Dislocation dynamics in carbon-doped titanium aluminide alloys

Christoph, U.; Appel, F.; Wagner, Richard

doi:10.1016/s0921-5093(97)00558-3

Cited by 79 publications

(44 citation statements)

References 8 publications

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“…The effective shear stress acting on the dislocation segments were determined by comparing their curvature with line tension configurations. [49] This led to an average value s c = 300 MPa which is in good agreement with the flow stress r = 1000 MPa, which had been applied during macroscopic compression to strain e = 3 %. r can be converted into an average shear stress s = r/M = 330 MPa using the Taylor factor M = 3.06.…”

Section: Precipitation Hardening Due To Carbon Additionssupporting

confidence: 63%

“…[48,49] A systematic series of carbon doped materials with the base line composition Ti±48.5 Al±(0.02±0.4) C were subjected to different thermal treatments. Annealing at 1523 K and quenching resulted in a carbon solid solution, whereas Ti 3 AlC precipitates of perovskite type were formed by subsequent ageing at 1050 K. The precipitates are elongated along the c-axis of the c matrix and exhibit significant coherency stresses due to their mismatch with the c matrix.…”

Section: Precipitation Hardening Due To Carbon Additionsmentioning

confidence: 99%

See 1 more Smart Citation

Recent Progress in the Development of Gamma Titanium Aluminide Alloys

Appel¹,

Brossmann²,

Christoph³

et al. 2000

Adv. Eng. Mater.

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353

103

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Intermetallic titanium aluminides offer an attractive combination of low density and good oxidation and ignition resistance with unique mechanical properties. These involve high strength and elastic stiffness with excellent high temperature retention. Thus, they are one of the few classes of emerging materials that have the potential to be used in demanding high‐temperature structural applications whenever specific strength and stiffness are of major concern. However, in order to effectively replace the heavier nickel‐base superalloys currently in use, titanium aluminides must combine a wide range of mechanical property capabilities. Advanced alloy designs are tailored for strength, toughness, creep resistance, and environmental stability. These concerns are addressed in the present paper through global commentary on the physical metallurgy and associated processing technologies of γ‐TiAl‐base alloys. Particular emphasis is paid on recent developments of TiAl alloys with enhanced high‐temperature capability.

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Section: Precipitation Hardening Due To Carbon Additionssupporting

confidence: 63%

Section: Precipitation Hardening Due To Carbon Additionsmentioning

confidence: 99%

Recent Progress in the Development of Gamma Titanium Aluminide Alloys

Appel¹,

Brossmann²,

Christoph³

et al. 2000

Adv. Eng. Mater.

Self Cite

353

103

View full text Add to dashboard Cite

show abstract

“…The flow stress was also found to be nearly independent of carbon concentration for solid solute carbon addition. [21] Thus, the residual stress of welding zone is around 370 MPa lower than that in the HAZ. The residual stress in the plate with cracking was also indicated in a previous work, [7] in which the stress distribution shows a double-peak morphology with a maximum value of 585 MPa.…”

Section: Resultsmentioning

confidence: 96%

Investigation of In Situ and Conventional Post‐Weld Heat Treatments on Dual‐Laser‐Beam‐Welded γ‐TiAl‐Based Alloy

