scholarly journals Influence of heat treatment on corrosion resistance of Mg-Al-Zn alloy processed by severe plastic deformation

2018 ◽  
Vol 8 (1) ◽  
pp. 391-394 ◽  
Author(s):  
Mária Zemková ◽  
Róbert Král ◽  
Jakub Čížek ◽  
Jana Šmilauerová ◽  
Peter Minárik
Keyword(s):  
Corrosion Resistance ◽  
Dislocation Density ◽  
Electrochemical Properties ◽  
Polarization Resistance ◽  
Electron Backscatter Diffraction ◽  
Positron Annihilation Spectroscopy ◽  
Second Phase ◽  
Angular Pressing ◽  
Second Phase Particles ◽  
Backscatter Diffraction

Abstract The effect of subsequent annealing on the electrochemical properties of an AZ31 magnesium alloy processed by extrusion and equal channel angular pressing (ECAP) was investigated. The electrochemical properties were evaluated using potentiodynamic tests in corrosion solution of 0.1 M sodium chloride. The electrochemical changes after annealing were correlated with microstructure evolution. The microstructure was analyzed by scanning electron microscope (SEM) and electron backscatter diffraction (EBSD). The evolution of dislocation density was determined by positron annihilation spectroscopy (PAS). The annealing for 1h at temperatures ranging from 150∘C to 250∘C resulted in higher polarization resistance in all cases. The polarization resistance of sample annealed at 250∘C was ~17% higher compared to just ECAPed material. Combination of gradual decrease of dislocation density, grain growth and second phase particles dissolution played the crucial role in the corrosion resistance improvement.

Microstructure, Texture and Property of Interstitial-Free (IF) Steel after Ultra-Fast Annealing

2015 ◽  
Vol 1120-1121 ◽  
pp. 1003-1007 ◽  
Author(s):  
He Long Cai ◽  
Jun Sheng Mou ◽  
Zi Yong Hou
Keyword(s):  
Electron Microscopy ◽  
Electron Backscatter Diffraction ◽  
Second Phase ◽  
Interstitial Free ◽  
If Steel ◽  
Steel Sheets ◽  
Transmission Electron ◽  
Second Phase Particles ◽  
Backscatter Diffraction ◽  
Equiaxed Grain

In this paper, common continous annealing (CCA) and ultra-fast annealing (UFA) were carried out on a cold-rolled interstitial-free (IF) steel, respectively. The microstructure of the annealed IF steel was characterized by means of scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The mechanical property was examined using tensile test. The optimum annealing process parameters were then obtained. The results showed that, the recrystallization occurs at the temperature in the range of 780-830°C. The fraction of equiaxed grain increases with the annealing temperature increasing. The well combination of mechanical properties and formability was obtained when the IF steel annealed at 820°C, which was the result of the fine dispersed second phase particles. {001} texture was absent in the whole thickness of all the annealed IF steels. In addition, the strongest γ texture was found, and this was a potential way to improve the deep drawability of annealed steel sheets.

scholarly journals Second Phase Precipitation in As-Welded and Solution Annealed Alloy 22 Welds

2006 ◽  
Vol 128 (4) ◽  
pp. 644-647 ◽  
Author(s):  
Bassem S. El-Dasher ◽  
Sharon G. Torres
Keyword(s):  
Large Scale ◽  
Thick Plate ◽  
Electron Backscatter Diffraction ◽  
Second Phase ◽  
Solution Annealing ◽  
Annealed Alloy ◽  
Precipitation Characteristics ◽  
Alloy 22 ◽  
Tcp Phases ◽  
Backscatter Diffraction

The precipitation characteristics of tetrahedrally close-packed (TCP) phases during the welding and the subsequent solution annealing process of Alloy 22 1 1∕2in. thick plate double-U prototypical welds are investigated. Electron backscatter diffraction was used to provide large scale microstructural observation of the weld cross section, and scanning electron microscopy was used to map the location of the TCP phases. Analysis shows that TCP precipitation occurs congruent to the weld passes, with the solution annealing reducing the sizes of coarser precipitates.

Recrystallization in Ultra-Fine Grain Structures of AA3104 Alloy Processed by ECAP and HPT

2012 ◽  
Vol 715-716 ◽  
pp. 346-353
Author(s):  
H. Paul ◽  
T. Baudin ◽  
K. Kudłacz ◽  
A. Morawiec
Keyword(s):  
High Pressure Torsion ◽  
Deformation Mode ◽  
Second Phase ◽  
Orientation Measurement ◽  
Angular Pressing ◽  
Second Phase Particles ◽  
Average Grain Size ◽  
The Matrix ◽  
Electron Microscopes ◽  
Different Strains

The objective of this study was to determine the effect of deformation mode on recrystallization behavior of severely deformed material. Commercial purity AA3104 aluminum alloy was deformed via high pressure torsion and equal channel angular pressing to different strains and then annealed to obtain the state of partial recrystallization. The microstructure and the crystallographic texture were analysed using scanning and transmission electron microscopes equipped with orientation measurement facilities. The nucleation of new grains was observed in bulk recrystallized samples and during in-situ recrystallization in the transmission microscope. Irrespective of the applied deformation mode, a large non-deformable second phase particles strongly influenced strengthening of the matrix through deformation zones around them. It is known that relatively high stored energy stimulates the nucleation of new grains during the recrystalization. In most of the observed cases, the growth of recrystallized grains occurred by the coalescence of neighboring subcells. This process usually led to nearly homogeneous equiaxed grains of similar size. The diameter of grains in the vicinity of large second phase particles was only occasionally significantly larger than the average grain size. Large grains were most often observed in places far from the particles. TEM orientation mapping from highly deformed zones around particles showed that orientations of new grains were not random and only strictly defined groups of orientations were observed.

