Multiple Laser Shock Processing Research Articles

Mechanical behaviour and subsurface characteristics of Ti-6Al-4V subjected to electropulsing-assisted multiple laser shock processing impacts

Mechanical behaviour and subsurface characteristics of Ti-6Al-4V subjected to electropulsing-assisted multiple laser shock processing impacts

Stepwise varying of laser parameters to enhance the residual stress field in multiple laser shock processing: numerical verification of single-point region

Stepwise varying of laser parameters to enhance the residual stress field in multiple laser shock processing: numerical verification of single-point region

Prediction about residual stress and microhardness of material subjected to multiple overlap laser shock processing using artificial neural network

Prediction about residual stress and microhardness of material subjected to multiple overlap laser shock processing using artificial neural network

Effect of multiple laser shock processing on nano-scale microstructure of an aluminum alloy

In this study, nano-scale microstructural evolution in 6061-T6 alloy after laser shock processing (LSP) was studied. 6061-T6 alloy plate was subjected to multiple LSP. The LSP treated area was characterized by X-ray diffraction and the microstructure of the samples was analyzed by transmission electron microscopy. Focused Ion Beam (FIB) tools were used to prepare TEM samples in precise areas. It was found that even though aluminum had high stacking fault energy, LSP yielded to formation of ultrafine grains and deformation faults such as dislocation cells, stacking faults. The stacking fault probability (PSF) was obtained in LSP-treated alloy using X-Ray diffraction. Deformation induced stacking faults lead to the peak position shifts, broadening and asymmetry of diffraction. XRD analysis and TEM observations revealed significant densities of stacking faults in LSP-treated 6061-T6 alloy. And mechanical properties of LSP-treated alloy were also determined to understand the hardening behavior with high concentration of structural defects.

Finite Element Modeling of the Technology of Multiple Laser Shock Processing of Materials Using the Eigenstrain Method

The laser shock processing (LSP) of material is an efficient modern technology of processing of metal materials, during which significant compressive residual stresses contributing to an increase in their strength and tribological and operational characteristics are generated in the subsurface area. The finite element modeling of the technology of multiple laser shock processing is carried out using the eigenstrain method. The level of the compressive residual stresses arising under LSP is determined. It is shown that the residual stresses on the surface of the VT-6 alloy grow from 510 to 830MPa with an increase in the number of pulses from 1 to 4, and the depth of the zone of the compressive residual stresses increases respectively from 1.26 mm after the first pulse to 1.60 mm after the fourth pulse.

Effect of multiple laser shock processing on nano-scale microstructure of an aluminum alloy

In this study, nano-scale microstructural evolution in 6061-T6 alloy after laser shock processing (LSP) were studied. 6061-T6 alloy plate were subjected to multiple LSP. The LSP treated area was characterized by X-ray diffraction and the microstructure of the samples was analyzed by transmission electron microscopy. Focused Ion Beam (FIB) tools were used to prepare TEM samples in precise areas. It was found that even though aluminum had high stacking fault energy, LSP yielded to formation of ultrafine grains and deformation faults such as dislocation cells, stacking faults. The stacking fault probability (PSF) was obtained in LSP-treated alloy using X-Ray diffraction. Deformation induced stacking faults lead to the peak position shifts, broadening and asymmetry of diffraction. XRD analysis and TEM observations revealed significant densities of stacking faults in LSP-treated 6061-T6 alloy. And mechanical properties of LSP-treated alloy were also determined to understand the hardening behavior with high concentration of structural defects.

Impacts of multiple laser shock processing on microstructure and mechanical property of high-carbon steel

Multiple laser shock processing (LSP) impacts on microstructures and mechanical properties were investigated through morphological determinations and hardness testing. Microscopic results show that without equal channel angular pressing (ECAP), the LSP-treated lamellar pearlite was transferred to irregular ferrite matrix and incompletely broken cementite particles. With ECAP, LSP leads to refinements of the equiaxed ferrite grain in ultrafine-grained microduplex structure from 400 to 150 nm, and the completely spheroidized cementite particles from 150 to 100 nm. Consequentially, enhancements of mechanical properties were found in strength, microhardness and elongations of samples consisting of lamellar pearlite and ultrafine-grained microduplex structure. After LSP, a mixture of quasi-cleavage and ductile fracture was formed, different from the typical quasi-cleavage fracture from the original lamellar pearlite and the ductile fracture of the microduplex structure.

多次激光冲击强化对ЭП866马氏体不锈钢组织 及残余应力的影响

多次激光冲击强化对ЭП866马氏体不锈钢组织 及残余应力的影响

Single and multiple laser shock processing of materials

Laser shock processing (LSP) is an innovative surface treatment technique. It can impart compressive residual stresses in material for improving the fatigue, corrosion, and wear resistance of metals. This technology has been used successfully for the treatment not only of traditional structural materials, but also for hard materials. FEM simulation is an effective method for the prediction of mechanical effects induced in material treated by laser shock processing. The FEM simulation of the single and multiple laser shock processing has been carried out to predict the residual stress field. The predicted residual stress field for single and multiple laser shock processing is well correlated with available experimental data. The simulation of multiple laser shocks has shown that compressive residual stresses and, thus, the strength properties of processed materials, can be extensively increased (up to 40%) with the increase of the laser shock number up to 5, and then they gradually reach a saturated state.

