EFFECT OF Al ON MICROSTRUCTURE AND PROPERTIES OF In718 ALLOY

2009 ◽  
Vol 23 (06n07) ◽  
pp. 1066-1073
Author(s):  
FANG LIU ◽  
SHULIN YANG ◽  
WENRU SUN ◽  
SHOUREN GUO ◽  
ZHUANGQI HU
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Room Temperature ◽  
Tensile Ductility ◽  
Sharp Decrease ◽  
Compact Form ◽  
Phase Precipitation ◽  
Σ Phase ◽  
Δ Phase

Compared with the conventional In 718 alloy, the addition of Al at the level of 1.24% and 1.50% greatly increases the precipitation of γ′ phase and the compact form of γ″/γ′/γ″ structure, which has been demonstrated in previous studies. The δ phase precipitation at the grain boundaries is noticeably suppressed. Large amount of Laves phase (( Fe , Ni , Cr )2( Nb , Mo )), small amount of M 7 C 3 carbide and σ phase (( Fe , Ni )( Cr , Mo , Nb )) are precipitated at the grain boundaries. After aging at 680°C, the grain boundary precipitates are increased significantly. Large amount needle-like σ phase is precipitated at the grain boundary in the alloy with 1.50% Al . After aging at 680°C for 1000h, the grain boundary precipitates are worsened further, but the coarsening of the compact form γ″/γ′/γ″ is lighter than the γ″ phase in the normal In 718 alloy. The tensile strength at room temperature and 680°C are increased due to Al increasing. While the tensile ductility and impact toughness of the alloy decrease significantly, and a sharp decrease has been found during the long term aging at 680°C. The mechanism by which Al influencing the microstructure and mechanical properties of In 718 alloy is to be discussed.

Room Temperature Tensile Ductility in Powder Processed B2 FeAi Alloys

1986 ◽  
Vol 81 ◽  
Author(s):  
M. A. Crimp ◽  
K. M. Vedula ◽  
D. J. Gaydosh
Keyword(s):  
Fracture Surface ◽  
Yield Strength ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Cooling Rate ◽  
Yield Stress ◽  
Room Temperature ◽  
Tensile Ductility ◽  
Strengthening Mechanism ◽  
General Yielding

AbstractIt has been shown that it is possible to obtain significant room temperature tensile ductility in FeAl alloys using iron-rich deviations from stoichiometry. A comparison of the room temperature tensile and compressive behaviors of Fe−50at% Al and Fe−40at% Al shows that FeAl is brittle at higher Al contents because it fractures along grain boundaries before general yielding. Lower aluminium contents reduce the yield stress substantially and hence some ductility is observed before fracture.Addition of boron results in measurable improvements in ductility of Fe−40at% Al and is accompanied by an increase in transgranular tearing on the fracture surface, suggesting a grain boundary strengthening mechanism.Increasing the cooling rate following annealing at 1273 K results in a large increase in the yield strength and a corresponding decrease in ductility.

Effect of Hafnium on the Microstructure and Creep Property of a Hot Corrosion Resistant Superalloy

2015 ◽  
Vol 816 ◽  
pp. 641-647 ◽  
Author(s):  
Jie Shan Hou ◽  
Jian Ting Guo ◽  
Chao Yuan ◽  
Yong An Guo ◽  
Gu Song Li ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Creep Property ◽  
Thermal Exposure ◽  
Boundary Phase ◽  
Primary Carbide ◽  
Bayesian Neural Network ◽  
Creep Life ◽  
Σ Phase

The effects of the selective addition of Hafnium (Hf) on the grain boundary, phase, carbides and creep properties of experimented nickel superalloy after standard heat treatment and long-term exposure were investigated. Predicted by the Bayesian neural network, the creep life is prolonged with Hf content of 0-0.6 mass%, which is more effective at low stresses. The decrease of creep life of Hf free alloy after long term exposure was pronounced. Comparative study showed that the mainly small, coherent, blocky and closely spaced MC(2)and M23C6carbides precipitated on the grain boundaries in the 0.4wt% Hf contained alloy, and that relatively larger, incoherent MC(1)carbides precipitated on the grain boundaries in the Hf free alloy. During long term thermal exposure, fine discrete M23C6carbides decomposed from primary carbide, inducing a layer along the grain boundary, and the coarsening of grain boundary in Hf free alloy is more pronounced. At high stresses, the Hf-free alloy exhibited a stronger tendency of rafting than the 0.4Hf alloy, while the tendency of appearance of rafting was very similar at low stresses. However, Hf can render the alloy prone to the formation of σ phase, according to D-electrons method. Thus, the Hf content needs to be controlled to a suitable level.

