Orientation and temperature dependence of yield stress and slip geometry of Ti3Al and Ti3Al-V single crystals

Umakoshi, Yukichi; Nakano, Takayoshi; Takenaka, T.; Sumimoto, K.; Yamane, Toshimi

doi:10.1016/0956-7151(93)90162-l

Cited by 101 publications

(37 citation statements)

References 14 publications

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“…Due to the atomic structure of the γ lattice, the slip systems in the γ phase are subdivided into so-called ordinary and super slip systems. It has been shown in γ and α 2 single-crystal experiments that their different slip and twinning mechanisms exhibit different critical resolved shear stresses [31,32]. However, the lamellar microstructure with the high aspect ratio of the lamellae imposes strong restrictions on activation barriers of different slip systems, so that single-crystal results are only of limited validity in the lamellar compound.…”

Section: Plastic Anisotropymentioning

confidence: 99%

“…After this maximum, the strength decreases rapidly. This behaviour, schematically depicted in Figure 4, is observed in γ and α 2 single crystals as well as in polysynthetically twinned crystals [12,31,32] and is here approximated by a continuous function of temperature f an (θ ), following a sinusoidal powerlaw…”

Section: Yield Stress Anomalymentioning

confidence: 99%

“…The critical resolved shear stresses of the α 2 phase -as the minority phase -are modelled here according to the findings from singlecrystal experiments [32]. The critical resolved shear stresses of the dominant γ phase are extracted from experiments with polysynthetically twinned crystals [12,49] to incorporate Hall-Petch strenghtening.…”

Section: Gpamentioning

confidence: 99%

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Thermomechanical modelling of polysynthetically twinned TiAl crystals

Butzke

Bargmann

2015

Philosophical Magazine

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In the present paper, a thermomechanically coupled hyperelastic-plastic model is set up to predict the yield stress of polysynthetically twinned TiAl crystals as a function of temperature, load angle, α 2 content, lamellar thickness and domain size. The elastic deformation is modelled in terms of the Helmholtz free energy density, and the deformation in the plastic regime is mapped by crystal plasticity theory. The yield stress temperature anomaly of intermetallics is incorporated in the model via the critical resolved shear stresses. The numerical results show a very good agreement with experimental results for a wide range of microstructural parameters and temperatures.

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Section: Plastic Anisotropymentioning

confidence: 99%

Section: Yield Stress Anomalymentioning

confidence: 99%

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Thermomechanical modelling of polysynthetically twinned TiAl crystals

Butzke

Bargmann

2015

Philosophical Magazine

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“…The average linear intersection lengths of APDBs were measured from micrographs with more than two hundred intersections. There are three types of APDBs in D0 19 structure with different element displacement vectors of…”

Section: Methodsmentioning

confidence: 99%

“…The a 2 -Ti 3 Al phase significantly affects the mechanical properties of Ti -Al based alloys [12,13]. Ti 3 Al has the D0 19 -type ordered structure which is based on the HCP structure [14]. Mechanical properties of Ti 3 Al have been studied by many experiments using single crystals with various compositions focusing on the anisotropy [15 -21].…”

Section: Introductionmentioning

confidence: 99%

Growth kinetics of antiphase domain in Ti₃Al intermetallic compound

Koizumi

Katsumura

Minamino

et al. 2004

Science and Technology of Advanced Materials

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Growth kinetics of antiphase domain (APD) which increases the yield strength of Ti 3 Al by a factor of five, was investigated in Ti 3 Al compounds with compositions of 22.6, 24.6 and 34.7 at.%Al by quenching from disordered state and subsequent isothermal annealing at 973 -1173 K. The variation in APD size exhibited positive deviation from the conventional 'parabolic-growth-law' in the early stage in all the compounds, while negative deviations were observed in the late stage in all the compounds except the stoichiometric one (Ti-25 at.%Al). The variation in the APD size in the stoichiometric compound was numerically calculated by considering the variation in the long range order in the matrix ðSÞ and that in the mobility of the APDBs which was enhanced by non-equilibrium excess vacancies which were introduced by the quenching. The calculated variations in APD size could be successfully fitted to the experimental results in the early stage, and therefore, the positive deviation was attributed to the enhancement of the mobility of APDBs by the excess vacancies. In the late stage, the segregation of excess atoms (i.e. Ti atoms in Ti-rich composition and Al atoms in Al-rich composition) was detected in the compounds of off-stoichiometric composition by energy-dispersive X-ray spectroscopy, while any heterogeneity of composition was not observed in the stoichiometric compound. Faceted APDBs were observed in this stage. The mechanism of the negative deviation was attributed to the segregation and the facet which decrease the mobility and/or the driving force of the APDB migration. q

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