The Potential of HAZ Property Improvement through Control of Grain Boundary Character in a Wrought Ni-Based Superalloy

2010 ◽  
Vol 654-656 ◽  
pp. 488-491 ◽  
Author(s):  
Hyun Uk Hong ◽  
In Soo Kim ◽  
Baig Gyu Choi ◽  
Hi Won Jeong ◽  
Seong Moon Seo ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Solution Treatment ◽  
Crystallographic Analysis ◽  
Treatment Temperature ◽  
Solution Treatment Temperature ◽  
Slow Cooling ◽  
Grain Coarsening ◽  
Boundary Character ◽  
Grain Boundary Character

The effects of grain boundary serration on grain coarsening and liquation behavior in simulated weld heat-affected-zone (HAZ) of a wrought Ni-based superalloy Alloy 263 have been investigated. Recently, the present authors have found that grain boundary serration occurs in the absence of adjacent coarse γ' particles or M23C6 carbides when a specimen is direct-aged with a combination of slow cooling from solution treatment temperature to aging temperature. This serration leads to a change in grain boundary character as special boundary based on the crystallographic analysis demonstrating that the grain boundaries tend to serrate to have specific segments approaching to one {111} low-index plane at a boundary. The present study was initiated to investigate the interdependence of the serration and HAZ property with a consideration of this serration as a potential for the use of a damage-tolerant microstructure. It was found that the serrated grain boundaries suppress effectively grain coarsening, and are highly resistant to liquation cracking in HAZ due to their lower tendency to be wetted and penetrated by the liquid phase. These results reflect closely a significant decrease in interfacial energy as well as grain boundary configuration by the serration.

A Study on the Formation of Serrated Grain Boundaries and its Applications in Nimonic 263

2010 ◽  
Vol 638-642 ◽  
pp. 2245-2250 ◽  
Author(s):  
Hyun Uk Hong ◽  
Hi Won Jeong ◽  
In Soo Kim ◽  
Baig Gyu Choi ◽  
Young Soo Yoo ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Creep Resistance ◽  
Solution Treatment ◽  
Interfacial Free Energy ◽  
Treatment Temperature ◽  
M23c6 Carbide ◽  
Solution Treatment Temperature ◽  
Lattice Image ◽  
Nickel Based Superalloy

The formation of serrated grain boundaries and its subsequent effect on creep resistance have been investigated in a wrought nickel based superalloy Nimonic 263. The grain boundaries were considerably serrated without the presence of γ' phases or M23C6 when a specimen was slow-cooled from the solution treatment temperature. The high resolution observation on the lattice image of the serrated grain boundary suggested that the grain boundaries tended to serrate to have specific segments approaching to one {111} low-index plane at a boundary in order to have lower interfacial free energy of grain boundary. The grain boundary serration led to a change in M23C6 carbide characteristics: the carbide morphology from granular to planar, a lowered density and their coherency pattern to two neighboring grains from consistent to zigzag. The improvement of creep resistance was noticeably observed by the introduction of GB serration without deterioration of basic mechanical properties. This improvement in creep resistance by the serration was associated with a lower rate of cavitation and crack propagation through the modification of carbide characteristics as well as grain boundary configuration.

Metal precipitation at grain boundaries in silicon: Dependence on grain boundary character and dislocation decoration

2006 ◽  
Vol 89 (4) ◽  
pp. 042102 ◽  
Author(s):  
T. Buonassisi ◽  
A. A. Istratov ◽  
M. D. Pickett ◽  
M. A. Marcus ◽  
T. F. Ciszek ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Character ◽  
Grain Boundary Character ◽  
Metal Precipitation

scholarly journals Stress Corrosion Cracks in Pipeline Steels

2019 ◽  
Author(s):  
Mohammad Ali Mohtadi Bonab
Keyword(s):  
Grain Boundary ◽  
Crack Propagation ◽  
Grain Boundaries ◽  
Stress Corrosion ◽  
Coincidence Site Lattice ◽  
Rolling Plane ◽  
Pipeline Steels ◽  
Factors Affecting ◽  
Boundary Character ◽  
Grain Boundary Character

