기계적 합금화한 $\sigma$-VFe합금의 중성자 및 X선 회절에 의한 상분석

이충효,조재문,이상진,심해섭,이창희,Lee, Chung-Hyo,Jo, Jae-Mun,Lee, Sang-Jin,Sim, Hae-Seop,Lee, Chang-Hui 한국재료학회 2001 한국재료학회지 Vol.11 No.8

$\sigma$-VFe 금속간화합물에 대한 기계적 합금화(MA) 효과를 중성자 및 X선 회절법으로 조사하였다. MA 분말의 구조분석은 X선 회절(Cu-K$\alpha$) 린 중성자회절(HRPD, λ=1.835$\AA$)을 이용하여 행하였다. $\sigma$-VFe화합물의 MA시 큰 구조변화가 관찰되었으며, MA 60시간의 경우 Fe-Fe 훤자분포는 unit cell에 30개의 원자를 포함하고 있는 $\sigma$상의 tetragonal구조에서 $120^{\circ}C$이상에서 안정하게 존재하는 $\alpha$-(V,Fe) 고용체의 bcc 구조로 상변화함을 알 수 있었다. 또한 $\alpha$-VFe 화합물에 대한 중성자 및 X선 회절패턴의 비교분석을 행하였으며 그 결과 $\sigma$상이 가지는 화학적 규칙성에 기인하는 (101)과 (111) 회절 피크가 중성자 회절에서 뚜렷하게 관찰됨을 알 수 있었다. The mechanical alloying (MA) effect in $\sigma$-VFe intermetallic compound was studied by neutron and X-ray diffraction. The structure of MA $\sigma$-VFe powders were characterized by the X- ray diffraction with Cu- $K\alpha$ radiation and neutron diffraction with monochromatic neutrons of $1.835\AA$ using a high resolution powder diffractometer (HRPD). Mechanical alloying of $\sigma$-VFe compound gives rise to a dramatic structural change. After 60 hours of MA, the Fe-Fe distribution of the $\sigma$- phase VFe tetragonal structure with 30 atoms in a unit cell is found to change into that of the $\sigma$-(V,Fe) solid solution with bcc structure, which is a stable phase at elevated temperature above $1200^{\circ}C$. A comparison of X-ray diffraction data for the $\alpha$-phase has been also made with the corresponding neutron diffraction data. The (101) and (111) diffraction peaks of the $\sigma$-phase was clearly observed only in neutron diffraction pattern, which is believed to be a characteristic feature due to the chemical atomic ordering of $\sigma$- VFe phase.

비고용 V-Cu계 MA합금의 중성자 및 X선 회절에 의한 상분석

이충효,조재문,이상진,김지순,Lee Chung-Hyo,Cho Jae-Moon,Lee Sang-Jin,Kim Ji-Soon 한국재료학회 2004 한국재료학회지 Vol.14 No.5

The mechanical alloying (MA) effect in immiscible V-Cu system with positive heat of mixing was studied by not only the neutron and X-ray diffraction but also the analysis of DSC spectra. The total energy, ΔHt accumulated during MA for the mixture of $V_{50}$ $Cu_{50}$ / powders increased with milling time and approached the saturation value of 14 kJ/mol after 120 h of milling. It can be seen that the free energy difference between the amorphous phase and the pure V and Cu powders with an atomic ratio 5:5 is estimated to be 11 kJ/mol by Miedema et al. This is thermodynamically taken as one of the evidences for the amorphization. The structural changes of V-Cu MA powders were characterized by the X-ray diffraction and neutron diffraction. We take a full advantage of a negligibly small scattering length of the V atom in the neutron diffraction measurement. The neutron diffraction data definitely indicate that the amorphization proceeds gradually but incompletely even after 120 h of MA and bcc-Cu Bragg peaks appears after 60 h of MA.

중성자 회절을 이용한 용접부위의 잔류응력 측정

박만진,장동영,최희동 대한용접접합학회 2002 대한용접·접합학회지 Vol.20 No.2

Residual stress is generated in the structures as a result of irregular elastic-plastic deformation during fabrication processes such as welding, heat treatment, and mechanical processing. There are several factors attributed to the origin of residual stresses, tensile or compressive. The stresses can be determined by destructive ways or nondestructive ways using X-ray or neutron diffraction. Although X-ray diffraction is a well established technique, it is practically limited to near-surface stresses. Neutrons penetrate easily into most materials and neutron diffraction permits non-destructive evaluation of lattice strain within the bulk of large specimens because the radiation is more deeply penetrating for metallic engineering components. This paper presented application of neutron diffraction technique to the residual stress measurement using 20 mm thick welded stainless steel plate($100{\times}100 \textrm{mm}^2$)

Stress-strain relationship between ferrite and martensite in a dual-phase steel studied by in situ neutron diffraction and crystal plasticity theories

Woo, W.,Em, V.T.,Kim, E.Y.,Han, S.H.,Han, Y.S.,Choi, S.H. Elsevier Science 2012 Acta materialia Vol.60 No.20

