Thermal Stability of Nanocrystalline Inconel 718 and Ni Prepared by High Velocity Oxy-Fuel (HVOF) Thermal Spraying

1998 ◽  
Author(s):  
H.G. Jiang ◽  
M.L. Lau ◽  
E.J. Lavernia
Keyword(s):  
Thermal Stability ◽  
Grain Size ◽  
Grain Growth ◽  
High Velocity ◽  
Inconel 718 ◽  
Isothermal Annealing ◽  
Growth Behavior ◽  
Hvof Spraying ◽  
Grain Growth Behavior ◽  
Thermal Stability Of

Abstract Nanocrystalline Inconel 718 and Ni powders were prepared using two approaches: methanol and cryogenic attritor milling. High velocity oxy-fuel (HVOF) spraying of milled Inconel 718 powders was then utilized to produce Inconel 718 coatings with a nanocrystalline grain size. Isothermal heat treatments were carried out to study the thermal stability of the methanol milled and cryomilled Inconel 718 powders, as well as the HVOF Inconel 718 coatings. All nanocrystalline Inconel 718 powders and coatings studied herein exhibited significant thermal stability against grain growth as evidenced by a grain size around 100 nm following annealing at 1273 K for 60 min. In the case of the cryomilled nanocrystalline Ni powders, isothermal grain growth behavior was studied, from which the parameters required for the prediction of the microstructural evolution during a non-isothermal annealing were acquired. The theoretical simulation of grain growth behavior of nanocrystalline Ni during non-isothermal annealing conditions yields results that are in good correspondence with the experimental results.

Grain Growth in Nanocrystalline Nickel

1999 ◽  
Vol 580 ◽  
Author(s):  
G.D. Hibbard ◽  
U. Erb ◽  
K.T. Aust ◽  
G. Palumbo
Keyword(s):  
Thermal Stability ◽  
Grain Size ◽  
Grain Growth ◽  
Size Distributions ◽  
Nanocrystalline Nickel ◽  
Scanning Calorimetry ◽  
Solute Content ◽  
Grain Size Distributions ◽  
Thermal Stability Of ◽  
Total Solute Content

AbstractIn this study, the effect of grain size distribution on the thermal stability of electrodeposited nanocrystalline nickel was investigated by pre-annealing material such that a limited amount of abnormal grain growth was introduced. This work was done in an effort to understand the previously reported, unexpected effect, of increasing thermal stability with decreasing grain size seen in some nanocrystalline systems. Pre-annealing produced a range of grain size distributions in materials with relatively unchanged crystallographic texture and total solute content. Subsequent thermal analysis of the pre-annealed samples by differential scanning calorimetry showed that the activation energy of further grain growth was unchanged from the as-deposited nanocrystalline nickel.

Grain Growth Behaviour Of Nanocrystalline Nickel

1991 ◽  
Vol 238 ◽  
Author(s):  
A. M. El-Sherik ◽  
K. Boylan ◽  
U. Erb ◽  
G. Palumbo ◽  
K. T. Aust
Keyword(s):  
Electron Microscopy ◽  
Thermal Stability ◽  
Grain Size ◽  
Grain Boundary ◽  
Grain Growth ◽  
Thermal Stabilization ◽  
Growth Behaviour ◽  
In Situ Electron Microscopy ◽  
Thermal Stability Of

ABSTRACTThe thermal stability of electrodeposited nanocrystalline Ni-1.2%P and Ni-0.12%S alloys is evaluated by in-situ electron microscopy studies. Isothermal grain size versus annealing time curves at 573K and 623K show an unexpected thermal stabilization in form of a transition from rapid initial grain growth to negligible grain growth. This behaviour is discussed in terms of the various grain boundary drag mechanisms which may be operative in these alloys.