The demand for pipeline steels has increased in the last several decades since they were able to provide an immune and economical way to carry oil and natural gas over long distances. There are two important damage modes in pipeline steels including stress corrosion cracking (SCC) and hydrogen induced cracking (HIC). The SCC cracks are those cracks which are induced due to the combined effects of a corrosive environment and sustained tensile stress. The present review article is an attempt to highlight important factors affecting the SCC in pipeline steels. Based on a literature survey, it is concluded that many factors, such as microstructure of steel, residual stresses, chemical Composition of steel, applied load, alternating current (AC) current and texture, and grain boundary character affect the SCC crack initiation and propagation in pipeline steels. It is also found that crystallographic texture plays a key role in crack propagation. Grain boundaries associated with {111}//rolling plane, {110}//rolling plane, coincidence site lattice boundaries and low angle grain boundaries are recognized as crack resistant paths while grains with high angle grain boundaries provide easy path for the SCC intergranular crack propagation. Finally, the SCC resistance in pipeline steels is improved by modifying the microstructure of steel or controlling the texture and grain boundary character.

SEM-ECP Analysis of Grain-Boundary Character Distribution in Polycrystalline Materials

1996 ◽  
Vol 54 ◽  
pp. 354-355
Author(s):  
Tadao Watanabe
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Migration ◽  
Polycrystalline Materials ◽  
Grain Boundary Character Distribution ◽  
Boundary Character ◽  
Grain Boundary Character ◽  
Character Distribution ◽  
Boundary Character Distribution

As demonstrated early 1980’s (1), the scanning electron rnicrocopy-electron channelling pattern (SEM-ECP) technique is very powerful in determination of orientation of individual grains and the character of grain boundaries in polycrystalline materials. Figure 1(a) and (b) show SEM and ECP images of a grain boundary in polycrystal line iron-6.5 mass % silicon ribbon produced by rapid solidification and subsequent annealing. We can intuitively recognize from the SEM-ECP image that the character of the boundary is of <100> tilt type with about 7° misorientation angle. This kind of direct observation is very useful for a study of grain boundary migration and grain growth.This paper discusses advantages of the SEM-ECP technique for the precise determination of the character of grain boundary and for statistical analysis of grain boundaries to bridge roles of individual grain boundaries and bulk properties in a polycrystal. The new microstructural parameter associated with grin boundary termed “grain boundary character distribution (GBCD)” which was introduced by the present author (2,3) and has been utilized in designing and engineering grain boundaries in order to produce desirable and/or high bulk performance in polycrystalline materials (4,5). GBCD describes the type and the frequency of different types of grain boundaries, ie. random general boundaries and special boundaries like low-angle boundaries and low Σ coincidence boundaries.

Influence of Overburning on Microstructure and Property of 6061 Aluminum Alloy

2012 ◽  
Vol 476-478 ◽  
pp. 118-121 ◽  
Author(s):  
Shi Xing Zhang ◽  
Shao Min Qu
Keyword(s):  
Mechanical Properties ◽  
Aluminum Alloy ◽  
Grain Boundary ◽  
Solution Treatment ◽  
Hardness Test ◽  
Treatment Temperature ◽  
Experimental Results ◽  
Solution Treatment Temperature ◽  
6061 Aluminum Alloy ◽  
Microstructure And Mechanical Properties

Process of solution treatment of 6061 aluminum alloy was done by hardness test and microanalysis in this paper. The effects of different solution treatment temperature on the microstructure and mechanical properties of 6061 aluminum alloy were studied and the influence of overburning on the microstructure and mechanical properties of 6061 aluminum alloy were also analyzed. The experimental results show that overburning occurring while 6061 aluminum alloy is heated above 580°C . The hardness measurements and microstructure analysis results show that the hardness decreased, grain boundary becomes trigemanal and compounded –melting structure (burnt structure) appeared when overburning occuring for this alloy .

scholarly journals Effects of Different Parameters on Initiation and Propagation of Stress Corrosion Cracks in Pipeline Steels: A Review

Metals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 590 ◽  
Author(s):  
M.A. Mohtadi-Bonab
Keyword(s):  
Grain Boundary ◽  
Crack Propagation ◽  
Grain Boundaries ◽  
Stress Corrosion ◽  
Coincidence Site Lattice ◽  
Rolling Plane ◽  
Pipeline Steels ◽  
Boundary Character ◽  
Grain Boundary Character ◽  
Initiation And Propagation

