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Liyuan Sheng - One of the best experts on this subject based on the ideXlab platform.

  • optimization of the microstructure and mechanical properties of a laves phase strengthened Hypoeutectic nial cr mo w Alloy by suction casting
    Strength of Materials, 2018
    Co-Authors: Liyuan Sheng, S. P. Zan, C. Lai, Junke Jiao, Y Gao
    Abstract:

    A niobium (Nb)-doped NiAl/Cr(Mo,W) Hypoeutectic Alloy was prepared by conventional and suction casting methods. Its microstructure and compression properties were studied to evaluate the effect of a manufacturing process. A coarse primary NiAl phase and NiAl/Cr(Mo) eutectic cell are demonstrated to be the main components of a NiAl/Cr(Mo,W)–Nb Hypoeutectic Alloy. The Nb addition promotes the formation of a Cr2Nb Laves phase along the eutectic cell boundary. The suction casting significantly refines a NiAl/Cr(Mo) eutectic cell, primary NiAl phase, eutectic lamella, intercellular region, and Cr2Nb Laves phase. This casting provides the uniform distribution of a Cr2Nb Laves phase and increases the solid solubility of the Alloy. At room temperature, the suction casting Alloy reaches its yield strength, compression strength, and ductility of 1495 MPa, 2030 MPa, and 36%, respectively, which are approximately 50, 30, and 100% higher than those of the conventional casting Alloy. A significant improvement of the mechanical properties at room temperature may be ascribed to optimization of the microstructure by suction casting. At 1273 K, the above Alloy exhibits almost similar mechanical properties, which is mainly associated with an enlarged intercellular region.

  • Optimization of the Microstructure and Mechanical Properties of a Laves Phase-Strengthened Hypoeutectic NiAl/Cr(Mo,W) Alloy by Suction Casting
    Strength of Materials, 2018
    Co-Authors: Liyuan Sheng, S. P. Zan, C. Lai, Junke Jiao, Y. B. Gao
    Abstract:

    A niobium (Nb)-doped NiAl/Cr(Mo,W) Hypoeutectic Alloy was prepared by conventional and suction casting methods. Its microstructure and compression properties were studied to evaluate the effect of a manufacturing process. A coarse primary NiAl phase and NiAl/Cr(Mo) eutectic cell are demonstrated to be the main components of a NiAl/Cr(Mo,W)–Nb Hypoeutectic Alloy. The Nb addition promotes the formation of a Cr2Nb Laves phase along the eutectic cell boundary. The suction casting significantly refines a NiAl/Cr(Mo) eutectic cell, primary NiAl phase, eutectic lamella, intercellular region, and Cr2Nb Laves phase. This casting provides the uniform distribution of a Cr2Nb Laves phase and increases the solid solubility of the Alloy. At room temperature, the suction casting Alloy reaches its yield strength, compression strength, and ductility of 1495 MPa, 2030 MPa, and 36%, respectively, which are approximately 50, 30, and 100% higher than those of the conventional casting Alloy. A significant improvement of the mechanical properties at room temperature may be ascribed to optimization of the microstructure by suction casting. At 1273 K, the above Alloy exhibits almost similar mechanical properties, which is mainly associated with an enlarged intercellular region.

  • Microstructure and mechanical properties of zirconium doped NiAl/Cr(Mo) Hypoeutectic Alloy prepared by injection casting
    IOP Conference Series: Materials Science and Engineering, 2017
    Co-Authors: Liyuan Sheng, J.t. Guo
    Abstract:

    NiAl based materials has been considered as most potential candidate of turbine blade, due to its excellent high-temperature properties. However the bad room-temperature properties handicap its application. In the present paper, the zirconium doped NiAl/Cr(Mo) Hypoeutectic Alloy is fabricated by conventional casting and injection casting technology to improve its room-temperature properties. The microstructure and compressive properties at different temperatures of the conventionally-cast and injection-cast were investigated. The results exhibit that the conventionally-cast Alloy comprises coarse primary NiAl phase and eutectic cell, which is dotted with irregular Ni2AlZr Heusler phase. Compared with the conventionally-cast Alloy, the injection-cast Alloy possesses refined the primary NiAl, eutectic cell and eutectic lamella. In addition, the Ni2AlZr Heusler phase become smaller and distribute uniformly. Moreover, the injection casting decrease the area fraction of primary NiAl phase at the cell interior or cell boundaries. The compressive ductility and yield strength of the injection-cast Alloy at room temperature increase by about 100% and 35% over those of conventionally-cast Alloy, which should be ascribed to the microstructure optimization.

