Fracture toughness of the bimodal size lamellar O phase microstructures in Ti-22Al-25Nb (at.%) orthorhombic alloy

Zheng, Youping; Zeng, Weidong; Li, Dong; Zhao, Qinyang; Liang, Xidong; Zhang, Jianwei; Ma, Xiong

doi:10.1016/j.jallcom.2017.03.184

Cited by 66 publications

(19 citation statements)

References 34 publications

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“…The X‐ray diffraction profiles in ref. prove that there is no detectable α 2 phase in such a bimodal size lamellar O phase microstructure. The precipitates are all O phases.…”

Section: Methodsmentioning

confidence: 90%

“…Ti–22Al–25Nb (at%) alloy was used in present study. The starting microstructure is the so called bimodal size lamellar O phase microstructure, of which the phase composition and the phase morphology have been introduced with details in our previous papers . The microstructures were obtained by deforming at B2 phase region and heat treating at B2 + O phase region.…”

Section: Methodsmentioning

confidence: 99%

“…A typical Ti 2 AlNb‐based alloy microstructure contains hcp phase α 2 , bcc phases B2 and orthorhombic phase Ti 2 AlNb (O phase) . It was reported that a so‐called bimodal size lamellar O phase microstructure that contains just lamellar O precipitates and B2 matrix got outstanding combination of high strength, good ductility, and excellent fracture toughness overcoming the intrinsic brittleness of an intermetallic material . However, high cycle fatigue (HCF) properties can never be ignored for hopeful aerospace application materials.…”

Section: Introductionmentioning

confidence: 99%

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High Cycle Fatigue Behaviors at High Temperatures of a Ti₂AlNb‐Based Alloy

et al. 2018

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High cycle fatigue (HCF) behaviors of the bimodal size lamellar O phase microstructures of Ti-22Al-25Nb alloy are studied at the potential service temperatures. The axially-tensile-compressing HCF strength limits of this alloy are measured to be 470 MPa at 650 C and 400 MPa at 700 C via the small sampling up-and-down method (SSUDM). The ratio of the maximum stress and the minimum stress (R ¼ σ max /σ min ) is À1 while the run out fatigue life is 10 7 cycles. It is found that transformation B2 ! β þ O occurs in the mode of cellular precipitations at initial B2 grain boundaries during the HCF tests. The transformation results in inhomogeneous regions in the microstructure. In those transformed regions, the acicular O phases are clearly coarser than in the normal regions. The HCF micro cracks preferentially initiate in the inhomogeneous regions along the slip lines in β phase or at the O/β boundaries perpendicular to the slip lines. The cleavage fracture characteristic of the bimodal size lamellar O phase microstructure of this Ti 2 AlNb-based alloy has significant effect on the HCF crack propagation. Flat fracture surface will form on cleavage planes in B2 grains. Moreover, different directions of cleavage planes in different B2 grains will deflect the straight HCF crack at B2 grain boundaries. It is the B2 matrix rather than the lamellar O phase in the bimodal size lamellar O phase microstructure that provides the crack-tip shielding effect. B2 grain boundaries are also beneficial to increase the inhibition of HCF crack propagation.

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“…The X‐ray diffraction profiles in ref. prove that there is no detectable α 2 phase in such a bimodal size lamellar O phase microstructure. The precipitates are all O phases.…”

Section: Methodsmentioning

confidence: 90%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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High Cycle Fatigue Behaviors at High Temperatures of a Ti₂AlNb‐Based Alloy

et al. 2018

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“…Among titanium aluminides, the orthorhombic Ti 2 AlNb-based alloys have higher ductility, higher yield strength, and better elevated temperature strength and fracture toughness [1][2][3]. Hence, considerable interest has been given to the Ti 2 AlNb-based alloys for various applications in aerospace components [4,5].…”

Section: Introductionmentioning

confidence: 99%

“…Over past decades, research in Ti 2 AlNb-based alloys was mainly focused on how to improve the mechanical properties of the alloys through alloying, thermo-mechanical processing and heat treatment etc. [1][2][3][4][5][6][7]. At present, many aviation components which were made by Ti 2 AlNb-based alloys are fitted in a trial run engine [8].…”

Section: Introductionmentioning

confidence: 99%

High-Temperature Tribological Behavior of the Ti-22Al-25Nb (at. %) Orthorhombic Alloy with Lamellar O Microstructures

