Metastable Phase Transformations in Ti-40Al-10V Alloy

1994 ◽  
Vol 364 ◽  
Author(s):  
G. Shao ◽  
P. Tsakiropoulos ◽  
A. P. Miodownik
Keyword(s):  
Phase Transformation ◽  
Phase Transformations ◽  
Volume Fraction ◽  
Metastable Phase ◽  
Equilibrium Phase ◽  
Rapid Quenching ◽  
Β Phase ◽  
Transformation Sequence ◽  
Melt Spun ◽  
Melt Spun Ribbons

AbstractThe microstructures in arc melted ingots and melt spun ribbons have been investigated by electron microscopy and thermodynamic modelling has been used to study the phase transformations. In the ingot, solidification starts with the bcc β phase and at room temperature the structure consists of B2, ωordered, γ and α2 phases. The calculated equilibrium phase transformation sequence during cooling is L → L+ β→β→β + α→β2+α → α+β2+γ → α2+γ + B2. The phase transformation sequence is dramatically changed by rapid quenching from the melt. Athermal ordered w phase is formed in metastable B2 and the α→α2 ordering process is completely suppressed in the melt spun ribbons. The volume fraction of the α precipitates is also dependent on cooling rates.

Phase transformation and magnetocaloric effect of Co-doped Mn–Ni–In melt-spun ribbons

2020 ◽  
Vol 128 (5) ◽  
pp. 055110
Author(s):  
Yiqiao Yang ◽  
Zongbin Li ◽  
César Fidel Sánchez-Valdés ◽  
José Luis Sánchez Llamazares ◽  
Bo Yang ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Magnetocaloric Effect ◽  
Melt Spun ◽  
Melt Spun Ribbons ◽  
Co Doped

Phase Transformations of the Ti-40% Nb Alloy Under External Influence

2016 ◽  
Vol 683 ◽  
pp. 174-180 ◽  
Author(s):  
Yuri P. Sharkeev ◽  
Zhanna G. Kovalevskaya ◽  
Margarita A. Khimich ◽  
Vladimir A. Bataev ◽  
Qi Fang Zhu ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Phase Transformation ◽  
Severe Plastic Deformation ◽  
Phase Transformations ◽  
Optical Metallography ◽  
External Influence ◽  
Β Phase ◽  
Α Phase ◽  
Pressing Operation ◽  
Loading Axis

The phase transformations of the alloy Ti-40 mas % Nb after tempering and severe plastic deformation are studied. The phase transformations of the alloy according to the type and conditions of external influences are analyzed using methods of XRD, SEM and optical metallography. It is determined that inverse phase transformation of the metastable α''-phase to equilibrium β-phase is carried out after severe plastic deformation. Complete phase transformation α'' → β is typical for the mode, which consists of three pressing operation with the change of the loading axis in cramped conditions, followed by a multi-pass rolling in grooved rolls.

Formation of Metastable Phases in Rapidly Quenched Binary Ti Alloys

1985 ◽  
Vol 58 ◽  
Author(s):  
S.H. Whang ◽  
C.S. Chi
Keyword(s):  
Mechanical Stress ◽  
Cooling Rate ◽  
Phase Formation ◽  
Systematic Study ◽  
Metastable Phase ◽  
Rapid Quenching ◽  
Metastable Phases ◽  
Β Phase ◽  
Ti Alloys ◽  
Metastable Phase Formation

ABSTRACTRapid quenching of binary Ti alloys from the melt results in various metastable phases. A systematic study has been conducted in order to elucidate principles associated with the formation of metastable phases in binary Ti alloys resulting from rapid quenching. These metastable phases that include α’, α” phases, metastable β phase, and w phase are discussed with regard to their occurrence and the extension of a phase as a function of cooling rate. Effect of cooling rate and mechanical stress applied during cooling on metastable phase formation was investigated.

In-situ phase transformation studies of Ni48Mn39In13 melt-spun ribbons

2012 ◽  
Vol 25 ◽  
pp. 126-130 ◽  
Author(s):  
D.M. Raj kumar ◽  
D.V. Sridhara Rao ◽  
N.V. Rama Rao ◽  
M. Manivel Raja ◽  
R.K. Singh ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Melt Spun ◽  
Melt Spun Ribbons

Investigation of the microstructure effect on the magnetoresistance of heterogeneous Au1-xCox melt-spun ribbons

1994 ◽  
Vol 52 ◽  
pp. 896-897
Author(s):  
A. Hütten ◽  
J. Bernardi ◽  
S. Friedrichs ◽  
G. Thomas
Keyword(s):  
Giant Magnetoresistance ◽  
Volume Fraction ◽  
Multilayered Structures ◽  
Microstructural Parameters ◽  
Large Volume Fraction ◽  
Melt Spun ◽  
Atomic Scattering ◽  
Melt Spun Ribbons ◽  
Matrix Concentration ◽  
Microstructure Effect

Giant magnetoresistance (GMR) of up to 65% at room temperature has been achieved in Cu/Co multilayers, far exceeding the 2.5% arising from permalloy, which is presently used in magnetoresistive read heads. The GMR effect is not restricted to multilayered structures only and has been also discovered in heterogeneous CulxCox thin films. At present, experimentally determined and statistically significant microstructural parameters, e.g., Co particle size distribution, composition of Co particles and Co matrix concentration, are still not available for Cu1-xCox films or melt-spun ribbons because of two reasons. First, the small difference in atomic scattering factors of Cu and Co and secondly, the Ashby-Brown contrast, which is expected for coherent precipitates, is not observed. The large volume fraction of Co precipitates results in overlap and cancellation of their strain fields. To overcome limitations in imaging Co precipitates, melt-spun AU1-xCox ribbons have been investigated regarding their GMR. AuCo has a similar phase diagram (Fig. 1) compared with CuCo, but it has the advantage of a large difference in atomic scattering factors of Au and Co. As a consequence Co-rich precipitates can be directly identified by their mass contrast.