The stress-strain relationship between ferrite and martensite phases in the commercial dual-phase DP980 steel was studied using in situ neutron diffraction and the crystal plasticity finite element method (CPFEM). The phase identification method based on the image quality of electron backscatter diffraction and a filtering process was used to obtain information concerning individual crystallographic orientations for ferrite and martensite phases in DP980 steel. The (200) and (211) lattice strains of ferrite and martensite phases were measured along the loading and transverse directions as a function of macroscopic stress using in situ neutron diffraction. A CPFEM based on representative volume elements (RVE) was applied to determine the microscopic hardening parameters for each phase by fitting the measured macroscopic stress and measured (200) and (211) lattice strains. The microscopic hardening parameters for each phase successfully captured the influence of the crystallographic orientation of the ferrite phase on the localization of shear strain and the behavior of ductile failure in RVE of the unit cell during uniaxial tension.

중성자 회절을 이용한 이중 층상형 산화철 (Lu,Ln)Fe2O4 (Ln=Er,Y)과 Lu(Fe,M)2O4 (M=Mn,Co)의]{중성자 회절을 이용한 이중 층상형 산화철 (Lu,Ln)Fe2O4 (Ln=Er,Y)과 Lu(Fe,M)2O4 (M=Mn,Co)의 층간 자기 결합 상태 변화 연구

성호진,정진원,정진환,노한진 한국물리학회 2010 새물리 Vol.60 No.8

We performed a neutron diffraction study to investigate the inter-layer magnetic coupling changes in the hexagonal bilayered iron oxide (Lu,Ln)Fe2O4 (Ln = Er and Y) and in Lu(Fe,M)2O4 (M = Mn and Co). The line shape analysis based on the theory of coupled bilayer two-dimensional magnetic diffraction revealed that the charge ordering was not sensitive to the Ln substitution and that the ferroelectricity of LuFe2O4 was strongly coupled with the charge order, implying strong coupling between the magnetism and the electricity. 전하 정렬을 통해 강유전성을 갖는 육각층상형 LuFe2O4의 Lu 일부를 Y, Er으로 치환하고, Fe 일부를 Mn, Co로 치환 하였을 때, 층간자기 모멘트 결합 상태 변화를 중성자 회절 실험을 통하여 관측하고,이중 층상 2D자기회절 이론(Theory Of Coupled Bilayer 2D Magnetic Diffraction)을 바탕으로 해석하였다. Fe 이온의 전하 정렬이 Y 혹은 Er 치환에 그다지 민감하지 않음을 알 수 있었고, LuFe2O4 강유전성원인이 전하정렬에 의한 것임을 확인시켜 주었으며, 또한 자기적 성질과전기적 성질이 강하게 연관되어 있음을 보여 주었다.

Neutron diffraction measurements of residual stresses in a 50mm thick weld

Woo, Wanchuck,Em, Vyacheslav,Mikula, Pavel,An, Gyu-Baek,Seong, Baek-Seok Elsevier 2011 Materials science & engineering. properties, micro Vol.528 No.12

<P><B>Research highlights</B></P><P>► Determined residual stresses through the thickness of the 50mm thick weld. ► Two-dimensional mapping of the longitudinal stress. Observed significant stresses along the heat-affected zone. ► Measured the maximum stress of 460MPa at 40mm below from the top surface.</P> <P><B>Abstract</B></P><P>Residual stresses were determined through the thickness of a 50mm thick ferrite steel weld plate using neutron diffraction. Whereas the limiting penetration depth for iron-based alloys is about 25mm in the most typical neutron diffractometers, we significantly enhanced the penetration depth up to 50mm with 2mm spatial resolution by using the neutron wavelength of 2.39Å. The selected wavelength minimizes the total neutron cross-section and beam attenuation, thereby, maximizes the neutron fluxes at depth. Two-dimensional mapping of the residual stresses shows that significant amounts of the tensile longitudinal stresses (over 90% of yield strength) were developed along the heat-affected zone of the weld.</P>

In situ neutron diffraction analyses of temperature and stresses during friction stir processing of Mg-3Al-1Zn magnesium alloy

Woo, W.,Feng, Z.,Clausen, B.,David, S.A. North-Holland 2017 Materials letters Vol.196 No.-

<P><B>Abstract</B></P> <P>The evolution of temperature and thermal stresses were examined during friction stir processing of a magnesium alloy using in situ neutron diffraction. Measured total lattice strains were de-convoluted into the thermal and stress components. It shows the maximum temperature of 464°C and compressive stress distributions up to −52MPa underneath the tool via the thermo-mechanical deformation in terms of the Zener-Hollomon parameter of 4.51×10<SUP>10</SUP> s<SUP>−1</SUP>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> In situ neutron diffraction were experimented during friction stir processing of an Mg alloy. </LI> <LI> The diffraction peaks were de-convoluted into the transient temperature and thermal stresses. </LI> <LI> Analyzed inhomogeneous distributions of temperature and stresses underneath the tool. </LI> <LI> The results are applied for the grain size estimation via the Zener-Hollomon parameter. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Amorphous–crystalline state transformation induced by annealing in R₂Fe₁₄B (R=Nd, Er) compounds