  • microstructure and mechanical properties of zirconium doped nial cr mo Hypoeutectic Alloy prepared by injection casting
    IOP Conference Series: Materials Science and Engineering, 2017
    Co-Authors: Liyuan Sheng, J.t. Guo
    Abstract:

    NiAl based materials has been considered as most potential candidate of turbine blade, due to its excellent high-temperature properties. However the bad room-temperature properties handicap its application. In the present paper, the zirconium doped NiAl/Cr(Mo) Hypoeutectic Alloy is fabricated by conventional casting and injection casting technology to improve its room-temperature properties. The microstructure and compressive properties at different temperatures of the conventionally-cast and injection-cast were investigated. The results exhibit that the conventionally-cast Alloy comprises coarse primary NiAl phase and eutectic cell, which is dotted with irregular Ni2AlZr Heusler phase. Compared with the conventionally-cast Alloy, the injection-cast Alloy possesses refined the primary NiAl, eutectic cell and eutectic lamella. In addition, the Ni2AlZr Heusler phase become smaller and distribute uniformly. Moreover, the injection casting decrease the area fraction of primary NiAl phase at the cell interior or cell boundaries. The compressive ductility and yield strength of the injection-cast Alloy at room temperature increase by about 100% and 35% over those of conventionally-cast Alloy, which should be ascribed to the microstructure optimization.

  • microstructure mechanical and tribological properties of the rapidly solidified nial cr mo dy Hypoeutectic Alloy
    Materials Science Forum, 2016
    Co-Authors: Liyuan Sheng
    Abstract:

    The NiAl/Cr (Mo,Dy) Hypoeutectic Alloy was fabricated by rapid solidification. The microstructure and mechanical properties as well as tribological properties for the Alloy at different temperatures were investigated. The results revealed that the rapidly solidified NiAl/Cr (Mo,Dy) Hypoeutectic Alloy was composed of primary NiAl, fine NiAl/Cr (Mo) eutectic lamella, Ni5Dy phase and Cr7Ni3 precipitate. The compression test showed that the rapid solidification improved the mechanical properties of the NiAl/Cr (Mo,Dy) Hypoeutectic Alloy obviously. The dry sliding test results showed that Alloy had excellent tribological properties at about 1073 K, which obtained wear rate of 4.9 10-14m3/m·N and friction coefficient of 0.16 μ. The excellent tribological properties at high temperature may be attributed to the continuous and intact protecting lubricant film which was composed of amorphous, Cr2O3 and Al2O3 nanoparticles. Between 700 K to 900 K, the Alloy demonstrated bad tribological properties, especially the high wear rate, which may be ascribed to the softening of NiAl and Cr (Mo) phases.

Ao Gao - One of the best experts on this subject based on the ideXlab platform.

  • Effects of high magnetic fields on solidified structures of Mn-90.4 wt% Sb Hypoeutectic Alloy
    Science and technology of advanced materials, 2009
    Co-Authors: Qiang Wang, Tie Liu, Chao Zhang, Ao Gao
    Abstract:

    Mn-90.4 wt% Sb Alloy specimens were solidified under both uniform magnetic field and magnetic field gradient conditions. The solidification behavior was examined to elucidate the effects of high magnetic fields on the solidified structure evolution of this Hypoeutectic Alloy. The macrostructures on the longitudinal section of the Alloys were investigated by optical microscopy and x-ray diffraction (XRD). The volume fraction of primary MnSb phases and the interrod spacing of the eutectic were measured by metallographic analysis. It was found that the segregation of the primary MnSb particles at the certain regions of the specimens occurred under the influence of high magnetic field gradients. The MnSb phases obtained under magnetic fields were oriented with their (h0 l) planes along the direction of the magnetic field. Both the volume fraction of primary MnSb phases and the interrod spacing of the eutectic were decreased upon the application of the high magnetic fields.

