Laser shock peening effect on the dislocation transitions and grain refinement of Al–Mg–Si alloy

Journal Article · Sat Nov 15 00:00:00 EST 2014 · Materials Characterization

DOI:https://doi.org/10.1016/J.MATCHAR.2014.08.020· OSTI ID:22403585

Trdan, U., E-mail: [e-mail] ^[1]; Skarba, M., E-mail: [e-mail] ^[2]; Grum, J., E-mail: [e-mail] ^[1]

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1. University of Ljubljana, Faculty of Mechanical Engineering, Askerceva 6, 1000 Ljubljana (Slovenia)
2. Slovak University of Technology in Bratislava, Faculty of Materials Science and Technology in Trnava, Paulínska 16, 917 24 Trnava (Slovakia)

This paper systematically investigates the effect of laser shock peening without coating parameters on the microstructural evolution, and dislocation configurations induced by ultra-high plastic strains and strain rates. Based on an analysis of optical microscopy, polarized light microscopy, transmission electron microscopy observations and residual stress analysis, the significant influence of laser shock peening parameters due to the effect of plasma generation and shock wave propagation has been confirmed. Although the optical microscopy results revealed no significant microstructural changes after laser shock peening, i.e. no heat effect zone and differences in the distribution of second-phase particles, expressive influence of laser treatment parameters on the laser shock induced craters was confirmed. Moreover, polarized light microscopy results have confirmed the existence of well-defined longish grains up to 455 μm in length in the centre of the plate due to the rolling effect, and randomly oriented smaller grains (20 μm × 50 μm) in the surface due to the static recrystallization effect. Laser shock peening is reflected in an exceptional increase in dislocation density with various configurations, i.e. dislocation lines, dislocation cells, dislocation tangles, and the formation of dense dislocation walls. More importantly, the microstructure is considerably refined due to the effect of strain deformations induced by laser shock peening process. The results have confirmed that dense dislocation structures during ultra-high plastic deformation with the addition of shear bands producing ultra-fine (60–200 nm) and nano-grains (20–50 nm). Furthermore, dislocation density was increased by a factor of 2.5 compared to the untreated material (29 × 10{sup 13} m{sup −2} vs. 12 × 10{sup 13} m{sup −2}). - Highlights: • LSPwC imparts high compressive residual stresses up to − 362 ± 31 MPa. • After LSPwC the microstructure is considerably refined via dislocation transitions. • Results confirmed ultra-fine (60–200 nm) and nano-grains (20–50 nm) after LSPwC. • Reasonable agreements between dislocation density and residual stress are obtained.

• OSTI ID: 22403585
• Journal Information: Materials Characterization, Vol. 97; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 1044-5803
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
COMPARATIVE EVALUATIONS
DEFORMATION
DISLOCATIONS
GRAIN REFINEMENT
MAGNESIUM ALLOYS
MICROSTRUCTURE
OPTICAL MICROSCOPY
PLASTICITY
RECRYSTALLIZATION
RESIDUAL STRESSES
ROLLING
SHEAR PROPERTIES
SHOCK WAVES
SHOT PEENING
SILICON ALLOYS
STRAIN RATE
STRAINS
TRANSMISSION ELECTRON MICROSCOPY
VISIBLE RADIATION