Low-Temperature Grain Boundary Diffusion Data Measured from Historical Artifacts

2004 ◽  
Vol 852 ◽  
Author(s):  
R.J. Kremer ◽  
M.A. Dayananda ◽  
A.H. King
Keyword(s):  
Low Temperature ◽  
Grain Boundary ◽  
Room Temperature ◽  
Boundary Diffusion ◽  
Diffusion Processes ◽  
Grain Boundary Diffusion ◽  
Accelerated Tests ◽  
Temperature Diffusion ◽  
Diffusion Profiles

ABSTRACTDiffusion processes in typical metals are slow at room temperature but there are many applications for which very long-term use is envisaged and stability needs to be assured over a timescale of 10, 000 years, where even slow processes can be important. It is common to perform accelerated tests at higher temperatures and extrapolate the necessary information from the measurements so obtained. We have tested the validity of this type of extrapolation for room-temperature, grain boundary diffusion in the copper-silver system, by measuring low-temperature diffusion profiles in antique samples of Sheffield plate.

scholarly journals The Internal Friction of Single Crystals, Bicrystals and Polycrystals of Pure Magnesium

2015 ◽  
Vol 60 (1) ◽  
pp. 371-375 ◽  
Author(s):  
W.B. Jiang ◽  
Q.P. Kong ◽  
L.B. Magalas ◽  
Q.F. Fang
Keyword(s):  
Activation Energy ◽  
Internal Friction ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Single Crystals ◽  
Room Temperature ◽  
Internal Friction Peak ◽  
Self Diffusion ◽  
Boundary Relaxation ◽  
The Difference

Abstract The internal friction of magnesium single crystals, bicrystals and polycrystals has been studied between room temperature and 450°C. There is no internal friction peak in the single crystals, but a prominent relaxation peak appears at around 160°C in polycrystals. The activation energy of the peak is 1.0 eV, which is consistent with the grain boundary self-diffusion energy of Mg. Therefore, the peak in polycrystals can be attributed to grain boundary relaxation. For the three studied bicrystals, the grain boundary peak temperatures and activation energies are higher than that of polycrystals, while the peak heights are much lower. The difference between the internal friction peaks in bicrystals and polycrystals is possibly caused by the difference in the concentrations of segregated impurities in grain boundaries.

The Effect of Cu Alloying on Al Alloy Thin Films: Microstructural Mechanisms That Enhance Electromigration Resistance

1993 ◽  
Vol 309 ◽  
Author(s):  
D. R. Frear ◽  
J. R. Michael ◽  
A. D. Romig
Keyword(s):  
Thin Films ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Room Temperature ◽  
Boundary Diffusion ◽  
Boundary Phase ◽  
Al Alloy ◽  
Cu Films ◽  
Isothermal Heat Treatments ◽  
Lower Temperature

AbstractThe microstructural evolution of unpatterned Al-2wt.%Cu thin films has been examined to elucidate the mechanism by which copper improves electromigration resistance. After annealing at 425°C and cooling to room temperature at a rate of approximately 1°C/min., the microstructure of the Al-Cu films consisted of 1 μm aluminum grains with θ-phase Al2Cu precipitates at grain boundaries and triple points. The grain size and precipitation distribution did not change with subsequent isothermal heat treatments in the temperature range of 200° to 400°C. Al-Cu thin films annealed at 400°C, a temperature just below the Al/Al+θ solvus, exhibited microstructures in which the aluminum grain boundaries were depleted in copper except for the presence of the pre-existing large, widely dispersed AI2Cu precipitates. Al-Cu thin films annealed at 200° to 300°C were enriched with copper at the aluminum grain boundaries. The large, widely dispersed Al2Cu precipitates remained after the lower temperature anneals. From these results, it is proposed that the presence of copper in aluminum thin films improves electromigration resistance due to the precipitation of a thin film of Al2Cu, or a substoichiometric precursor, along the grain boundaries. The grain boundary phase retards grain boundary diffusion in the thin films, thereby reducing total mass transport and improving electromigration resistance.