  • effects of high magnetic fields on solidified structures of mn 90 4 wt sb Hypoeutectic Alloy
    Science and Technology of Advanced Materials, 2009
    Co-Authors: Qiang Wang, Tie Liu, Chao Zhang, Ao Gao
    Abstract:

    Mn-90.4 wt% Sb Alloy specimens were solidified under both uniform magnetic field and magnetic field gradient conditions. The solidification behavior was examined to elucidate the effects of high magnetic fields on the solidified structure evolution of this Hypoeutectic Alloy. The macrostructures on the longitudinal section of the Alloys were investigated by optical microscopy and x-ray diffraction (XRD). The volume fraction of primary MnSb phases and the interrod spacing of the eutectic were measured by metallographic analysis. It was found that the segregation of the primary MnSb particles at the certain regions of the specimens occurred under the influence of high magnetic field gradients. The MnSb phases obtained under magnetic fields were oriented with their (h0 l) planes along the direction of the magnetic field. Both the volume fraction of primary MnSb phases and the interrod spacing of the eutectic were decreased upon the application of the high magnetic fields.

F H Froes - One of the best experts on this subject based on the ideXlab platform.

  • microstructural evolution during annealing of the melt spun ternary Hypoeutectic al 7 6si 3 3fe in wt Alloy
    Journal of Alloys and Compounds, 2002
    Co-Authors: Necip Unlu, A Genc, M L Ovecoǧlu, E J Lavernia, F H Froes
    Abstract:

    Abstract A ternary Hypoeutectic Al–7.6 wt.%Si–3.3 wt.%Fe Alloy was rapidly quenched at cooling rates between 10 6 and 10 7 K/s using the melt-spinning technique. Differential scanning calorimetry (DSC) scan of the as-quenched ribbon revealed a small exothermic peak at 348 °C, attributed to the silicon particle coarsening and two endothermic peaks: one at 585 °C and the other at 600 °C corresponding to ternary eutectic and liquidus transformation, respectively. On the basis of the DSC analyses, the as-quenched ribbons were annealed at T =390, 560, 600 and 632 °C. The annealed ribbons were characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. From the XRD scans, a solid solubility extension value of 1.75 at.% Si in α-Al was measured for the as-quenched ribbon and the β-Al 5 FeSi intermetallic phase start temperature was determined as 560 °C. TEM investigations revealed the coarsening of Si particles in the α-Al matrix and the increase of the β-Al 5 FeSi intermetallic phase particle size from 80 to 100 nm at the annealing temperature of 560 °C to about 700 nm at the annealing temperature of 632 °C. The microhardness value of the as-quenched Hypoeutectic Alloy was measured as 146 kg/mm 2 which is 2.5 times more than that of the conventionally cast counterpart. The microhardness values decreased gradually with increase in annealing temperatures.

  • characterization investigations of melt spun ternary al xsi 3 3fe x 10 20 wt Alloys
    Journal of Alloys and Compounds, 2001
    Co-Authors: Necip Unlu, A Genc, M L Ovecoglu, Niyazi Eruslu, F H Froes
    Abstract:

    Abstract Two ternary Al– x Si–3.3Fe Alloys, one with the Hypoeutectic ( x =10 wt.% Si) and the other with the hypereutectic ( x =20 wt.% Si) composition were rapidly quenched from the melt at cooling rates between 10 6 and 10 7 K/s using the melt-spinning technique. The resulting melt-spun ribbons were characterized using optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) and microhardness techniques. On the basis of the Al peak shifts measured in the XRD scans, solid solubility extension values of 3.01 and 2.97 at.% Si in Al were determined for the Hypoeutectic and hypereutectic Alloy, respectively. Whereas SEM investigations showed the presence of dendrites rich in Al, TEM investigations revealed nanosized spherically-shaped Si crystals 5–10 nm in size in the Hypoeutectic Alloy and those equiaxed in shape having a size range between 50 and 70 nm. Both XRD and TEM investigations confirmed the absence of any intermetallic phase formation for both Alloys. The microhardness values of the Hypoeutectic and hypereutectic ternary Al–Si–Fe Alloys were measured as 251 and 297 kg/mm 2 , respectively.

