Yuying Wu

Shandong University, Chi-nan-shih, Shandong Sheng, China

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Publications (24)30.03 Total impact

  • [show abstract] [hide abstract]
    ABSTRACT: The hypereutectic Al–Si (A390) matrix composite reinforced with TiB2 particles was successfully prepared by Al melt reaction method. In the composite, TiB2 particles have a size range from 0.5 to 1.5 μm and a block-like morphology. Some TiB2 particles are inside the primary Si, suggesting that they were engulfed during solidification. It is considered that TiB2 particles tend to be adsorbed into the primary Si, because of their high surface energy and strong adsorbability. Crystallographic analysis of TiB2 and Si was carried out with the edge-to-edge model. It is found that there exists good lattice matching coherence, which belongs to the matching planes and directions, 1 1 2Si/1 0 1¯ 0TiB2, {1 1 1}Si/{0 0 0 1}TiB2.{1 1 1}Si/{0 0 0 1}TiB2. Furthermore, with 3 wt% TiB2 particles addition, the mechanical properties of the base alloy, including the ultimate tensile strength at 300 °C, percentage elongation and wear resistance, have been obviously improved.
    Materials Science and Engineering A 03/2014; 546:146–152. · 2.11 Impact Factor
  • Pengting Li, Yuying Wu, Xiangfa Liu
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    ABSTRACT: TiB2 microcrystals with different morphologies, including hexagonal plate-like, tower-like and dendritic, were fabricated by aluminum melt reaction method in this study. The growth mechanisms of these microcrystals are also discussed based on the fundamental crystal growth theories. It is found that the growth of TiB2 is controlled by two-dimensional nucleation in aluminum melt. If the atomic concentration, reaction rate and atomic diffusion rate in the melt are high, TiB2 microcrystals exhibit hierarchical tower-like and dendritic morphologies. Otherwise, the single crystal of hexagonal plate-like morphology is obtained. The growth of the hierarchical TiB2 microcrystals is controlled by two steps, intermittent two-dimensional nucleation and continuous lateral spreading of layers on the growth faces.
    Materials Research Bulletin. 06/2013; 48(6):2044–2048.
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    ABSTRACT: A facile method for the synthesis of titanium diboride core–shell structure particles (TiB2@C) was developed utilizing the transformation from TiC to TiB2 in aluminum melt. The particles display hexagonal platelet morphology, with a length of about 800 nm and a thickness of about 200 nm. Carbon layers 4 nm thick are homogeneously coated on the TiB2. Grain refining tests on commercial pure aluminum alloy indicate that TiB2@C particles display a higher grain refining efficiency than TiB2.
    Scripta Materialia. 05/2013; 68(10):789–792.
  • Jinfeng Nie, Xiangfa Liu, Yuying Wu
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    ABSTRACT: The influences of B dopant on the crystal structure of TiCx and nucleation efficiency on α-Al are investigated in this paper. It was found that B solute atoms in the melt easily diffused into the crystal lattice of TiCx, meanwhile the f.c.c. crystal structure was preserved according to the EDS and TEM analysis. The doping effect of B in TiCx was reflected on the X-ray diffraction (XRD) patterns, in which the diffraction peak of (2 0 0) plane rose correspondingly. TiCx showed strong (1 1 1) orientation, but shifted to strong (2 0 0) after trace B doped. Furthermore, the grain refining ability of TiCx with strong (2 0 0) orientation induced by B dopant on commercial pure Al was improved obviously and the excellent refining performance was kept in a long holding time, which indicated that the structural stability of TiCx was enhanced after B doped.
    Materials Research Bulletin. 04/2013; 48(4):1645–1650.
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    ABSTRACT: In this work, a series of CrB2/A390 composite alloys have been prepared and analyzed by a field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD). Firstly, in situ CrB2 has been prepared by reducing reaction that occurred in Al melt: AlB2 + [Cr] → Al + CrB2. The CrB2 particles exhibit regular hexagonal platelet morphology and distribute uniformly in the Al matrix. Then, A390 alloys with different CrB2 additions have been prepared. With the addition of CrB2, the size of primary Si can be reduced remarkably. The generation of CrB2 particles and their diffuse distribution can improve the mechanical properties of A390 alloy obviously. The mechanical properties of the base alloy, including ultimate tensile strength at 25 °C (UTS25 °C), the coefficient of thermal expansion (CTE) and wear resistance have been studied and the composite alloy with 3 wt.% CrB2 particle addition showed the best performance.
    Materials Characterization. 01/2013; 86:296–302.
