A TEM study of the crystallography and interphase boundary structure of α precipitates in a Zr-2.5 wt% Nb alloy

Zhang, W.-Z.; Purdy, G.R.

doi:10.1016/0956-7151(93)90084-6

Cited by 66 publications

(31 citation statements)

References 9 publications

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“…As can be seen from (8) in the  2 lattice. As it is well known that the true habit plane parallels (0001) 2 // (111)  in lamellar titanium aluminide alloys [23], the improved foil thickness method exhibits satisfactory accuracy because the deviation of the determined habit plane from the true one is less than 0.5.…”

Section: 1mentioning

confidence: 59%

“…The habit plane in some systems, in particular between metal matrix and metal oxide, carbide or nitride [2][3][4][5] parallels a lowindices crystallographic plane in one or both lattices adjoining the interface whereas the habit plane in other systems cannot be simply expressed by any low-indices planes in either lattice and hence it is usually termed irrational habit plane. The irrational habit planes are commonly observed in a precipitation system, such as {5 3 3} Cu habit plane between Cr-rich precipitates and Cu matrix [6], {11, 11, 13}  habit plane between proeutectoid  phase and  matrix in a Ti-Cr alloy [7], {3.0, 2.2, 3.4}  habit plane between proeutectoid  phase and  phase in a Zr-Nb alloy [8], and {1 1 4}  habit plane between proeutectoid cementite and austenite in a hypereutectoid steel [9]. The irrational habit planes are also reproducibly observed in many martensitic transformations, including the wellknown {2 2 5}  , {2 5 9}  and {5 5 7}  habit plane in ferrous alloys [10,11] and {3 3 4}  habit plane in Ti alloys [12].…”

Section: Accepted Manuscriptmentioning

confidence: 99%

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A simple and inclusive method to determine the habit plane in transmission electron microscope based on accurate measurement of foil thickness

Qiu

Zhang

2014

Materials Characterization

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A simple and inclusive method is proposed for accurate determination of the habit plane between bicrystals in Transmission Electron Microscope. Whilst this method can be regarded as a variant of surface trace analysis, the major innovation lies in the improved accuracy and efficiency of foil thickness measurement, which involves a simple tilt of the thin foil about a permanent tilting axis of the specimen holder, rather than cumbersome tilt about the surface trace of the habit plane.Experimental study has been done to validate this proposed method in determining the habit plane between lamellar  2 plates and  matrix in a Ti-Al-Nb alloy. Both high accuracy (1) and high precision (1) have been achieved by using the new method. The source of the experimental errors as well as the applicability of this method is discussed. Some tips to minimise the experimental errors are also suggested.

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Section: 1mentioning

confidence: 59%

Section: Accepted Manuscriptmentioning

confidence: 99%

A simple and inclusive method to determine the habit plane in transmission electron microscope based on accurate measurement of foil thickness

Qiu

Zhang

2014

Materials Characterization

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“…The Zr-2.5Nb alloy has a bcc b Zr crystal structure above 850°C but on cooling below this temperature the hcp a-Zr phase is formed. The b-to a-Zr transformation follows a near Burgers vector orientation relationship, viz., ð0 0 0 1Þ aÀZr % jjð1 1 0Þ bÀZr and ½1 1 2 0 aÀZr ffi ½1 1 1 bÀZr [49]. The misfit at the a/b interface is accommodated by a single set, or a combination of two or three different sets, of dislocations.…”

Section: Microstructure Of Zr-25nb Alloysmentioning

confidence: 99%

Hydride Phases, Orientation Relationships, Habit Planes, and Morphologies

Püls¹

2012

The Effect of Hydrogen and Hydrides on the Integrity of Zirconium Alloy Components