Effects of grain size and porosity on strength of Li 2 TiO 3 tritium breeding pebbles and its grain growth behavior

2016 ◽  
Vol 482 ◽  
pp. 163-169 ◽  
Author(s):  
Maoqiao Xiang ◽  
Yingchun Zhang ◽  
Yun Zhang ◽  
Chaofu Wang ◽  
Wei Liu ◽  
...  
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Growth Behavior ◽  
Tritium Breeding ◽  
Grain Growth Behavior

scholarly journals Thermal Stability of Nanocrystalline Gradient Inconel 718 Alloy

Crystals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 53
Author(s):  
Jie Ding ◽  
Yifan Zhang ◽  
Tongjun Niu ◽  
Zhongxia Shang ◽  
Sichuang Xue ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Grain Size ◽  
Inconel 718 ◽  
Treatment Technique ◽  
Mechanical Grinding ◽  
Inconel 718 Alloy ◽  
Transmission Electron ◽  
Nickel Based Alloy ◽  
Energy Configurations ◽  
Thermal Stability Of

Gradient structures containing nanograins in the surface layer have been introduced into Inconel 718 (IN718) nickel-based alloy using the surface mechanical grinding treatment technique. The thermal stability of the gradient IN718 alloy was investigated. Annealing studies reveal that nanograins with a grain size smaller than 40 nm exhibited significantly better thermal stability than those with larger grain size. Transmission electron microscopy analyses reveal that the enhanced thermal stability was attributed to the formation of grain boundaries with low energy configurations. This study provides new insight on strategies to improve the thermal stability of nanocrystalline metals.

A TEM characterization of precipitates evolution and their effect on the grain-growth behavior of gas atomized superalloy A-286

1992 ◽  
Vol 50 (1) ◽  
pp. 178-179
Author(s):  
Keesam Shin
Keyword(s):  
Grain Size ◽  
Sample Preparation ◽  
Grain Growth ◽  
Smooth Surface ◽  
Growth Behavior ◽  
Tem Characterization ◽  
Heat Treated ◽  
Thin Electron ◽  
Grain Growth Behavior

It is generally accepted that the refined grain size and stable grain boundaries observed in rapid-solidification-processed (RSP) materials are due to the fine precipitates produced during and after the processing. This is based on the observation of the materials after consolidation of the powders. Though there is little doubt that the as-atomized powder structure is crucial for the understanding of the consolidated sample, there are few studies of the powder. This is mainly because of the difficulty in preparation of thin electron-transparent samples.The most common method of powder sample preparation uses two or three different embedding materials whose polishing conditions are usually not identical. In this study, a monolayer of powder was gold coated, electroplated with nickel, and then electropolished. Electropolishing provided a nice and smooth surface without any surface artifact. In this study, as-atomized and heat treated powders were studied by TEM (JEOL JEM 200CX) and STEM (VG HB501). Because of the fineness of the defects involved, TEM observation is crucial.

Grain growth behavior in Fe3Al alloys fabricated by different methods

1994 ◽  
Vol 9 (6) ◽  
pp. 1384-1391 ◽  
Author(s):  
B.H. Rabin ◽  
J.K. Wright ◽  
R.N. Wright ◽  
C.H. Sellers
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Hot Isostatic Pressing ◽  
Hot Extrusion ◽  
Growth Behavior ◽  
Elemental Powder ◽  
Ingot Metallurgy ◽  
Prealloyed Powder ◽  
The Difference ◽  
Grain Growth Behavior

Grain sizes were measured after various heat treatments in three Fe3Al alloys having similar composition that were fabricated using the techniques of ingot metallurgy (cast and wrought), hot extrusion of prealloyed powder, and hot isostatic pressing (HIP) of elemental powders. The ingot metallurgy (I/M) material exhibited normal grain growth behavior at temperatures above 750 °C, in agreement with previous observations. Both powder metallurgy (P/M) materials displayed unusual resistance to grain growth compared to the I/M alloy. In the case of the prealloyed P/M material, the initial (recrystallized) grain size was larger than the initial grain size of the I/M material, although little grain growth was observed for heat-treatment temperatures up to 1100 °C. At higher temperatures grain growth occurred at a rate comparable to that observed to the I/M alloy. The elemental powder P/M material exhibited similar grain growth behavior to the prealloyed P/M material, although the initial (as-HIPed) grain size was considerably smaller. Transmission electron microscopy (TEM) indicated that the grain growth resistance of the P/M materials could be attributed to grain boundary pinning by oxide particles presumed to originate from the powder particle surfaces. The difference in the stable grain size between the prealloyed and elemental powder P/M materials was attributed to the nature of the particle dispersions resulting from processing.

