Appearance of textures with a c-axis parallel to the extrusion direction in Mg alloys

2022 ◽  
Vol 210 ◽  
pp. 114422
Author(s):  
Jun Wang ◽  
Mahmoud Reza Ghandehari Ferdowsi ◽  
Sitarama Raju Kada ◽  
Steven Babaniaris ◽  
Bevis Hutchinson ◽  
...  
Keyword(s):  
Extrusion Direction ◽  
Mg Alloys ◽  
Axis Parallel

scholarly journals Superplasticity at Intermediate Temperatures of ZK60 Magnesium Alloy Processed by Indirect Extrusion

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 606
Author(s):  
César Palacios-Trujillo ◽  
José Victoria-Hernández ◽  
David Hernández-Silva ◽  
Dietmar Letzig ◽  
Marco A. García-Bernal
Keyword(s):  
Magnesium Alloy ◽  
Magnesium Alloys ◽  
Deformation Mechanism ◽  
Extrusion Direction ◽  
Grain Boundary Sliding ◽  
Mg Alloys ◽  
Homogeneous Microstructure ◽  
Texture Measurement ◽  
Average Grain Size ◽  
Zk60 Magnesium Alloy

Magnesium alloys usually exhibit excellent superplasticity at high temperature. However, many Mg alloys have poor formation ability near room temperature. Therefore, preparation of Mg alloys with suitable microstructures to show low or intermediate temperature superplasticity is an important goal. In this work, the superplastic behavior at intermediate temperatures of a commercial ZK60 magnesium alloy processed by indirect extrusion was investigated. After extrusion, the alloy showed a refined and homogeneous microstructure with an average grain size of 4 ± 2 μm. Overall texture measurement indicated that the alloy showed a strong prismatic texture with the highest intensity oriented to pole ⟨101¯0⟩. A texture component ⟨1¯21¯1⟩ parallel to the extrusion direction was found; this type of texture is commonly observed in Mg alloys with rare earth additions. Tensile tests were performed at temperatures of 150, 200, and 250 °C at three strain rates of 10−2, 10−3, and 10−4 s−1. A very high ductility was found at 250 °C and 10−4 s−1, resulting in an elongation to failure of 464%. Based on calculations of the activation energy and on interpretation of the deformation mechanism map for magnesium alloys, it was concluded that grain boundary sliding (GBS) is the dominant deformation mechanism.

SEM/FESEM imaging of lamellar structures in melt extruded polyethylene films

1992 ◽  
Vol 50 (2) ◽  
pp. 1142-1143
Author(s):  
R.T. Chen ◽  
M.G. Jamieson ◽  
R. Callahan
Keyword(s):  
Imaging Techniques ◽  
Membrane Surface ◽  
High Stress ◽  
Extrusion Direction ◽  
Polymeric Membranes ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Crystalline Polymers ◽  
Lamellar Structures ◽  
Resolution Imaging

“Row lamellar” structures have previously been observed when highly crystalline polymers are melt-extruded and recrystallized under high stress. With annealing to perfect the stacked lamellar superstructure and subsequent stretching in the machine (extrusion) direction, slit-like micropores form between the stacked lamellae. This process has been adopted to produce polymeric membranes on a commercial scale with controlled microporous structures. In order to produce the desired pore morphology, row lamellar structures must be established in the membrane precursors, i.e., as-extruded and annealed polymer films or hollow fibers. Due to the lack of pronounced surface topography, the lamellar structures have typically been investigated by replica-TEM, an indirect and time consuming procedure. Recently, with the availability of high resolution imaging techniques such as scanning tunneling microscopy (STM) and field emission scanning electron microscopy (FESEM), the microporous structures on the membrane surface as well as lamellar structures in the precursors can be directly examined.The materials investigated are Celgard® polyethylene (PE) flat sheet membranes and their film precursors, both as-extruded and annealed, made at different extrusion rates (E.R.).

The limits of strain and lattice parameter measurements by CBED

1989 ◽  
Vol 47 ◽  
pp. 518-519
Author(s):  
Hamish L. Fraser
Keyword(s):  
Electron Beam ◽  
Mirror Symmetry ◽  
Local Symmetry ◽  
Lattice Parameter ◽  
Growth Direction ◽  
Surface Relaxation ◽  
Strained Layer ◽  
Axis Parallel ◽  
Local Lattice ◽  
Strained Layer Superlattice

