Grain growth in nanocomposite Ti–B–N films during deposition: The effect of amorphous phase precipitation

2006 ◽  
Vol 21 (1) ◽  
pp. 82-87 ◽  
Author(s):  
Z-J. Liu ◽  
Y.H. Lu ◽  
Y.G. Shen
Keyword(s):  
Grain Size ◽  
Grain Boundaries ◽  
Grain Growth ◽  
Amorphous Phase ◽  
Amorphous Materials ◽  
Film Deposition ◽  
Growth Exponent ◽  
Experimental Investigations ◽  
Phase Precipitation ◽  
X Ray

Experimental investigations by high-resolution transmission electron microscopy, x-ray photoelectron spectroscopy, and x-ray diffraction show that during sputter-deposition of Ti–B–N films amorphous materials, e.g., TiB2 and BN, are found to precipitate at the grain boundaries, resulting in a decrease in grain size when the boron concentration or the amount of amorphous phase increases. To understand these experimental observations, we have used Monte Carlo simulations to investigate the effect of the amorphous phase precipitation on grain growth during film deposition. Our simulations demonstrate that the precipitation of amorphous phase at the grain boundaries can lower the grain growth exponent and thus leads to a low grain growth rate, particularly in the case of large amounts of amorphous phase. As a result, an exponential decay in grain size with the amount of amorphous phase can be observed in our simulations, which is in reasonably good agreement with the experimental results.

A High-Temperature Study of Phase Precipitation in Superalloys

1959 ◽  
Vol 3 ◽  
pp. 365-375
Author(s):  
John F. Radavich
Keyword(s):  
Heat Treatment ◽  
Electron Diffraction ◽  
Grain Boundaries ◽  
Fluorescence Analysis ◽  
Phase Precipitation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Suitable Heat Treatment ◽  
Nickel Base ◽  
High Temperature Study

AbstractMany of the iron- and nickel-base superalloys exhibit brittle properties on heat treatment, welding, or other fabrication processes at temperatures of about 2000°F or higher. Studies have been carried out by means of electron microscopy, electron diffraction, and X-ray diffraction and fluorescence analysis of the precipitation in the metal and in an isolated form.Results of the electron microscope study of the surface of the metal show a grain boundary constituent to be present which increases in amount as the temperature is increased. Studies on the isolated residue of such samples show a very thin “featherlike” film to be located at the grain boundaries and enclosing the grains. Electron diffraction, X-ray diffraction, and X-ray fluorescence analysis studies of the thin films indicate that they are a TiC phase with very little alloying elements in solution.At temperatures above 2000°F the thin film becomes quite thick and tends to force the grains apart. It is believed that this form of the TiC phase promotes the severe embrittling nature of these alloys at high temperatures. Suitable heat treatment at lower temperatures causes the TiC film to agglomerate and the grain boundaries become “tight,” and a more ductile condition results.

Effect of Isothermal Sintering Time on the Properties of the Ceramic Composite ZrO2-Al2O3

2006 ◽  
Vol 530-531 ◽  
pp. 526-531 ◽  
Author(s):  
Claudinei dos Santos ◽  
L.H.P. Teixeira ◽  
J.K.M.F. Daguano ◽  
Kurt Strecker ◽  
Carlos Nelson Elias
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Ceramic Composite ◽  
Growth Exponent ◽  
Microstructural Development ◽  
Growth Equation ◽  
Sintering Time ◽  
Al2o3 Composite ◽  
Average Grain Size ◽  
Grain Size Distributions

In this work the influence of isothermal sintering time on the microstructural development of ZrO2-Al2O3 composite was studied. Powder mixture of ZrO2 containing 20 wt% Al2O3 was prepared by milling, compaction and sintering at 16000C, in air. The isothermal sintering time at 16000C was varied between 0 and 1440 min. The sintered samples were characterized in terms of phase composition and relative density. Their microstructures were characterized by grain size distributions and average grain size. These results were evaluated using the classic grain growth equation as a function of time, determining the grain growth exponent of these materials. Furthermore, the microstructural aspects were related to the mechanical properties (Vicker’s hardness and fracture toughness) of these composites.

