Phase transformations in a β-solidifying γ-TiAl based alloy during rapid solidification

Kastenhuber, Michael; Klein, Thomas; Rashkova, Boryana; Weißensteiner, Irmgard; Clemens, Helmut; Mayer, Svea

doi:10.1016/j.intermet.2017.08.017

Cited by 50 publications

(31 citation statements)

References 51 publications

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“…The finest powder with a diameter less than 15 µm is dominated by the α 2 phase, with only a minor fraction of the γ phase. As reported in the literature, the metastable α 2 phase could easily form during rapid solidification [18,19]. Thus, in the present work, the appearance of the α 2 phase in the high-Nb TiAl powders indicated that the cooling rate in the gas atomization process is rather high.…”

Section: Methodssupporting

confidence: 75%

Size-Dependent Structural Properties of a High-Nb TiAl Alloy Powder

Liu

Wang

et al. 2020

Materials

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TiAl-based alloys are promising light weight structural materials for high temperature applications in the field of aerospace. Recently, fabrication technologies starting from powders including powder metallurgy and additive manufacturing have been developed to overcome the difficulties in the processing, machining and shaping of TiAl-based alloys. Spherical alloy powders with different particle size distributions are usually used in these fabrication techniques. The purpose of this study is to reveal the size-dependent structural properties of a high-Nb TiAl powder for these fabrication technologies starting from powders. A high-Nb TiAl pre-alloyed powder with nominal composition of Ti-48Al-2Cr-8Nb (at. %) was prepared by the electrode induction melting gas atomization (EIGA) method. The phase structure and morphology of the as-atomized powders were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The size-dependent structural changes of the as-atomized powders with different sizes were studied by differential scanning calorimetry (DSC) and in situ high temperature XRD. It was found that with decreasing the powder size, the content of the γ-TiAl phase decreases and the α2-Ti3Al phase increases. The α2-Ti3Al to γ-TiAl phase transformation was found in the temperature range of 600–770 °C. Based on the present work, the structural characteristics of TiAl powders are strongly dependent on their particle size, which should be considered in optimizing the process parameters of TiAl alloys fabricated from powders.

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Section: Methodssupporting

confidence: 75%

Size-Dependent Structural Properties of a High-Nb TiAl Alloy Powder

Liu

Wang

et al. 2020

Materials

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“…The CR is provoked by the fine lamellae causing a high amount of interface surfaces, thus decreasing the thermal stability of the α 2 /γ-colonies. At aging or service temperature, this fine lamellar α 2 /γ-colonies are prone to decompose in (α 2 + β o + γ) cellular , starting from the colony boundaries that deteriorates the high temperature properties, as reported in References [5,17,26,27].…”

Section: Resultsmentioning

confidence: 81%

Microstructural Evolution and Mechanical Properties of an Advanced γ-TiAl Based Alloy Processed by Spark Plasma Sintering

Wimler

Lindemann²,

Clemens

et al. 2019

Materials

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Intermetallic γ-TiAl based alloys are innovative lightweight structural high-temperature materials used in aerospace and automotive applications due to already established industrial-scale processing routes, like casting and hot-working, i.e., forging. A promising alternative method of production, regarding manufacturing of near net-shape components, goes over the powder metallurgy route, more precisely by densification of TiAl powder via spark plasma sintering. In this study, gas atomized powder from the 4th generation TNM alloy, Ti-43.5Al-4Nb-1Mo-0.1B (in at.%), was densified and the microstructure was investigated by means of electron microscopy and X-ray diffraction. The sintered microstructure exhibits lamellar α2-Ti3Al /γ-TiAl colonies surrounded by globular γ- and ordered βo-TiAl phase. The coarse lamellar spacing stems from the low cooling rate after densification at sintering temperature. Against this background, subsequent heat treatments were designed to decrease the lamellar widths by a factor of ten. Accompanying, tensile tests and creep experiments at different temperatures revealed that the modified almost fully lamellar microstructure is enhanced in strength and creep resistance, where a small volume fraction of globular γ-phase provides ductility at ambient temperatures.

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“…Beide Merkmale wirken sich negativ auf die Rieselfähigkeit aus und behindern so eine optimale Verteilung im Pulverbett [12]. Die Oberflächen weisen unterschiedlich große Domänen auf, deren Ursprung auf Dendritenbildung während der Erstarrung zurückgeführt werden kann [13]. Die Größe der Domänen ist unabhängig von der Pulvergröße und setzt sich innerhalb der Partikel fort.…”

Section: Charakterisierung Der Pulverunclassified

“…Die Größe der Domänen ist unabhängig von der Pulvergröße und setzt sich innerhalb der Partikel fort. An den Domänengrenzen kommt es zu einer Anreicherung von Al während der Erstarrung [13]. In den Querschliffen konnten vereinzelt Inhomogenitäten festgestellt werden, welche mittels Pfeile markiert sind.…”

Section: Charakterisierung Der Pulverunclassified

Mikrostrukturelle Charakterisierung einer pulvermetallurgisch hergestellten mehrphasigen TiAl-Legierung

Burtscher

Pürstl

Schloffer

et al. 2019

Berg Huettenmaenn Monatsh

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Zusammenfassung: Intermetallische Titanaluminide werden bei erhöhten Temperaturen als Turbinenschaufeln in Flugzeugtriebwerken, als Laufräder in Turboladern sowie als Ventile im Rennsport eingesetzt. Um neue Herstellungswege zu nutzen und endkonturnahe 3D gedruckte Teile produzieren zu können, müssen geeignete Pulver für additive Fertigungsprozesse verfügbar sein. Dazu wurden zwei vielversprechende Legierungsvarianten herangezogen und entsprechende Pulver hergestellt. Anschließend wurden die Pulver heißisostatisch verdichtet. Um die Qualität der Pulver sicherzustellen und mögliche mikrostrukturelle Inhomogenitäten des Materials auszuschließen, erfolgte eine Defektanalyse mittels Lichtmikroskopie in Kombination mit Rasterelektronenmikroskopie. Dazu wurden einzelne Defekte im Lichtmikroskop mittels Härteeindrücken markiert und deren lokale chemische Information über detaillierte Flächenscans im Rasterelektronenmikroskop ermittelt. Die Ergebnisse dieser Untersuchung können dazu verwendet werden, Fehlerquellen bei der Herstellung sensibler Titanaluminid-Pulver zu vermeiden und so die Qualität der erzeugten Bauteile zu steigern.

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Phase transformations in a β-solidifying γ-TiAl based alloy during rapid solidification

Cited by 50 publications

References 51 publications

Size-Dependent Structural Properties of a High-Nb TiAl Alloy Powder

Size-Dependent Structural Properties of a High-Nb TiAl Alloy Powder

Microstructural Evolution and Mechanical Properties of an Advanced γ-TiAl Based Alloy Processed by Spark Plasma Sintering

Mikrostrukturelle Charakterisierung einer pulvermetallurgisch hergestellten mehrphasigen TiAl-Legierung

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