Chukalkin, Yu.G.,Teplykh, A.E.,Kudrevatykh, N.V.,Choo, K.N.,Lee, S.,Andreev, A.V.,Pirogov, A.N. Elsevier 2014 JOURNAL OF ALLOYS AND COMPOUNDS Vol.615 No.-

<P><B>Abstract</B></P> <P>Magnetization and neutron diffraction measurements have been carried out to study evolution of structure and magnetic states of amorphous Nd<SUB>2</SUB>Fe<SUB>14</SUB>B and Er<SUB>2</SUB>Fe<SUB>14</SUB>B alloys under isothermal annealing at 295–1025K. The amorphization have been performed by neutron irradiation which provides a homogeneous state in different with other methods of amorphization. The annealing induces a rise of α-Fe phase content in alloys and a recrystallization into Nd<SUB>2</SUB>Fe<SUB>14</SUB>B-type phase. Neutron diffraction data show that the recrystallization occurs over narrow temperature interval (590–638) K in Er<SUB>2</SUB>Fe<SUB>14</SUB>B and at around 800K in Nd<SUB>2</SUB>Fe<SUB>14</SUB>B. Magnetic measurements testify that in both samples the magnetization and coercive field increase with annealing temperature above 800K.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Annealing of R<SUB>2</SUB>Fe<SUB>14</SUB>B amorphized by fast neutrons. </LI> <LI> Annealing leads to crystallization above 600 K (R = Er) and 800 K (R = Nd). </LI> <LI> Crystallization is accompanied by increase of magnetization and coertivity. </LI> </UL> </P>

Evaluation of the stress-strain relationship of constituent phases in AlSi10Mg alloy produced by selective laser melting using crystal plasticity FEM

Kim, Dong-Kyu,Hwang, Ji-Hyun,Kim, Eun-Young,Heo, Yoon-Uk,Woo, Wanchuck,Choi, Shi-Hoon Elsevier 2017 JOURNAL OF ALLOYS AND COMPOUNDS Vol.714 No.-

<P><B>Abstract</B></P> <P>The present study was an evaluation of the stress-strain relationship between Al and Si constituents in AlSi10Mg alloy produced by selective laser melting (SLM) under uniaxial tension at room temperature. <I>In-situ</I> neutron diffraction was used to separately measure the (311) lattice strains of Al and Si phases as a function of macroscopic stress. The crystal plasticity finite element method (CPFEM) was utilized to determine the microscopic hardening parameters for constituent phases by fitting the macroscopic stress response and lattice strain measured by <I>in-situ</I> neutron diffraction. Digital image correlation (DIC) revealed that deformation heterogeneity yields diffuse necking followed by fracture that can be caused by only a small amount of plastic deformation. High-resolution TEM analysis provided evidence of plastic deformation by the formation of stacking faults and mechanical twins in hard Si nano particles in the Al matrix. This elucidates the highly nonlinear elastic-plastic stress-strain relationship of the Si phase, as measured by <I>in-situ</I> neutron diffraction.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The stress-strain relationship between Al and Si constituents in AlSi10Mg alloy was evaluated. </LI> <LI> CPFEM was utilized to determine the microscopic hardening parameters for constituent phases. </LI> <LI> HR TEM analysis provided evidence of plastic deformation of hard Si nano particles. </LI> <LI> DIC technique revealed that the deformation heterogeneity yields diffuse necking followed by fracture. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Investigation of magnetic phase transition on the layered inorganic-organic hybrid perovskites (C₆H₅CH₂CH₂NH₃)₂MnCl₄ by single-crystal neutron diffraction

Park, Garam,Oh, In-Hwan,Park, J.M. Sungil,Park, Seong-Hun,Hong, Chang Seop,Lee, Kwang-Sei Elsevier 2018 PHYSICA B-CONDENSED MATTER - Vol.551 No.-

<P><B>Abstract</B></P> <P>In previous work, the inorganic-organic hybrid perovskite system (C<SUB>6</SUB>H<SUB>5</SUB>CH<SUB>2</SUB>CH<SUB>2</SUB>NH<SUB>3</SUB>)<SUB>2</SUB>MnCl<SUB>4</SUB> exhibit well-isolated 2D Heisenberg antiferromagnetc properties, including a canted antiferromagnet below T<SUB>N</SUB> = 44.3 K. This study looked at the antiferromagnetic spin structure of the titled compound using single-crystal neutron diffraction. At 43 K, a new forbidden (−1 0 0) peak was observed and this peak showed a clear temperature dependence. Additionally, non-integer forbidden peaks were found. It was assumed that the magnetic cell was equal to the chemical cell for Mn-PEA system (<I>k</I> = 0). No magnetic peaks were observed along the c-axis. From this data it can be assumed that the spin is parallel to the <I>c</I>-axis. This result coincides with previous magnetic measurement studies. According to Turov, in the case of an antiferromagnetic structure with weak ferromagnetism, the magnetic cell should be equal to the chemical cell. Our neutron diffraction measurement and former study strongly support the hypothesis of Turov.</P>