Thermal Stability of CP-Aluminium during Annealing after ECAE

2004 ◽  
Vol 467-470 ◽  
pp. 1319-1324 ◽  
Author(s):  
Stijn Poortmans ◽  
Bert Verlinden
Keyword(s):  
Thermal Stability ◽  
Grain Size ◽  
Image Quality ◽  
Dislocation Density ◽  
Grain Growth ◽  
Common Pattern ◽  
Structure Changes ◽  
Hot Rolled ◽  
Thermal Stability Of

Samples of a hot-rolled AA1050 Aluminium alloy have been deformed by ECAE for 4 and 8 passes following route C. The structural stability of the samples after annealing treatments in the range 200°C to 350°C during 1 to 1000 minutes has been investigated. After 4 ECAE passes, the microstructure is not homogeneous. EBSD-scans show that the former grains can still be identified and that these grains show a different stage of subdivision. After 8 passes the structure is more homogeneous. During subsequent annealing the (sub)structure changes following a common pattern, but with different kinetics in all former grains. At first the dislocation density decreases, illustrated by an increase in image quality of the EBSD-scans and a sharpening of the (sub)structure can be observed. The (sub)grain size remains practically constant during this phase. At a given time, different from one (original) grain to another, some (sub)grains start to grow following an ‘abnormal grain growth’ pattern. This happens at all investigated temperatures. The kinetics and mechanisms of this microstructural evolution will be discussed.

The Effect of Small Amounts of Yttrium Addition on Static and under Superplastic Deformation Grain Growth in Newly Developed α+β Type, Ti-4.5Al-6Nb-2Mo-2Fe Alloy

2006 ◽  
Vol 15-17 ◽  
pp. 970-975 ◽  
Author(s):  
Behrang Poorganji ◽  
S. Hotta ◽  
Taichi Murakami ◽  
Takayuki Narushima ◽  
Yasutaka Iguchi ◽  
...  
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Grain Growth ◽  
Hot Deformation ◽  
Superplastic Deformation ◽  
Superplastic Forming ◽  
Growth Behavior ◽  
Two Phase ◽  
Yttrium Addition ◽  
Grain Growth Behavior

New α+β type titanium alloy with Ti-4.5Al-6Nb-2Mo-2Fe was developed on the basis of using biocompatible elements and eliminating the cytotoxic ones such as Vanadium, while achieving the desirable mechanical properties such as appropriate strength, cold workability and low superplastic forming (SPF) temperature. The present study was conducted to investigate the effect of yttrium addition of less than 0.05% into this alloy on static and under superplastic deformation grain growth behavior. The new alloy bar manufactured by α+β processing and annealed at 1073K yielded extremely fine two-phase microstructure with α grain size around 2μm. Specimens were heated at temperatures of 1048, 1073 and 1098K and kept for times between 3.6 to 172.8KS. Yttrium forms in-situ Y2O3 particles, and the presence of these particles yield finer two phase microstructure due to their retardation effect on β phase grain growth. Grain growth behavior during hot deformation was investigated by hot compression test in use of a hot working simulator of THERMEC-Master Z. Strain rate was varied from 2×10-2 to 2×10-4S-1 and strain was 0.69. Grain size of both α and β phases increased with a reduction of strain rate, and Y2O3 particle was also effective to retard grain growth under hot deformation. It was confirmed from comparison of grain growth during isothermal heating with and without hot deformation that grain growth was much accelerated by deformation. All of these results were discussed based on grain growth mechanism or model for two-phase microstructures as well as superplastic deformation mechanism.

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