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    ABSTRACT: TiC particles with various morphologies from octahedron to cube were synthesized and investigated by Field emission scanning electron microscopy (FESEM) in three-dimensional space. The morphological evolution of TiC grain and its growth mechanism were also discussed. TiC particles prefer an octahedral morphology (equilibrium shape) enclosed by eight {111} facets with minimized total surface free energy in Al–Ti–C alloy, while they tend to form a cube enclosed by six {100} facets under the influence of Ni in Al–Ni–Ti–C alloy. Due to the strong interaction between Ni–3d and C–2p orbitals, Ni atoms in the melt selectively absorb on {100} faces of the growing TiC crystal rather than on the polar {111} faces and reduce the specific surface energy of {100}. According to Wuff's theorem, the growth rate of {100} is lowered correspondingly, while the relative growth rate of {111} is accelerated. Thus, the higher growth rate along <111> direction will lead to the shrinkage of {111} faces gradually, while six {100} faces are reserved to form a TiC cube because of their lower growth rates. Furthermore, a similar morphology evolution to TiC crystals can also be found in Fe- and Co-containing melts. It is revealed that the crystal growth of TiC follows the same model under the effect of groupVIII elements (Fe, Co and Ni).
    CrystEngComm 02/2012; 14(6):2213-2221. · 3.88 Impact Factor
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    ABSTRACT: The microstructure and elevated-temperature strength of an Al–Si piston alloy with 0.5 wt.% Cr and 0.8 wt.% Fe addition were investigated in this paper. The addition of Cr and Fe leads to the formation of α-Al(Fe,Cr)Si phase, which maintains the crystal structure of α-Al(Fe,Mn,Cr)Si phase but has different stoichiometry and morphology from the phase in previous works. Besides, the morphology of δ-Al3CuNi phase changes because of solid-solved Cr. These changes result in the formation of closed and semi-closed network eutectic colonies. The Cr-rich phases, acting as effective supportive strengthening phase, integrate organically with Ni-rich phases, acting as main strengthening phases. So α-Al phases are successfully encircled by eutectic intermetallic phases, and the slide of α-Al under stress at elevated temperature can be effectively hindered. Thus the ultimate tensile strength of the examined alloy is increased by 26% after 0.5 wt.% Cr and 0.8 wt.% Fe addition.Research highlights► The UTS of the alloy is increased by 26% at 350 °C. ► Supportive strengthening phase α-Al(Fe,Cr)Si forms and integrates organically with Ni-rich phases. ► The morphology of δ-Al3CuNi phase changes because of solid-solved Cr. ► Closed and semi-closed network eutectic colonies form and α-Al phases are successfully encircled.
    Materials Science and Engineering A 01/2011; 528:4427-4430. · 2.11 Impact Factor
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    ABSTRACT: The aim of this work is to investigate the eutectic structural evolution of hypereutectic Al–20% Mg2Si with Ni addition under a gravity casting process. Three-dimensional morphologies of eutectic phases were observed in detail using field emission scanning electron microscopy, after Al matrix was removed by deep etching or extraction. The results show that Al–Mg2Si binary eutectic gradually evolves into Al–Mg2Si–NiAl3 ternary eutectic with the increase of Ni content, and flake-like eutectic Mg2Si transforms into rods. The ternary eutectic presents a unique double rod structure that rod-like NiAl3 and Mg2Si uniformly distribute in Al matrix. Further, the high temperature (350°C) tensile strength of the alloy increases by 23% due to the eutectic structure evolution, and the mechanism of structural evolution was discussed and analyzed in terms of the detailed microstructural observations.
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing - MATER SCI ENG A-STRUCT MATER. 01/2010; 528(2):573-577.
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    ABSTRACT: Eutectic nucleation in hypereutectic Al-25wt.%Si alloy with the addition of P was studied by calculating the activation energy and nucleation work. The results indicate that P refinement, which can decrease the activation energy as well as nucleation work of eutectic solidification, can increase the eutectic nucleation frequency of Al-25wt.%Si alloy, so the addition of P can refine the eutectic structures of hypereutectic Al-Si alloys. According to the calculations, there is a certain relationship between the precipitation of primary silicon and eutectic solidification, and the eutectic nucleation mode is independent of morphology transition.
    Rare Metals 01/2010; 29(1):62-65. · 0.49 Impact Factor
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    ABSTRACT: Al/WC composite coatings in Al–12.6Si alloy have been prepared by high energy milling, and the mechanism has been discussed in this work. The results show that there is reaction between Al and WC powders, i.e. 12xAl+WC⇔xWAl12+W1−xC, which increased the link between Al and WC. There is great influence of milling time and heat treatment on the reaction: the onset temperature of the reaction decreases with increasing milling time, and the reaction processes by heat treatment. Moreover, the microhardnesses of Al/WC composite coatings have been measured, and it is improved greatly by heat treatment and increasing milling time. The microhardness of Al/WC coating milling by 14h and with heat treatment is 380HV, 21.02% higher than that without heat treatment, and 466.32% higher than that of Al–12.6Si matrix.