scholarly journals Effect of Strain Hardening on Precipitation Kinetics in ATI 718Plus

2017 ◽  
Vol 907 ◽  
pp. 167-172
Author(s):  
Bilal Hassan ◽  
Yann Jansen ◽  
Sebastien Nouveau ◽  
Jonathan Corney
Keyword(s):  
Heat Treatment ◽  
Grain Boundaries ◽  
Strain Hardening ◽  
Inconel 718 ◽  
Important Process ◽  
Compression Tests ◽  
Precipitation Kinetics ◽  
Phase Precipitation ◽  
Heat Treated ◽  
Δ Phase

ATI 718Plus components are manufactured by forging a wrought billet in stages to obtain the desired geometry and microstructure. Parts are then heat treated to optimized proportions of γ’ and η phases. η phase is a plate-like phase that precipitates on the grain boundaries of ATI 718Plus, similar to δ phase in Inconel 718. However, the complete kinetic behaviour of η phase precipitation during forging and heat treatment is still not fully understood. This paper investigates the effects of strain hardening on η phase precipitation kinetics in ATI 718Plus. This is achieved through the use of isothermal hot compression tests and heat treatment. Strain hardening was found to affect the η precipitation kinetics considerably. The results reported are a contribution to a fuller understanding of this important process

Grain Boundary Corrosion and Alteration Phase Formation During the Oxidative Dissolution of UO2 Pellets

1996 ◽  
Vol 465 ◽  
Author(s):  
David J. Wronkiewicz ◽  
Edgar C. Buck ◽  
John K. Bates
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Alkaline Earth ◽  
Solid Phase ◽  
Test Conditions ◽  
Time Periods ◽  
Uranyl Silicates ◽  
Intergrain Boundaries ◽  
Preferential Dissolution

ABSTRACTThe alteration behavior of UO2 pellets following their reaction under unsaturated drip-test conditions, at 90°C, for time periods of up to 10 years has been examined by solid phase and leachate analyses. Sample reactions were characterized by preferential dissolution of grain boundaries between the original press-sintered UO2 granules comprising the samples, development of a polygonal network of open channels along the intergrain boundaries, and spallation of surface granules that had undergone severe grain boundary corrosion. The development of a dense mat of alteration phases after two years of reaction trapped loose granules, resulting in reduced rates of particulate uranium release. The paragenetic sequence of alteration phases that formed on the present samples was similar to that observed in surficial weathering zones of natural uraninite (UO2) deposits, with alkali and alkaline earth uranyl silicates representing the long-term solubility-limiting phases for uranium in both systems.

Mechanism of Ductility Improvement In L12 Compounds by Interstitial Elements

1990 ◽  
Vol 213 ◽  
Author(s):  
T. K. Chaki
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Room Temperature ◽  
Boundary Segregation ◽  
Grain Boundary Segregation ◽  
Room Temperature Ductility ◽  
Interstitial Atoms ◽  
Interstitial Elements

ABSTRACTInterstitial boron atoms are known to increase room temperature ductility in Ni-rich Ni3Al and Ni3Si. Inerstitial carbon atoms increase ductility in Ni-rich Ni3Si, but not in Ni3Al. It is argued that grain boundary segregation of B or C is not the cause of the increase in ductility. Instead, strong Ni-B bonding and antisite Ni defects reduce the strength of directional Ni-Al bonding in ordered Ni3Al so that Ni and Al atoms can relax more easily to fill up the microcavities at the grain boundaries, thereby strengthening the boundaries. The reduced Ni-Al bonding will also enhance the ductility in the interior of the grains so that dislocations can be easily generated to shield the tips of the cracks at the grain boundary. In Ni3Si, strong Si-C bonds distort the directionality of Ni-Si bonding. Evidence for this model is presented. Estimates of the concentration of interstitial atoms to achieve maximum ductility are made and the estimate agrees well with the experimental value.

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