scholarly journals Phase Transformation Path in Aluminum Under Ramp Compression; Simulation and Experimental Study

2021 ◽  
Author(s):  
Lijie He ◽  
Danae Polsin ◽  
Shuai Zhang ◽  
Gilbert W. Collins ◽  
Niaz Abdolrahim
Keyword(s):  
Phase Transformation ◽  
High Strain ◽  
Great Accuracy ◽  
Atomic Level ◽  
Transformation Path ◽  
Transformation Pathway ◽  
Density Response ◽  
Simulation Results ◽  
Diffraction Patterns ◽  
Non Equilibrium Molecular Dynamics

Abstract Identifying structure phase transformation path is essential but challenging in plastic deformation under high-pressure high-strain rate experiments. In this paper, we adopt a framework based on non-equilibrium molecular dynamics and virtual diffraction to reproduce the phase transformation event observed in laser-driven ramp compression. Our simulation results reveal the detailed phase transformation pathway with atomic-level deformation physics while the simulated stress-density response and virtual diffraction patterns match the experimental observation with great accuracy.

Design Approaches and Achievements of Novel Wrought TiAl Alloys for Jet Engine Applications

MRS Advances ◽  
2019 ◽  
Vol 4 (25-26) ◽  
pp. 1465-1470
Author(s):  
Hideki Wakabayashi ◽  
Loris J. Signori ◽  
Ali Shaaban ◽  
Ryosuke Yamagata ◽  
Hirotoyo Nakashima ◽  
...  
Keyword(s):  
Phase Diagram ◽  
Phase Transformation ◽  
Hot Workability ◽  
Tial Alloys ◽  
Jet Engine ◽  
Crack Propagation Resistance ◽  
Β Phase ◽  
Transformation Pathway ◽  
Component Systems ◽  
Multi Component System

AbstractDesign approaches and achievements for the development of wrought TiAl alloys to be used for LPT and HPC blades are constructed. In case of Ti-Al-M1-M2 quaternary systems, conventional equivalency concept does not work for the alloy design, and a new thermodynamic database for phase diagram calculations in multi-component systems of the alloys is built by introducing the interaction parameters among four phases of β−Ti, α2−Ti3Al, α−Ti and γ−TiAl phases in the systems, in order to reproduce the experimentally determined phase diagrams. Based on the phase diagram calculations, the composition range of a unique phase transformation pathway of β+α→α→β+γ in the multi-component system can be identified, and thus model alloys with excellent hot workability even at higher strain rate and mechanical properties can be successfully proposed. It can be concluded that an introduction of bcc β phase and the morphology control through the phase transformation pathway make it possible to improve the room temperature ductility, creep and fatigue crack propagation resistance.

scholarly journals In Situ Neutron Diffraction Study of Phase Transformation of High Mn Steel with Different Carbon Content

Crystals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 101
Author(s):  
Youngsu Kim ◽  
Wookjin Choi ◽  
Hahn Choo ◽  
Ke An ◽  
Ho-Suk Choi ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Neutron Diffraction ◽  
Strain Hardening ◽  
High Strain ◽  
Tensile Deformation ◽  
Austenite Phase ◽  
Transformation Rate ◽  
Ε Martensite ◽  
In Situ Neutron Diffraction

In situ neutron diffraction was employed to examine the phase transformation behavior of high-Mn steels with different carbon contents (0.1, 0.3, and 0.5 wt.%C). With increasing carbon contents from 0.1 C to 0.5 C, the austenite phase fraction among the constituent phases increased from ~66% to ~98%, and stacking fault energy (SFE) increased from ~0.65 to ~16.5 mJ/m2. The 0.1 C and 0.3 C steels underwent phase transformation from γ-austenite to ε-martensite or α’-martensite during tensile deformation. On the other hand, the 0.5 C steel underwent phase transformation only from γ-austenite to ε-martensite. The 0.3 C steel exhibited a low yield strength, a high strain hardening rate, and the smallest elongation. The high strain hardening of the 0.3 C alloy was due to a rapid phase transformation rate from γ-austenite to ε-martensite. The austenite of 0.5 C steel was strengthened by mechanical twinning during loading process, and the twinning-induced plasticity (TWIP) effect resulted in a large ductility. The 0.5 wt.% carbon addition stabilized the austenite phase by delaying the onset of the ε-martensite phase transformation.

