Ultrafine-grained microstructure in a Cu–Zn alloy produced by electropulsing treatment

2003 ◽  
Vol 18 (8) ◽  
pp. 1991-1997 ◽  
Author(s):  
Yizhou Zhou ◽  
Wei Zhang ◽  
Baoquan Wang ◽  
Jingdong Guo
Keyword(s):  
High Current Density ◽  
Coarse Grained ◽  
Heating And Cooling ◽  
Β Phase ◽  
Α Phase ◽  
Ultrafine Grained ◽  
Solid State Phase Transformation ◽  
Two Phases ◽  
Electropulsing Treatment ◽  
Zn Alloy

High-current-density electropulsing was applied to a coarse-grained Cu–Zn alloy with two phases of α-phase and β′-phase. It was found that with an electropulsing treatment, ultrafine-grained (UFG) microstructure could be formed in the α-phase, but could not be formed in the β-phase. The results indicated that the formation of UFG microstructure was dependent on solid-state phase transformation. The main reason for the formation of UFG microstructure by electropulsing treatment resulted from the effect of a decrease in thermodynamic barrier and enhancement of nucleation rate in a current-carrying system, but not from the high heating and cooling rate during electropulsing treatment. The bulk UFG samples prepared by electropulsing treatment were free of porosity and contamination and had no large microstrain. It was reasonable to anticipate that a new method might be developed to produce ideal bulk UFG samples directly from the conventional coarse-grained materials by application of electropulsing.

Formation of nanophases in a Cu–Zn alloy under high current density electropulsing

2000 ◽  
Vol 15 (10) ◽  
pp. 2065-2068 ◽  
Author(s):  
W. Zhang ◽  
M. L. Sui ◽  
K. Y. Hu ◽  
D. X. Li ◽  
X. N. Guo ◽  
...  
Keyword(s):  
Current Density ◽  
High Current Density ◽  
High Energy ◽  
Coarse Grained ◽  
High Current ◽  
Transmission Electron ◽  
Average Grain Size ◽  
Before And After ◽  
Electropulsing Treatment ◽  
Zn Alloy

The microstructure of samples before and after a high current density electropulsing treatment was characterized by using high-resolution transmission electron microscopy. It has been found that in the coarse-grained Cu–Zn alloy subjected to the electropulsing treatment, two nanophases were formed, α–Cu(Zn) and β′–(CuZn), the average grain size of which is about 11 nm. A possible mechanism for the formation of nanophases was proposed. The experimental results indicated that electropulsing, as an instantaneous high-energy input, plays an important role in the nonequilibrium microstructural changes in materials and serves as a potential processing approach to synthesize nanostructured materials.

HRTEM Observation of α-Phase in Cu-Zn Alloy Annealed at Lower Temperature

2007 ◽  
Vol 26-28 ◽  
pp. 1279-1282 ◽  
Author(s):  
Koji Kato ◽  
Daisuke Hamatani ◽  
Kenji Matsuda ◽  
Tokimasa Kawabata ◽  
Yasuhiro Uetani ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Single Phase ◽  
Phase Decomposition ◽  
Β Phase ◽  
Α Phase ◽  
Transmission Electron ◽  
Hrtem Observation ◽  
Lower Temperature ◽  
Zn Alloy

It is known that the phase-decomposition process of 60/40 Cu-Zn alloy is so-called the bainitic transformation, and decomposition of α-phase from the β’-phase is as follow: β’ → α9R → αfcc. In this work,decomposition of α-phase from the β’ single phase of Cu-40.26at.%Zn alloy has been investigated by high-resolution transmission electron microscopy (HRTEM) to understand the phase transformation of this alloy. Especially, striations in the α-phase has been focused on the special feature for the change of the structure and hardening of this alloy during annealing. The result of a comparison between this alloy and the Si added alloy is also reported.

