Internal Stresses in Nanocrystalline Nickel and Nickel-Iron Alloys

2012 ◽  
Vol 706-709 ◽  
pp. 1607-1611 ◽  
Author(s):  
J.D. Giallonardo ◽  
Uwe Erb ◽  
G. Palumbo ◽  
G.A. Botton ◽  
C. Andrei
Keyword(s):  
Grain Size ◽  
Internal Stress ◽  
Structural Difference ◽  
Intrinsic Stress ◽  
Internal Stresses ◽  
Second Phase ◽  
Nickel Iron ◽  
Second Phase Particles ◽  
Second Phases ◽  
Rule Out

Nanocrystalline metals are often produced in a state of stress which can adversely affect certain properties, e.g. corrosion resistance, wear, fatigue strength, etc. This stress is referred to as internal or “intrinsic” stress since it is not directly caused by applied loads. The structural causes of these stresses in nanocrystalline materials are not fully understood and are therefore an area of particular interest. The internal stresses of nanocrystalline Ni and Ni-16wt%Fe were measured and found to increase with the addition of iron. Characterization using HR-TEM revealed no signs of porosity, second phase particles, or a high density of dislocations. Both materials possessed well defined high-angle grain boundaries. The main structural difference between the two materials was found to be grain size and correspondingly, a decrease in grain size resulted in an increase in internal stress which supports the applicability of the coalescence theory. The current study also provides evidence to rule out the effect of voids (or porosity), dislocations, and second phases as possible causes of internal stress.

Structure of second phases in TiAl alloys containing Cr and B

1991 ◽  
Vol 49 ◽  
pp. 576-577
Author(s):  
Ernest L. Hall ◽  
Shyh-Chin Huang
Keyword(s):  
Grain Size ◽  
Second Phase ◽  
Structure And Properties ◽  
Tial Alloys ◽  
Second Phases ◽  
Interstitial Elements

Addition of interstitial elements to γ-TiAl alloys is currently being explored as a method for improving the properties of these alloys. Previous work in which a number of interstitial elements were studied showed that boron was particularly effective in refining the grain size in castings, and led to enhanced strength while maintaining reasonable ductility. Other investigators have shown that B in γ-TiAl alloys tends to promote the formation of TiB2 as a second phase. In this study, the microstructure of Bcontaining TiAl alloys was examined in detail in order to describe the mechanism by which B alters the structure and properties of these alloys.

Internal stresses due to dislocation walls around second phase particles

1979 ◽  
Vol 10 (7) ◽  
pp. 855-860 ◽  
Author(s):  
C. Carry ◽  
S. Dermarkar ◽  
J. L. Strudel ◽  
B. C. Wonsiewicz
Keyword(s):  
Internal Stresses ◽  
Second Phase ◽  
Second Phase Particles ◽  
Dislocation Walls

scholarly journals Influence of Grain Refinement on Oxidation Behavior of Two-Phase Cu–Cr Alloys at 973–1,073 K in Air

2016 ◽  
Vol 35 (10) ◽  
pp. 1005-1011
Author(s):  
T. J. Pan ◽  
J. Chen ◽  
Y. X. He ◽  
W. Wei ◽  
J. Hu
Keyword(s):  
Grain Size ◽  
Spatial Distribution ◽  
Oxidation Behavior ◽  
Second Phase ◽  
Two Phase ◽  
Reactive Component ◽  
Parabolic Law ◽  
Second Phase Particles ◽  
Kinetics Of ◽  
Lower Oxidation

AbstractThe oxidation behavior of grain-refined Cu–7.0 Cr alloy (GR Cu–7.0 Cr) in air at 973–1,073 K was investigated in comparison with normal casting Cu–7.0 Cr alloy (CA Cu–7.0 Cr). The oxidation of CA Cu–7.0 Cr alloy nearly followed parabolic law, while the oxidation kinetics of GR Cu–7.0 Cr slightly deviated from parabolic law. Both alloys almost produced multi-layered scales consisting of the outer layer of CuO and the inner layer of mixed Cr2O3 and Cu2O oxides plus internal oxidation zones of chromium. The grain-refined Cu–7.0 Cr alloy produced a more amount of Cr2O3 in the inner layer of the scale, and thus was oxidized at much lower oxidation rate than that of CA Cu–7.0 Cr with normal grain size. The experimental results indicated that the differences in oxidation behavior between two alloys may be ascribed to the different size and spatial distribution of the second-phase particles and the reactive component contents in localized zone.

Optimization of Particle Size and Distribution by Hydrostatic Extrusion

2007 ◽  
Vol 561-565 ◽  
pp. 869-872 ◽  
Author(s):  
Małgorzata Lewandowska ◽  
Kinga Wawer
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Grain Size ◽  
Aluminium Alloys ◽  
Hydrostatic Extrusion ◽  
Nanometer Scale ◽  
Second Phase ◽  
Size Refinement ◽  
Second Phase Particles ◽  
Fatigue And Fracture

Hydrostatic extrusion (HE) as a method of metals forming is known for about 100 years. Recently, it has been utilized as an efficient way of grain size refinement down to nanometer scale. In the case of engineering metals, HE processing alters not only grain size but also second phase particles such as intermetallic inclusions and precipitates. During HE processing, these particles significantly change their size, shape and spatial distribution. These changes are accompanied by improvement in properties of processed metals such as fatigue and fracture toughness. In the present work, changes of second phase particles induced by HE are described in a quantitative way for aluminium alloys. Their impact on mechanical properties is also discussed.

