scholarly journals Influence of Nanoscale Inhomogeneity Incorporating Interface Effect on Crack Nucleation at Intersection of Twin and Grain Boundary in Nanocomposite

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6718
Author(s):  
Yongshu Tao ◽  
Liang Li ◽  
Guanghong Miao ◽  
Jilei Dong
Keyword(s):  
Grain Boundary ◽  
Elastic Constants ◽  
Deformation Twin ◽  
Tensile Ductility ◽  
Crack Nucleation ◽  
High Strength ◽  
External Stress ◽  
Interface Effect ◽  
Residual Tension ◽  
The Matrix

Nanocracks can generate at the intersection of the deformation twin and grain boundary (GB). A mathematical model is built to study the nanoinhomogeneity effect on nanocrack nucleation and propagation in the nanocrystalline matrix. The boundary condition at the interface between the nanoinhomogeneity and the matrix is modified by incorporating the interface effect. The influence of the nanoinhomogeneity shear modulus, the nanoinhomogeneity radius, the nanoinhomogeneity position, the interface effect, and the external stress on the nanocrack nucleation and propagation is investigated in detail. The results indicate that the stiff nanoinhomogeneity suppresses nanocrack nucleation and propagation and thereby improves the tensile ductility of nanocomposites without loss of their predominantly high strength. Both the positive interface residual tension and interface elastic constants suppress nanocrack nucleation and propagation, while the negative interface residual tension and interface elastic constants promote nanocrack nucleation and propagation. Furthermore, the effect of interface residual tension is rather significant. The interface elastic constants have a weak effect on nanocrack nucleation and propagation.

Study on Interior Fracture Property of High Strength Steel in Very High Cycle Regime

2012 ◽  
Vol 482-484 ◽  
pp. 1169-1175
Author(s):  
Ren Hao Jiang ◽  
Wei Li ◽  
Yan Ping Shi ◽  
Jiang He
Keyword(s):  
Crack Propagation ◽  
Fracture Property ◽  
Crack Nucleation ◽  
Fatigue Property ◽  
High Strength ◽  
Bearing Steel ◽  
Stable Crack Propagation ◽  
The Matrix ◽  
Fish Eye ◽  
Very High

Based on the fracture mechanics theory and fracture surface topography analysis (FRASTA) method, the interior fracture property of a bearing steel in very high cycle regime was studied by means of rotary bending fatigue test. As a result, this bearing steel represents the duplex S-N curves characteristic, where the interior inclusion-induced fracture is the predominant fracture mode in very high cycle regime. The rough granular bright facet (GBF) area corresponding to smaller inclusion is usually formed in the lifetime larger than 106 cycles, whose formation progress can be interpreted as the slow crack nucleation based on decohesion of spherical carbide from the matrix. The fatigue property in the fish-eye region outside of GBF can be interpreted as the stable crack propagation progress and that outside of fish-eye is instable crack propagation progress. The stress intensity factor ranges of GBF and fish-eye, ΔKGBF and ΔKfish-eye, can be regarded as the threshold values of controlling stable propagation and instable propagation of interior crack, respectively.

The Effect of Thermomechanical Treatment on the Microstructure and the Mechanical Behavior of a Supersaturated Cu-Ag Alloy

2015 ◽  
Vol 812 ◽  
pp. 53-58 ◽  
Author(s):  
Jenő Gubicza ◽  
K. Sitarama Raju ◽  
Vadlamani Subramanya Sarma ◽  
A. Kauffmann ◽  
Zoltán Hegedűs ◽  
...  
Keyword(s):  
Dislocation Density ◽  
Cold Rolling ◽  
Solute Atom ◽  
Tensile Ductility ◽  
High Strength ◽  
Lower Strength ◽  
Solute Content ◽  
Ag Particles ◽  
The Matrix ◽  
Short Time

Supersaturated Cu-3at.% Ag alloy was processed by cold rolling and short-time annealing in order to achieve a combination of high strength and good tensile ductility. After annealing of the rolled samples a heterogeneous solute atom distribution was developed due to the dissolution of nanosized Ag particles in some volumes of the matrix. In regions with higher solute content, the high dislocation density formed due to rolling was stabilized, while in other volumes the dislocation density decreased. The heterogeneous microstructure obtained after annealing exhibited a much higher ductility and only a slightly lower strength than in the as-rolled state.

