http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Mattern, N.,Han, J.H.,Pradeep, K.G.,Kim, K.C.,Park, E.M.,Kim, D.H.,Yokoyama, Y.,Raabe, D.,Eckert, J. Elsevier Sequoia 2014 JOURNAL OF ALLOYS AND COMPOUNDS Vol.607 No.-
<P>The influence of Ag addition on the microstructure of rapidly quenched (Cu0.5Zr0.5)(100-x)Ag-x melts was investigated (x = 0-40 at.%). Fully glassy alloys were obtained for 0 <= x <= 20 at.% Ag, which are characterized by a homogeneous microstructure without any indication of phase separation. For 30 <= x <= 40 at.% Ag a composite structure is formed consisting of fcc-Ag nano-crystallites 5 nm in size and an amorphous matrix phase Cu40Zr40Ag20. With higher Ag-content the volume fraction of the fcc-Ag phase becomes increased mainly due to crytal growth during quenching. The primary formation of fcc-Ag for 30 <= x <= 40 at.% Ag is confirmed by the analysis of the microstructure of mold cast bulk samples which were fully crystalline. From the experimental results we conclude that the miscibility gap of the liquid phase of the ternary Ag-Cu-Zr system may occur only for x > 40 at.% Ag. For the bulk glass forming quaternary Cu40Zr40Al10Ag10 alloy a homogeneous element distribution is observed in accordance with the microstructure of ternary (Cu0.5Zr0.5)(100-x)Ag-x glasses (x = 10, 20 at.%). (C) 2014 Elsevier B.V. All rights reserved.</P>
He, J.,Mattern, N.,Tan, J.,Zhao, J.Z.,Kaban, I.,Wang, Z.,Ratke, L.,Kim, D.H.,Kim, W.T.,Eckert, J. Elsevier Science 2013 ACTA MATERIALIA Vol.61 No.6
The Zr-Ce-La system is characterized by a miscibility gap and a monotectic reaction. It separates into Zr-rich and CeLa-rich liquids upon cooling through the gap. Based on this system, a new Zr-Ce-La-Al-Co monotectic system was created to synthesize liquid-phase-separated bulk metallic glasses (LPS-BMGs) by copper mold casting. A systematical investigation was performed for the effects of the relative atomic ratios of Zr:CeLa, Co:Al and Ce:La on the microstructure features and chemical compositions of the two coexistent phases. Dual atom pairs with positive heat of mixing (Zr-Ce: +12kJmol<SUP>-1</SUP> and Zr-La: +13kJmol<SUP>-1</SUP>) are originally adopted to develop such LPS-BMGs. A series of in situ formed LPS-BMGs with a critical thickness of 2.5mm has been successfully synthesized. By combining the kinetics of liquid-liquid phase separation with the formation of metallic glasses, the mechanisms of phase formation and the microstructure evolution in the rapidly cooled alloys are discussed in detail. Furthermore, a thermodynamic model is proposed for LPS-BMG design, attempting to build a bridge from monotectic/immiscible (M/I) alloys to LPS-BMGs. This work not only provides opportunities for new insights into the synthesis of LPS-BMGs and their properties but also opens new perspectives for processing and research of M/I alloys.
Han, J.H.,Mattern, N.,Vainio, U.,Shariq, A.,Sohn, S.W.,Kim, D.H.,Eckert, J. Elsevier Science 2014 Acta materialia Vol.66 No.-
The influence of Gd addition on the microstructure of Zr<SUB>56</SUB>Co<SUB>28</SUB>Al<SUB>16</SUB> metallic glasses was investigated for the exchange of Zr by up to 20 at.% Gd. Due to the large positive enthalpy of mixing between Zr and Gd, liquid-liquid phase separation occurs during rapid quenching of the melt. For a low concentration of Gd (x=2 at.%), a homogeneous amorphous structure is obtained for the as-quenched state. Early stages of spinodal decomposition are observed in the as-quenched state of the glasses with x=5 and 10 at.% Gd. Gd-enriched clusters 4-7nm in size are formed, as shown by atom probe tomography (APT). Annealing below the crystallization temperature T<SUB>x</SUB> leads to an increase in the amplitude of compositional fluctuations and the analysis of the spatial atomic distribution by APT provides direct evidence of the spinodal character of the decomposition by uphill diffusion of Gd into the clusters. For higher Gd content (x=15 and 20 at.%), a coarsened microstructure of the phase-separated glass is obtained due to growth and coalescence while quenching the melt. The microstructure formation is essentially determined by the thermodynamic properties of the metastable undercooled liquid.
