Hydride Phases, Orientation Relationships, Habit Planes, and Morphologies

2012 ◽  
pp. 53-107
Author(s):  
Manfred P Puls
Keyword(s):  
Orientation Relationships ◽  
Habit Planes ◽  
Hydride Phases

Use of 2½ D imaging in analysis of NiTi martensite

1978 ◽  
Vol 36 (1) ◽  
pp. 610-611
Author(s):  
G. M. Michal
Keyword(s):  
Memory Effect ◽  
Monoclinic Phase ◽  
Reaction Path ◽  
Structural Characteristics ◽  
Salient Feature ◽  
Martensite Phase ◽  
Orientation Relationships ◽  
Low Symmetry ◽  
Hydride Phases ◽  
Unusual Shape

Several TEM investigations have attempted to correlate the structural characteristics to the unusual shape memory effect in NiTi, the consensus being the essence of the memory effect is ostensible manifest in the structure of NiTi transforming martensitic- ally from a B2 ordered lattice to a low temperature monoclinic phase. Commensurate with the low symmetry of the martensite phase, many variants may form from the B2 lattice explaining the very complex transformed microstructure. The microstructure may also be complicated by the enhanced formation of oxide or hydride phases and precipitation of intermetallic compounds by electron beam exposure. Variants are typically found in selfaccommodation groups with members of a group internally twinned and the twins themselves are often observed to be internally twinned. Often the most salient feature of a group of variants is their close clustering around a given orientation. Analysis of such orientation relationships may be a key to determining the nature of the reaction path that gives the transformation its apparently perfect reversibility.

The orientation relationships of nanobelt-like Si2Hf precipitates in an Al–Si–Mg–Hf alloy

2016 ◽  
Vol 49 (4) ◽  
pp. 1223-1230 ◽  
Author(s):  
Xueli Wang ◽  
Huilan Huang ◽  
Xinfu Gu ◽  
Yanjun Li ◽  
Zhihong Jia ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Coincident Site Lattice ◽  
Orthorhombic Structure ◽  
Orientation Relationships ◽  
Lattice Distribution ◽  
Site Lattice ◽  
Transmission Electron ◽  
Habit Planes ◽  
Al Matrix

The orientation relationships (ORs) between the Al matrix and Si2Hf precipitates with an orthorhombic structure in an Al–Si–Mg–Hf alloy after heat treatment at 833 K for 20 h were investigated by transmission electron microscopy and electron diffraction. Four ORs are identified as (100)Al||(010)p, (0\overline {1}1)Al||(101)pand [011]Al||[\overline {1}01]p; (11\overline {1})Al||(010)pand [011]Al||[\overline {1}01]p; (12\overline {1})Al||(010)p, (101)Al||(100)pand [1\overline {11}]Al||[001]p; (\overline {11}1)Al||(010)pand [112]Al||[\overline {1}01]p. The habit planes of these four ORs are rationalized by the fraction of good atomic matching sites at the interface. In addition, the formation of Si2Hf precipitates with a nanobelt-like morphology is interpreted on the basis of the near-coincident site lattice distribution.

Orientation Studies of α-Al(Fe,Mn)Si Dispersoids in 3xxx Al Alloys

2014 ◽  
Vol 794-796 ◽  
pp. 39-44 ◽  
Author(s):  
Astrid Marie Flattum Muggerud ◽  
Yan Jun Li ◽  
Randi Holmestad
Keyword(s):  
Mechanical Properties ◽  
Low Temperature ◽  
Orientation Relationship ◽  
Aluminum Matrix ◽  
Al Alloys ◽  
Orientation Relationships ◽  
The Matrix ◽  
The Common ◽  
Habit Planes ◽  
Al Matrix

Dispersoids are important in 3xxx Al alloys, influencing mechanical properties, texture and recrystallization. In this work α-Al (Fe,Mn)Si dispersoids have been studied after low temperature homogenisation. The common orientation relationship between dispersoids and Al matrix has been reported in earlier studies. Here a systematic study on the orientation relationship and its exceptions is presented. It is found that most of the dispersoids follow the common orientation relationship, [1-1 1] α //[1-1 1]Al , (5-2 -7 ) α //(0 1 1)Al . Here the dispersoids are semi coherent with the Aluminum matrix. Different morphologies and habit planes are possible. Deviations from the most commonly observed orientation relationships are presented and discussed, to underline the complexity of the phase and its relation to the matrix.