X-Ray Diffraction Studies of Grain Growth in an Ultra-fine Grained 6060 Aluminium Alloy

2007 ◽  
Vol 558-559 ◽  
pp. 1299-1304 ◽  
Author(s):  
Børge Forbord ◽  
Ragnvald H. Mathiesen ◽  
Hans Jørgen Roven
Keyword(s):  
Aluminium Alloy ◽  
Grain Growth ◽  
Effective Strain ◽  
Growth Curves ◽  
Grain Structure ◽  
Growth Exponent ◽  
X Ray Diffraction ◽  
X Ray ◽  
Fine Grained ◽  
Angular Pressing

In-situ synchrotron X-ray diffraction has been applied in order to study grain growth in an ultra-fine grained (D~400 nm) 6060 aluminium alloy at 270°C. The submicron grain structure was produced by Equal Channel Angular Pressing (ECAP) to an effective strain of ~6 without rotation of the billet. As the material was textured after ECAP, the initial stages of grain growth were seldom detected, but in the grain size interval available for studies a grain growth exponent of 3.6±0.3 was obtained. By interpolation of the grain growth curves to D=D0 (determined by EBSD) the effect of growth on the softening of the alloy was estimated. The interpolated average curve indicates that the initial stages of softening are not due to uniform grain growth, but rather reconfiguration and annihilation of dislocations as well as overaging of hardening precipitates.

Influence of Annealing Time on Microstructure of Ni-W Alloys

2013 ◽  
Vol 747-748 ◽  
pp. 613-618
Author(s):  
Qiao Zhang ◽  
Shu Hua Liang ◽  
Chen Zhang ◽  
Jun Tao Zou
Keyword(s):  
Electron Microscopy ◽  
Solid Solution ◽  
Grain Size ◽  
Grain Boundaries ◽  
Annealing Time ◽  
Single Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Average Grain Size ◽  
Scanning Electron

The as-cast Ni-W alloys with 15wt%W, 25wt%W and 30wt%W were annealed in hydrogen at 1100. The effect of the annealing time on the microstructure of Ni-W alloys was studied, and the phase constituents and microstructure of annealed Ni-W alloys were characterized by the X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that no any phase changed for Ni-15%W, Ni-25%W and Ni-30%W alloys annealed for 60 min, 90 min and 150 min, which were still consisted of single-phase Ni (W) solid solution. However, microstructure had a significant change after annealing. With increase of annealing time, the microstructure of Ni-15%W alloy became more uniform after annealing for 90 min, and the average grain size was 95μm, whereas the grain size of Ni-15%W alloy increased significantly after annealing for 150 min. For Ni-25%W and Ni-30%W, there was no obvious change on the grain size with increase of annealing time, and the amount of oxides at grain boundaries gradually reduced. After annealing for 150 min, the impurities at grain boundaries almost disappeared. Subsequently, the annealing at 1100 for 150 min was beneficial for the desired microstructure of Ni-25%W and Ni-30%W alloys.

Effect of titanium addition on a Ni-Al-Co alloy

1990 ◽  
Vol 48 (4) ◽  
pp. 938-939
Author(s):  
L. S. Lin ◽  
G. W. Levan ◽  
S. M. Russell ◽  
C. C. Law
Keyword(s):  
Grain Size ◽  
Grain Boundaries ◽  
Room Temperature ◽  
Volume Fraction ◽  
X Ray Diffraction ◽  
Titanium Addition ◽  
X Ray ◽  
Gamma Prime ◽  
Room Temperature Ductility ◽  
Ti Addition

AEM examinations of a NiAlCo alloy of composition Ni-29 at.% Al-21 at.% Co after room temperature compression show that the microstructure consists of a twinned tetragonal matrix (L10, marked A in Figure 1a) and ordered fcc gamma prime precipitates (L12, marked B in Figure 1a) along grain boundaries. The compressive yield strengths of this alloy at room temperature and 760°C are 754 MPa and 163 MPa respectively. It also has superior room temperature ductility as compared to binary NiAl. An addition of 5 at.% Ti at the expense of Ni was made to this alloy in order to increase the yield strengths. The quarternary alloy shows compressive yield strengths of 976 MPa and 403 MPa at room temperature and 760°C, respectively, indicating that the Ti addition is having the desired effect.Comparison of the microstructures of the two alloys after room temperature compression (Figures la and lb) shows that the Ti containing alloy has a smaller grain size. X-ray diffraction data indicate that the gamma prime volume fraction increases from 10% to 20% as the result of the Ti addition. Titanium was also found to stabilize the B2 matrix (marked A in Figure lb) as no tetragonal L10 phase was found. All precipitates along grain boundaries were identified by micro-diffraction to be gamma prime.