Effect of Bi Addition on the Corrosion Behavior of Zirconium Alloys

2013 ◽  
Author(s):  
M. Y. Yao ◽  
B. X. Zhou ◽  
Q. Li ◽  
W. P. Zhang ◽  
L. Zhu ◽  
...  
Keyword(s):  
Solid Solution ◽  
Corrosion Resistance ◽  
Corrosion Behavior ◽  
Mass Fraction ◽  
Zirconium Alloys ◽  
Deionized Water ◽  
Second Phase ◽  
Micro Structure ◽  
Second Phase Particles ◽  
Structure Observation

In order to investigate systematically the effect of Bi addition on the corrosion resistance of zirconium alloys, different zirconium-based alloys, including Zr-4 (Zr-1.5Sn-0.2Fe-0.1Cr), S5 (Zr-0.8Sn-0.35Nb-0.4Fe-0.1Cr), T5 (Zr-0.7Sn-1.0Nb-0.3Fe-0.1Cr) and Zr-1Nb, were adopted to prepare the zirconium alloys containing Bi of 0∼0.5% in mass fraction. These alloys were denoted as Zr-4+xBi, S5+xBi, T5+xBi and Zr-1Nb+xBi, respectively. The corrosion behavior of these specimens was investigated by autoclave testing in lithiated water with 0.01 M LiOH or deionized water at 360°C/18.6 MPa and in superheated steam at 400 °C/10.3 MPa. The micro structure of the alloys was examined by TEM and the second phase particles (SPPs) were analyzed by EDS. Micro structure observation shows that the addition of Bi promotes the precipitation of Sn as second phase particles (SPPs) because Sn is in solid solution in α-Zr matrix in Zr-4, S5 and T5 alloys. The concentration of Bi dissolved in α-Zr matrix increase with the increase of Nb in the alloys, and the excess Bi precipitates as Bi-containing SPPs. The corrosion results show that the effect of Bi addition on the corrosion behavior of different zirconium-based alloys is very complicated, depending on their compositions and corrosion conditions. In the case of higher Bi concentration in α-Zr, the zirconium alloys exhibit better corrosion resistance. However, in the case of precipitation of Bi-containing SPPs, the corrosion resistance gets worse. This indicates that the solid solution of Bi in α-Zr matrix can improve the corrosion resistance, while the precipitation of the Bi-containing SPPs is harmful to the corrosion resistance.

Effects of Heat Treatment on Corrosion of Zr-1.0Nb-1.0Sn-0.1Fe

2005 ◽  
Vol 475-479 ◽  
pp. 1401-1404
Author(s):  
J.H. Baek ◽  
Yong Hwan Jeong
Keyword(s):  
Heat Treatment ◽  
Corrosion Resistance ◽  
Annealing Time ◽  
Tetragonal Phase ◽  
Second Phase ◽  
Tetragonal Zro2 ◽  
Monotectoid Reaction ◽  
Second Phase Particles ◽  
Mean Size ◽  
The Mean

The effects of annealing at 570oC and 640oC on the microstructural and corrosion characteristics for Zr-1.0Nb-1.0Sn-0.1Fe alloy were elucidated. After annealing at 570oC below the temperature of a monotectoid reaction in the Zr-Nb system, both orthorhombic Zr3Fe and the bcc b-Nb particles were uniformly found and the mean size of the second phase particles was increased with an increasing of the annealing time. In the case of an annealing at 640oC for 2 h above the monotectoid reaction temperature, the Zr3Fe was observed intermittently and after a longer annealing of 1000 h the b-Zr particles were well developed. The corrosion resistance after the 570oC anneal was improved as the annealing time increased, while that after the 640oC anneal decreased as the annealing time increased. The fraction of the tetragonal phase within the ZrO2 oxide increased as the corrosion resistance was improved. It was concluded that the equilibrium Nb concentration and the formation of the tetragonal ZrO2 due to the b-Nb phase would lead to improving the corrosion resistance of the alloy.

Effect of ECAP Pass on Corrosion Behavior of High-Al Content Magnesium Alloys

2013 ◽  
Vol 747-748 ◽  
pp. 270-275
Author(s):  
Qiang Fan ◽  
Wei Liang ◽  
Li Ping Bian ◽  
Man Qing Cheng
Keyword(s):  
Corrosion Resistance ◽  
Corrosion Behavior ◽  
Performance Test ◽  
Corrosion Current ◽  
Second Phase ◽  
Al Content ◽  
Microstructure Observation ◽  
Angular Pressing ◽  
The Matrix ◽  
High Al Content

In view of low strength and poor corrosion resistance of Mg alloys, a Mg-12Al-0.7Si alloy was designed, fabricated and subjected to equal channel angular pressing (ECAP) in order to refine the microstructure. Microstructure observation and electrochemical performance test were conducted to investigate the influence of the microstructural variation subjected to multi-pass ECAP processing on the corrosion behavior of the alloy. The results showed that both α-Mg matrix and β-Mg17Al12of the alloy were significantly refined after processing for different passes (2,4,6,8) through route BC, and the 4-pass ECAPed alloy in 3.5% NaCl solution presents the lowest weight loss, lower corrosion current and higher corrosion potential in the polarization curves. The reason for high corrosion resistance of 4-pass ECAPed alloy and the effects of grain size of the matrix and the particle size, distribution of second phase and dynamic precipitates on corrosion behavior of the alloy were discussed.

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