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X C Tong - One of the best experts on this subject based on the ideXlab platform.

  • Fabrication of in situ TiC reinforced aluminum matrix composites Part I: Microstructural characterization
    Journal of Materials Science, 1998
    Co-Authors: X C Tong
    Abstract:

    In the present work traditional Ingot Metallurgy plus rapid solidification techniques were used to in situ produce Al-TiC composites with refined microstructures and enhanced dispersion hardening of the reinforcing phases. Microstructural characterization of the experimental materials were comprehensively done by optical, electron microscopy and X-ray diffraction. The results show that the in situ synthesized TiC particles possess a metastable fcc crystal structure with an atomic composition of TiC08 and a lattice parameter of 0.431 nm. The typical Ingot Metallurgy microstructures exhibit aggregates of TiC particle phase segregated generally at the α-Al subgrain or grain boundaries and consisted of fine particles of 0.2–1.0 μm. After re-melting of the Ingots and hence rapid solidification, the microstructures formed under certain thermal history conditions contained uniform fine-scale dispersion of TiC phase particles with a size range of 40–80 nm in an Al supersaturated matrix of 0.30–0.85 μm grain size. In the most case these dispersed TiC particles have a semi-coherent relationship with the α-Al matrix.

  • al tic composites in situ processed by Ingot Metallurgy and rapid solidification technology part i microstructural evolution
    Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 1998
    Co-Authors: X C Tong, Hongsheng Fang
    Abstract:

    The present work was undertaken to highlight a novel in situ process in which traditional Ingot Metallurgy plus rapid solidification techniques were used to produce Al-TiC composites with refined microstructures and enhanced dispersion hardening of the reinforcing phases. Microstructures of the experimental materials were comprehensively characterized by optical microscopy, electron microscopy, and X-ray diffraction. The results show that the in situ-synthesized TiC particles possess a face-centered cubic crystal structure with an atomic composition of TiC0.8 and a lattice parameter of 0.431 nm. The typical Ingot Metallurgy microstructures exhibit aggregates of TiC particles segregated generally at the α-Al subgrain or grain boundaries and consisting of fine particles of 0.2 to 1.0 µm in size. The rapidly solidified microstructures formed under certain thermal history conditions contained a uniform, fine-scale dispersion of TiC phase particles with a size range of 40 to 80 nm in an α-Al supersaturated matrix of 0.30 to 0.85 µm in grain size. These dispersed TiC particles generally have a semicoherent relationship with the α-Al matrix. Based on the experimental results, a comprehensive kinetic mechanism of in situ TiC synthesis, which includes a solid-liquid interface reaction between the carbon particles and the Al melt and multiple nucleation and growth of TiC from the Al melt, was proposed. Then, the evolution of the aggregate TiC particles in a superheated melt before rapid solidification, i.e., dissolution, nucleation, and growth of the regenerated TiC dispersed particles, was analyzed. Furthermore, the behavior of rapid solidification kinetics, the nucleation of α-Al on TiC-dispersed particles, and the interaction between TiC particles and the solidification front were documented experimentally and theoretically. These studies provided the theoretical criteria and an experimental basis for the optimum design of this kind of composite.

  • Al-TiC composites in situ-processed by Ingot Metallurgy and rapid solidification technology: Part II. Mechanical behavior
    Metallurgical and Materials Transactions A, 1998
    Co-Authors: X C Tong, Hongsheng Fang
    Abstract:

    In Part II of this article, the high-strength Al-Si/TiC composite and the elevated-temperature-resistant Al-Fe(-V-Si)/TiC composite, developed on the basis of the in situ Al-TiC composites (Part I of the article),[8] have been evaluated for their room- and elevated-temperature mechanical behavior. The microstructural characteristics of Ingot Metallurgy (IM) or rapid solidification (RS) Al-Si/TiC and Al-Fe(-V-Si)/TiC composites could be thought of as a combination of the related alloy matrix microstructures and the IM or RS Al/TiC composites. The IM Al/TiC and the Al-Si/TiC composites show superior strength and ductility to the relevant aluminum-based composites. The RS Al/TiC and the Al-Fe-V-Si/TiC exhibit high Young’s moduli and substantial improvements in room- and elevated-temperature tensile properties compared to those of rapidly solidified alloys and conventional composites. The Young’s modulus values of RS Al/TiC and Al-Fe-V-Si/TiC composites are well within Hashin-Shtrikman (H-S) limits, in keeping with the strong interfacial bonding. In the micro-mechanics approach, the principal strengthening mechanisms for the present dispersed, particle-hardened RS in situ Al-TiC composites would include Orowan strengthening, grain-size and substructure strengthening, and solid-solution strengthening.

Enrique J. Lavernia - One of the best experts on this subject based on the ideXlab platform.