Vacancy-Assisted Precipitation in a 18 W/O Cr - 10 W/O ni - 0.3 W/O P Steel

1981 ◽  
Vol 39 ◽  
pp. 332-333
Author(s):  
A. R. Pelton
Keyword(s):  
Stainless Steel ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Austenitic Steels ◽  
Orientation Relationships ◽  
Precipitation Behavior ◽  
Vacancy Defects ◽  
Transmission Electron ◽  
Nucleation And Growth Mechanisms ◽  
Habit Planes

Although many similarities exist in the precipitation behavior in ferritic and austenitic steels, the nucleation and growth mechanisms in these systems have eluded full comprehension. However, it is apparent that the initial clustering of substitutional and interstitial atoms can dictate the structure and orientation relationships of subsequent phases. Hence, in order to realize the benefits of these decomposition transformations, a better understanding of the incipient nucleation event is imperative. Therefore, a transmission electron microscopy study of a quenched-aged 18-10 stainless steel doped with 0.3 w/o P was undertaken as part of a more comprehensive research program. The precipitation reactions in this austenitic stainless steel were originally surveyed by Rowcliffe and Nicholson [1] and Rowcliffe and Eyre [2], These investigators observed a variety of defects ranging from vacancy defects on {100} planes at lower aging temperatures to Cr3P laths with {100} habit planes at higher aging temperatures.

On the multiple orientation relationship of the Mg/γ-Mg17Al12precipitation system

2012 ◽  
Vol 45 (2) ◽  
pp. 224-233 ◽  
Author(s):  
Hongwei Liu ◽  
Jiangwen Liu ◽  
Liuzhang Ouyang ◽  
Chengping Luo
Keyword(s):  
Orientation Relationship ◽  
Simple Structure ◽  
Close Packing ◽  
Orientation Relationships ◽  
Complicated Structure ◽  
Starting Point ◽  
The Matrix ◽  
Gross Energy ◽  
Relationship Of ◽  
Habit Planes

The six orientation relationships (ORs) found in the Mg/γ-Mg17Al12precipitation system were summarized and systematically interpreted based on the atomic structure of the precipitate γ-Mg12Al17and the invariant deformation element (IDE) model for diffusional phase transformations. It was found that the pseudo-twinning relationship between the six ORs is a reflection of the pseudo-twinning relationship between the close- or near-close-packing planes ({\overline 8}\hskip.75{\overline 7}\hskip.75{\overline 7}), ({\overline 4}11), (033), (411) and (8{\overline 7}\hskip.75{\overline 7}) in the precipitate γ-Mg12Al17. As a result, the Pitsch–Schrader OR is the starting point for the other five ORs. Multiple morphologies, growth directions and habit planes could be rationally interpreted by the IDE model. This implies that a multiple orientation relationship between the variants of precipitates is favourable in order to minimize the gross energy of precipitation systems in which the matrix has a simple structure while the precipitate has a complicated structure, such as Mg/γ-Mg12Al17, Mg/δ-Zn2Zr3and Mg/η-MgZn2couples.

New insights into crystallographic correlations between ferrite and cementite in lamellar eutectoid structures, obtained by SEM–FEG/EBSD and an indirect two-trace method

2007 ◽  
Vol 40 (5) ◽  
pp. 849-856 ◽  
Author(s):  
Y. D. Zhang ◽  
C. Esling ◽  
M. Calcagnotto ◽  
X. Zhao ◽  
L. Zuo
Keyword(s):  
Matching Condition ◽  
Electron Back Scatter Diffraction ◽  
Deep Insight ◽  
Eutectoid Steel ◽  
Orientation Relationships ◽  
Edge Matching ◽  
Pearlitic Transformation ◽  
Habit Planes ◽  
Insight Into ◽  
Scanning Electron

Four different ferrite/cementite orientation relationships (ORs) in near-eutectoid steel are derived using SEM–FEG/EBSD (scanning electron microscopy–field emission gun/electron back-scatter diffraction) and an indirect two-trace method. They show a common feature of close-packed plane parallelism between ferrite and cementite. Their crystallographic compatibility with habit planes shows a variety of possible habit planes and excludes the existence of the exact conventional Bagaryatsky and Pitsch–Petch ORs. Each of these new ferrite/cementite ORs is correlated with a different edge-to-edge matching condition between austenite and pearlitic ferrite, and between austenite and pearlitic cementite, and possesses specific morphological features. The present results may give deep insight into the crystallography of pearlitic transformation and provide useful information for materials design through interface tailoring in steels.

