상으로 실대형실험을 수행하여 반복재하에 따른 누적 침하량을 측정하였고, 노반 재료의 반복삼축압축실험 결과와 비교, 분석을 통해 소성 변형률 예측식인 지수 함수모델에 필요한 변수를 산정하였다. 이를 기존의 누적 소성 예측 모델과 비교하여 타당성을 검토한 후, 유한요소해석에 적용하여 표준 성토 단면에 대한 3차원 해석을 실시하였고 반복하중에 의한 노반의 장기적인 누적 소성 침하 거동을 예측하였다. Deformation of roadbed under the cyclic loading can be divided into recoverable and permanent or plastic deformation. The primary plastic deformation behavior of roadbed causing excessive axial settlements affects the stability and maintenance of the track structure. Therefore, it is necessary to predict plastic settlement behavior by cyclic train loading. Herein, full-scale test for the concrete slab track was carried out. The parameters of the power model for permanent plastic deformation were determined. Validity of parameters was confirmed by comparing with the existing models. Three-dimensional finite element analysis using cumulative plastic model for standard roadbed section was conducted.

Post Deformation at Room and Cryogenic Temperature Cooling Media on Severely Deformed 1050-Aluminum

M. Sarkari Khorrami,M. Kazeminezhad 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.2

The annealed 1050-aluminum sheets were initially subjected to the severe plastic deformation through two passes of constrainedgroove pressing (CGP) process. The obtained specimens were post-deformed by friction stir processing at roomand cryogenic temperature cooling media. The microstructure evolutions during mentioned processes in terms of grainstructure, misorientation distribution, and grain orientation spread (GOS) were characterized using electron backscattereddiffraction. The annealed sample contained a large number of “recrystallized” grains and relatively large fraction (78%) ofhigh-angle grain boundaries (HAGBs). When CGP process was applied on the annealed specimen, the elongated grainswith interior substructure were developed, which was responsible for the formation of 80% low-angle grain boundaries. TheGOS map of the severely deformed specimen manifested the formation of 43% “distorted” and 51% “substructured” grains. The post deformation of severely deformed aluminum at room temperature led to the increase in the fraction of HAGBsfrom 20 to 60%. Also, it gave rise to the formation of “recrystallized” grains with the average size of 13 μm, which werecoarser than the grains predicted by Zener–Hollomon parameter. This was attributed to the occurrence of appreciable graingrowth during post deformation. In the case of post deformation at cryogenic temperature cooling medium, the grain sizewas decreased, which was in well agreement with the predicted grain size. The cumulative distribution of misorientationwas the same for both processing routes. Mechanical properties characterizations in terms of nano-indentation and tensiletests revealed that the post deformation process led to the reduction in hardness, yield stress, and ultimate tensile strengthof the severely deformed aluminum.

Skutterudite: Reproducibility of Thermoelectric Performance of P-type RyFe4-xCoxSb12 Bulky Compacts

Aman Gupta,Ranjeet Kumar,Lalit Kaushik,Sourabh Shukla,Vipin Tandon,Shi-Hoon Choi 대한금속·재료학회 2024 대한금속·재료학회지 Vol.62 No.7

The stacking fault energy (SFE) of face-centered cubic (FCC) alloys is a critical parameter thatcontrols microstructural and crystallographic texture evolution during deformation and annealingtreatments. This review focuses on several FCC alloys, aluminum (Al), copper (Cu), austenitic stainlesssteels (ASSs), and high entropy alloys (HEAs), all of which exhibit varying SFEs. These alloys are oftensubjected to thermo-mechanical processing (TMP) to enhance their mechanical properties. TMP leads to theevolution of deformation-induced products, such as shear bands (SBs), strain-induced martensite (SIM), andmechanical/deformation twins (DTs) during plastic deformation, while also influencing crystallographictexture. High-medium SFE materials, such as Al and Cu, typically exhibit the evolution of Copper-typetexture during room temperature rolling (RTR), while low SFE materials, such as ASSs and HEAs, displayBrass-type texture at high reduction ratios. Moreover, the presence of second-phase particles/precipitatescan also impact the microstructure and texture evolution in Al and Cu alloys. Particle-stimulated nucleation(PSN) during the annealing treatment has been reported for Al, Cu, ASSs, and HEAs, which causes textureweakening. Another interesting observation in severely deformed Cu alloys is the room-temperaturesoftening phenomenon, which is discussed in the reviewed work. Additionally, plastic deformation and heattreatment of ASSs result in phase transformation, which was not observed in Al, Cu, or HEAs. Furthermore, the dependence of special boundaries in HEAs on plastic deformation temperature, strainrate, and annealing temperature is also discussed. Thus, this review comprehensively reports on the impactof TMP on microstructural and crystallographic texture evolution during plastic deformation and theannealing treatment of Al, Cu, ASSs, and HEAs FCC materials, using results obtained from electronmicroscopy.