The topic of strain and lattice parameter measurements using CBED is discussed by reference to several examples. In this paper, only one of these examples is referenced because of the limitation of length. In this technique, scattering in the higher order Laue zones is used to determine local lattice parameters. Work (e.g. 1) has concentrated on a model strained-layer superlattice, namely Si/Gex-Si1-x. In bulk samples, the strain is expected to be tetragonal in nature with the unique axis parallel to [100], the growth direction. When CBED patterns are recorded from the alloy epi-layers, the symmetries exhibited by the patterns are not tetragonal, but are in fact distorted from this to lower symmetries. The spatial variation of the distortion close to a strained-layer interface has been assessed. This is most readily noted by consideration of Fig. 1(a-c), which show enlargements of CBED patterns for various locations and compositions of Ge. Thus, Fig. 1(a) was obtained with the electron beam positioned in the center of a 5Ge epilayer and the distortion is consistent with an orthorhombic distortion. When the beam is situated at about 150 nm from the interface, the same part of the CBED pattern is shown in Fig. 1(b); clearly, the symmetry exhibited by the mirror planes in Fig. 1 is broken. Finally, when the electron beam is positioned in the center of a 10Ge epilayer, the CBED pattern yields the result shown in Fig. 1(c). In this case, the break in the mirror symmetry is independent of distance form the heterointerface, as might be expected from the increase in the mismatch between 5 and 10%Ge, i.e. 0.2 to 0.4%, respectively. From computer simulation, Fig.2, the apparent monocline distortion corresponding to the 5Ge epilayer is quantified as a100 = 0.5443 nm, a010 = 0.5429 nm and a001 = 0.5440 nm (all ± 0.0001 nm), and α = β = 90°, γ = 89.96 ± 0.02°. These local symmetry changes are most likely due to surface relaxation phenomena.

Electron-Probe Quantitative Energy-Dispersive Analysis of Trace Magnesium Concentrations in Ag-Mg Alloys

1996 ◽  
Vol 54 ◽  
pp. 510-511
Author(s):  
R. B. Marinenko
Keyword(s):  
Electron Probe ◽  
Energy Dispersive Spectrometry ◽  
Mg Alloys ◽  
Energy Dispersive ◽  
Energy Dispersive Analysis ◽  
High Tc ◽  
Alloy Wire ◽  
High Tc Superconductor ◽  
Eds Analysis ◽  
Superior Mechanical Properties

Internally oxidized Ag-Mg alloys are used as sheaths for high Tc superconductor wires because of their superior mechanical properties. The preparation and characteristics of these materials have been reported. Performance of the sheaths depends on the concentration of the magnesium which generally is less than 0.5 wt. percent. The purpose of this work was to determine whether electron probe microanalysis using energy dispersive spectrometry (EDS) could be used to quantitate three different Ag-Mg alloys. Quantitative EDS analysis can be difficult because the AgL escape peak occurs at the same energy (1.25 keV) as the Mg Kα peak. An EDS spectrum of a Ag-Mg alloy wire is compared to a pure Ag spectrum in Fig. 1.

Effect of CaO Addition on the High-Temperature Oxidation of Mg Alloys

2016 ◽  
Vol 54 (6) ◽  
pp. 390-399 ◽  
Author(s):  
Dong Bok Lee ◽  
Shae Kwang Kim ◽  
Soon Yong Park
Keyword(s):  
High Temperature ◽  
High Temperature Oxidation ◽  
Mg Alloys ◽  
Temperature Oxidation

Occurrence and Development of a Dorsal Gland in the Leaves of Twelve Cultivars of Ficus benjamina L. (Weeping Fig)

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 537b-537
Author(s):  
Svoboda V. Pennisi ◽  
Dennis B. McConnell ◽  
Richard W. Henley
Keyword(s):  
Leaf Size ◽  
Dark Spot ◽  
Ficus Benjamina ◽  
Axis Parallel ◽  
Glandular Cells ◽  
Phenolic Substances ◽  
Dark Color ◽  
Columnar Cells ◽  
Dorsal Gland ◽  
Colorimetric Reaction

Ficus benjamina plants are an integral part of most modern interior landscapes. Reports from growers and interiorscape managers have drawn attention to a specific problem related to large F. benjamina plants, namely the occurrence of a dark oval spot on the abaxial surface of the leaf base. Twelve cultivars of F. benjamina were examined: Christine, Citation, Florida Spire, Kelly, Kiki, Midnight, Monique, Stacey, Wintergreen, Dwarf Nikita, Spearmint, and Starlight. Anatomically, the dorsal gland consisted of one to several layers of densely stained, columnar cells. Positive colorimetric reaction for phenolics was obtained in the glandular cells. Developmentally, the gland cells could not be distinguished from the regular epidermal cells until ≈30% of final leaf size was reached. The cells of the outermost glandular layer changed shape from rectangular with long axis parallel to the leaf surface to elongate with long axis perpendicular to the surface. In a mature leaf, the thickness of the glandular layer was between 20 and 30 μm. Externally, at this stage, no dark spot, indicative of the gland's location, could be observed. In older leaves, however, an accumulation of phenolic substances led to appearance of dorsal dark spot. All cultivars possessed glandular layer. However, this area did not darken in all cultivars; Christine, Citation, Florida Spire, Kelly, Kiki, and Stacey developed small dark spots, while Dwarf Nikita and Starlight had numerous, well-pronounced glandular regions. This study showed that the dark spots in F. benjamina cultivars were a normal morphological feature. Although the gland was present in every cultivar, only a few cultivars developed a dark color.

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