The Experts below are selected from a list of 237 Experts worldwide ranked by ideXlab platform
Wen-zheng Zhang - One of the best experts on this subject based on the ideXlab platform.
-
Interpretation of the Habit Plane of δ Precipitates in Superalloy Inconel 718
Acta Metallurgica Sinica (English Letters), 2017Co-Authors: Xiao-peng Yang, Wen-zheng ZhangAbstract:A calculation method based on a combination of ∆ g parallelism rule, good matching site (GMS) analysis, CSL/DSCL (coincidence site lattice/displacement shift complete lattice) and the O-lattice theory has been applied to interpret the observation of the Habit Plane (HP) of the δ precipitates and the linear defects in the HP in an Inconel 718 superalloy. The small scattering in the HP orientation around an ideal rational Plane is interpreted by the existence of a mixture of two types of steps with different heights and inclinations. These steps play a significant role to enhance the degree of matching in the HP. They are associated with secondary dislocations, with Burgers vectors of \(1/6\left[ {1\;1\;\bar{2}} \right]_{\gamma } / 1/3[0\;0\;1]_{\delta }\), and with a direction parallel to a near-invariant line along \([1\;\bar{1}\;0]_{\gamma }\). The spacing of the secondary dislocations projected on the terrace Plane is around 6.3 nm. The calculated dislocation structure is in good agreement with the observation.
-
A new orientation relationship between cementite and austenite and coexistence of pseudo-primary and secondary dislocations in the Habit Plane
Philosophical Magazine, 2017Co-Authors: Wen-zheng ZhangAbstract:A new orientation relationship (OR) is found between Widmanstatten cementite precipitates and the austenite matrix in a 1.3C-14Mn steel. The associated Habit Plane (HP) and the dislocations in the ...
-
Precipitation crystallography of plate-shaped Al6(Mn,Fe) dispersoids in AA5182 alloy
Acta Materialia, 2012Co-Authors: Wen-zheng Zhang, Knut MarthinsenAbstract:Abstract The Habit Plane, orientation relationship (OR) and interfacial structure between the plate-shaped Al 6 (Mn,Fe) dispersoids and Al matrix in an AA 5182 alloy have been systematically studied by transmission electron microscopy, selected-area electron diffraction and crystallographic simulation. The published OR data about the dispersoids precipitated in different Al alloys has been critically assessed. A precise OR has been determined as (0 0 1) p //(3 −1 5) m and [−1 1 0] p //[2 1 −1] m , while the Habit Planes are determined as (0 0 1) p and (3 −1 5) m . The OR and Habit Plane have been discussed in terms of the Δ g approach. The dislocation arrangements at the interphase boundary of the Habit Planes are calculated by using O-lattice theory, which has been used to explain the mechanism of the OR selection and morphology development of dispersoids. It is revealed that an atom-to-atom matching exists in the good matching regions between the dislocations in the Habit Plane.
-
Dislocation description of martensite interfaces based on misfit analysis
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006Co-Authors: Wen-zheng ZhangAbstract:Abstract It is shown how the methodology and theoretical relationships developed in the framework of the O-lattice theory can be applied for study of martensite interfaces containing a single set of dislocations. The observed orientation relationship, the Habit Plane orientation, matching or mismatching of certain sets of Planes in the Habit Plane of lath martensite in an Fe–Ni–Mn alloy can be explained consistently by the present approach. Attention is drawn to the use of measurable Δ g vectors for characterizing the Habit Plane and for interpreting Plane matching in the Habit Plane.
