Metallurgical processing of titanium aluminides on industrial scale

Güther, Volker; Allen, Melissa; Klose, Joachim; Clemens, Helmut

doi:10.1016/j.intermet.2018.09.006

Cited by 84 publications

(35 citation statements)

References 4 publications

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“…The ingots needed for this process were produced according to refs. [21,22] by GfE Metalle und Materialen GmbH, Germany. A powder fraction smaller than 150 µm was utilized for the SPS experiment, which was carried out on a SPS device of the type HP D 25 by FCT Systems GmbH, Germany, at the Technische Universität Bergakademie Freiberg, Germany.…”

Section: Methodsmentioning

confidence: 99%

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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Section: Methodsmentioning

confidence: 99%

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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“…The TNM material was processed by GfE Metalle und Materialien GmbH, Nuremberg, Germany, using double VAR followed by ISM [ 20 ]. For this purpose, the feedstock was melted in a water-cooled copper crucible where the melt is steered in a native skull of solidified TiAl until the whole ingot has liquefied.…”

Section: Methodsmentioning

confidence: 99%

“…For this purpose, the feedstock was melted in a water-cooled copper crucible where the melt is steered in a native skull of solidified TiAl until the whole ingot has liquefied. This allowed an excellent homogenization of the heavy alloying elements such as Nb and Mo [ 20 , 21 ]. Afterwards, the melt was centrifugal cast under vacuum in a rotating mold wheel.…”

Section: Methodsmentioning

confidence: 99%

“…Thus, a homogeneous and fine-grained microstructure as well as a good deformability at elevated temperature, where, e.g., processes such as hot extrusion, forging, and rolling are carried out, can be achieved as reported in [ 14 , 18 , 19 ]. This alloy system fundamentally extends the opportunity to reach a broader customer base, by providing a cost-effective product while ensuring long-term sustainability in the evermore cost-sensitive high-performance racing market [ 20 ]. In order to meet the already mentioned demands and to withstand the different mechanical load conditions, a homogeneous, fine-grained, and defect-free microstructure is required.…”

Section: Introductionmentioning

confidence: 99%

“…In order to meet the already mentioned demands and to withstand the different mechanical load conditions, a homogeneous, fine-grained, and defect-free microstructure is required. Therefore, a new ingot production route was used that provides aviation-grade TNM material for the valve production [ 20 , 21 ]. Hence, the raw material was produced by a combination of vacuum arc remelting (VAR) and induction skull melting (ISM) as comprehensively described in [ 20 ].…”

Section: Introductionmentioning

confidence: 99%

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An Advanced TiAl Alloy for High-Performance Racing Applications

Burtscher

Klein

Lindemann³

et al. 2020

Materials

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Requirements and strict regulations for high‑performance racing applications involve the use of new and innovative lightweight structural materials. Therefore, intermetallic γ‑TiAl-based alloys enable new opportunities in the field due to their lower density compared to commonly used Ni‑base superalloys. In this study, a β‑solidifying TiAl alloy was examined toward its use as structural material for inlet and outlet valves. The nominal composition of the investigated TNM alloy is Ti–43.5Al–4Nb–1Mo–0.1B (in at%), which enables an excellent formability at elevated temperatures due to the presence of bcc β‑phase. Different hot‑extrusion tests on an industrial scale were conducted on the cast and hot isostatic pressed material to determine the ideal microstructure for the respective racing application. To simulate these operation conditions, hot tensile tests, as well as rotational bending tests, at room temperature were conducted. With a higher degree of deformation, an increasing strength and fatigue limit was obtained, as well as a significant increment of ductility. The fracture surfaces of the rotational bending test specimens were analyzed using scanning electron microscopy, revealing the relationship between crack initiation and microstructural constituents. The results of this study show that the mechanical performance of extruded TiAl material can be tailored via optimizing the degree of hot-extrusion.

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Sintering and Creep Resistance of Powder‐Metallurgy‐Processed Ti‐(43‐47)Al‐5Nb‐0.2B‐0.2C

et al. 2020

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The effect of Al variations in the sintering behavior and creep resistance is investigated in powder‐metallurgy‐processed titanium aluminides based on the alloy TNB‐V5 (Ti‐45Al‐5Nb‐0.2B‐0.2C at%). Two compositions are prepared with Al‐contents of 43 and 47 at%, varying Al‐content by ±2 at% relative to the reference material TNB‐V5. Specimen preparation is conducted by metal injection molding using feedstock prepared with mixtures of prealloyed and elemental powders. The sinterability of alloys with addition of elemental powders decreases in comparison to the reference material, according to dilatometry experiments. However, in experiments with the sintering furnace, it is possible to obtain porosity with values of ≈10% by sintering at 1450 °C, whereas sintering at 1500 °C decreases the porosity to less than 1% in case of 43 at% and 45 at% of Al. Even though the alloy containing 47 at% Al shows higher porosity of about 7%, the creep resistance is superior to 43 at% Al, which can be attributed to a larger colony size. In tensile tests at room temperature, the effect of porosity is very detrimental leading to significantly reduced tensile strength and total elongation. Nevertheless, in compressive creep tests, the effect of porosity is secondary to colony size.

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Metallurgical processing of titanium aluminides on industrial scale

Cited by 84 publications

References 4 publications

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

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

An Advanced TiAl Alloy for High-Performance Racing Applications

Sintering and Creep Resistance of Powder‐Metallurgy‐Processed Ti‐(43‐47)Al‐5Nb‐0.2B‐0.2C

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