Superplasticity and Microstructural Evolution of a Large-Grained Mg Alloy

2000 ◽  
Author(s):  
Yi Liu ◽  
Kelly Shue ◽  
Xin Wu ◽  
Zhicheng Li ◽  
Yongbo Xu
Keyword(s):  
Grain Size ◽  
Electron Microscope ◽  
Strain Rate ◽  
Grain Boundaries ◽  
Grain Growth ◽  
Large Angle ◽  
Dislocation Creep ◽  
Rate Dependent ◽  
Average Grain Size ◽  
Elongation To Failure

Abstract Commercial Mg-3Al-Zn alloys (AZ31) with initial large grains (∼250μm) has been found superplastic at a strain rate of 0.5×10−2s−1 and at 350–500 C. The maximum elongation to failure of 170% at 500°C was obtained. Scanning electron microscope observations with electron back-scattering diffraction technique (SEM-EBSD) indicate that during deformation significant grain size reduction occurred, the average grain size reduced from about 250μm before deformation to about 50μm after deformation at temperatures from 300 C to 400°C, it reduced to about 100μm if deformed at above 400°C. The observed grain refinement at lower temperature and grain growth at higher temperature during the superplastic deformation is believed to be the result of the competing processes between dynamic recrystallization and dynamic grain growth, which are temperature and strain rate dependent. Transmission electron microscope (TEM) observations indicates that most of the grain boundaries are large-angle grain boundaries, though small amount of small-angle grain boundaries are also observed. The density of dislocations in the grains is very low in these superplasticlly deformed samples. It is evident that grain boundary played a role as the source and sink of the dislocation, being responsible for combined dislocation creep and diffusional creel. Therefore, the very large elongation obtained at the very high strain rates and high temperatures is attributed to dynamic dislocation hardening, recovery and recrystallization.

High-temperature stability of nanocrystalline structure in a TiAl alloy prepared by mechanical alloying and hot isostatic pressing

1998 ◽  
Vol 13 (12) ◽  
pp. 3399-3410 ◽  
Author(s):  
O. N. Senkov ◽  
N. Srisukhumbowornchai ◽  
M. L. Öveçoglu ◽  
F. H. Froes
Keyword(s):  
Grain Size ◽  
Mechanical Alloying ◽  
Grain Growth ◽  
Hot Isostatic Pressing ◽  
Nanocrystalline Structure ◽  
Temperature Stability ◽  
Growth Exponent ◽  
Pinning Force ◽  
High Temperature Stability ◽  
Isostatic Pressing

A fully dense nanocrystalline compact of the Ti–47Al–3Cr (at. %) alloy was produced by mechanical alloying and hot isostatic pressing at 725 °C. Microstructure characteristics and grain growth behavior of this compact were studied after annealing for up to 800 h in the temperature range of 725 to 1200 °C, using analytical transmission electron microscopy techniques. The temperature and time dependencies of the grain sizes and the grain size distributions were determined. The grain growth occurred, with a timeand temperature-invariant single-peak grain size distribution (when normalized by the mean grain size), which was consistent with normal grain growth. The experimentally measured grain growth exponent decreased from 10 to 4.6 when the temperature was increased. The grain growth kinetics was described by a single thermally activated rate process limited by a permanent pinning force on the grain boundaries. The microhardness decreased on annealing and followed the Hall–Petch relationship with the parameters Hυo = 5.8 GPa and KH = 1.6 MPa m0.5.

scholarly journals Experimental grain growth of quartz aggregates under wet conditions and its application to deformation in nature

2019 ◽  
Author(s):  
Junichi Fukuda ◽  
Hugues Raimbourg ◽  
Ichiko Shimizu ◽  
Kai Neufeld ◽  
Holger Stünitz
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Growth Parameters ◽  
Growth Exponent ◽  
High Porosity ◽  
Grain Sizes ◽  
Two Samples ◽  
Growth Laws ◽  
Water Fugacity ◽  
Quartz Aggregates

