Dislocation pinning effects induced by nano-precipitates during warm laser shock peening: Dislocation dynamic simulation and experiments

Liao, Yiliang; Ye, Chang; Huang, Gao; Kim, Bong Joong; Suslov, Sergey; Stach, Eric A.; Cheng, Gary J.

doi:10.1063/1.3609072

Cited by 36 publications

(11 citation statements)

References 36 publications

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“…For example, in 2015, Liao et al [14] reviewed the processing techniques of warm laser shock peening (WLSP) and thermal engineered-laser shock peening (TE-LSP) systematically and explained the fundamental process mechanisms clearly. According to the review, a dislocation pinning effect based on the dynamic strain aging (DSA) and dynamic precipitation (DP) is the main reason for improvement of residual stress and microstructure stability of WLSP [14,15]. Chen et al [16] in Jiangsu University studied the effects of warm laser peening (WLP) on thermal stability of the A356 alloy and found that WLP can effectively improve the thermal stability of residual stress compared with LP.…”

Section: Introductionmentioning

confidence: 99%

Tensile Properties and Microstructures of a 2024-T351 Aluminum Alloy Subjected to Cryogenic Treatment

Zhou

Huang

et al. 2016

Metals

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Abstract:The aim of this study was to investigate the effects of the cryogenic treatment (CT) using liquid nitrogen on tensile properties and microstructures of the 2024-T351 aluminum alloy. Tensile tests were carried out, and tensile fractures were observed using a scanning electron microscope (SEM). The microstructure evolution of 2024-T351 subjected to CT was also studied using both an optic microscope (OM) and a SEM. The components of the second phase were tested with an energy dispersive spectrometer (EDS). The results showed that both the ultimate strength and the yield strength of the 2024-T351 aluminum alloy could be improved through CT without the sacrifice of elongation. In addition, tensile fractures showed that the plasticity of 2024-T351 aluminum might also be improved, as the dimples in the fracture of the CTed specimens were markedly more uniform compared with the untreated specimen. The phenomenon of grains refinement (GR) was found through microstructure observation. It was also found that the second phases were distributed more uniformly after CT. A conceivable mechanism concerning the shrinking effect and crystal grain movement was raised to explain the experimental phenomena. The effects of CT on residual stress in the 2024-T351 aluminum alloy are discussed herein. Measurements showed that tensile residual stress in 2024-T351 was removed, and slight compressive residual stress was generated after CT. This may also contribute to the improvement of the tensile properties of the alloy.

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Section: Introductionmentioning

confidence: 99%

Tensile Properties and Microstructures of a 2024-T351 Aluminum Alloy Subjected to Cryogenic Treatment

Zhou

Huang

et al. 2016

Metals

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“…With an increase in the radiation intensity and, hence, in the pressure and strain rate, the dislocation structure formed in the shock wave develops in the fol lowing sequence: uniform dislocation density distri bution-cellular dislocation structure-uniform dislo cation density distribution with stacking faults, and, finally, at pressures above 60 GPa, the formation of a strain induced structure consisting of microtwins [1][2][3][4]. In polycrystals, the character of the dislocation structure in a shock wave is determined by the grain size [5][6][7], whereas in alloys, the dislocation structure depends on the presence of precipitates in the material [7,8] and on the stacking fault energy [9]. As the pres sure increases above 1-10 GPa, the generation of geo metrically necessary dislocations at the shock wave front becomes a significant factor [4,10].…”

Section: Introductionmentioning

confidence: 99%

“…Apart from the real physical experiment, the char acter of dislocation structures formed in a shock wave has also been investigated using methods of molecular dynamics [10,11] and discrete dislocation dynamics [8,12] simulation. Owing to the visibility of computer simulation, these methods supplement experimental results and allow one to observe the formation of a dis location structure or its individual elements at differ ent scale levels.…”

Section: Introductionmentioning

confidence: 99%

Synergetics of the interaction of mobile and immobile dislocations in the formation of dislocation structures in a shock wave. Effect of the stacking fault energy