High-resolution TEM and analytical study of second-phase particles in Al2O3

1983 ◽  
Vol 41 ◽  
pp. 46-47
Author(s):  
K. J. Morrissey ◽  
Y. Kouh ◽  
C. B. Carter
Keyword(s):  
Grain Size ◽  
High Resolution ◽  
Grain Boundaries ◽  
Hot Pressing ◽  
Analytical Study ◽  
Second Phase ◽  
Initial Powder ◽  
Compact Density ◽  
Second Phase Particles ◽  
High Resolution Tem

The influence of additives such as MgO, NiO, and ZrO2 and impurities such as Na, K, and Ca on the sintering of alumina compacts has been the focus of a considerable amount of research. Since these additives affect compact density and grain size it is of interest to determine the behavior of the elements during processing. That is, it is important to know whether Ca and Mg segregate to grain boundaries or are located in the second-phase particles. Current results suggest that Ca is found uniformly at the grain boundaries and that Mg is accommodated in the second-phase particles.The present investigation is concerned with identifying second-phase particles in different commercially-produced Al2O3 compacts and studying both their structure and composition. Preliminary results have been discussed previously. The investigation has dealt mainly with two different alumina compacts. One compact was prepared from an initial powder containing 0.25% MgO, a small amount of intentionally added Ni, and was prepared by hot pressing.

Static Recrystallization of FeAl in the Presence of Second Phase Particles: Experimental and Modeling Investigations

2004 ◽  
Vol 467-470 ◽  
pp. 975-980 ◽  
Author(s):  
Sofiane Guessasma ◽  
E. Suzon ◽  
N. Rouag ◽  
Thierry Grosdidier
Keyword(s):  
Grain Size ◽  
Static Recrystallization ◽  
Particle Distribution ◽  
Grain Morphology ◽  
Second Phase ◽  
Significant Control ◽  
Second Phase Particles ◽  
Particle Alignment ◽  
Oxide Particles ◽  
Ods Alloy

This paper presents some preliminarily results on microstructure modifications associated with static recrystallization in an ODS alloy. The morphology of the grains issued from static recrystallization is influenced significantly by the alignment of the oxide particles in the as-extruded starting material. Grain growth modeling confirms the effect of particle alignment on the grain morphology and shows significant control of the particle distribution nature and the initial grain size on the grain anisotropy.

Particle-Stimulated Nucleation of Recrystallization for Grain-Size Control in 01420 Al-Li Alloy

2007 ◽  
Vol 546-549 ◽  
pp. 889-892 ◽  
Author(s):  
Ling Ying Ye ◽  
Xin Ming Zhang ◽  
Yu Xuan Du ◽  
Zhi Hui Luo
Keyword(s):  
Grain Size ◽  
Grain Refinement ◽  
Size Control ◽  
S Phase ◽  
Second Phase ◽  
Β Phase ◽  
Nucleation Sites ◽  
Second Phase Particles ◽  
Average Grain Size ◽  
Grain Size Control

Grain refinement of 01420 Al-Li alloy through particle stimulated nucleation(PSN) of recrystallization is reported. The results showed that the rolling in the overaged 01420 Al-Li alloy resulted in the formation of the deformation zones associated with the second phase particles larger than 0.80 μm which can act as the nucleation sites for recrystallized grains. The precipitates larger than 0.80 μm are sticked shaped S-phase(Al2MgLi) and globular β-phase(Mg2Al3), and the density of β-phase particles is approximately as two to three times as the S-phase particles. The S-phase particles can’t be as PSN sites since they were broken to small dispersoid particles during rolling. The average grain size of 01420 Al-Li alloy solutioned at 470°C for 2h, aged at 300 °C for 48h, 81% rolled at 300 °C and finally recrystallized at 500 °C for 10min is approximately 10 μm.

Microstructural Evolution of Nuclear Power Steel A508-III in the Creep Process at 800°C

2016 ◽  
Vol 853 ◽  
pp. 153-157
Author(s):  
Zhi Gang Xie ◽  
Yan Ming He ◽  
Jian Guo Yang ◽  
Zeng Liang Gao
Keyword(s):  
Electron Microscopy ◽  
Phase Transition ◽  
Grain Size ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
Microstructural Evolution ◽  
Creep Process ◽  
Second Phase ◽  
Creep Stage ◽  
Second Phase Particles

The A508-III steel is widely used to manufacture the lower heads of commercial reactor pressure vessels (RPV). In severe accident, the reactor core in the RPV begins to melt and meanwhile the technology of in-vessel retention (IVR) exerts its role. In this case the inner surface of RPV will expose to temperatures over a phase transition temperature. However, the significant nonlinear feature of creep curve of A508-III steel suffered heterogeneous damage was not studied. In this work, the creep tests were performed for the steel at the phase transition temperature of 800°C. The microstructural evolution at different creep stages was characterized by scanning electron microscopy and transmission electron microscopy. The results show that, at the second creep stage, more coarsening second phase particles occur in the steel. With the creep processing, the grain size and diameter of second phase particles increase. At the tertiary creep stage, the grain size increases significantly, and the second phase particles coarsen during the process of atom migration. In addition, Micro-cracks and voids also come into being in the situation and they can become larger by combing each other during the creep process. At this stage, the growth of cavities and second phase particles coarsening become the main mechanism of creep damage. The trend of microstructural evolution is consistent with the creep constitutive equation obtained for the A508-III steel at the phase transition temperature of 800°C. The results obtained provide indispensable foundation to establish the relationship between the macroscopic creep and microscopic damage.

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