  • Processing, microstructure and fracture behaviour of a spray atomized and deposited aluminium-silicon alloy
    Journal of Materials Science, 1997
    Co-Authors: S Anand, T. S Srivatsan, Enrique J. Lavernia
    Abstract:

    In this study a hypereutectic aluminium–silicon alloy was synthesized by spray atomization and deposition technique. Microstructure characterization studies were performed to provide an understanding of the influence of spray processing on microstructure of the hypereutectic alloy. Ambient and elevated temperature tensile tests reveal the spray-processed alloy to have better strength and ductility than a conventional Ingot Metallurgy processed alloy having the same chemical composition. The quasi-static fracture characteristics of the spray-processed alloy is presented and discussed in light of processing and intrinsic microstructural effects.

  • Innovations in light metals synthesis for the 1990's
    1991
    Co-Authors: Francis H. Froes, G. E. Bobeck, Challapalli Suryanarayana, Enrique J. Lavernia
    Abstract:

    Improved light metals based on aluminum, magnesium, titanium and the intermetallic titanium aluminides are necessary to enhance the performance capability of aerospace systems. Key to these developments are innovative synthesis techniques which will allow novel microstructures and improved mechanical property combinations Developments in eight areas are reviewed in this paper: Ingot Metallurgy, castings, rapid solidification, mechanical alloying, spray deposition, electron beam vapor deposition, thermochemical processing, and engineered materials (metal matrix composites).

Leandro Bolzoni - One of the best experts on this subject based on the ideXlab platform.

  • Comparison of the Cracking Behavior of Powder Metallurgy and Ingot Metallurgy Ti-5Al-5Mo-5V-3Cr Alloys during Hot Deformation.
    Materials (Basel Switzerland), 2019
    Co-Authors: Qinyang Zhao, Fei Yang, Rob Torrens, Leandro Bolzoni
    Abstract:

    The hot workability of metallic materials is significantly dependent on its ability to form plastic without cracking and fracturing. In this work, the cracking behavior of powder Metallurgy (PM) Ti-5Al-5Mo-5V-3Cr (Ti-5553) alloy, consolidated from powder mixture, at a deformation temperature range of 600 °C–850 °C and strain rate of 0.1 s−1–10 s−1, was investigated through isothermal compression tests. The cracking behavior of the as-cast Ingot Metallurgy (IM) Ti-5553 alloy, at a deformation temperature of 700 °C was also investigated for comparison. Results suggested that the PM Ti-5553 alloy had a better hot workability, with a larger cracking-free processing window, and a lower deformation resistance than the IM counterpart. 45° shear fracture occurred in the PM alloy, compressed at the condition of 600 °C/10 s−1, and edge cracking was observed at the 700 °C/10 s−1. 45° shear fracture was also significant in the IM alloy specimen tested at 700 °C/10 s−1, and all the other IM alloy specimens compressed at 700 °C displayed longitudinal cracking. Moreover, the microscopic cracking observation showed that ductile dimple cracking can be found in the IM alloy, but brittle cleavage fracture was dominant in the cracking surface of PM alloy with a relatively low cracking ductility.

  • Comparison of hot deformation behaviour and microstructural evolution for Ti-5Al-5V-5Mo-3Cr alloys prepared by powder Metallurgy and Ingot Metallurgy approaches
    Materials & Design, 2019
    Co-Authors: Qinyang Zhao, Fei Yang, Rob Torrens, Leandro Bolzoni
    Abstract:

    Abstract To realize the systematic comparison of the hot workability and guide the further hot-processing of powder Metallurgy (PM) and Ingot Metallurgy (IM) Ti-5Al-5V-5Mo-3Cr (Ti-5553) alloys, the hot deformation behaviour and microstructural evolution of the two alloys were investigated at a wide temperature range of 700 °C–1100 °C and strain rate of 0.001 s−1-10 s−1. The activation energy maps and processing maps for both PM and IM alloys were constructed, as well as the specific deformation mechanisms were identified for each processing region. The results showed that PM alloy has lower deformation resistance, smaller activation energy and larger optimal processing windows than those of IM alloy. The dynamic α precipitation mechanisms in PM alloy were diffusional globularization and coarsening, rather than diffusionless shearing and fracturing in IM alloy. The extensive dynamic recrystallization (DRX) happened at 900 °C–1050 °C for PM alloy and at 1000 °C–1100 °C for IM alloy. The DRX process was dominated by discontinuous dynamic recrystallization (DDRX) for PM alloy while continuous dynamic recrystallization (CDRX) for IM alloy. Furthermore, PM alloy had smaller flow instability region than IM counterpart in the hot processing map. The schematic deformation mechanism maps were eventually developed for both PM and IM Ti-5553 alloys.