Abstract. The grain growth of quartz was investigated using two samples of quartz (powder and quartzite) with water under pressure and temperature conditions of 1.0–2.5 GPa and 800–1100 °C. The compacted powder preserved a large porosity, which caused a slower grain growth than in the dense quartzite. We assumed a grain-growth law of dn-d0n = k0 fH2Or exp⁡(−Q/RT)t with grain size d (µm) at time t (second), initial grain size d0 (µm), growth exponent n, a constant k0 (µmn MPa−r s−1), water fugacity fH2O (MPa) with the exponent r, activation energy Q (kJ/mol), gas constant R, and temperature T in Kelvin. The parameters we obtained were n = 2.5 ± 0.4, k0 = 10−8.8 ± 1.4, r = 2.3 ± 0.3, and Q = 48 ± 34 for the powder, and n = 2.9 ± 0.4, k0 = 10−5.8 ± 2.0, r = 1.9 ± 0.3, and Q = 60 ± 49 for the quartzite. The grain-growth parameters obtained for the powder may be of limited use because of the high porosity of the powder with respect to crystalline rocks, even if the differences between powder and quartzite vanish when grain sizes reach ~ 70 µm. Extrapolation of the grain-growth laws to natural conditions indicates that the contribution of grain growth to plastic deformation in the middle crust may be small. However, grain growth might become important for deformation in the lower crust when the strain rate is

scholarly journals EBSD characterization of the effect of welding parameters on HAZ of AISI409

2012 ◽  
Vol 48 (1) ◽  
pp. 115-121 ◽  
Author(s):  
E. Ranjbarnodeha ◽  
S. Weissb ◽  
S. Hankeb ◽  
A. Fischerb
Keyword(s):  
Grain Size ◽  
Grain Boundaries ◽  
Grain Growth ◽  
Welding Parameters ◽  
Final State ◽  
Ferritic Stainless Steels ◽  
Stress Relieving ◽  
Complete Recrystallization ◽  
Local Misorientation

One of the main problems during the welding of ferritic stainless steels is severe grain growth in the heat affected zone (HAZ). In the present study, microstructural characteristics of tungsten inert gas (TIG) welded AISI409 ferritic stainless steel were investigated. The effect of the welding parameters on grain size? local misorientation and low angle grain boundaries was studied. It was found that the base metal was partly in recrystallization state. Complete recrystallization followed by severe grain growth occurs after joining process due to welding heating cycle. A decrease in the number of low angle grain boundaries in HAZ was observed. Nevertheless, the welding plastic strain increases the density of local misorientation and low angle grain boundaries. This investigation shows that the final state of strain is the result of the competition between welding plastic strains and stress relieving from recrystallization but the decisive factor in determining the grain size in HAZ is heat input.

scholarly journals Grain-size evolution of polar firn: a new empirical grain growth parameterization based on X-ray microcomputer tomography measurements

2012 ◽  
Vol 58 (212) ◽  
pp. 1245-1252 ◽  
Author(s):  
Stefanie Linow ◽  
Maria W. Hörhold ◽  
Johannes Freitag
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Microwave Frequency ◽  
Effective Radius ◽  
Spherical Approximation ◽  
Large Variability ◽  
Near Surface ◽  
X Ray ◽  
Size Evolution ◽  
Grain Properties

AbstractFirn microstructure properties from six different sites in Greenland and Antarctica are investigated by means of X-ray microcomputer tomography. The optical effective radius is calculated from the specific surface area (SSA) and used as a measure of grain size. It is shown that the recently introduced spherical approximation of firn grains using the effective radius Reff is representative of grain size in the microwave frequency region. The measured profiles show the well-known increase of grain size with depth at all sites, where the increase is largest at near-surface depths. A large variability in grain size on the decimeter-to-centimeter scale as a result of different grain properties of single layers is superimposed on the overall trend at each site. A simple empirical parameterization of grain-size evolution is developed which allows the rapid grain growth in the uppermost layers of the firn to be predicted. The growth is driven by strong seasonal and diurnal temperature gradients. The model can be used to simulate grain-size profiles required by models of firn/microwave interaction (e.g. for retrieval of accumulation rates from satellite microwave sensors) in a more realistic fashion.

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