Effect of Stabilizing Treatment on the Intergranular Corrosion Behavior of High Strength Al-Mg Alloys

2014 ◽  
Vol 794-796 ◽  
pp. 253-258 ◽  
Author(s):  
Chun Yan Meng ◽  
Di Zhang ◽  
Hua Cui ◽  
Ji Shan Zhang ◽  
Lin Zhong Zhuang
Keyword(s):  
Corrosion Resistance ◽  
Grain Boundary ◽  
Intergranular Corrosion ◽  
High Strength ◽  
Mg Alloys ◽  
The Matrix ◽  
Strong Relation ◽  
Mechanical Properties And Corrosion ◽  
Al Mg Alloys ◽  
Intergranular Corrosion Resistance

In order to improve the intergranular corrosion resistance of high strength Al-Mg alloys, the effect of stabilizing treatment was systematically investigated. Microstructure evolutions of Al-Mg alloys after different stabilizing treatments have been studied by scanning electron microscopy and optical microscopy. Mechanical properties and corrosion resistance were measured. It was found that the mass loss of samples after sensitizing treatment decreased with an increase in the stabilizing temperature. It was suggested that the susceptibility to intergranular corrosion for high strength Al-Mg alloys has a strong relation to the stabilizing temperature that modify the morphology and distribution of precipitates. The precipitates continuously precipitated along the grain boundary when the stabilizing temperature was lower than 250°C, corresponding to a poor corrosion resistance. However, the precipitates randomly precipitated in the matrix as globular particles, and discontinuously precipitated at the grain boundary after stabilized at 250°C and 275°C, resulted in an improved intergranular corrosion resistance.

scholarly journals Influence of hard and soft inclusions inside a ferritic matrix

2019 ◽  
Vol 300 ◽  
pp. 10002
Author(s):  
Riccardo Fincato ◽  
Seiichiro Tsutsumi ◽  
Tatsuo Sakai ◽  
Kenjiro Terada
Keyword(s):  
Crystallographic Orientation ◽  
Crack Nucleation ◽  
Manganese Sulfide ◽  
Spherical Inclusion ◽  
High Strength Steels ◽  
Local Stress ◽  
High Strength ◽  
Ferritic Matrix ◽  
The Matrix

In the case of an interior fracture mode in fatigue, material impurities play a fundamental role in the generation and the propagation of cracks. In general, the presence of hard or soft inclusions, voids, materials imperfections, etc., alter the local stress state in the matrix generating the accumulation of plastic deformations which lead to the crack formation. In terms of inclusions, high strength steels are often characterized by the presence of aluminum oxides Al2O3 or Manganese sulfide MnS. The experimental works reported by several authors pointed out that the critical location for the crack nucleation is, often, at the edge of the inclusion and it subsequently propagates on a plane orthogonal to the loading direction. In a previous work, the authors investigated the stress distribution around a spherical inclusion inside a ferritic matrix, pointing out the role of the material anisotropy and the different crystallographic orientation of the matrix. However, the investigations dealt with simple loading conditions and linear elasticity. The present paper aims to extend the field of investigations to the elasto-plastic domain, focusing the attention on the role of the crystallographic orientation and comparing the results with the previous study.

Effect of Si content on the cracking behavior of selective laser melted Al7050

2019 ◽  
Vol 25 (10) ◽  
pp. 1592-1600
Author(s):  
Ting Qi ◽  
Haihong Zhu ◽  
Xiaoyan Zeng ◽  
Jie Yin
Keyword(s):  
Aluminum Alloy ◽  
Grain Boundary ◽  
Silicon Content ◽  
Crack Density ◽  
High Strength ◽  
Total Surface Area ◽  
Cracking Behavior ◽  
Content Type ◽  
The Matrix ◽  
Si Content

Purpose It is a crucial issue to eliminate cracks for selective laser melting (SLM) 7xxx series aluminum alloy. This paper aims to study the effect of silicon content on the cracking behavior and the mechanism of eliminating crack of SLMed Al7050 alloy. Design/methodology/approach Six different silicon contents were added to the Al7050 powder. The crack density and crack count measuring from optical micrographs were utilized to judge the cracking susceptibility. The low melting phases analyzing from Jmatpro and the microstructure observing by EPMA and SEM were used to discuss the mechanism of eliminating the crack. Findings The cracking susceptibility of SLMed Al7050 alloy decreases with the increase of adding silicon content. When adding silicon, two new low-melting phases appeared: Mg2Si and Al5Cu2Mg8Si6. These low-melting phases offer much liquid feeding along the grain boundary and decrease the cracking susceptibility. Moreover, the grains are obviously refined after adding silicon. The fine grain can increase the total surface area of the grain boundary, which can reinforce the matrix and decrease the cracking susceptibility. High silicon content results in more low-melting phases and fine grains, which decreases the cracking susceptibility. Originality/value The investigation results can help to obtain crack-free SLMed Al7050 parts and deep knowledge on eliminating cracking mechanism of high-strength aluminum alloy fabricated by SLM.

