Development of novel microstructures in zirconia-toughened alumina using rapid solidification and shock compaction

A rapidly solidified alumina-zirconia eutectic material containing nanocrystalline t-ZrO2 has been synthesized. When heated, the microstructure contained a mixture of t-ZrO2 and m-ZrO2, each of which can facilitate toughening of the composite. Dynamic shock compaction was used to accelerate densification of the material, producing crack-free specimens with high green densities. After sintering to densities measuring ∼95% of theoretical, the shock-compacted specimens fabricated with unstabilized alumina-zirconia were extensively microcracked due to an overabundance of the m-ZrO2 phase. Experiments employing Y2O3 as a chemical stabilizer have shown that the extent of the phase transformation can be controlled, and the microstructure that developed in the stabilized material contained an acceptable level of the microcrack generating m-ZrO2 phase.

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Microstructure & Phase Transformation in Rapidly Solidified V-Ga Alloys

MRS Proceedings ◽

10.1557/proc-80-285 ◽

1986 ◽

Vol 80 ◽

Author(s):

M. W. Park ◽

S. H. Whang ◽

S. Karmarkar ◽

D. Divecha

Keyword(s):

Heat Treatment ◽

Phase Transformation ◽

Grain Refinement ◽

Rapid Solidification ◽

Rapid Quenching ◽

X Ray Diffraction ◽

X Ray ◽

Rapidly Solidified ◽

A15 Phase

AbstractThe A15 Phase forming V-Ga alloys were processed into ribbons and foils by rapid solidification techniques. Microstructures and phase transformation in these alloys by rapid solidification and succeeding heat treatment were investigated by x-ray diffraction and TEM. It is shown that equilibrium A15 phases can readily be suppressed by rapid quenching in these alloys. A significant grain refinement resulting from the rapid solidification also was observed. Microhardnesses of these alloys as a function of Ga concentration were determined.

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Lorentz electron microscopy of magnetic domains in rapidly solidified and annealed Pt-Co-B alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100088233 ◽

1991 ◽

Vol 49 ◽

pp. 784-785

Author(s):

N. Qiu ◽

J. E. Wittig

Keyword(s):

Rapid Solidification ◽

Ion Beam ◽

Magnetic Behavior ◽

High Coercivity ◽

Magnetic Domains ◽

Beam Angle ◽

Tem Analysis ◽

Intrinsic Coercivity ◽

Hard Magnets ◽

Rapidly Solidified

PtCo hard magnets have specialized applications owing to their relatively high coercivity combined with corrosion resistance and ductility. Increased intrinsic coercivity has been recently obtained by rapid solidification processing of PtCo alloys containing boron. After rapid solidification by double anvil splat quenching and subsequent annealing for 30 minutes at 650°C, an alloy with composition Pt42Co45B13 (at.%) exhibited intrinsic coercivity up to 14kOe. This represents a significant improvement compared to the average coercivities in conventional binary PtCo alloys of 5 to 8 kOe.Rapidly solidified specimens of Pt42Co45B13 (at.%) were annealed at 650°C and 800°C for 30 minutes. The magnetic behavior was characterized by measuring the coercive force (Hc). Samples for TEM analysis were mechanically thinned to 100 μm, dimpled to about 30 nm, and ion milled to electron transparency in a Gatan Duomill at 5 kV and 1 mA gun current. The incident ion beam angle was set at 15° and the samples were liquid nitrogen cooled during milling. These samples were analyzed with a Philips CM20T TEM/STEM operated at 200 kV.

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Shock consolidation of Ni-Ti alloy powder

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100143730 ◽

1986 ◽

Vol 44 ◽

pp. 430-431

Author(s):

Naresh N. Thadhani ◽

Thad Vreeland ◽

Thomas J. Ahrens

Keyword(s):

Alloy Powder ◽

Amorphous Material ◽

Ti Alloy ◽

Two Phase ◽

Near Surface ◽

Optical Micrograph ◽

Shock Compaction ◽

Powder Particles ◽

Ti Powder ◽

Rapidly Solidified

A spherically-shaped, microcrystalline Ni-Ti alloy powder having fairly nonhomogeneous particle size distribution and chemical composition was consolidated with shock input energy of 316 kJ/kg. In the process of consolidation, shock energy is preferentially input at particle surfaces, resulting in melting of near-surface material and interparticle welding. The Ni-Ti powder particles were 2-60 μm in diameter (Fig. 1). About 30-40% of the powder particles were Ni-65wt% and balance were Ni-45wt%Ti (estimated by EMPA).Upon shock compaction, the two phase Ni-Ti powder particles were bonded together by the interparticle melt which rapidly solidified, usually to amorphous material. Fig. 2 is an optical micrograph (in plane of shock) of the consolidated Ni-Ti alloy powder, showing the particles with different etching contrast.