Finite element analysis of plastic deformation of CP-Ti by multi-pass equal channel angular extrusion at medium hot-working temperature

Zhang, Z.J.,Son, I.H.,Im, Y.T.,Park, J.K. Elsevier Sequoia 2007 Materials science & engineering. properties, micro Vol.447 No.1

The plastic deformation of commercially pure (CP) titanium by multi-pass equal channel angular extrusion (ECAE), at medium hot-working temperature, was simulated using finite element method. The effect of ECAE deformation was to uniformly deform the middle billet by simple shear and to induce a side shift of un-deformed and un-moved billet-ends so as to preserve its original shape during deformation. Unlike the single ECAE pass, where the corner gap is important, it was the repetitive billet-end side-shift of less-deformed billet-ends which are responsible for the development of the non-uniformly deformed zone in the multi-pass ECAE processing via route A. The deformation zone was however little affected in the multi-pass EACE processing via route C, because of the alternate sense of billet-end side-shift. The simulation well predicted the inclination angles of elongated-grain in the multi-pass ECAE deformation.

Simple Shear Model of Twist Extrusion and Its Deviations

Marat I. Latypov,이명규,Yan Beygelzimer,Roman Kulagin,김형섭 대한금속·재료학회 2015 METALS AND MATERIALS International Vol.21 No.3

Twist extrusion (TE) is a severe plastic deformation method with a potential for commercialization. Advancing TE toward industrial use requires in-depth understanding of deformation during the process and its dependence on processing factors. The helical flow model introduced with the concept of TE provides for a concise description of deformation in the process. To date, however, it was unclear under which conditions the helical flow model yields accurate predictions of deformation in TE. This paper presents a systematic finite-element study performed to identify effects of some key process and material factors on deformation in TE and its departure from the ideal deformation described by the helical flow model. It was found that high strain-hardening rate and friction lead to violations of the assumptions of the helical flow model and that these violations result in departure from the ideal deformation. Deviations from the ideal deformation tend to increase on decreasing the length of the twist channel. Friction effects appear especially critical to be considered for accurate prediction of deformation in TE. Finite-element simulations taking friction into account show good qualitative agreement with earlier marker-insert experiments. The results of the present finite-element study allowed for defining the simple shear model of TE.

Quantitative Analysis of Strength and Plasticity of a 304 Stainless Steel Based on the Stress-strain Curve

Lixin Li,Sheng Liu,Ben Ye,Shengde Hu,Zhifeng Zhou 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.3

A constitutive model including the kinetics of twinning and martensitic transformation has been established based on the dislocation theory and the mixture law. The stress-strain curve of a 304 stainless steel has been measured by a tensile test. The material constants for the constitutive model are then found through an inverse analysis of the stress-strain curve measured experimentally, determining the stress-strain relationship equation and the kinetics of twinning and martensitic transformation of the investigated alloy. The volume fractions of martensitic transformation have been measured by the magnetic tester of Fischer Model MP3C. It has been shown that the calculated stress-strain curve and the volume fractions of martensitic transformation are in agreement with those obtained from experimental measurements, demonstrating that the material constants found by using the stress-strain curve can capture the underlying materials science of deformation. On this basis, the influence of twins, martensitic transformation, and mechanical behavior of austenite and martensite on the strength and plasticity of the 304 stainless steel has been discussed further.

Finite-Element Analysis of Radial Extrusion for a Thin Disk with Severe-Plastic Deformation

박종진 대한금속·재료학회 2012 METALS AND MATERIALS International Vol.18 No.3

Severe plastic deformation is an effective method to obtain fine or ultrafine grains in metallic materials. In the present study, a radial extrusion of a round bar was investigated for the capability of producing a thin disk by severe plastic deformation by the rigid-plastic finite-element method. Similar to the deformation mechanism in the ECAP, the shear deformation was observed to develop at the corner of the container; its magnitude increases as the radius of the corner decreases. Additional plastic deformation was obtained as the material flowed in the radial direction. However, waviness of the sheet in the radial direction and occurrence of cracking were observed at the periphery of the disk. To resolve these problems, the bottom surface of the container was conically designed in order to provide an inclination angle along the radial direction. This process was further modified to a radial extrusion of a pipe for a hollow disk or thin ring with severe-plastic deformation.

Influences of high strain rate, low temperature, and deformation direction on microstructural evolution and mechanical properties of copper

Ahn, Dong-Hyun,Kang, Minju,Park, Lee Ju,Lee, Sunghak,Kim, Hyoung Seop Elsevier Sequoia 2017 Materials science & engineering Structural materia Vol.684 No.-

<P><B>Abstract</B></P> <P>Step-wise deformations are applied to pure copper along uniaxial direction or multiaxial directions in three conditions of speed and temperature: static and room temperature, dynamic and room temperature, or dynamic and low temperature. Through examinations of total 36 deformation stages, the influences of strain rate, temperature, and deformation direction on microstructural evolution and mechanical properties are investigated. According to the results, the deformation mechanism at extreme conditions (high strain rate and low temperature) changes from only dislocation slip to dislocation slip and deformation twinning. Although deformation-direction change has no significant effect on the final mechanical properties and total dislocation densities measured from X-ray diffraction results, the evolutions of grain-boundary misorientation and geometrically necessary dislocations (GNDs) are clearly influenced. The trend of microstructural evolution, i.e. larger grain size and lower GND densities by multi-axial deformation than the uniaxial case, is reversed when twinning occurred. Based on the results, we suggest four evolution models: uniaxial or multi axial cases with dislocation slip, or with dislocation slip and deformation twining. Even if the homogenous and almost fully twinned microstructure producing improved mechanical strength was obtained by applying the extreme deformations, poor ductility of the processed specimen were observed.</P>