Strain-induced martensite effects on transgranular carbide precipitation in type 304 stainless steels

1991 ◽  
Vol 49 ◽  
pp. 604-605
Author(s):  
A.H. Advani ◽  
L.E. Murr ◽  
D. Matlock
Keyword(s):  
Heat Treatment ◽  
Grain Boundary ◽  
Stress Corrosion Cracking ◽  
Stainless Steels ◽  
Deformation Twin ◽  
Austenitic Stainless Steels ◽  
Carbide Precipitation ◽  
Strain Induced Martensite ◽  
Type 304

Thermomechanically induced strain is a key variable producing accelerated carbide precipitation, sensitization and stress corrosion cracking in austenitic stainless steels (SS). Recent work has indicated that higher levels of strain (above 20%) also produce transgranular (TG) carbide precipitation and corrosion simultaneous with the grain boundary phenomenon in 316 SS. Transgranular precipitates were noted to form primarily on deformation twin-fault planes and their intersections in 316 SS.Briant has indicated that TG precipitation in 316 SS is significantly different from 304 SS due to the formation of strain-induced martensite on 304 SS, though an understanding of the role of martensite on the process has not been developed. This study is concerned with evaluating the effects of strain and strain-induced martensite on TG carbide precipitation in 304 SS. The study was performed on samples of a 0.051%C-304 SS deformed to 33% followed by heat treatment at 670°C for 1 h.

Third Order Elastic Constants and Rayleigh Wave Dispersion of Shot Peened Aero-Engine Materials

2013 ◽  
Vol 768-769 ◽  
pp. 201-208 ◽  
Author(s):  
Marek Rjelka ◽  
Martin Barth ◽  
Sven Reinert ◽  
Bernd Koehler ◽  
Joachim Bamberg ◽  
...  
Keyword(s):  
Residual Stress ◽  
Rayleigh Wave ◽  
Elastic Constants ◽  
Cold Work ◽  
High Strength ◽  
Wave Dispersion ◽  
Third Order ◽  
Third Order Elastic Constants ◽  
Aero Engine ◽  
Rayleigh Wave Dispersion

Aero-engine components exposed to high mechanical stresses are made of high-strength alloys and additionally, they are surface treated by shot peening. This process introduces compressive residual stress into the material making it less sensitive to stress corrosion cracking and fatigue and therefore benefits the components performance and lifetime. Moreover cold work is induced in an amount depending on the peening parameters. To approximate the remaining lifetime, a quantitative, non-destructive method for stress assessment is required. It was shown that surface treatment of such alloys can be characterized by broadband Rayleigh wave dispersion measurements. However, the relative contributions of residual stress and cold work, respectively, remained an open point. This paper presents the determination of third order elastic constants (TOEC) for IN718 and Ti6246, providing, together with a model for the inversion of dispersion data, a quantitative access to the acoustoelastic effect. Finally, some measurements of differently treated samples are given.

An Experimental Study of Cavity Nucleation During Superplastic Deformation

1990 ◽  
Vol 196 ◽  
Author(s):  
Jiang Xinggang ◽  
Cui Jianzhong ◽  
Ma Longxiang
Keyword(s):  
Grain Boundary ◽  
Superplastic Deformation ◽  
Thermomechanical Processing ◽  
High Stress ◽  
High Strength ◽  
Optical Microscope ◽  
Grain Boundary Sliding ◽  
Cavity Nucleation ◽  
High Stress Concentration ◽  
Voltage Electron

ABSTRACTCavity nucleation during superplastic deformation of a high strength aluminium alloy has been studied using a high voltage electron microscope and an optical microscope. The results show that cavities nucleation is due only to superplastic deformation and not to pre-existing microvoids which may be introduced during thermomechanical processing. The main reason for cavity nucleation is the high stress concentration at discontinuties in the plane of the grain boundary due to grain boundary sliding.

Molecular Dynamics Simulation of Crack Initiation of Aluminum under Tensile Deformation

2011 ◽  
Vol 378-379 ◽  
pp. 7-10
Author(s):  
Gui Xue Bian ◽  
Yue Liang Chen ◽  
Jian Jun Hu ◽  
Li Xu
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Elastic Constants ◽  
Tensile Deformation ◽  
Crack Nucleation ◽  
Tensile Load ◽  
Dynamics Simulation ◽  
Metal Aluminum ◽  
Impurity Metal

Molecular dynamics simulation was used to simulate the tension process of purity and containing impurity metal aluminum. Elastic constants of purity and containing impurity metal aluminum were calculated, and the effects of impurity on the elastic constants were also studied. The results show that O-Al bond and Al-Al bond near oxygen atoms could be the sites of crack nucleation or growth under tensile load, the method can be extended to research mechanical properties of other metals and alloys structures.

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