-
dislocation structure of non Habit Plane of α precipitates in a ti 7 26 wt cr alloy
Acta Materialia, 2006Co-Authors: Wen-zheng ZhangAbstract:Abstract The dislocation structures of edge facet and end face of proeutectoid α precipitates in a β matrix in a Ti–7.26 wt.% Cr alloy were studied using transmission electron microscopy. Two sets of dislocations, which are parallel to the dislocations on the Habit Plane of the α plate, were observed on the edge facet. The spacing of one set of coarse-spaced dislocations is about 9.4 nm. Their Burgers vector is [1 0 0] β ([2 −1 −1 0] α /3) determined by g · b contrast analyses. The spacing of the other set of fine-spaced dislocations is about 1.8 nm. Their Burgers vector possibly is [1 1 1] β /2([1 1 −2 0] α /3). A dislocation network on the end face is formed by the dislocations on the Habit Plane and edge facet looping around the α plate. Another set of dislocations was observed on the end face at intersections between the dislocations on the Habit Plane and the coarse-spaced dislocations on the edge facet. Their Burgers vector possibly is [1 1 −1] β /2([2 −1 −1 −3] α /6). Based on the observations, a three-dimensional model of the dislocation structure of the α plate was constructed.
Dong Qiu - One of the best experts on this subject based on the ideXlab platform.
-
a simple and inclusive method to determine the Habit Plane in transmission electron microscope based on accurate measurement of foil thickness
Materials Characterization, 2014Co-Authors: Dong Qiu, Mingxing ZhangAbstract:Abstract 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 α2 plates and γ 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.
-
a tem study of the Habit Plane structure of intragrainular proeutectoid α precipitates in a ti 7 26 wt cr alloy
Acta Materialia, 2004Co-Authors: W Z Zhang, Dong QiuAbstract:The crystallography and the structure of the Habit Plane of proeutectoid alpha precipitates in beta matrix in a Ti-7.26 wt%Cl were studied using TEM. The orientation relationship was found to deviate slightly from the ideal Burgers orientation relationship. The Habit Plane of precipitates was found to be normal to a particular set of Deltag's. A set of dislocations, about 11 nm apart, were observed on the Habit Plane of the precipitates. The Burgers vector of the dislocations, as determined by g (.) b contrast analyses, is [1 -11](beta)/2([2-1-13](alpha)/6). This Burgers vector is different from those determined by previous investigations. The observations are discussed in terms of an analytical O-line model and tend to Support the prediction of the O-line model. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
-
A TEM study of the Habit Plane structure of intragrainular proeutectoid α precipitates in a Ti–7.26 wt%Cr alloy
Acta Materialia, 2004Co-Authors: Wen-zheng Zhang, Dong QiuAbstract:The crystallography and the structure of the Habit Plane of proeutectoid alpha precipitates in beta matrix in a Ti-7.26 wt%Cl were studied using TEM. The orientation relationship was found to deviate slightly from the ideal Burgers orientation relationship. The Habit Plane of precipitates was found to be normal to a particular set of Deltag's. A set of dislocations, about 11 nm apart, were observed on the Habit Plane of the precipitates. The Burgers vector of the dislocations, as determined by g (.) b contrast analyses, is [1 -11](beta)/2([2-1-13](alpha)/6). This Burgers vector is different from those determined by previous investigations. The observations are discussed in terms of an analytical O-line model and tend to Support the prediction of the O-line model. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
W Z Zhang - One of the best experts on this subject based on the ideXlab platform.
-
interpretation of the orientation relationship and Habit Plane orientation of the equilibrium β phase in an mg y nd alloy
Scripta Materialia, 2008Co-Authors: Min Zhang, W Z ZhangAbstract:The Habit Plane of the equilibrium β(Mg14Nd2Y) phase in Mg–Y–Nd alloys was found to deviate from (1 −1 2)β/(1 0 −1 0)α by about 3°. The present work analyzed the interface structure and orientation relationship (OR) by CSL/DSC model and Δg parallelism rule. For a better matching degree in the Habit Plane, the stepped interface containing a quasi-invariant line with a terrace of (1 −1 2)β/(1 0 −1 0)α is preferred, which requires a small rotation of 0.24° from Burgers OR. The simulation results are consistent with experimental observations.