A phase transformation study in the BaO · Al2O3 · 2SiO2 (BAS)–Si3N4 system

1995 ◽  
Vol 10 (12) ◽  
pp. 3143-3148 ◽  
Author(s):  
A. Bandyopadhyay ◽  
P.B. Aswath
Keyword(s):  
Phase Transformation ◽  
Phase Transformations ◽  
Metastable Phase ◽  
Heat Treating ◽  
Intermediate Step ◽  
Hexagonal Form ◽  
Heat Treated ◽  
Different Temperatures ◽  
Barium Aluminosilicate ◽  
Transformation Study

A phase transformation study was carried out with barium aluminosilicate (BAS) forming powders (BaCO3, Al2O3, and SiO2) in a BAS-Si3N4 system. Powders were heat-treated in air at 1 atm pressure at different temperatures from 600 to 1150 °C at an interval of 50 °C to study the phase transformations during the formation of BAS. The phase transformations of α to β-Si3N4 is studied by heat-treating the powders at 1600 °C for different sintering times in a nitrogen environment at 1 atm pressure. Formation of different phases was identified by using powder x-ray diffraction. Formation of different forms of barium silicates occurs as an intermediate step between 650 and 950 °C and hexagonal BAS forms between 900 and 950 °C. The hexagonal form of BAS always forms first and persists as a metastable phase in the composites with no evidence of the monoclinic phase. An attempt made to fully transform hexagonal BAS to monoclinic BAS by using LiF as a mineralizer proved to be successful. The hexagonal form of BAS forms first when heat-treated at 1000 °C and is fully transformed to monoclinic BAS when heat-treated at 1100 °C.

Evolution of order in amorphous-to-crystalline phase transformation of MgF2

2013 ◽  
Vol 46 (4) ◽  
pp. 1105-1116 ◽  
Author(s):  
Xiaoke Mu ◽  
Sridhar Neelamraju ◽  
Wilfried Sigle ◽  
Christoph T. Koch ◽  
Nico Totò ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Electron Diffraction ◽  
Short Range ◽  
Volume Fraction ◽  
Metastable Phase ◽  
Dynamics Simulation ◽  
Structure Evolution ◽  
Stable Phase ◽  
Type Phase ◽  
Short Range Ordering

Structural disorder and distortion play a significant role in phase transformations. Experimentally, electron diffraction in the transmission electron microscope offers the ability to characterize disorderviathe pair distribution function (PDF) at high spatial resolution. In this work, energy-filteredin situelectron diffraction is applied to measure PDFs of different phases of MgF2from the amorphous deposit through metastable modifications to the thermodynamically stable phase. Despite the restriction of thick specimens resulting in multiple electron scattering, elaborate data analysis enabled experimental and molecular dynamics simulation data to be matched, thus allowing analysis of the evolution of short-range ordering. In particular, it is possible to explain the theoretically not predicted existence of a metastable phase by the presence of atomic disorder and distortion. The short-range ordering in the amorphous and crystalline phases is elucidated as three steps: (i) an initial amorphous phase exhibiting CaCl2-type short-range order which acts as a crystallization nucleus to guide the phase transformation to the metastable CaCl2-type phase and thus suppresses the direct appearance of the rutile-type phase; (ii) a metastable CaCl2-type phase containing short-range structural features of the stable rutile type; and (iii) the formation of a large volume fraction of disordered intergranular regions which stabilize the CaCl2-type phase. The structure evolution is described within the energy landscape concept.

scholarly journals Non-Equilibrium Processing of Ni-Si Alloys at High Undercooling and High Cooling Rates

2014 ◽  
Vol 790-791 ◽  
pp. 22-27 ◽  
Author(s):  
Andrew M. Mullis ◽  
Lei Gang Cao ◽  
Robert F. Cochrane
Keyword(s):  
Metastable Phase ◽  
Equilibrium Phase ◽  
Equilibrium Phase Diagram ◽  
Eutectic Structure ◽  
Eutectic Solidification ◽  
Drop Tube ◽  
High Undercooling ◽  
Cooling Rates ◽  
Β Phase ◽  
High Cooling Rates

Melt encasement (fluxing) and drop-tube techniques have been used to solidify a Ni-25 at.% Si alloy under conditions of high undercooling and high cooling rates respectively. During undercooling experiments a eutectic structure was observed, comprising alternating lamellae of single phase γ (Ni31Si12) and Ni-rich lamellae containing of a fine (200-400 nm) dispersion of β1-Ni3Si and α-Ni. This is contrary to the equilibrium phase diagram from which direct solidification to β-Ni3Si would be expected for undercoolings in excess of 53 K. Conversely, during drop-tube experiments a fine (50 nm) lamellar structure comprising alternating lamellae of the metastable phase Ni25Si9 and β1-Ni3Si is observed. This is also thought to be the result of primary eutectic solidification. Both observations would be consistent with the formation of the high temperature form of the β-phase (β2/β3) being suppressed from the melt.

Sign in / Sign up

Export Citation Format

Share Document