scholarly journals Über Verbindungen subvalenter Hauptgruppenmetallkationen mit Dithiolaten, 1. Mitteilung. Das dimorphe Blei(II)-l,l-dicyanoethylen-2,2-dithiolat: Darstellung und Kristallstrukturen / Compounds of Subvalent Main Group Metal Cations with Dithiolates, 1. Contribution. Dimorphie Lead(II) l,l-Dicyanoethylene-2,2-dithiolate: Preparation and Crystal Structures

1988 ◽  
Vol 43 (4) ◽  
pp. 389-398 ◽  
Author(s):  
Hans-U. Hummel ◽  
Hermann Meske
Keyword(s):  
Crystal Structures ◽  
Lone Pair ◽  
Metal Cations ◽  
Hydrothermal Conditions ◽  
Space Group ◽  
Β Phase ◽  
Α Phase ◽  
Small Crystals ◽  
Main Group Metal ◽  
Two Phases

Abstract By reaction of Pb(CH3COO)2 · 3H2O with Na2S2C=C(CN)2 · 3H2O in water, α-PbS2C=C(CN)2 is obtained. Hydrothermal conditions give small crystals of the α-and β-phase. The crystal structures of the two phases have been determined. The α-phase is monoclinic with space group P21/n and a = 11.879(5), b = 12.027(5), c = 4.655(1) Å, β = 96.94(3)°, Z = 4. The compound contains PbS2C4N2 molecules with Pb-S = 2.66 and 2.90 Å. Two molecules are connected to dimers with Pb···Pb = 4.44 Å. The β-phase also crystallizes monoclinically, space group C2/c, a = 9.613(1), b = 13.579(1), c -16.052(2) Å, β = 98.36°, and Z = 12. There are two independent lead positions, with the metals integrated in PbS2C = C(CN)2 groups with a stereochemically active lone-pair, and dimers Pb2(S2C4N2)2 with Pb···Pb distance = 3.80 Å.

scholarly journals Microstructural Evolution and Element Partitioning in the Phase Transformation of Ti-17 Alloy under Continuous Heating and Cooling Conditions

Metals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1054
Author(s):  
Xudong An ◽  
Xin Cai ◽  
Mingpan Wan ◽  
Min Lei ◽  
Chaowen Huang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Phase Transformation ◽  
Continuous Heating ◽  
Alloying Element ◽  
Heating And Cooling ◽  
Β Phase ◽  
Cooling Conditions ◽  
Α Phase ◽  
Element Partitioning ◽  
The Matrix

The microstructural evolution and alloying element partitioning in the α + β ↔ β phase transformation of Ti-17 alloy were explored under continuous heating and cooling conditions using the dilatometric method. Scanning electron microscopy and transmission electron microscopy were used to evaluate microstructural characteristics and trace alloying element partitioning behaviors occurring at different temperatures during heating and cooling. Results showed that the finer needle-like α phase first dissolved into the β phase in the matrix with increasing temperature, while the grain boundary α phase first coarsened and then transformed gradually into β phase during continuous heating. The dissolution of α phase of the alloy with the alloying element partitioning during continuous heating was observed. On the contrary, αGB formed at the prior β grain of the alloy during continuous cooling, which might be the nuclei of α colony, thus resulting in the formation of α colony in the matrix. As the temperature decreased, the elements’ concentrations in the α and β phases became increasingly varied due to element partition. Moreover, Al and Cr, which had higher diffusion coefficients than Mo, easily reached the concentration equilibrium of alloying elements in the α and β phases, respectively. The shrinkage of dilatometric curves during heating in the Ti-17 alloy are mainly attributed to the change of α-HCP (hexagonal close-packed) lattice to β-BCC (body-centered cubic) lattice; while the element partitioning during the β → α + β transformation plays an important role in the shrinkage of the dilatometric curves of the Ti-17 alloy during cooling.