Sumanth Shankar - One of the best experts on this subject based on the ideXlab platform.

  • X-ray nano-diffraction study of Sr intermetallic phase during solidification of Al-Si Hypoeutectic Alloy
    Applied Physics Letters, 2014
    Co-Authors: Jeyakumar Manickaraj, Anton Gorny, Zhonghou Cai, Sumanth Shankar
    Abstract:

    The evolution of strontium (Sr) containing intermetallic phase in the eutectic reaction of Sr-modified Al-Si Hypoeutectic Alloy was studied with high energy synchrotron beam source for nano-diffraction experiments and x-ray fluorescence elemental mapping. Contrary to popular belief, Sr does not seem to interfere with the Twin Plane Re-entrant Edge (TPRE) growth mechanism of eutectic Si, but evolves as the Al2Si2Sr phase during the eutectic reaction at the boundary between the eutectic Si and Al grains.

  • XAFS studies on a modified Al-Si Hypoeutectic Alloy
    Journal of Physics: Conference Series, 2009
    Co-Authors: V S Prakash Srirangam, Soma Chattopadhyay, Tomohiro Shibata, James A. Kaduk, Jeffrey T. Miller, Carlo U. Segre, Sumanth Shankar
    Abstract:

    To understand the role of Sr in doped aluminium-silicon Alloys, we have conducted for the first time, Sr- K edge XAFS measurements on Al-3%Si-0.04%Sr. Aluminium-Silicon Alloys are widely used in automobile and aerospace applications. Modification of these Alloys with addition of trace levels of Sr (200–400 ppm) results in changing the morphology of Si eutectic from "plate" like structure to "fibrous" structure. Several theories have been proposed to understand the mechanism of modification of eutectic phases with Sr addition in these Alloys, but there is no conclusive evidence in support of these theories. From our XAFS analysis, we suggest Sr-Si bonds and Sr-Sr correlations may be responsible for the morphological transformation observed in the Alloy.

  • nucleation mechanism of the eutectic phases in aluminum silicon Hypoeutectic Alloys
    Acta Materialia, 2004
    Co-Authors: Sumanth Shankar, Y W Riddle, Makhlouf M Makhlouf
    Abstract:

    Abstract A theory is presented to explain the mechanism of formation of the eutectic phases in Al–Si Hypoeutectic Alloys. Results include optical, scanning and transmission electron microscopy, as well as selected area electron diffraction analysis and elemental X-ray mapping performed on Al–Si Hypoeutectic Alloy samples. The Alloy samples had precisely controlled chemistry and were solidified at various cooling rates. The data presented support the proposed theory with microstructural and crystallographic evidence.

  • Nucleation mechanism of the eutectic phases in aluminum–silicon Hypoeutectic Alloys
    Acta Materialia, 2004
    Co-Authors: Sumanth Shankar, Y W Riddle, Makhlouf M Makhlouf
    Abstract:

    Abstract A theory is presented to explain the mechanism of formation of the eutectic phases in Al–Si Hypoeutectic Alloys. Results include optical, scanning and transmission electron microscopy, as well as selected area electron diffraction analysis and elemental X-ray mapping performed on Al–Si Hypoeutectic Alloy samples. The Alloy samples had precisely controlled chemistry and were solidified at various cooling rates. The data presented support the proposed theory with microstructural and crystallographic evidence.

J.t. Guo - One of the best experts on this subject based on the ideXlab platform.