S. A. Brown - One of the best experts on this subject based on the ideXlab platform.

  • Elevated temperature deformation of several quaternary L1 2 Al 3 Ti based alloys reinforced with TiB 2 particles
    Journal of Materials Science, 1995
    Co-Authors: J. D. Whittenberger, K.s. Kumar, M.s. Dipietro, S. A. Brown
    Abstract:

    Concurrent with an investigation of quaternary cast and forged L12 modified Al3Ti's containing 9 at% Cr, Fe and/or Mn, a similar series of four alloys was produced via XDTM technology, whereby 20 vol% of ∼ 0.5 μm TiB2 particles was incorporated as a reinforcement. Following densification by hot pressing and slow isothermal forging, small diameter compression test samples were machined from each compact and tested. The 0.2% yield strength measurements revealed a strength advantage for the particulate reinforced materials over the unreinforced Ingot Metallurgy matrices to about 1175 K. Furthermore, 900 and 1100 K constant velocity testing indicated that the TiB2 containing materials were stronger than the Ingot Metallurgy matrices down to strain rates of ∼ 10−7s−1. None of the quaternary L12 alloys + 20 TiB2 consistently displayed a strength advantage over others. However, extrapolation of the present mechanical property data into slower strain regimes indicated that the composites will not possess any strength advantage overthe unreinforced versions. Such losses in strength appeared to be caused by small grains in the particulate reinforced alloys, which promoted grain boundary weakening mechanisms.

  • Mechanical behavior of TiB2-particulate-reinforced Al66Ti25Mn9 produced by Ingot Metallurgy
    Materials Science and Engineering: A, 1993
    Co-Authors: S. A. Brown, K.s. Kumar, J. D. Whittenberger
    Abstract:

    Abstract A cast and isothermally forged particulate composite of Al 66 Ti 25 Mn 9 + 3 vol.% TiB 2 was evaluated in compression, three-point bending and uniaxial tension. Compared with previous results on a monolithic material of the same composition, the composite was stronger in compression at all temperatures and strakin rates examined. A similar trend was noted in tension in the temperature range 923 K - 1073 K. Three-point bend tests (300 K - 873 K), however, revealed a smaller degree of plastic deformation in the composite compared to its monolithic counterpart. Serrated flow was observed between 623 K and 923 K in compression, bending and tension for the monolithic material, whereas in the composite it was noted at 573 K in compression. In tension, the composite exhibits brittle failure at 923 K. Above 923 K, the ductility is roughly one half of the monolithic alloy. Transgranular cleavage fracture in the composite changes to an intergranular mode at a higher temperature relative to the monolithic material.

T. J Garosshen - One of the best experts on this subject based on the ideXlab platform.

  • Evaluation of the tensile and fatigue behaviour of Ingot Metallurgy beryllium/aluminium alloys
    Journal of Materials Science, 1997
    Co-Authors: V. C Nardone, T. J Garosshen
    Abstract:

    The tensile and fatigue behaviour of Ingot Metallurgy beryllium/aluminium alloys produced by Nuclear Metals, Inc., is determined as a function of temperature. The wrought alloy and the casting alloy are both shown to have a very high stiffness to density ratio compared with common structural materials. The wrought alloy was found to have superior fatigue strength, tensile strength and ductility relative to the casting alloy; it also maintained a greater fraction of its tensile strength as a function of temperature. The stiffness of the materials can be readily explained using standard composite theory, where the material is treated as a discontinuous beryllium-reinforced aluminium matrix composite. The strength of the casting alloy is controlled to a large extent by the strength of its aluminium alloy matrix. In contrast, strengthening increments from both dislocation-based mechanisms and load transfer appear to be operative for the wrought material. Fractographic analysis of tensile specimens showed that preferential failure of the aluminium regions or the beryllium/aluminium interfacial regions occurs under certain circumstances. Fracture analysis of fatigue samples revealed no obvious fracture initiation sites and no evidence of limited/controlled crack growth regions.

  • evaluation of the tensile and fatigue behaviour of Ingot Metallurgy beryllium aluminium alloys
    Journal of Materials Science, 1997
    Co-Authors: V. C Nardone, T. J Garosshen
    Abstract:

    The tensile and fatigue behaviour of Ingot Metallurgy beryllium/aluminium alloys produced by Nuclear Metals, Inc., is determined as a function of temperature. The wrought alloy and the casting alloy are both shown to have a very high stiffness to density ratio compared with common structural materials. The wrought alloy was found to have superior fatigue strength, tensile strength and ductility relative to the casting alloy; it also maintained a greater fraction of its tensile strength as a function of temperature. The stiffness of the materials can be readily explained using standard composite theory, where the material is treated as a discontinuous beryllium-reinforced aluminium matrix composite. The strength of the casting alloy is controlled to a large extent by the strength of its aluminium alloy matrix. In contrast, strengthening increments from both dislocation-based mechanisms and load transfer appear to be operative for the wrought material. Fractographic analysis of tensile specimens showed that preferential failure of the aluminium regions or the beryllium/aluminium interfacial regions occurs under certain circumstances. Fracture analysis of fatigue samples revealed no obvious fracture initiation sites and no evidence of limited/controlled crack growth regions.