Effect of Equal Channel Angular Pressing and Annealing on Corrosion Resistance of Cu-Zn Alloy

2013 ◽  
Vol 706-708 ◽  
pp. 78-81 ◽  
Author(s):  
D.R. Fang ◽  
F.F. Liu ◽  
Chun Liu
Keyword(s):  
Corrosion Resistance ◽  
Low Temperature ◽  
Equal Channel Angular Pressing ◽  
Annealing Treatment ◽  
Coarse Grained ◽  
Nacl Solution ◽  
Angular Pressing ◽  
Low Temperature Annealing ◽  
Ultrafine Grained ◽  
Zn Alloy

Cu-32wt.%Zn alloy was subjected to equal channel angular pressing (ECAP) and subsequent low temperature annealing treatment, and the corrosion resistance of the samples was investigated by potentiodynamic polarization measurements in 3.5% NaCl solution. The results show that the corrosion rate of the ultrafine-grained alloy decreases, in comparison with the coarse-grained alloy. Meanwhile, it is noted that the corrosion resistance of the sample subjected to ECAP can be further improved by relief annealing.

Formation of a Nanostructure in a Low-carbon Steel Under High Current Density Electropulsing

2002 ◽  
Vol 17 (5) ◽  
pp. 921-924 ◽  
Author(s):  
Yizhou Zhou ◽  
Wei Zhang ◽  
Manling Sui ◽  
Douxing Li ◽  
Guanhu He ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Current Density ◽  
High Current Density ◽  
Low Carbon Steel ◽  
Coarse Grained ◽  
High Current ◽  
Low Carbon ◽  
Crystalline Materials ◽  
Transmission Electron ◽  
Electropulsing Treatment

The microstructure of a low-carbon steel after high current density electropulsing treatment was characterized by high-resolution transmission electron microscopy. It was found that nanostructured γ-Fe could be formed in the coarse-grained steel after the electropulsing treatment. The mechanism of the formation of a nanostructure was discussed. It was thought that change of the thermodynamic barrier during phase transformation under electropulsing was a factor that cannot be neglected. It was reasonable to anticipate that a new method might be developed to produce nanostructured materials directly from the conventional coarse-grained crystalline materials by applying high current density electropulsing.

scholarly journals Softening Behaviors of Severely Deformed Zn Alloy Studied by the Nanoindentation

Coatings ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 803
Author(s):  
Jiangjiang Hu ◽  
Shuo Sun ◽  
Wei Zhang ◽  
Guangjian Peng ◽  
Shuang Han ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Room Temperature ◽  
Sliding Friction ◽  
Coarse Grained ◽  
Lower Stress ◽  
Friction Treatment ◽  
Ultrafine Grained ◽  
Dislocation Reaction ◽  
Deformed Layer ◽  
Zn Alloy

Zamak 3 alloy treatment by sliding-friction treatment (SFT) was investigated by nanoindentation to explore the influence of microstructure and strain rate on nanoscale deformation at room temperature. The results show that obvious material softening occurs in the ultrafine-grained (UFG) Zn alloy and strain-hardening happens in the twinning-deformed layer, respectively. It can be concluded that almost constant values of V in the UFG Zn alloy contribute to the dislocations moving along the grain boundary (GB) not cross the grain interior. In the twinning-deformed layer, the highly frequent dislocation–twinning boundary (TB) interactions are responsible for subsequent inverse Cottrell–Stokes at lower stress, which is quite different from dislocation–dislocation reaction inside the grain in their coarse-grained (CG) counterpart.

