Development of a TiAl Alloy by Spark Plasma Sintering

Couret, Alain; Voisin, Thomas; Thomas, Marc; Monchoux, Jean‐Philippe

doi:10.1007/s11837-017-2549-6

Cited by 29 publications

(27 citation statements)

References 29 publications

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“…At this high temperature, diffusion is largely efficient enough to activate climb, as previously observed for ordinary dislocations in particular at low strain rate and low stress [2]. The small size of the γ grains of the borders (a few microns long and about 1 μm wide - [13]) and the proximity of lamellar interfaces is another factor enhancing the diffusion effects through the presence of numerous interfaces. The climb of dissociated superlattice dislocations with antiphase boundary lying in (001) or (111) type planes must involve local rearrangements of the atoms which complicate the occurring of such a mechanism.…”

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confidence: 58%

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Pure climb of [001] dislocations in TiAl at 850 °C

et al. 2018

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This paper presents a study by Transmission Electron Miscroscopy of the deformation microstructure in the γ phase of a TiAl alloy crept at 850°C under 150 MPa. A never observed population of dislocations is evidenced and characterized. It is shown that their Burgers vector is of [001] type and that they are moving by pure climb in the (001) planes. The reasons of the presence of these dislocations are discussed.

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confidence: 58%

“…The alloy investigated is an IRIS alloy (Ti -48Al -2W -0.08B) obtained by the densification of a pre-alloyed powder by Spark Plasma Sintering [12]. Its microstructure is formed by small lamellar grains surrounded by borders made of single phased γ grains that contain B2 precipitates [13]. The alloy was crept at 850°C under 150 MPa up to 1.5% of strain.…”

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Pure climb of [001] dislocations in TiAl at 850 °C

et al. 2018

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“…In this context, near‐net shaping of TiAl turbine blades using the SPS technique is described here . Mechanical properties at both room and elevated temperatures of an optimized alloy with Ti 49,92 Al 48 W 2 B 0,08 composition are also presented. To our knowledge, this is the first time in the literature that the manufacturing of comparable, complex‐shaped parts using the SPS technique is being reported.…”

Section: Comparison Between the Targeted Properties And Those Obtainementioning

confidence: 99%

“…To attain these targeted mechanical properties, our aim was to develop an alloy having a fine microstructure with two main features: a hardened γ phase and a predominance of refined lamellar colonies. Accordingly, the Ti 49,92 Al 48 W 2 B 0,08 composition, named IRIS, was selected for the following two reasons . Firstly, boron has been found to reduce grain growth during SPS densification through a grain‐boundary pinning mechanism on TiB 2 precipitates .…”

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confidence: 99%

An Innovative Way to Produce γ‐TiAl Blades: Spark Plasma Sintering

et al. 2015

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Increased demands are reported from the commercial and military sectors for longer range, greater endurance, and improved durability aircraft, thus requiring more efficient turbine engines with reduced fuel consumption. The durability of components in aircraft engines, such as blades, depends on their ability to withstand the extreme thermomechanical stresses to which they are subjected under operational conditions. Meanwhile, the International Civil Aviation Organization (ICAO) is expected to implement further regulation in order to protect the environment from noise and greenhouse gas emissions, thus pushing engine developers to develop improved emission control systems. Therefore, there is still a strong need to develop cleaner and more efficient engines, which require technological advances in the thermal and mechanical properties of highperformance materials. With this increased demand of new generation engines requiring higher thrust/mass ratios, gamma titanium aluminide (g-TiAl) intermetallic alloys have a combination of properties which offer many benefits for low pressure turbine blades of aircraft engines. In this Communication, we show that the production of turbine blades in gTiAl alloys through spark plasma sintering (SPS) is a viable manufacturing route, by demonstrating that near-net shaping of g-TiAl blades is successful, and by developing an alloy with balanced and outstanding mechanical properties at room and high temperatures in a single run and without subsequent thermal treatments.It is recalled that intermetallic compounds are defined by a combination of two or more metal elements with simple atomic concentrations (50/50, 75/25, etc.) which results in an ordered crystallographic structure. In the aeronautic sector where qualities of strength and lightness prevail, TiAl was the first intermetallic compound to be investigated for substitution to conventional Ti-based alloys and Ni-based superalloys. Replacing nickel-based superalloys (density %8 g cm À3 ) by such intermetallic g-TiAl alloys (density %4 g cm À3 ) with high specific modulus and mechanical strength, combined with an exceptional resistance to oxidation, is an effective contribution to the development of lighter aircraft engines with high performance.Strong interest traces back to the late seventies with the difficulties to increase the operating temperature of Ti-based alloys due to serious problems of oxidation above 600°C. Since the early 1980s, Wright-Patterson Air Force Laboratories envisaged g-TiAl for applications in military turbine engines, but were confronted to its low deformability. The National Research Institute for Metals (NRIM) in Japan devoted extensive work based on alloying addition for ductilizing TiAl compound with some success. [1] Meanwhile, general electric developed in 1989 the reference Ti-48Al-2Cr-2Nb (at%) alloy [48-2-2], which is still widely studied today for turbine blade application. [2] Chromium and niobium elements were added to improve the tensile ductility and resistance to oxidation, respectivel...

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“…However, remnant α 2 /γ lamellar structures, which would compromise the ductility of the TiAl based alloys, are difficult to eliminate completely. Powder metallurgy, such as HIP [ 13 , 14 ] and spark plasma sintering (SPS) [ 15 , 16 ], could produce TiAl based alloys with NG microstructure directly. HIP is a convenient and versatile technique for fabricating TiAl based alloys with NG microstructure by adopting pre-alloyed powders [ 13 , 14 ].…”

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confidence: 99%

Hot Deformation Behavior and Pulse Current Auxiliary Isothermal Forging of Hot Pressing Sintering TiAl Based Alloys

2017

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This paper focuses on the fabrication of as-forged Ti46.5Al2Cr1.8Nb-(W, B) alloy via pulse current auxiliary isothermal forging (PCIF). The starting material composed of near gamma (NG) microstructure was fabricated by adopting pre-alloyed powders via hot pressing sintering (HPS) at 1300 °C. Isothermal compression tests were conducted at a strain rate range of 0.001–0.1 s−1 and a temperature range of 1125–1275 °C to establish the constitutive model and processing map. The optimal hot deformation parameters were successfully determined (in a strain rate range of 10−3–2.5 × 10−3 s−1 and temperature range of 1130–1180 °C) based on the hot processing map and microstructure observation. Accordingly, an as-forged TiAl based alloy without cracks was successfully fabricated by PCIF processing at 1175 °C with a nominal strain rate of 10−3 s−1. Microstructure observation indicated that complete dynamic recrystallization (DRX) and phase transformation of γ→α2 occurred during the PCIF process. The elongation of as-forged alloy was 136%, possessing a good secondary hot workability, while the sintered alloy was only 66% when tested at 900 °C with a strain rate of 2 × 10−4 s−1.

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Development of a TiAl Alloy by Spark Plasma Sintering

Cited by 29 publications

References 29 publications

Pure climb of [001] dislocations in TiAl at 850 °C

Pure climb of [001] dislocations in TiAl at 850 °C

An Innovative Way to Produce γ‐TiAl Blades: Spark Plasma Sintering

Hot Deformation Behavior and Pulse Current Auxiliary Isothermal Forging of Hot Pressing Sintering TiAl Based Alloys

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