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Most of the studies on this topic were carried out from the early 1960s to the mid 1980s. As is described in Chap. 2, hydrides can form as one of three phases, each of which has a different crystal structure and composition. A broad consensus had emerged by the 1980s that the fct c-hydride (c/a [ 1) is a metastable phase while the stable hydride phases are the face-centered-cubic (fcc) d-hydride and the face-centered-tetragonal (fct) e-hydride (c/a \ 1) phases, the stoichiometric compositions of these phases being, respectively, ZrH, ZrH 1.5 , and ZrH 2 . However, recent experimental results have reinvigorated an earlier suggestion that the c-hydride phase could be the stable phase below a peritectoid transformation temperature of *286°C. This issue concerning which phase is the stable one when the solvus concentration is exceeded below the a/b Zr eutectoid temperature of *550°C is not specifically addressed in this book. However, the issue has not been entirely ignored as various aspects of its role in fracture and phase relationships are raised in various places throughout this book, specifically in Chaps. 2, 6, 7, 8 and 9. Regarding the hydride habit planes, a consensus had emerged by the mid 1980s that the predominant habit of d-and c-zirconium hydrides in Zircaloy-2 and Zr-2.5Nb is on the near-basal, hexagonal-close-packed (hcp) a-Zr {1 0 1 7} planes (14°from the basal plane [6], carried out detailed examinations using transmission electron microscopy of the morphology, orientation, dislocations generated, and strain fields in and around hydride precipitates formed in high purity Zr, Zircaloy-2, Zr-1 % Al, and Zr-1 % Cr. All the hydrides observed by Carpenter et al. [12] in these low-H-containing materials were of the c-hydride phase. Figure 3.1 shows dislocations that had been generated by two needle-shaped hydrides nucleated in close proximity of an intermetallic particle. The dislocations around the hydrides were in the form of loop segments attached to the ends of the needles with Burgers vectors of type \1120 [ lying on or near the basal plane. Figure 3.2 shows schematically in a projection on the (0 0 0 1) plane the hydride orientations, dislocation loops, and their Burgers vectors observed. Large strain fields were associated with these small hydrides as seen in Fig. 3.3 which also shows how this strain field made it difficult to reveal the dislocations generated closest to the hydride's interface. Similar strong strain contrast was observed along the basal pole (c) axis direction, but none along the needle direction. Similar results for hydride shapes and dislocations emitted were obtained for the Zr-1 % Cr and Zr-1 % Al materials except that the orientations of the c-hydrides in the latter material were in the \1 0 1 0 [ aÀZr directions. Less regular features for the dislocations generated by hydrides in Zr were found as shown in Figs. 3.4 and 3.5 examined in electron microscopes at 100 kV and 1 MeV, respectively. Nevertheless, these dislocations had similar Burgers vectors as those found attache...

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“…One widely used analytical approach applies to semicoherent interfaces and describes interface structures in terms of intrinsic dislocations using the closely related Frank-Bilby [4,24,52] and O-lattice [6,52,57] techniques. Both procedures require the selection of a reference state, within which the Burgers * Email address: aurelien.vattre@cea.fr vectors of individual interface dislocations are defined.…”

Section: Introductionmentioning

confidence: 99%

Determining the Burgers vectors and elastic strain energies of interface dislocation arrays using anisotropic elasticity theory

Vattré

Demkowicz

2013

Acta Materialia

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A general dislocation-based formalism linking the Frank-Bilby equation and heterogeneous anisotropic elasticity theory under the fundamental condition of vanishing far-field stresses is developed. The present approach gives rise to the determination of the non-arbitrary reference state, within which the Burgers vectors of individual interface dislocations are defined. A solution strategy is also formulated to predict the correct reference state in accordance with the geometric structures of interfaces and the (unequal) partitioning of elastic fields between neighboring crystals. From this dual description of interfaces, the elastic strain energies of dislocation arrays are computed using solutions of short-range fields. Examples of several simple interfaces, namely symmetric tilt and twist grain boundaries as well as pure misfit heterophase interfaces are presented.

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A TEM study of the crystallography and interphase boundary structure of α precipitates in a Zr-2.5 wt% Nb alloy

Cited by 66 publications

References 9 publications

A simple and inclusive method to determine the habit plane in transmission electron microscope based on accurate measurement of foil thickness

A simple and inclusive method to determine the habit plane in transmission electron microscope based on accurate measurement of foil thickness

Hydride Phases, Orientation Relationships, Habit Planes, and Morphologies

Determining the Burgers vectors and elastic strain energies of interface dislocation arrays using anisotropic elasticity theory

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