A TEM study of the influence of microstructure on the superplastic behavior of a U-5.8 wt.% Nb alloy

1986 ◽  
Vol 44 ◽  
pp. 568-569
Author(s):  
G. Mackiewicz Ludtka
Keyword(s):  
Grain Size ◽  
Heating Rate ◽  
Phase Field ◽  
Single Phase ◽  
Superplastic Behavior ◽  
Two Phase ◽  
Single Phase Field

Historically, metals exhibit superplasticity only while forming in a two-phase field because a two-phase microstructure helps ensure a fine, stable grain size. In the U-5.8 Nb alloy, superplastici ty exists for up to 2 h in the single phase field (γ1) at 670°C. This is above the equilibrium monotectoid temperature of 647°C. Utilizing dilatometry, the superplastic (SP) U-5.8 Nb alloy requires superheating to 658°C to initiate the α+γ2 → γ1 transformation at a heating rate of 1.5°C/s. Hence, the U-5.8 Nb alloy exhibits an anomolous superplastic behavior.

Recovery and Recrystallization during Thermo-Mechanical Processing of Ti-6.5Al-1.5Zr-3.5Mo-0.3Si Alloy

2014 ◽  
Vol 783-786 ◽  
pp. 549-555
Author(s):  
Hui Qin Chen ◽  
Xiao Dong Zhao ◽  
Yue Sheng Chai ◽  
Chun Xiao Cao
Keyword(s):  
Grain Size ◽  
Kinetic Model ◽  
Dynamic Recrystallization ◽  
Grain Boundaries ◽  
Phase Field ◽  
Single Phase ◽  
Strain Rates ◽  
Mechanical Processing ◽  
Two Phase ◽  
Alpha Beta

In this investigation, microstructure evolution of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy during thermo-mechanical processing at temperatures in beta single-phase and alpha+beta two-phase fields was studied. Microstructure analyses indicate that: (1) in the beta single-phase field, dynamic recovery accompanied by geometric dynamic recrystallization at large strains takes place dominantly within elongated large prior beta grains with serrate grain boundaries during deformation at higher temperatures and lower strain rates; and discontinuous dynamic recrystallization occurs along elongated small prior beta grain boundaries during deformation at lower temperatures and higher strain rates. During discontinuous dynamic recrystallization, recrystallized grain size is a function of Zener–Hollomon parameter, and a modified Avrami recrystallized kinetic model was established. (2) In the alpha+beta two-phase field, the globularization process is a thermally activated process controlled by parameters of temperature and strain rate. A modified Avrami globularized kinetic model was established. The primary alpha grain size is a function of Z on a ln-ln scale.

The Disordering Process in an Ll2 Ordered Alloy

1984 ◽  
Vol 39 ◽  
Author(s):  
J. A. Horton ◽  
A. Dasgupta ◽  
C. T. Liu
Keyword(s):  
Electron Microscopy ◽  
Phase Field ◽  
Room Temperature ◽  
Single Phase ◽  
Antiphase Boundary ◽  
Two Phase ◽  
Ripening Process ◽  
Transmission Electron ◽  
Complete Alignment ◽  
Single Phase Field

ABSTRACTThe antiphase boundary (APB) structure and the disordering process have been studied by transmission electron microscopy (TEM) in a long-rangeordered alloy with Ll2 structure and composition (Ni70Fe30)3(V58Al40Ti2). With an increase in temperature from a single-phase field into a two-phase field, disordering occurs both homogeneously within ordered domains and heterogeneously along APBs. Disordering continues by a ripening process with the disordered islands shrinking while the disordered bands on the prior APBs grow. The APBs are partially aligned on {100} while the material is single phase. As disordering proceeds, the degree of alignment of the disordered bands on {100} increases until complete alignment results. A correlation of the APB structure with room temperature mechanical properties indicates no dramatic change at the transition to the two-phase structure.

scholarly journals Modular Rotor Single Phase Field Excited Flux Switching Machine with Non-Overlapped Windings

Energies ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1576 ◽  
Author(s):  
Lutf Ur Rahman ◽  
Faisal Khan ◽  
Muhammad Afzal Khan ◽  
Naseer Ahmad ◽  
Hamid Ali Khan ◽  
...  
Keyword(s):  
Phase Field ◽  
Single Phase ◽  
Dead Zone ◽  
Optimization Technique ◽  
Rotor Design ◽  
Iron Losses ◽  
Excitation Coil ◽  
Electromagnetic Performance ◽  
Copper Losses ◽  
Single Phase Field