-
Interpretation of the orientation relationship and Habit Plane orientation of the equilibrium β-phase in an Mg–Y–Nd alloy
Scripta Materialia, 2008Co-Authors: Min Zhang, W Z ZhangAbstract:The Habit Plane of the equilibrium β(Mg14Nd2Y) phase in Mg–Y–Nd alloys was found to deviate from (1 −1 2)β/(1 0 −1 0)α by about 3°. The present work analyzed the interface structure and orientation relationship (OR) by CSL/DSC model and Δg parallelism rule. For a better matching degree in the Habit Plane, the stepped interface containing a quasi-invariant line with a terrace of (1 −1 2)β/(1 0 −1 0)α is preferred, which requires a small rotation of 0.24° from Burgers OR. The simulation results are consistent with experimental observations.
-
a tem study of the Habit Plane structure of intragrainular proeutectoid α precipitates in a ti 7 26 wt cr alloy
Acta Materialia, 2004Co-Authors: W Z Zhang, Dong QiuAbstract:The crystallography and the structure of the Habit Plane of proeutectoid alpha precipitates in beta matrix in a Ti-7.26 wt%Cl were studied using TEM. The orientation relationship was found to deviate slightly from the ideal Burgers orientation relationship. The Habit Plane of precipitates was found to be normal to a particular set of Deltag's. A set of dislocations, about 11 nm apart, were observed on the Habit Plane of the precipitates. The Burgers vector of the dislocations, as determined by g (.) b contrast analyses, is [1 -11](beta)/2([2-1-13](alpha)/6). This Burgers vector is different from those determined by previous investigations. The observations are discussed in terms of an analytical O-line model and tend to Support the prediction of the O-line model. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
-
why do the solutions of the Habit Plane of lath martensite converge an application of decomposition of the transformation displacement field
Scripta Materialia, 1997Co-Authors: W Z Zhang, G C WeatherlyAbstract:Abstract The decomposition of the total displacement field is an alternative approach to the separation of a transformation strain. The analytical relationship between the vector elements in the decomposed displacement field is clearer than the one implied in the double shear version of the PTMC. According to this relationship, we conclude that the Habit Plane depends only on the orientation relationship for all lattice invariant shear systems suggested by Kelly [3]. Based on the reciprocal principle of vector elements in the shear fields and the construction of the p-unit cell we have analyzed the effect of rotation of a pair of faces of the p-unit cell, p2′, on other vector elements and the total displacement field. We have demonstrated that the condition that the transformation displacement associated with [1 1−1]bcc is parallel to [−1 1 1]bcc (i.e., TAd2 //-Ad3) is the key reason for the convergence of the Habit Plane; in this condition rotations of p2′ do not affect the total displacement field. For a selected set of shear Planes p3′, the above condition is satisfied only for a particular orientation relationship. For this orientation relationship, the solutions of the Habit Plane appear to converge while other elements can still be variable. The present analytical conclusions are completely consistent with the numerical results reported by Kelly [3].
R.c. Pond - One of the best experts on this subject based on the ideXlab platform.
-
Martensitic interfaces and transformation crystallography in Pu–Ga alloys
Journal of Materials Science, 2011Co-Authors: R.c. PondAbstract:The face-centered cubic (δ) to monoclinic (α) martensitic transformation in Pu–Ga is unusual because it produces a relative large change of volume up to 20%. Moreover, the transformation crystallography is not predicted satisfactorily by the classical phenomenological theories of martensite crystallography, which is based on the hypothesis that the Habit Plane is an invariant Plane of the total shape change. In this study we use the recently developed topological model where the Habit Plane, i.e., the interface between the parent and martensite phases, is envisaged as a semi-coherent configuration with coherent terraces reticulated by a network of disconnections or transformation dislocations, and defects producing lattice-invariant deformation. The authors show explicitly that this network not only accommodates the coherency strains, so that no long-range strain field arises, but also produces diffusionless transformation by motion of the disconnections across the interface. It was show that the predicted Habit Plane inclination with respect to the parent and martensite phases in a Pu–Ga alloy is in good agreement with published experimental observations when the lattice-invariant deformation is \( (201)_{\alpha } /[10\overline{2} ]_{\alpha } \) twinning, as observed experimentally.