In situ observation of phase transformation in an Fe–Zn system at high temperatures using an image plate

1998 ◽  
Vol 5 (3) ◽  
pp. 983-985 ◽  
Author(s):  
Masao Kimura ◽  
Muneyuki Imafuku ◽  
Masao Kurosaki ◽  
Siro Fujii
Keyword(s):  
Phase Transformation ◽  
High Temperatures ◽  
Heating System ◽  
Crystallographic Structure ◽  
In Situ Observation ◽  
Image Plate ◽  
Unique System ◽  
Different Types ◽  
Diffraction Patterns

A unique system has been developed for in situ observation of phase transformation at high temperatures. Changes in powder-diffraction patterns from a heated specimen can be measured continuously by scanning an image plate located behind a slit. A heating system has been designed for a sheet specimen (∼5 × 6 mm) using Joule heating, and it can heat the specimen up to 1100 K at a rate of up to 160 K s−1, where effects of thermal expansion are minimized by a mechanism releasing stress. This system was applied to Zn-coated (∼8 µm in thickness) steel. At temperatures higher than the melting point of Zn, different types of Fe–Zn intermetallics formed sequentially through rapid interdiffusion. Changes in phase and crystallographic structure were monitored with a time resolution of less than a few seconds. It has been found that an addition of a small amount of an element, such as P, into Fe changes the incubation time before the alloying reaction starts. This system has been shown to have the potential for application to in situ observation of other reactions at high temperatures.

Atomic-level simulation of epitaxial recrystallization and phase transformation in SiC

2006 ◽  
Vol 21 (6) ◽  
pp. 1420-1426 ◽  
Author(s):  
F. Gao ◽  
R. Devanathan ◽  
Y. Zhang ◽  
M. Posselt ◽  
W.J. Weber
Keyword(s):  
Molecular Dynamics ◽  
Phase Transformation ◽  
Amorphous Layer ◽  
Atomic Level ◽  
Low Energy ◽  
Triple Junctions ◽  
Important Process ◽  
Atomic Simulation ◽  
Subsequent Phase ◽  
Simulation Cell

A nano-sized amorphous layer embedded in an atomic simulation cell was used to study the amorphous-to-crystalline (a-c) transition and subsequent phase transformation by molecular-dynamics computer simulations in 3C–SiC. The recovery of bond defects at the interfaces is an important process driving the initial epitaxial recrystallization of the amorphous layer, which is hindered by the nucleation of a polycrystalline 2H–SiC phase. The kink sites and triple junctions formed at the interfaces between 2H– and 3C–SiC provide low-energy paths for 2H–SiC atoms to transform to 3C–SiC atoms. The spectrum of activation energies associated with these processes ranges from below 0.8 eV to about 1.9 eV.

scholarly journals PHASE-TRANSFORMATION DYNAMICS AND CHARACTERIZATION OF PRECIPITATES IN THE Cu-3Ti-3Ni-0.5Si ALLOY

2021 ◽  
Vol 55 (4) ◽  
Author(s):  
Jia Liu ◽  
Jituo Liu ◽  
Xianhui Wang ◽  
Chong Fu ◽  
Yanlong Wang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Electrical Conductivity ◽  
Phase Transformation ◽  
Volume Fraction ◽  
Formation Enthalpy ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron ◽  
The Matrix ◽  
Diffraction Patterns ◽  
Precipitated Phases

In this paper we investigated the phase-transformation dynamics of the Cu-3Ti-3Ni-0.5Si alloy by applying the Avrami method to phase-transformation dynamics and electrical conductivity based on the relationship between the electrical conductivity and the volume fraction of precipitates in the Cu-3Ti-3Ni-0.5Si alloy. The results corroborated well with the experimental data. The microstructure and precipitated phases were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The analysis of the selected-area electron-diffraction patterns indicated that the precipitates formed in the matrix of the Cu-3Ti-3Ni-0.5Si alloy during aging, correspond to the Ni3Ti, Ni3Si, and Ni2Si phases. According to the values of formation enthalpy and cohesive energy determined by first-principle calculations, the formation of the Ni2Si phase is more favorable compared to the Ni3Si and Ni3Ti phases, and the Ni3Ti exhibits improved structural stability compared to the Ni2Si and Ni3Si phases.

scholarly journals A New Reversible Phase Transformation of Intermetallic Ti3Sn

Materials ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2484
Author(s):  
Minshu Du ◽  
Lishan Cui ◽  
Feng Liu
Keyword(s):  
Phase Transformation ◽  
Variable Temperature ◽  
Lithium Ion ◽  
Orthorhombic Phase ◽  
X Ray Diffraction ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron ◽  
Expansion Curve ◽  
Diffraction Patterns ◽  
Reversible Phase

Ti3Sn has received increasing attention as a high damping metallic material and as an anode material for rechargeable lithium-ion batteries. However, a heated dispute concerning the existence of solid state phase transformation of stoichiometric Ti3Sn impedes its development. Here, thermal-induced reversible phase transformation of Ti3Sn is demonstrated to happen at around 300 K by the means of in-situ variable-temperature X-ray diffraction (XRD) of Ti3Sn powder, which is also visible for bulk Ti3Sn on the thermal expansion curve by a turning at 330 K. The new phase’s crystal structure of Ti3Sn is determined to be orthorhombic with a space group of Cmcm and the lattice parameters of a = 5.87 Å, b = 10.37 Å, c = 4.76 Å respectively, according to selected area electron diffraction patterns in transmission electron microscope (TEM) and XRD profiles. The hexagonal → orthorhombic phase transformation is calculated to be reasonable and consistent with thermodynamics theory. This work contributes to a growing knowledge of intermetallic Ti3Sn, which may provide fundamental insights into its damping mechanism.

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