This paper aims to propose and compare three new structures of single-phase field excited flux switching machine for pedestal fan application. Conventional six-slot/three-pole salient rotor design has better performance in terms of torque, whilst also having a higher back-EMF and unbalanced electromagnetic forces. Due to the alignment position of the rotor pole with stator teeth, the salient rotor design could not generate torque (called dead zone torque). A new structure having sub-part rotor design has the capability to eliminate dead zone torque. Both the conventional eight-slot/four-pole sub-part rotor design and six-slot/three-pole salient rotor design have an overlapped winding arrangement between armature coil and field excitation coil that depicts high copper losses as well as results in increased size of motor. Additionally, a field excited flux switching machine with a salient structure of the rotor has high flux strength in the stator-core that has considerable impact on high iron losses. Therefore, a novel topology in terms of modular rotor of single-phase field excited flux switching machine with eight-slot/six-pole configuration is proposed, which enable non-overlap arrangement between armature coil and FEC winding that facilitates reduction in the copper losses. The proposed modular rotor design acquires reduced iron losses as well as reduced active rotor mass comparatively to conventional rotor design. It is very persuasive to analyze the range of speed for these rotors to avoid cracks and deformation, the maximum tensile strength (can be measured with principal stress in research) of the rotor analysis is conducted using JMAG. A deterministic optimization technique is implemented to enhance the electromagnetic performance of eight-slot/six-pole modular rotor design. The electromagnetic performance of the conventional sub-part rotor design, doubly salient rotor design, and proposed novel-modular rotor design is analyzed by 3D-finite element analysis (3D-FEA), including flux linkage, flux distribution, flux strength, back-EMF, cogging torque, torque characteristics, iron losses, and efficiency.

Superconductivity in the (Nd,Ce,Ca)2Cuo4-Z System

1989 ◽  
Vol 169 ◽  
Author(s):  
Takeshi Sakurai ◽  
Toru Yamashita ◽  
Sumio Ikegawa ◽  
H. Yamauchi
Keyword(s):  
Phase Field ◽  
Carrier Density ◽  
Single Phase ◽  
Superconducting Transition ◽  
X Ray ◽  
Analysis Techniques ◽  
Density Relationship ◽  
Micro Analysis ◽  
T Phase ◽  
Single Phase Field

AbstractWe have controlled the carrier (electron) density in Nd2CuO2 of the T’ structure by introducing both Ce and Ca into the Nd‐sites, and studied the superconducting transition temperature versus carrier density relationship. The phase relations in the (Nd1‐x‐yCexCay)2CuO4‐z system were studied by means of powder X‐ray dirfractron and electron‐probe micro‐analysis techniques. For the phase diagram of the (Nd1‐x‐yCexCay)2CuO4‐z system, the single phase field of the T’ phase was established. Samples of the (Nd0.9‐yCe0.1Cay)2CuO4‐z system with compositions included in the single phase field were synthesized. The carrier density in these samples was varied by controlling the Ca content. The Hall effect and DC resistivity were measured to elucidate the relation between Tc and the carrier density.

Clinopyroxene with Si < AlIV in the join CaFeAISiO6-CaTiAl2O6

1980 ◽  
Vol 43 (331) ◽  
pp. 851-856 ◽  
Author(s):  
Kosuke Onuma ◽  
Masahide Akasaka
Keyword(s):  
Solid Solution ◽  
Solid Solutions ◽  
Phase Field ◽  
Single Phase ◽  
Tetrahedral Sites ◽  
Single Phase Field

SummaryUnusual clinopyroxenes were synthesized in the study of the join CaFeAlSiO6-CaTiAl2O6 in air at I atm. Clinopyroxene solid solution, hibonite solid solution, X-phase, perovskite, and corundum are present, and at subsolidus temperatures the clinopyroxene singlephase field extends up to about 19 wt% CaTiAl2O6. The CaTiAl2O6 component in the clinopyroxene however increases beyond the clinopyroxene single-phase field and attains 23 wt%. These clinopyroxene solid solutions are extremely poor in SiO2 and extremely rich in Al2O3, Fe2O3, and TiO2, and more than half of tetrahedral sites are occupied by AlIV, contravening the aluminium avoidance principle.

scholarly journals Deformation Behavior of a β-Solidifying TiAl Alloy within β Phase Field and Its Effect on the β→α Transformation

Metals ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 605 ◽  
Author(s):  
Yi Chen ◽  
Liang Cheng ◽  
Guang Yang ◽  
Yalin Lu ◽  
Fengbo Han
Keyword(s):  
Phase Field ◽  
Deformation Behavior ◽  
Single Phase ◽  
Tial Alloy ◽  
Volume Fraction ◽  
Dislocation Creep ◽  
Strain Rates ◽  
Texture Intensity ◽  
Β Phase ◽  
Single Phase Field

In this study, the deformation behavior of a Ti-40Al-10V (at.%) alloy within β single phase field was examined by means of isothermal compression at 1300 °C under strain rates of 2 s−1, 0.2 s−1, and 0.02 s−1, as well as its effect on the subsequent β→α transformation. The results showed that the alloy behaved steady-state flow with dislocation creep as the predominant rate-controlling process. Dynamic recrystallization (DRX) evidently occurred during deformation, and its volume fraction was dramatically increased so that at the lowest strain rate (0.02 s−1), a full-DRX β structure was obtained. The preferentially dynamic migration of grain boundaries with <100> orientation was demonstrated to be the major DRX mechanism. The texture was characterized by a <100> + <111> double-fiber at 2 s−1, but gradually transformed into a simple rotated cube orientationunder 0.02 s−1, accompanied by a decreasing texture intensity. During the subsequent β→α transformation, two types of α morphology wereproduced with evident variant selection, namely, the Widmannstatten colony and martensitic laths. Texture simulation revealed that the α texture was solely determined by parent β texture, despite of the variant selections.

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