    Journal of Alloys and Compounds 01/2010; 497(1):139-141. · 2.39 Impact Factor
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    ABSTRACT: The different contributions of ɛ-Al3Ni, δ-Al3CuNi and γ-Al7Cu4Ni phases to the elevated-temperature strength of Al–Si piston alloys were investigated in this paper. Four kinds of Al–Si alloy containing different Ni-containing phases were prepared and their UTS values were obtained. The volume fractions and morphology characteristics of ɛ-Al3Ni, δ-Al3CuNi and γ-Al7Cu4Ni phases were calculated by the analysis of multicomponent phase diagrams and ImageJ software. The different contributions of ɛ-Al3Ni, δ-Al3CuNi and γ-Al7Cu4Ni phases to the elevated-temperature properties were analyzed. The δ-Al3CuNi phase was found to have the most effective volume utilization and possess the most efficient contribution to the elevated-temperature strength among the examined three Ni-containing phases, and the strip-like morphology was proved to be the most favorable morphology in the improvement of elevated-temperature strength.
    Materials Science and Engineering A 01/2010; · 2.11 Impact Factor
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    ABSTRACT: In situ nano-scale Cu–Cu2O composites have been prepared by addition of K2TiF6 and KBF4 into Cu melt, and the microstructure, resistivity and microhardness of Cu–Cu2O composites have been studied in this work. Cu2O (100–300nm) in the Cu matrix can be obtained by addition of oxidation agent (K2TiF6 and KBF4), and when the addition level is 3wt%, hyper-Cu–Cu2O can be obtained with constitutes of copper matrix, reinforcing particles-Cu2O (100–300nm), and some nano-scale particles. It is found that the resistivity of Cu–Cu2O composites are close to those of pure copper at 20°C. In addition, the hardness of the composite has been improved significantly as compared to those of pure Cu.
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing - MATER SCI ENG A-STRUCT MATER. 01/2010; 527(6):1544-1547.
  • Chong Li, Yuying Wu, Hui Li, Xiangfa Liu
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    ABSTRACT: In the present work, the microstructure and the solidification process of an ingot metallurgy hypereutectic Al–Mg2Si alloy with extra Si were studied. Primary Mg2Si phase is surrounded by Al–Mg2Si binary eutectic and then by Al–Mg2Si–Si ternary eutectic structure. Primary Mg2Si phase at the centers shows dendritic or polyhedral morphologies. Al–Mg2Si binary eutectic cells with regular morphologies have flake-like Mg2Si surrounded by α-Al. Al–Mg2Si–Si ternary eutectic cells distribute among binary eutectic cells and make binary eutectic cells separated to be relatively independent “islands”.
    Journal of Alloys and Compounds 01/2009; 477:212-216. · 2.39 Impact Factor
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    ABSTRACT: The co-addition effect of RE, Mn and Fe on the microstructure and high-temperature strength of A390 has been conducted. The alloying effect of RE has also been explored. Formation of detrimental long-acicular RE-rich phase is not observed. The AlSiCuCeLa phase, α-Al(Mn,Fe)–Si phase and another complex phase composed of Al, Si, Mn, Fe, Cu and RE are observed to form after addition. RE can decrease the diffusion rates of Cu, Mg in the aging process and the intermetallics nucleate on a localized scale, but could not become coarse during heat-treatment. The electronegativity differences between RE and Al or Si are larger than those between Cu and Al or Si, so the RE-rich intermetallic compounds in Al–Si alloys are more stable. The co-addition of RE, Mn and Fe proves to be an effective method to enhance the high-temperature strength of A390. The high-temperature strength of A390 is increased by 25% in this article using this method.
    Materials Science and Engineering A 01/2009; 527(1):146-149. · 2.11 Impact Factor
  • Chong Li, Xiangfa Liu, Yuying Wu
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    ABSTRACT: Refinement and modification performance of Al–3P master alloy on primary Mg2Si in Al–12.67Mg–10.33Si alloys were investigated in this paper. The experimental results show that the perfect effect can be obtained after the addition of 3% Al–3P master alloy into the Al–Mg–Si alloys. The morphologies of primary Mg2Si particulates change from dendritic to polygonal shape, and their average sizes decrease from ∼100 to ∼20μm. Further, the ultimate tensile strength increases from 252 to 275MPa. Also, the melt treating technological parameters were established in this paper, treating temperature is 850°C, holding time is 30min. EPMA results show that AlP particles act as the nuclei of primary Mg2Si.
    Journal of Alloys and Compounds 01/2008; 465(1):145-150. · 2.39 Impact Factor