2015

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A kinetic equation for the density of dislocations, which reflects the main stages of the formation of dislocation structures of different types in a shock wave, has been formulated based on the analysis of the interaction of two kinetic processes described by reaction-diffusion type equations for densities of mobile dislocations and dislocations forming immobile dipoles, respectively. It has been shown that an inhomoge neous (cellular) dislocation structure is formed at relatively low pressures behind the front of a shock wave, whereas a uniform distribution of the dislocation density with stacking faults appears at high pressures. The transition from a cellular dislocation density distribution to a uniformly distributed dislocations with stacking faults depends on the stacking fault energy γ D of the metal: the lower is the stacking fault energy, the lower is the pressure in the shock wave σ c at which the cellular dislocation structure transforms into the structure with a uniform dislocation density distribution. It has been found that the dependence of the critical pressure on the stacking fault energy γ D is described by the law σ c ~ (γ D /μb) 2/3 (where μ is the shear modulus and b is the Burgers vector), which is confirmed in the experiment.

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“…The laser shock induced by pulse laser ablation under a confinement has been widely investigated because of its great potential for industrial applications, such as LSP [1][2][3][4][5][6], laser dynamic forming [7,8], and laser-assisted micromachining [9,10]. The capability, efficiency, and application range of these laser-based techniques are strongly governed by the intensity of laser shock.…”

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confidence: 99%

Enhanced Laser Shock by an Active Liquid Confinement—Hydrogen Peroxide

Liao

Yang

Cheng

2012

Journal of Manufacturing Science and Engineering

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This letter investigates a unique process to generate enhanced laser shock by applying an active liquid confinement-hydrogen peroxide (H2O2). The mechanism of fast chemical etching-assisted laser ablation is proposed. As a result, comparing with utilizing water as confinement, the efficiency of laser shock peening (LSP) of aluminum alloy 6061 with an active liquid confinement is improved by 150%, and the ablation rate of pulse laser ablation (PLA) of zinc is enhanced by 300%. This method breaks the major limitation of underwater pulsed laser processing caused by the breakdown plasma, with additional mechanisms to generate higher ablation rate and shock pressure under the same laser intensities.The laser shock induced by pulse laser ablation under a confinement has been widely investigated because of its great potential for industrial applications, such as LSP [1-6], laser dynamic forming [7,8], and laser-assisted micromachining [9,10]. The capability, efficiency, and application range of these laser-based techniques are strongly governed by the intensity of laser shock. Thus, enhancing the laser shock draws a great attention in this research field. The laser shock is ruled over by not only the laser power condition but also the confining media. Currently, the selection of confining media brings a major limitation to enhance the laser shock. For example, the solid confinements like glass are inconvenient for processing 3D surfaces, and they are also too brittle to stand the high power laser pulse. On the other hand, even if the liquid confinements like water are relatively more fiexible and practical, and have been widely used in industrial applications, they still suffer from the major drawback: When the laser intensity is above a threshold, the breakdown of liquid confinements screens the incident laser power and results in a saturation of laser shock and peak pressure [1,4,11,12]. Thus, it is worthwhile exploring other approaches to enhance the laser shock.In this letter, we study a unique process to enhance the laser shock by applying active liquid confinements like H2O2. The concept originates from that the laser shock is mostly dependent on the high density of laser-induced plasma, which is determined by the ablation rate of target materials through laser-material interactions [2,9,13,14]. Thus, we could effectively enhance the laser shock by using active liquid confinements because of the more effective ablation caused by the fast chemical etching reaction taking place simultaneously during laser ablation process. This idea is demonstrated by experimental results that the surface hardness and plastic deformation depth of aluminum alloy 6061 (AA6061) after LSP are effectively increased by using H2O2 as the confinement instead of H2O. LSP efficiency is improved by 150% with the application of H2O2. Our proposed mechanism suggests that the enhanced laser shock by H2O2 is majorly due to the higher ablation rate caused by the mutual promotion between the laser ablation and chemical etching. In addition, this mec...

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Dislocation pinning effects induced by nano-precipitates during warm laser shock peening: Dislocation dynamic simulation and experiments

Cited by 36 publications

References 36 publications

Tensile Properties and Microstructures of a 2024-T351 Aluminum Alloy Subjected to Cryogenic Treatment

Tensile Properties and Microstructures of a 2024-T351 Aluminum Alloy Subjected to Cryogenic Treatment

Synergetics of the interaction of mobile and immobile dislocations in the formation of dislocation structures in a shock wave. Effect of the stacking fault energy

Enhanced Laser Shock by an Active Liquid Confinement—Hydrogen Peroxide

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