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Transmission Electron Microscopic Observations of Al3Li and Al3Ti Precipitation in A Rapidly Solidified Al-3Li-0.2Ti ALLOY

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s1431927600001422 ◽

1980 ◽

Vol 38 ◽

pp. 336-337

Author(s):

J. E. O’Neal ◽

K. K. Sankaran ◽

S. M. L. Sastry

Keyword(s):

Rapid Solidification ◽

Metallic Substrate ◽

Deformation Characteristics ◽

Phase Decomposition ◽

Electron Microscopic ◽

Transmission Electron ◽

Supersaturated Solid Solutions ◽

Transmission Electron Microscopic ◽

Rapidly Solidified ◽

Microstructural Homogeneity

Rapid solidification of a molten, multicomponent alloy against a metallic substrate promotes greater microstructural homogeneity and greater solid solubility of alloying elements than can be achieved by slower-cooling casting methods. The supersaturated solid solutions produced by rapid solidification can be subsequently annealed to precipitate, by controlled phase decomposition, uniform 10-100 nm precipitates or dispersoids. TEM studies were made of the precipitation of metastable Al3Li(δ’) and equilibrium AL3H phases and the deformation characteristics of a rapidly solidified Al-3Li-0.2Ti alloy.

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New Fe-Ni Based Metal-Metalloid Glassy Alloys Prepared by Mechanical Alloying and Rapid Solidification

MRS Proceedings ◽

10.1557/proc-455-489 ◽

1996 ◽

Vol 455 ◽

Cited By ~ 3

Author(s):

J. J. Suñol ◽

M. T. Clavaguera-Mora ◽

N. Clavaguera ◽

T. Pradell

Keyword(s):

Mechanical Alloying ◽

Rapid Solidification ◽

Melt Spinning ◽

Magnetic Interaction ◽

Processing Route ◽

Mechanically Alloyed ◽

Scanning Calorimetry ◽

Glassy Alloys ◽

Rapidly Solidified ◽

Thermal Stability Of

ABSTRACTMechanical alloying and rapid solidification are two important routes to obtain glassy alloys. New Fe-Ni based metal-metalloid (P-Si) alloys prepared by these two different processing routes were studied by differential scanning calorimetry and transmission Mössbauer spectroscopy. Mechanical alloyed samples were prepared with elemental precursors, and different nominal compositions. Rapidly solidified alloys were obtained by melt-spinning. The structural analyses show that, independent of the composition, the materials obtained by mechanical alloying are not completely disordered whereas fully amorphous alloys were obtained by rapid solidification. Consequently, the thermal stability of mechanically alloyed samples is lower than that of the analogous material prepared by rapid solidification. The P/Si ratio controls the magnetic interaction of the glassy ribbons obtained by rapid solidification. The experimental results are discussed in terms of the degree of amorphization and crystallization versus processing route and P/Si ratio content.

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Thermodynamic in γ→ϵ Phase Transformation and γ→α′ Phase Transformation in Fe-Mn Alloy during Near-Rapid Solidification

TMS2013 Supplemental Proceedings ◽

10.1002/9781118663547.ch108 ◽

2013 ◽

pp. 869-875

Author(s):

Qin Peng ◽

Changjiang Song ◽

Wenbin Xia ◽

Qijie Zhai

Keyword(s):

Phase Transformation ◽

Rapid Solidification ◽

Α Phase

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Zirconia Phase Transformation in Zirconia-Toughened Alumina Ceramic Femoral Heads: An Implant Retrieval Analysis

The Journal of Arthroplasty ◽

10.1016/j.arth.2019.07.014 ◽

2019 ◽

Vol 34 (12) ◽

pp. 3094-3098 ◽

Cited By ~ 1

Author(s):

Thu M. Nguyen ◽

Lydia Weitzler ◽

Christina I. Esposito ◽

Alessandro A. Porporati ◽

Douglas E. Padgett ◽

...

Keyword(s):

Phase Transformation ◽

Alumina Ceramic ◽

Retrieval Analysis ◽

Femoral Heads ◽

Zirconia Phase ◽

Zirconia Toughened Alumina

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Microstructural Characterization of Rapidly Solidified Ultrahigh Strength Aluminum Alloys

Microscopy and Microanalysis ◽

10.1017/s1431927600020614 ◽

1998 ◽

Vol 4 (S2) ◽

pp. 98-99

Author(s):

D. H. Ping ◽

K. Hono ◽

A. Inoue

Keyword(s):

Rapid Solidification ◽

Microstructural Characterization ◽

Atom Probe ◽

Probe Field ◽

Amorphous Phases ◽

Ultrahigh Strength ◽

Icosahedral Phases ◽

Transmission Electron ◽

Solidification Processes ◽

Rapidly Solidified

Recently, Inoue et al. succeeded in fabricating ultrahigh-strength Al-based alloys consisting of a nanoscale mixture of α-Al and amorphous phases or a mixture of a-Al, amorphous and icosahedral phases in Al-TM-Ce, Al-TM-Ln (TM: transition metals) and Al-Cr-Co-Ce systems by rapid solidification [1-3]. In order to understand the mechanism of the nanoscale microstructural evolution during the rapid solidification processes in these nanocomposite alloys, we have characterized the microstructures of rapidly solidified Al94.5Cr3Co1.5Ce1 and Al96V4Fe2 alloys by atom probe field ion microscopy (APFIM) and high resolution transmission electron microscopy (HREM).TEM investigations have revealed that the as-quenched Al94.5Cr3Co1.5Ce1 alloy is composed of a nanoscale mixture of amorphous and α-Al. A typical TEM bright field micrograph is shown in Fig. 1. The microdiffraction patterns taken at various locations in the darkly contrasted region have shown that the region consists of a few interconnected α-Al grains and many localized amorphous regions which are trapped within the Al grains.

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