Wang

Zhou

Wang

et al. 2018

Metals

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Tribological behavior of the isothermally forged and heat-treated Ti-22Al-25Nb (at. %) orthorhombic alloy with lamellar O microstructures was investigated. The friction experiments using a tribometer (UMT-3 CETR) against Si 3 N 4 and Al 2 O 3 were conducted at the load of 10N from 20 to 750 • C and a constant speed of 0.188 m/s. The experiment results indicated that for the friction pair of Al 2 O 3 , the coefficient of friction (COF) was decreased from 0.906-0.359, and for the friction pair of Si 3 N 4 , COF was decreased from 0.784-0.457 as the friction temperature increased from room temperature to 750 • C. The wear rate of the alloy against Al 2 O 3 is in the range of 2.63-8.15 × 10 −4 mm 3 N −1 m −1 , the wear rate against Si 3 N 4 is in the range of 2.44-5.83 × 10 −4 mm 3 N −1 m −1 , respectively. The wear mechanisms of the alloy were changed from plastic deformation and ploughing at lower temperature (20-400 • C) to adhesive wear and oxidative mechanism at higher temperature (600 and 750 • C). The friction and wear behavior of the Al 2 O 3 friction pair was comparable to that of the Si 3 N 4 friction pair.

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Microstructure and Mechanical Properties of Ti₂AlNb‐Based Alloys Synthesized by Spark Plasma Sintering from Pre‐Alloyed and Ball‐Milled Powder

Cai

Liu

et al. 2017

Adv Eng Mater

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Ti 2 AlNb-based alloys are synthesized by spark plasma sintering from prealloyed and ball-milled Ti-22Al-25Nb powder, and the structure of the alloys is regulated by aging at 800 C for 0.5, 1, 2, and 3 h. Comparison of phase composition, microstructure, and mechanical properties are made in this study. Aging in the B2 þ O phase region refers to the reversible transformation of B2 $ O. Complete B2 þ O Widmanstätten structure is obtained in the aged alloys synthesized from pre-alloyed powder, and the ones from milled powder contain acicular O and B2 þ O Widmanstätten structure. Ball milling eliminates the B2 þ O colonies, facilitates the continuous transformation of O ! B2, and induces acicular O in the alloys; however, the hardness of these alloys is decreased in contrast with that of the ones synthesized from prealloyed powder. Owing to the precipitation strengthening based on a large amount of fine O-phase precipitates, the 3 h aged alloy from pre-alloyed powder exhibits comprehensive mechanical properties with Vickers hardness of 448 AE 9 HV, ultimate tensile strength of 730 MPa, and elongation of 0.43%.

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Fracture toughness of the bimodal size lamellar O phase microstructures in Ti-22Al-25Nb (at.%) orthorhombic alloy

Cited by 66 publications

References 34 publications

High Cycle Fatigue Behaviors at High Temperatures of a Ti₂AlNb‐Based Alloy

High Cycle Fatigue Behaviors at High Temperatures of a Ti₂AlNb‐Based Alloy

High-Temperature Tribological Behavior of the Ti-22Al-25Nb (at. %) Orthorhombic Alloy with Lamellar O Microstructures

Microstructure and Mechanical Properties of Ti₂AlNb‐Based Alloys Synthesized by Spark Plasma Sintering from Pre‐Alloyed and Ball‐Milled Powder

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Fracture toughness of the bimodal size lamellar O phase microstructures in Ti-22Al-25Nb (at.%) orthorhombic alloy

Cited by 66 publications

References 34 publications

High Cycle Fatigue Behaviors at High Temperatures of a Ti2AlNb‐Based Alloy

High Cycle Fatigue Behaviors at High Temperatures of a Ti2AlNb‐Based Alloy

High-Temperature Tribological Behavior of the Ti-22Al-25Nb (at. %) Orthorhombic Alloy with Lamellar O Microstructures

Microstructure and Mechanical Properties of Ti2AlNb‐Based Alloys Synthesized by Spark Plasma Sintering from Pre‐Alloyed and Ball‐Milled Powder

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Product

Resources

About

High Cycle Fatigue Behaviors at High Temperatures of a Ti₂AlNb‐Based Alloy

High Cycle Fatigue Behaviors at High Temperatures of a Ti₂AlNb‐Based Alloy

Microstructure and Mechanical Properties of Ti₂AlNb‐Based Alloys Synthesized by Spark Plasma Sintering from Pre‐Alloyed and Ball‐Milled Powder