The demand for pipeline steels has increased in the last several decades since they were able to provide an immune and economical way to carry oil and natural gas over long distances. There are two important damage modes in pipeline steels including stress corrosion cracking (SCC) and hydrogen induced cracking (HIC). The SCC cracks are those cracks which are induced due to the combined effects of a corrosive environment and sustained tensile stress. The present review article is an attempt to highlight important factors affecting the SCC in pipeline steels. Based on a literature survey, it is concluded that many factors, such as microstructure of steel, residual stresses, chemical composition of steel, applied load, alternating current (AC) current and texture, and grain boundary character affect the SCC crack initiation and propagation in pipeline steels. It is also found that crystallographic texture plays a key role in crack propagation. Grain boundaries associated with {111}∥rolling plane, {110}∥rolling plane, coincidence site lattice boundaries and low angle grain boundaries are recognized as crack resistant paths while grains with high angle grain boundaries provide easy path for the SCC intergranular crack propagation. Finally, the SCC resistance in pipeline steels is improved by modifying the microstructure of steel or controlling the texture and grain boundary character.

Dislocation density based crystal plasticity finite element simulation of Al bicrystal with grain boundary effects

2014 ◽  
Vol 1651 ◽  
Author(s):  
Zhe Leng ◽  
David P. Field ◽  
Alankar Alankar
Keyword(s):  
Finite Element ◽  
Dislocation Density ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Crystal Plasticity ◽  
Microstructure Evolution ◽  
Polycrystalline Materials ◽  
Boundary Character ◽  
Crystal Plasticity Finite Element ◽  
Grain Boundary Character

ABSTRACTCrystal plasticity finite element method is a useful tool to investigate the anisotropic mechanical behaviors as well as the microstructure evolution of metallic materials and it is widely used on single crystals and polycrystalline materials. However, grain boundary involved mechanisms are barely included in the polycrystalline models, and modeling the interaction between the dislocation and the grain boundaries in polycrystalline materials in a physically consisstent way is still a long-standing, unsolved problem. In our analysis, a dislocation density based crystal plasticity finite element model is proposed, and the interaction between the dislocation density and the grain boundaries is included in the model kinematically. The model is then applied to Al bicrystals under 10% compression to investigate the effects of grain boundary character, e.g. grain boundary misorientation and grain boundary normal, on the stress state and the microstructure evolution. The modeling results suggest a reasonable correspondence with the experimental result and the grain boundary character plays a crucial role in the stress concentration and dislocation patterning.

Effect of Solid Solution Treatment on Corrosion Resistance of Al-Cu-Mg-Ag Alloy

2021 ◽  
Vol 1032 ◽  
pp. 213-219
Author(s):  
Zhen Hua Cui ◽  
Xiao Yan Liu ◽  
Yan Qin Wang ◽  
Hong Ru Yang ◽  
Zhen Jie Cui ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Grain Boundary ◽  
Intergranular Corrosion ◽  
Solution Treatment ◽  
Electrochemical Corrosion ◽  
Treatment Temperature ◽  
Boundary Structure ◽  
Solution Treatment Temperature ◽  
Grain Boundary Structure ◽  
Electrochemical Corrosion Resistance

In this experiment, Al-Cu-Mg-Ag alloy was used as material and solution temperature was used as variable to investigate its effect on the corrosion properties of the alloy and Hardness test, metallographic observation, electrochemical test, intergranular corrosion and exfoliation corrosion test were carried out on three groups of samples. The results show that the intergranular corrosion resistance of the alloy decreases with the increase of solution treatment temperature, and the sample treated at 505 °C has the best performance. This is mainly because grain boundary structure plays a role in increasing PFZ and expanding corrosion channels. The exfoliation corrosion resistance of Al-Cu-Mg-Ag alloy increases first and then decreases, and the sample treated at 515 °C has the best performance. This is due to the dual effects of grain boundary structure and grain morphology. On the one hand, the solution treatment temperature increases, which widens the precipitation-free zone and reduces the electrochemical corrosion resistance of the alloy. On the other hand, the increase of recrystallized grains decreases the cohesion of corrosion products and enhances the electrochemical corrosion resistance of the alloy.

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