High-strength bulk Al-based bimodal ultrafine eutectic composite with enhanced plasticity
Park, Jin Man,Mattern, Norbert,Kü,hn, Uta,Eckert, Jü,rgen,Kim, Ki Buem,Kim, Won Tae,Chattopadhyay, Kamanio,Kim, Do Hyang Cambridge University Press (Materials Research Soc 2009 Journal of materials research Vol.24 No.8
<P>An in situ bulk ultrafine bimodal eutectic Al-Cu-Si composite was synthesized by solidification. This heterostructured composite with microstructural length scale hierarchy in the eutectic microstructure, which combines an ultrafine-scale binary cellular eutectic (α-Al + Al2Cu) and a nanometer-sized anomalous ternary eutectic (α-Al + Al2Cu + Si), exhibits high fracture strength (1.1 ± 0.1 GPa) and large compressive plastic strain (11 ± 2%) at room temperature. The improved compressive plasticity of the bimodal-nanoeutectic composite originates from homogeneous and uniform distribution of inhomogeneous plastic deformation (localized shear bands), together with strong interaction between shear bands in the spatially heterogeneous structure.</P>
Schwarz, B.,Vainio, U.,Mattern, N.,Sohn, S.W.,Oswald, S.,Kim, D.H.,Eckert, J. North-Holland 2011 Journal of non-crystalline solids Vol.357 No.6
CuZr as well as CoZr are well known metallic glass-formers in a wide compositional range. Since the binary Cu-Co system exhibits a metastable liquid-liquid miscibility gap, i.e. Cu and Co tend to separate from each other, the ternary Cu-Co-Zr system is a promising candidate to form phase separated glass-glass composites. In this work (Cu<SUB>60</SUB>Co<SUB>40</SUB>)<SUB>1-x</SUB>Zr<SUB>x</SUB> metallic glasses with relatively low Zr contents of x=37 and x=32 were prepared by melt spinning and investigated by in-situ small-angle and wide-angle X-ray scattering (SAXS/WAXS) and differential scanning calorimetry (DSC). Certain heat treated samples were additionally investigated by high-resolution transmission electron microscopy (HRTEM). Even for x=32 there are no indications for any kind of phase separation in the as-quenched state within experimental resolution, i.e. the critical temperature T<SUB>c</SUB> for a liquid-liquid phase separation has already decreased from 1556K for binary Cu<SUB>60</SUB>Co<SUB>40</SUB> to a temperature below the glass transition temperature T<SUB>g</SUB>=762(5)K found for (Cu<SUB>60</SUB>Co<SUB>40</SUB>)<SUB>68</SUB>Zr<SUB>32</SUB>. Combined in-situ SAXS/WAXS and HRTEM investigations reveal that thermal annealing also does not induce an amorphous-amorphous phase separation. Instead the formation of nano crystallites of a so far unknown Cu-rich/Zr-poor phase with relatively low activation energy for crystallization E<SUB>a</SUB>=116(7)kJ/mol at temperatures far below the crystallization temperature deduced from DSC measurements is observed.
Microstructural Modulations Enhance the Mechanical Properties in Al–Cu–(Si, Ga) Ultrafine Composites
Park, Jin Man,Pauly, Simon,Mattern, Norbert,Kim, Do Hyang,Kim, Ki Buem,Eckert, Jü,rgen WILEY‐VCH Verlag 2010 Advanced Engineering Materials Vol.12 No.11
<P><B>Abstract</B></P><P>Adding small amounts of Si or Ga (3 at.%) to the eutectic Al<SUB>83</SUB>Cu<SUB>17</SUB> alloy yields an ultrafine bimodal eutectic composite microstructure upon solidification. The as‐solidified alloys exhibit a distinct microstructural length‐scale hierarchy leading to a high fracture strength of around 1 GPa combined with a large compressive plastic strain of up to 30% at room temperature. The present results suggest that the mechanical properties of the ultrafine bimodal eutectic composites are strongly related to their microstructural characteristics, namely phase evolution, length‐scales, and distribution of the constituent phases.</P>
Park, Jin Man,Kim, Do Hyang,Kim, Ki Buem,Mattern, Norbert,Eckert, Jü,rgen Cambridge University Press (Materials Research Soc 2011 Journal of materials research Vol.26 No.3
<▼1><B>Abstract</B><P/></▼1><▼2><P>The constituent phases, the microstructure, and the mechanical properties of a series of Fe87-<I>x</I>Ti7Zr6B<I>x</I> (<I>x</I> = 0, 2, 4, 6, 8, 10, and 12) alloys produced by copper mold casting were investigated. Partial substitution of iron by boron in the Fe87Ti7Zr6 ultrafine eutectic alloy induces phase/microstructural evolution and simultaneously changes the mechanical properties. In the composition range of 2 ≤ <I>x</I> ≤ 6, the typical lamellar structure slightly changes into a spherical cellular-type eutectic. For 8 ≤ <I>x</I> ≤ 12, multiphase composites containing a glassy phase form. The ultrafine eutectic composites exhibit a high compressive strength of ~2.9-3.1 GPa and a distinct plasticity of ~2-8%, whereas the glassy matrix composites show a high strength of ~3.1-3.3 GPa but no observable macroscopic plasticity before failure. These findings reveal that the plasticity of heterogeneous multiphase composites is strongly related to the length scale variables and the crystallinity of the constituent phases.</P></▼2>