Polysynthetic twinned TiAl single crystals for high-temperature applications

Chen, Guang; Peng, Yujia; Zheng, Gong; Qi, Zhixiang; Wang, Minzhi; Yu, Haiyang; Dong, Chaofang; Liu, C. T.

doi:10.1038/nmat4677

Cited by 537 publications

(93 citation statements)

References 46 publications

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“…18,19 In order to further analyze the difference between the COR-I and the COR-II, the Bramifit planar disregistry equation is used 20 : = the interatomic spacing along ½uvw Al 2 O 3 , d ½uvw YAG = the interatomic spacing along ½uvw YAG . The lattice strain or disregistry at the interface is one of the main contributions (interfacial strain and ionic charge balance) to the interfacial energy.…”

Section: Discussionmentioning

confidence: 99%

“…The lattice strain or disregistry at the interface is one of the main contributions (interfacial strain and ionic charge balance) to the interfacial energy. 18,19 In order to further analyze the difference between the COR-I and the COR-II, the Bramifit planar disregistry equation is used 20 : = the interatomic spacing along ½uvw Al 2 O 3 , d ½uvw YAG = the interatomic spacing along ½uvw YAG . Figure 4A shows the crystallographic relationship model of the COR-I.…”

Section: Discussionmentioning

confidence: 99%

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Effect of interfacial energy on microstructure of a directionally solidified Al₂O₃/YAG eutectic ceramic

Zhong

Wang

et al. 2017

J Am Ceram Soc

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An Al2O3/Y3Al5O12 eutectic ceramic was prepared with a c‐axis sapphire seed by an optical floating zone furnace. The crystallographic relationships in the initial and the steady growth sections of the as‐grown eutectic ceramic were investigated by electron backscattering diffraction and transmission electron microscopy. The corresponding results were: <111 > {101}Y3Al5O12 || <0001 > {112¯0}Al2O3 and <110 > {21¯1}Y3Al5O12 || <11¯00 > {0001}Al2O3, respectively. The steady orientation of the latter one shows smaller planar disregistry. Interfacial strain played the decisive role in affecting the solidification behavior of the Al2O3/Y3Al5O12 eutectic ceramic. The stability of interfaces with minimum interfacial strain and better ionic charge balance in irregular microstructure prevail upon the constraint of the seed. These results might cast light for the interfacial design of the Al2O3/Y3Al5O12 binary eutectic ceramic.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Effect of interfacial energy on microstructure of a directionally solidified Al₂O₃/YAG eutectic ceramic

Zhong

Wang

et al. 2017

J Am Ceram Soc

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“…This finding is important for seeking a way to improve the ductility of TiAl. Because twinning would not deteriorate the high-temperature strength of TiAl [70], tailoring the chemical composition to promote deformation twinning might help to improve the ductility of TiAl while still maintaining excellent strength at elevated temperatures.…”

Section: Deformation Twinning and Its Influence On Mechanical Propertiesmentioning

confidence: 99%

Crystal plasticity analysis of deformation anisotropy of lamellar TiAl alloy: 3D microstructure-based modelling and in-situ micro-compression