Formation and Dissolution of Hydride Precipitates in Zirconium Alloys: Crystallographic Orientation Relationships and Stability after Temperature Cycling

2016 ◽  
Vol 879 ◽  
pp. 2330-2335 ◽  
Author(s):  
Egle Conforto ◽  
Stephane Cohendoz ◽  
Cyril Berziou ◽  
Patrick Girault ◽  
Xavier Feaugas
Keyword(s):  
Hydrogen Content ◽  
Hydrogen Diffusion ◽  
Zirconium Alloys ◽  
Temperature Cycling ◽  
Nuclear Industry ◽  
X Rays ◽  
Orientation Relationships ◽  
Hydrogen Distribution ◽  
Cycle Number ◽  
Hydride Phases

Hydride precipitation due to the spontaneous and fast hydrogen diffusion is often pointed as causing embrittlement and rupture in zirconium alloys used in the nuclear industry. Transmission Electron Microscopy (TEM) and X-Rays Diffraction (XRD) have been used to study the precipitation of hydride phases in zirconium alloys as a function of the hydrogen content. The orientation relationships observed between the hydride phase and the substrate were similar to those previously observed in Titanium hydrides grown on Titanium. Dislocation emission from the hydride precipitates has been directly related to the relaxation of the misfit stresses appearing during the transformation. The stability of the hydride phases after several dissolution-reprecipitation cycles have been studied by DSC, TEM and XRD for different total hydrogen content in several alloys. The energy of precipitation observed is lower than that of the dissolution in each case studied. The temperature associated with these two processes slightly increase as a function of the cycle number, as a result of the homogenizing hydrogen distribution in the alloy bulk. The same hydrides phases present before cycling were also observed after 20 cycles. However, transition phases poorer in hydrogen than the dominant one may precipitate at the interface with the substrate. The evolution of these transitions phases with the temperature increase will be investigated by TEM in-situ heating in the next future.

scholarly journals Solute hydrogen and hydride phase implications on the plasticity of zirconium and titanium alloys: a review and some recent advances

2017 ◽  
Vol 375 (2098) ◽  
pp. 20160417 ◽  
Author(s):  
E. Conforto ◽  
I. Guillot ◽  
X. Feaugas
Keyword(s):  
Prismatic Slip ◽  
Misfit Dislocations ◽  
Orientation Relationships ◽  
Compact Structure ◽  
Hardening Process ◽  
Pyramidal Slip ◽  
Recent Advances ◽  
The Impact ◽  
Thermal Stability Of ◽  
Hydride Phases

In this contribution, we propose a review of the possible implications of hydrogen on mechanical behaviour of Zr and Ti alloys with emphasis on the mechanisms of plasticity and strain hardening. Recent advances on the impact of oxygen and hydrogen on the activation volume show that oxygen content hinders creep but hydrogen partially screens this effect. Both aspects are discussed in terms of a locking–unlocking model of the screw dislocation mobility in prismatic slip. Additionally, possible extension of this behaviour is suggested for the pyramidal slip. The low hydrogen solubility in both Zr and Ti leads in many cases to hydride precipitation. The nature of these phases depends on the hydrogen content and can show crystallographic orientation relationships with the hexagonal compact structure of the alloys. Some advances on the thermal stability of these phases are illustrated and discussed in relation with the deepening of the misfit dislocations. Under tensile loading, we showed that hydrides enhance the hardening process in relation with internal stress due to strain incompatibilities between the Zr and Ti matrix and hydride phases. Different plastic yielding processes of hydrides were identified, which progressively reduce these strain incompatibilities. This article is part of the themed issue ‘The challenges of hydrogen and metals’.

Sign in / Sign up

Export Citation Format

Share Document