  • Microstructure and mechanical properties of zirconium doped NiAl/Cr(Mo) Hypoeutectic Alloy prepared by injection casting
    IOP Conference Series: Materials Science and Engineering, 2017
    Co-Authors: Liyuan Sheng, J.t. Guo
    Abstract:

    NiAl based materials has been considered as most potential candidate of turbine blade, due to its excellent high-temperature properties. However the bad room-temperature properties handicap its application. In the present paper, the zirconium doped NiAl/Cr(Mo) Hypoeutectic Alloy is fabricated by conventional casting and injection casting technology to improve its room-temperature properties. The microstructure and compressive properties at different temperatures of the conventionally-cast and injection-cast were investigated. The results exhibit that the conventionally-cast Alloy comprises coarse primary NiAl phase and eutectic cell, which is dotted with irregular Ni2AlZr Heusler phase. Compared with the conventionally-cast Alloy, the injection-cast Alloy possesses refined the primary NiAl, eutectic cell and eutectic lamella. In addition, the Ni2AlZr Heusler phase become smaller and distribute uniformly. Moreover, the injection casting decrease the area fraction of primary NiAl phase at the cell interior or cell boundaries. The compressive ductility and yield strength of the injection-cast Alloy at room temperature increase by about 100% and 35% over those of conventionally-cast Alloy, which should be ascribed to the microstructure optimization.

  • microstructure and mechanical properties of zirconium doped nial cr mo Hypoeutectic Alloy prepared by injection casting
    IOP Conference Series: Materials Science and Engineering, 2017
    Co-Authors: Liyuan Sheng, J.t. Guo
    Abstract:

    NiAl based materials has been considered as most potential candidate of turbine blade, due to its excellent high-temperature properties. However the bad room-temperature properties handicap its application. In the present paper, the zirconium doped NiAl/Cr(Mo) Hypoeutectic Alloy is fabricated by conventional casting and injection casting technology to improve its room-temperature properties. The microstructure and compressive properties at different temperatures of the conventionally-cast and injection-cast were investigated. The results exhibit that the conventionally-cast Alloy comprises coarse primary NiAl phase and eutectic cell, which is dotted with irregular Ni2AlZr Heusler phase. Compared with the conventionally-cast Alloy, the injection-cast Alloy possesses refined the primary NiAl, eutectic cell and eutectic lamella. In addition, the Ni2AlZr Heusler phase become smaller and distribute uniformly. Moreover, the injection casting decrease the area fraction of primary NiAl phase at the cell interior or cell boundaries. The compressive ductility and yield strength of the injection-cast Alloy at room temperature increase by about 100% and 35% over those of conventionally-cast Alloy, which should be ascribed to the microstructure optimization.

  • Effect of withdrawal rate on microstructure and mechanical properties of a directionally solidified NiAl-based Hypoeutectic Alloy doped with trace Hf and Ho
    Intermetallics, 2011
    Co-Authors: J.t. Guo, Liyuan Sheng, Lisha Zhou, Yongchun Liang
    Abstract:

    The Hypoeutectic Alloy, with nominal composition NiAl-31Cr-2.9Mo-0.1Hf-0.05Ho (at.%), was directionally solidified at three different withdrawal rates by liquid metal (Sn) cooling technique. Microstructural examination reveals that directional solidification gave rise to a shift in the coupled zone for the eutectic growth towards the Cr(Mo) phase. With the withdrawal rates increasing from 3 mm/min to 15 mm/min, the volume fraction of primary dendritic NiAl increases from 21.1% to 25.9%, while the size and the arm spacing of NiAl primary dendrite reduces simultaneously. The room temperature (RT) fracture toughness and the tensile strength at RT and elevated temperature (1373 K) present the valley value at intermediate rate (8 mm/min) among the withdrawal rate range which could be attributed to the decrease in volume fraction of eutectic NiAl/Cr(Mo) microstructure and the refinement of microstructure resulted from the increase of withdrawal rates. In terms of RT tensile elongation, the DS Alloy grown at different withdrawal rates all break with no plastic flow. (C) 2010 Elsevier Ltd. All rights reserved.