Electronic structure and chemical bonding of α- and β-Ta4AlC3 phases: Full-potential calculation

2008 ◽  
Vol 23 (9) ◽  
pp. 2350-2356 ◽  
Author(s):  
Wei Lu ◽  
Xiaohui Deng ◽  
Hai Wang ◽  
Haitao Huang ◽  
Lianlong He
Keyword(s):  
Electronic Structure ◽  
Chemical Bonding ◽  
First Principles ◽  
Heat Of Formation ◽  
Full Potential ◽  
Generalized Gradient ◽  
Β Phase ◽  
Α Phase ◽  
Two Phases ◽  
The Stability

First-principles total-energy and heat of formation calculations on α and β polymorphs of Ta4AlC3 have been made with a full-potential electronic structure program with the generalized gradient approximation, which shows that α phase is more stable than β phase. The charge transfer and chemical bonding of the two phases were investigated quantitatively by using Bader’s quantum theory of atoms in molecules (AIM). The results show that the bonding between Ta1-C2 is stronger in α phase than β phase, which leads to the stability of α phase.

scholarly journals Phase Transformations upon Ageing in Ti15Mo Alloy Subjected to Two Different Deformation Methods

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1230
Author(s):  
Kristína Bartha ◽  
Josef Stráský ◽  
Anna Veverková ◽  
Jozef Veselý ◽  
Jakub Čížek ◽  
...  
Keyword(s):  
High Pressure Torsion ◽  
Positron Annihilation Spectroscopy ◽  
Lattice Defects ◽  
Coarse Grained ◽  
Two Phase ◽  
Rotary Swaging ◽  
Α Phase ◽  
Ultrafine Grained ◽  
Isothermal Ageing ◽  
Α Particles

Ti15Mo alloy was subjected to two techniques of intensive plastic deformation, namely high pressure torsion and rotary swaging at room temperature. The imposed strain resulted in the formation of an ultrafine-grained structure in both deformed conditions. Detailed inspection of the microstructure revealed the presence of grains with a size of around 100 nm in both conditions. The microstructure after rotary swaging also contained elongated grains with a length up to 1 µm. Isothermal ageing at 400 °C and 500 °C up to 16 h was applied to both conditions to investigate the kinetics of precipitation of the α phase and the recovery of lattice defects. Positron annihilation spectroscopy indicated that the recovery of lattice defects in the β matrix had already occurred at 400 °C and, in terms of positron trapping, was partly compensated by the precipitation of incoherent α particles. At 500 °C the recovery was fully offset by the formation of incoherent α/β interfaces. Contrary to common coarse-grained material, in which the α phase precipitates in the form of lamellae, precipitation of small and equiaxed α particles occurred in the deformed condition. A refined two-phase equiaxed microstructure with α particles and β grain sizes below 1 μm is achievable by simple rotary swaging followed by ageing.

scholarly journals Microstructural Features and Surface Hardening of Ultrafine-Grained Ti-6Al-4V Alloy through Plasma Electrolytic Polishing and Nitrogen Ion Implantation

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 696
Author(s):  
Marina K. Smyslova ◽  
Roman R. Valiev ◽  
Anatoliy M. Smyslov ◽  
Iuliia M. Modina ◽  
Vil D. Sitdikov ◽  
...  
Keyword(s):  
Surface Layer ◽  
Ion Implantation ◽  
Surface Hardening ◽  
High Energy ◽  
Coarse Grained ◽  
Α Phase ◽  
Electrolytic Polishing ◽  
Ultrafine Grained ◽  
Phase Size ◽  
Plasma Electrolytic

This work studies a near-surface layer microstructure in Ti-6Al-4V alloy samples subjected to plasma electrolytic polishing (PEP) and subsequent high-energy ion implantation with nitrogen (II). Samples with a conventional coarse-grained (CG) structure with an average α-phase size of 8 μm and an ultrafine-grained (UFG) structure (α-phase size up to 0.35 μm) produced by equal channel angular pressing were used in the studies. Features of phase composition and substructure in the thin surface layers are shown after sequential processing by PEP and II of both substrates with CG and UFG structures. Irrespective of a substrate structure, the so-called “long-range effect” was observed, which manifested itself in enhanced microhardness to a depth of surface layer up to 40 μm, exceeding the penetration distance of an implanted ion he. The effect of a UFG structure on depth and degree of surface hardening after PEP and ion-implantation is discussed.

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