Chen

Edwards

Gioacchino

et al. 2019

International Journal of Plasticity

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Detailed microstructure characterisation and in-situ micropillar compression were coupled with crystal plasticity-based finite element modelling (CP-FEM) to study the micromechanisms of plastic anisotropy in lamellar TiAl alloys. The consideration of microstructure in both simulation and in-situ experiments enables in-depth understanding of micromechanisms responsible for the highly anisotropic deformation response of TiAl on the intralamella and inter-lamella scales. This study focuses on two specific configurations of / 2 lamellar microstructure with the / 2 interfaces being aligned 25 and 55 to the loading direction. Microstructure-based CP-FEM shows that longituginal slip of super and ordinary dislocations are most responsible for the plastic anisotropy in the 25 micropillar while the anisotropy of the 55 micropillar is due to longitudinal superdislocations and longitudinal twins. In addition, transversal superdislocations were more active, making the deformation in the 25 micropillar less localised than that in the 55 micropillar. Moreover, the CP-FEM 2 / 42 model successfully predicted substantial build-up of internal stresses at / 2 interfaces, which is believed to be detrimental to the ductility in TiAl. However, as evidenced by the model, the detrimental internal stresses can be significantly relieved by the activation of transverse deformation twinning, suggesting that the ductility of TiAl can be improved by promoting transverse twins. IntroductionTitanium aluminide (TiAl) alloys have a density approximately half that of nickel-based superalloys [1] and specific strength that is comparable with nickel-based alloys up to temperatures as high as 700 o C [2], resulting in a potentially wide application of the alloys in aero-engines [3,4]. However, the application of TiAl alloys is limited by their low ductility, which is mainly due to the anisotropy of constituent microstructure in TiAl, and insufficient understanding of the microstructure-property relationships. In-depth understanding of the relationships would lead to wider applications of these lightweight alloys in aerospace, leading to the weight reduction, thereby, increase in the fuel efficiency and decrease in the CO2 emissions. Although there have been significant efforts in understanding the relationships between chemical composition, microstructure and mechanical properties of TiAl alloys, in particular regarding the TiAl lamellar microstructure [1, 5-7], there have been no detailed studies in which both in-situ mechanical testing and microstructure-based modelling are carried out to provide more insights into the direct relationships between constituent microstructures and mechanical properties. This present study aims to integrate modelling and in-situ tests to seek possible solutions to the low ductility of TiAl. The poor ductility of lamellar TiAl alloys is partly due to its strong plastic anisotropy because of the respective anisotropy of constituent phases. Lamellar TiAl alloys consist of two phases: -face centred tetragonal (f.c.t.) and ...

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“…Other elements, such as Nb, Ta, and W improve strength of TiAl alloys through solid solution strengthening at elevated temperatures . The elements like Nb, W, Ta, and Hf influence kinetics of phase transformation and improve the oxidation and creep resistance …”

Section: Introductionmentioning

confidence: 99%

Boride Formation, Microstructure Evolution, and Mechanical Properties of Ti42Al6Nb2.6C0.8Ta Alloyed by Boron

et al. 2018

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In order to improve mechanical properties by grain boundary and precipitation strengthening, Ti42Al6Nb2.6C0.8Ta-xB (at%) alloys with x ¼ ranging from 0 to 2.0 at% are prepared by vacuum arc melting. Microstructure evolution especially boride formation and mechanical properties of these alloys are studied. The results show that volume fraction of TiB particles increases and volume fraction of B2 phase decreases with increasing content of B. Three morphologically different types of boride particles are identified in the studied alloys: granular (C), plate (P), and flake (F). Volume fraction of F type borides increases remarkably with increasing content of B. Lamellar colony size decreases with increasing content of B up to 0.8 at%. Lamellar colony size increases with increasing content of B above from 0.8 to 2.0 at%. Compressive strength increases from 1710 to 2084 MPa and compressive strain increases from 10.6 to 19.0% with increasing content of B. Ultimate tensile strength increases from 426 to 613 MPa and tensile strain increases from 3.4 to 4.6% at 750 C with increasing content of B. Precipitation strengthening by TiB, decreasing of volume fraction of B2 and increasing volume fraction of γ phase are mainly responsible for improvement in mechanical properties.

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Polysynthetic twinned TiAl single crystals for high-temperature applications

Cited by 537 publications

References 46 publications

Effect of interfacial energy on microstructure of a directionally solidified Al₂O₃/YAG eutectic ceramic

Effect of interfacial energy on microstructure of a directionally solidified Al₂O₃/YAG eutectic ceramic

Crystal plasticity analysis of deformation anisotropy of lamellar TiAl alloy: 3D microstructure-based modelling and in-situ micro-compression

Boride Formation, Microstructure Evolution, and Mechanical Properties of Ti42Al6Nb2.6C0.8Ta Alloyed by Boron

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Polysynthetic twinned TiAl single crystals for high-temperature applications

Cited by 537 publications

References 46 publications

Effect of interfacial energy on microstructure of a directionally solidified Al2O3/YAG eutectic ceramic

Effect of interfacial energy on microstructure of a directionally solidified Al2O3/YAG eutectic ceramic

Crystal plasticity analysis of deformation anisotropy of lamellar TiAl alloy: 3D microstructure-based modelling and in-situ micro-compression

Boride Formation, Microstructure Evolution, and Mechanical Properties of Ti42Al6Nb2.6C0.8Ta Alloyed by Boron

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Effect of interfacial energy on microstructure of a directionally solidified Al₂O₃/YAG eutectic ceramic

Effect of interfacial energy on microstructure of a directionally solidified Al₂O₃/YAG eutectic ceramic