Deformation behavior of HCP Ti-Al alloy single crystals

Williams, James C.; Baggerly, Roy G.; Paton, N. E.

doi:10.1007/s11661-002-0153-y

Cited by 402 publications

(139 citation statements)

References 7 publications

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“…The lattice orientations of the grains in the indented zones were not measured in this work. Although the grain orientation is expected to play an important role in the indentation properties of hcp metals [45][46][47][48][49], these dependencies are most clearly seen in indentations performed with smaller indenter tips where the indented zones are fully embedded in a single grain. In fact, most of the prior work on the use of spherical indentation stress-strain curves was focused on single-phase coarse-grained polycrystalline samples [10,37].Only recently, these protocols have begun to be applied to multiphase polycrystalline samples [7].…”

Section: Structure-property Correlationsmentioning

confidence: 99%

High Throughput Assays for Additively Manufactured Ti-Ni Alloys Based on Compositional Gradients and Spherical Indentation

Gong

Mohan

Mendoza

et al. 2017

Integr Mater Manuf Innov

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Recent advances in additive manufacturing (AM) reveal an exciting opportunity to build materials with novel internal structures combined with intricate part geometries that cannot be achieved by traditional manufacturing approaches. The large space of potential material chemistries combined with non-equilibrium microstructures obtained in AM presents a significant challenge for a systematic exploration and optimization of the final properties exhibited by AM parts when using the existing knowledge databases established for conventionally processed materials. In this paper, we demonstrate novel high throughput assays that can be used to prototype a large library of material chemistries (and possibly different process histories) in small quantities, and subsequently apply spherical indentation stress-strain protocols to screen them for their mechanical performance. The potential of these new assays is demonstrated on a class of Ti-Ni alloys, whose Ni composition ranges between 0 and 11%wt.

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Section: Structure-property Correlationsmentioning

confidence: 99%

High Throughput Assays for Additively Manufactured Ti-Ni Alloys Based on Compositional Gradients and Spherical Indentation

Gong

Mohan

Mendoza

et al. 2017

Integr Mater Manuf Innov

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“…The hc + ai dislocations are thus essential to achieving generalized plastic flow and, consequently, high ductility. Moreover, experiments demonstrate that the activation of hc + ai cross-slip has strong effects on plastic flow evolution and strengthening of hcp metals (7)(8)(9)(10). Frequent cross-slip of hc + ai dislocations can occur in early stage, room temperature deformation (10)(11)(12)(13)(14)(15).…”

mentioning

confidence: 99%

Mechanism and energetics of 〈c + a〉 dislocation cross-slip in hcp metals

Curtin

2016

Proc. Natl. Acad. Sci. U.S.A.

105

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Hexagonal close-packed (hcp) metals such as Mg, Ti, and Zr are lightweight and/or durable metals with critical structural applications in the automotive (Mg), aerospace (Ti), and nuclear (Zr) industries. The hcp structure, however, brings significant complications in the mechanisms of plastic deformation, strengthening, and ductility, and these complications pose significant challenges in advancing the science and engineering of these metals. In hcp metals, generalized plasticity requires the activation of slip on pyramidal planes, but the structure, motion, and cross-slip of the associated 〈c + a〉 dislocations are not well established even though they determine ductility and influence strengthening. Here, atomistic simulations in Mg reveal the unusual mechanism of 〈c + a〉 dislocation cross-slip between pyramidal I and II planes, which occurs by cross-slip of the individual partial dislocations. The energy barrier is controlled by a fundamental step/ jog energy and the near-core energy difference between pyramidal 〈c + a〉 dislocations. The near-core energy difference can be changed by nonglide stresses, leading to tension-compression asymmetry and even a switch in absolute stability from one glide plane to the other, both features observed experimentally in Mg, Ti, and their alloys. The unique cross-slip mechanism is governed by common features of the generalized stacking fault energy surfaces of hcp pyramidal planes and is thus expected to be generic to all hcp metals. An analytical model is developed to predict the cross-slip barrier as a function of the near-core energy difference and applied stresses and quantifies the controlling features of cross-slip and pyramidal I/II stability across the family of hcp metals.P lastic deformation of crystalline materials occurs mainly by slip along low-index atomic planes. Slip regions are bounded by line defects called dislocations (1), which are characterized by the crystallographic slip increment known as the Burgers vector b and the local line direction ξ. The transition from slipped to unslipped regions is resolved at the atomic scale by local atomic rearrangements creating a dislocation "core" structure. Slip occurs by motion of this core, and the surrounding elastic fields, driven by an applied stress. Plasticity is thus controlled by the details of the core region, which differ significantly among face-centered cubic (fcc), bodycentered cubic (bcc), and hexagonal close-packed (hcp) metals (2). The motion of the dislocation core is usually confined to glide within the slip plane defined by the normal vector n = b × ξ. Screw dislocations have b × ξ = 0, however, and so do not have a unique slip plane and can therefore "cross-slip" among glide planes that share a common Burgers vector. Cross-slip is a crucial process in plasticity, acting to spread slip spatially on multiple nonparallel planes and to enable dislocation multiplication and annihilation processes; all of these processes affect ductility and ultimate strength of the material. Whereas the atomistic mecha...

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“…For example, when compared with loading in TT, loading in RD1 or RD2 results in less grains being well aligned for hai type slip. Experiments on Ti-Al single crystals by Williams et al [6] have shown that the ratio of slip system strength between hc þ ai type slip and hai type slip is of the order of 3-4 at room temperature, although more recent results set the value at 1-1.5 [28]. Therefore, when loading along a given material direction, increasing the number of grains with their c-axis orientated in the direction of loading will result in a higher macroscopic yield strength, as observed here.…”

Section: Resultsmentioning

confidence: 99%

“…In the hcp a phase of titanium, the easy glide of dislocations occurs in the h11 20i directions along the {10 10}, (0001) and {10 11} planes [6]. These are also known as the prismatic, basal and pyramidal planes, respectively.…”

Section: Introductionmentioning

confidence: 99%

Characterising the Effects of Strain Rate, Crystallographic Texture and Direction of Loading on the Mechanical Behaviour of Ti-6Al-4V

Wielewski

Arthington

Siviour

et al. 2015

J. dynamic behavior mater.

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A cross-rolled plate of the industrially important titanium alloy, Ti-6Al-4V, has been microstructurally and mechanically characterised using a range of different experimental techniques. The microstructure of the material has been studied using backscatter electron (BSE) microscopy and electron backscatter diffraction (EBSD), with the crystallographic orientation data from the EBSD used to reconstruct the orientation distribution function of the dominant a phase. The mechanical behaviour of the material has been investigated at quasi-static and high strain rates in the three orthogonal material orientations in both tension and compression. A novel in situ optical measurement technique has been used to measure the geometry of the specimens during both quasi-static and high strain rate mechanical testing, improving the accuracy of the mechanical testing results and providing unprecedented information about the evolving geometries of the specimens. The macroscopic stress-strain response and the evolution of specimen cross-sectional profiles have been qualitatively linked to the macroscopic crystallographic texture in the plate.

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Deformation behavior of HCP Ti-Al alloy single crystals

Cited by 402 publications

References 7 publications

High Throughput Assays for Additively Manufactured Ti-Ni Alloys Based on Compositional Gradients and Spherical Indentation

High Throughput Assays for Additively Manufactured Ti-Ni Alloys Based on Compositional Gradients and Spherical Indentation

Mechanism and energetics of 〈c + a〉 dislocation cross-slip in hcp metals

Characterising the Effects of Strain Rate, Crystallographic Texture and Direction of Loading on the Mechanical Behaviour of Ti-6Al-4V

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