-
Phase Transformation Crystallography of Lath Martensite
MRS Proceedings, 2006Co-Authors: R.c. PondAbstract:Our current understanding of martensitic transformations has been based on the Phenomenological Theory of Martensite Crystallography developed in the 1950s. Recently, a Topological Model of martensitic transformations has been presented wherein the Habit Plane is a semi-coherent structure, and the transformation mechanism is shown explicitly to be diffusionless. This approach is used here to model phase transformation crystallography of lath martensite in ferrous alloys. A range of network geometries is predicted corresponding to orientation relationships varying from Nishiyama-Wasserman to Kurdjumov-Sachs. Experimental observations from the literature of the dislocation and disconnection arrays, Habit Plane and orientation relationship are in good agreement with the model.
Patrick M. Kelly - One of the best experts on this subject based on the ideXlab platform.
-
Crystallography of carbide-free bainite in a hard bainitic steel
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006Co-Authors: Mingxing Zhang, Patrick M. KellyAbstract:The convergent beam Kikuchi line diffraction technique has been used to accurately determine the orientation relationships between bainitic ferrite and retained austenite in a hard bainitic steel. A reproducible orientation relationship has been uniquely observed for both the upper and lower bainite. It is [GRAPHICS] However, the Habit Plane of upper bainite is different from that of lower bainite. The former has Habit Plane that is either within 5 degrees of (221)(A) or of (259)(A). The latter only corresponds with a Habit Plane that is within 5 degrees of (259)(A). The determined orientation relationship is completely consistent with reported results determined using the same technique with an accuracy of +/- 0.5 degrees in lath martensite in an Fe-20 wt.% Ni-6 wt.% Mn alloy and in a low carbon low alloy steel. It also agrees well with the orientation relationship between granular bainite and austenite in an Fe-19 wt.% Ni-3.5 wt.% Mn-0.15 wt.% C steel. Hence it is believed that, at least from a crystallographic point view, the bainite transformation has the characteristics of martensitic transformation. (c) 2006 Elsevier B.V. All rights reserved.
-
Comments on edge-to-edge matching and the equivalence of the invariant line, Δg and Moiré Fringe approaches to the crystallographic features of precipitates
Scripta Materialia, 2005Co-Authors: Patrick M. Kelly, Mingxing ZhangAbstract:Three apparently distinct and different approaches have been proposed to account for the crystallographic features of diffusion-controlled precipitation. These three models are based on (a) an invariant line in the Habit Plane, (b) the parallelism of a pair of Deltags that are perpendicular to the Habit Plane and (c) the parallelism of a pair of Moire fringes that are in turn parallel to the Habit Plane. The purpose of the present paper is to show that these approaches are in fact absolutely equivalent and that when certain conditions are satisfied they are essentially the same as the recent edge-to-edge matching model put forward by the authors. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
-
Determination of Habit Planes using trace widths in TEM
Materials Characterization, 1999Co-Authors: Mingxing Zhang, Patrick M. Kelly, J. D. GatesAbstract:A simple and accurate method of determining the Habit Planes from the determination of beam and Habit Plane trace directions using Kikuchi line diffraction patterns and the measurement of the thickness of the thin foil has been developed. The thickness of the thin foil can be calculated from the measurements of the widths of the Habit Plane trace at two different positions. The first orientation is with the foil normal to the electron beam (zero tilt) and the second one is where the foil has been tilted by a known amount about an axis parallel to the original trace at zero tilt. From the beam and the trace directions and thickness of the thin foil, the indices of the Habit Plane normal may be calculated. The technique has been tested using {111} annealing twin interfaces in stainless steel and shown to be capable of determining Habit Planes to within a degree or two. Extension of this method to the measurement of martensite Habit Planes is described.