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    ABSTRACT: Many four-branched compounds coupled Si and iron-rich intermetallics were observed in near eutectic Al–Si alloy modified with Al–P master alloy. Such four-branched compounds have never been reported before, but in our case it seems to be commonly observed. In this work the growth characterization of the four-branched compounds are scrutinized with a JXA-8800 electron microprobe (EPMA). More deep study of the formation of four-branched compounds is performed by SEM and TEM analysis. The characterization of the four-branched compounds is that of a primary silicon in the center with four iron-rich intermetallics around. Experimental results also show that the precipitation of primary silicon is the key factor for the formation of four-branched compounds. And WHS-theory explains the growth mechanism of the four-branched compounds. In detail, subsequent twinning within the primary silicon provides four-fold coordination sites on the surface, and then the α-Al(Fe,Mn)–Si phase nucleates on the surface of the primary silicon.
    Journal of Alloys and Compounds 01/2007; 437(1):80-83. · 2.39 Impact Factor
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    ABSTRACT: The refinement for the primary silicon in Cu–50wt.%Si by pure Al and Cu–P master alloy was investigated in this work. The experimental results reveal that, similar to hypereutectic Al–Si alloys, AlP particles can also act as the heterogeneous nucleating sites for primary silicon in Cu–Si alloys, and the primary Si can also be refined with the AlP particles. Another discovery is that pure Al can refine primary Si in Cu–50wt.%Si alloys since Al4Cu9 can form a loop around the primary Si. To get round and small primary Si particle, it is important for AlP and surplus Al coexisting in the melt, and the addition level of Al and P should be Al:P>1.
    Journal of Alloys and Compounds 01/2007; 433(1):175-179. · 2.39 Impact Factor
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    ABSTRACT: A novel method to induce the precipitation of primary silicon in near eutectic Al–Si alloy (ZL109) was investigated in this work. Ni–38wt.%Si master alloy was added into the ZL109 alloy melt to induce the precipitation of primary silicon, and this technology was optimized by considering several parameters, such as the inducement temperature, the addition level, and the holding time. It was found that there was good inducement efficiency of Ni–38wt.%Si master alloy for ZL109 alloy when the addition level was above 1% and held at 740°C for above 30min. Meanwhile, the efficiency can last for above 600min. Finally, the precipitation of primary silicon in ZL109 alloy with Ni–38wt.%Si master alloy was not induced by the increasing silicon containing, but induced by the addition of Ni–38wt.%Si master alloy.
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing - MATER SCI ENG A-STRUCT MATER. 01/2007; 457(1):109-113.
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    ABSTRACT: The eutectic nucleation of Ni–38wt.%Si alloys with AlP particles addition was investigated in this paper. It is found that AlP and NiSi2 have similar lattice parameters, and the disregistry for the case along the (220) of AlP particles and the (400) of the NiSi phase is 6.77pct, a value which implies good coherency between the two phases. So a new discovery in this study is that AlP particles can act as the nucleation substrate for NiSi2 and NiSi phases, and the addition of AlP particles changes the nucleation mechanism of the Ni–38wt.%Si alloys. Another discovery is that the addition of AlP particles decreases the driving force for the heterogeneous nucleation (ΔG′k) and the degree of the supercooling (ΔT), and the beginning of the exothermic peak for Ni–38wt.%Si alloys with AlP particles is 17°C higher than that without AlP particles addition.
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing - MATER SCI ENG A-STRUCT MATER. 01/2006; 427(1):69-75.
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    ABSTRACT: The effect of Ca impurity on solidification structure of near eutectic Al–Si piston alloy (ZL109), the origin of the presence of calcium (Ca) and the transformation of Ca compounds in the alloy were investigated. It has been found that many kinds of Ca compounds exist in commercial pure silicon, which are the main source of the Ca impurity in ZL109 alloy. It has also been shown that calcium can modify eutectic Si and enhance the formation of α-Al dendrites and fibrous eutectic Si in the alloy, even retaining the structural characteristics after addition of sodium. The abnormal phenomenon is due to the formation of CaxSiyPz compounds which are more stable than AlP phases in the melt. However, the Ca level can be reduced from 216ppm to 30ppm and then the P modification efficiency can be recovered after a refinement treatment by C2Cl6 because of the reaction: Cl2 + Ca → CaCl2(s), and the transformation: Al + Mg + CaxSiyPz(s) + Cl2 → (Al5, Mg0.85 + Ca0.15) P(s) + CaCl2(s) + MgCl2(s), the (Al5, Mg0.85, Ca0.15) P compounds serving as heterogeneous nucleating sites of the primary Si phases.
    Journal of Alloys and Compounds 01/2005; 388(1):83-90. · 2.39 Impact Factor

Publication Stats

37 Citations
401 Views
30.03 Total Impact Points

Institutions

  • 2005–2014
    • Shandong University
      • Key Laboratory for Liquid Structure and Heredity of Materials
      Chi-nan-shih, Shandong Sheng, China