et al. 2012

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The g-TiAl materials is an attractive alternative candidate for aerospace and automotive applications because of its properties, such as low density (%3.8 g cm À3 ), high specific yield strength at high temperature, and high creep and oxidation resistance. [1][2][3][4][5] The high niobium containing TNB alloy with the composition of Ti-45Al-5Nb-0.2C-0.2B (at.%) has been developed by the Helmholtz-Zentrum Geesthacht (HZG) for applications in turbine construction. The alloy shows excellent mechanical properties, with 907-939 MPa yield strength, 917-1033 MPa ultimate tensile strength and 1.08-1.44% of elongation to fracture for rolled sheet material at 23 8C. [6] However, the low ductility and fracture toughness of g-TiAl-based alloys at ambient temperature and their limited weldability restrict their industrial and commercial application. [1] Laser beam and electron beam welding has been tried to produce sound TiAl joint. However, longitudinal and transverse cracks were observed in the welding seam. [7][8][9] The material is intrinsically brittle and the high cooling rate results in a welding zone with high residual stress and thermal strain.Nevertheless, it was reported that with proper selection of the cooling rate, butt joining can be achieved for small work pieces. [9] Thus, the goal of the present work is to improve the welding zone microstructure and reduce the residual stress of laser beam-welded specimens via post-weld heat treatments, which is important for increasing the weldable specimen size. Materials and ExperimentsTNB powder material was produced using a powder metallurgical approach by means of gas atomization in the PIGA (plasma melting induction guiding gas atomization) facility at HZG. The powder particles were degassed, welded, hot-isostatically pressed (HIP), and finally extruded into a cylindrical rod. Plates of 13 Â 50 Â 2 mm 3 were extracted by electro-discharge machining (EDM) and subsequently cleaned to remove oxides and remnants. The two laser beams were simultaneously generated by two Nd:YAG laser operation stations (power output P 1 : 0-2200 W, P 2 : 0-3300 W). A robot was used to operate the work station and laser beam movement (Figure 1a). One laser beam for in situ heat treatment was defocused into a large spot size and used for whole-plate (d ¼ 60 mm, see Figure 1b) and local (d ¼ 20-40 mm, see Figure 1b) pre-heating, to ensure the temperature of the welding line was above the brittleductile transition region. The second laser was used for keyhole welding. The plates were positioned in a closed chamber, which was filled with argon to protect the specimen from oxidation. Helium was used as the working gas, and it was injected from the welding cone from above. During butt welding, a minimal clamping force was applied on the work pieces to keep them in place. COMMUNICATION[*] J. This paper describes a way to improve the microstructure and mechanical properties of welding seams by in situ and conventional post-weld heat treatments for laser beam welding of the Ti-45Al-5Nb-0.2C-0.2B allo...

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“…Carbon was added to this alloy, in order to implement hardening by a fine dispersion of carbides; [47] this results in good structural stability and creep resistance (Figure 7). The metallographic examination shown in Figure 19 revealed features similar to those observed in the other Nb-bearing alloys (Figures 12 and 15), i.e., a disperse a 2 BL and the frequent occurrence of annealing twins in the c grains within the DRX regions.…”

Section: A Effects Of Alloy Compositionmentioning

confidence: 99%

Diffusion Bonding of γ(TiAl) Alloys: Influence of Composition, Microstructure, and Mechanical Properties

Herrmann

Appel

2009

Metall Mater Trans A

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The metallurgical factors governing the solid-state diffusion bonding of TiAl alloys have been characterized using scanning electron microscopy together with energy-dispersive X-ray (EDX) spectroscopy and electron backscattered diffraction (EBSD) analysis. The investigations were performed on TiAl alloys with various compositions and microstructures, which had been thoroughly mechanically characterized. The process zone of the bonds typically consists of a fine-grained layer of a 2 (Ti 3 Al) phase at the former contact plane, followed by relatively large, defect-free c(TiAl) grains and a region of deformed parent material. The evolution of the process zone involves phase transformation and recrystallization processes, which are triggered by asperity deformation at the contact plane and the unavoidable contamination of the diffusion couple with oxygen and nitrogen. The structural details depend on the alloy composition and the bonding conditions. In the final section of the article, technical aspects, including the tensile strength of diffusion bonds, will be discussed.

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Dislocation dynamics in carbon-doped titanium aluminide alloys

Cited by 79 publications

References 8 publications

Recent Progress in the Development of Gamma Titanium Aluminide Alloys

Recent Progress in the Development of Gamma Titanium Aluminide Alloys

Investigation of In Situ and Conventional Post‐Weld Heat Treatments on Dual‐Laser‐Beam‐Welded γ‐TiAl‐Based Alloy

Diffusion Bonding of γ(TiAl) Alloys: Influence of Composition, Microstructure, and Mechanical Properties

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