Microstructure and Mechanical Properties of Laser Shocked an Ultra-fine Grained High Carbon Steel

Microstructure and mechanical properties of the ultra- fine grained high carbon steel Fe-0.8C after multiple laser shock processing(LSP) were investigated by using scanning electron microscopy(SEM), transmission electron microscopy(TEM), mini-tensile tests and microhardness measurements.The results show that the ultrafine micro-duplex structure(ferrite+cementite) of the steel was obviously re fined due to the ultra-high plastic strain induced by LSP. Equiaxed ferrite grains were refined from 400 nm to 200 nm and the particle diameter of cementite lamellae decreased from 150 nm to 100 nm. Accordingly, the strength and microhardness increased greatly and the plasticity was also improved. However, the tensile fracture morphology changed from typical ductile fracture to a mixture of quasi-cleavage and ductile fracture after LSP.

Microstructure Evolution and Microhardness of Ultrafine-grained High Carbon Steel during Multiple Laser Shock Processing

Surface microstructure and microhardness of (ferrite + cementite) microduplex structure of the ultrafine-grained high carbon steel after laser shock processing (LSP) with different impact times were investigated by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and microhardness measurements. Equiaxed ferrite grains were refined from 400 to 150 nm, and the cementite lamellae were fully spheroidized, with a decrease of the particle diameter from 150 to 100 nm as the impact times increased. The cementite dissolution was enhanced significantly. Correspondingly, the lattice parameter of α-Fe and microhardness increased with the impact times.

Effect of Multiple Laser Shock Processing on Microstructure and Mechanical Properties of Ti-5Al-4Mo-4Cr-2Sn-2Zr Titanium Alloy

Abstract The effects of the impact times and laser energy on the mechanical properties and microstructures of the Ti-5Al-4Mo-4Cr-2Sn-2Zr titanium alloy during multiple laser shock processing (LSP) were investigated. Residual stress and microhardness were tested on the samples to analyze the mechanical properties, and X-ray diffraction (XRD) and transmission electron microscope (TEM) observation was conducted to study micro-structural evolution. It's found that laser energy and impact number have an influence on the residual stresses and the hardness. Both the hardness and the residual stress of Ti-5Al-4Mo-4Cr-2Sn-2Zr titanium alloy have been improved, forming a severe plastic deformation layer, and increasing of impact number or laser energy will improve the amplitude and enhance affected depth. XRD tests of the specimen surfaces with different impacts and power density show that the positions of diffraction peaks do not change, but the Bragg diffraction peaks broaden. The TEM observation indicates that a layer of nanocrystalline with a size of 30∼60 nm has been fabricated on the surface of the titanium alloy after 3 impacts, and adopts random orientation. Dislocation activity is the main reason of the grain refinement for Ti-5Al-4Mo-4Cr-2Sn-2Zr titanium alloy.

Laser Shock Processing of Titanium Alloy Blade and FEM Simulation

The aim of this article is to analyze the residual stresses field in a TC4 titanium alloy blade by laser shock processing (LSP).LSP is a new surface processing technology, it uses the laser shock wave to act on the surface of the target and form residual compressive stresses field. The ABAQUS software is applied to simulate the LSP of TC4 titanium alloy blade, and the distributions of the residual stresses field are analysed.After single LSP,the maximum value of residual stress on the surface is 309 MPa.The residual stresses on the surface increase first and then decrease.The residual stresses at the depth continue decreasing with the increase of the depth.After multiple LSP,the maximum value of residual stress on the surface is increased and plastically affected depth is increased.

Effects of laser shock processing on surface microstructure and mechanical properties of ultrafine-grained high carbon steel

Ultrafine micro-duplex structure (ferrite (α)+cementite (θ)) formed in a pearlitic Fe–0.8C steel after four passes of equal channel angular pressing (ECAP) at 923K via route Bc. Subsequently the surface of the ultra-micro-duplex structure was treated by multiple laser shock processing (LSP) impacts with different laser pulse energies. The microstructure was obviously refined due to the ultra-high plastic strain induced by LSP. The lattice parameter of α-Fe increased with the laser pulse energy, indicating that the cementite dissolution was enhanced. In addition, residual stress and microhardness increased with the LSP pulse energy.

Effect of initial surface topography on the surface status of LY2 aluminum alloy treated by laser shock processing

Samples manufactured by LY2 aluminum (Al) alloy with different initial surface topography were treated by laser shock processing (LSP), and then the surface topographies before and after LSP were carefully investigated with a non-contact optical profiler (NCOP). Moreover, the residual stress and microhardness were also examined. Results showed the following three aspects: (a) Initial surface topography will influence the surface roughness of LY2 when treated by LSP. The values of surface roughness of all the tested samples would tend to be stable after one LSP impact, and there was an ultimate value for the surface roughness after multiple LSP impacts, which was about 0.58 μm. (b) With the increase of initial surface roughness, the compressive residual stress decreased when subjected to one LSP impact. The surface residual stress of all the samples tended to be saturated after three LSP impacts, and the saturated value was nearly equal. (c) With the increase of initial surface roughness, the microhardness of all the samples increased when subjected to one LSP impact.

Investigated on Fatigue Properties of Aluminum Ally 7050T7451 with Fastener Holes by Laser Shock Processing

Based on the FEM code ABAQUS and MSC.Fatigue, the process of LSP before hole-drilling was adopted to study the residual stress field of aluminum alloy7050T7451 with Fastener Holes after Laser shock processing (LSP), and the fatigue life of the specimens by LSP was analyzed in this paper. The results indicate that multiple laser shock processing can improve the residual compressive stress and fatigue life to a certain degree, and with the increasing number of shot, the strengthening effect gradually decreases. The ratio of the fatigue life of specimens treated by LSP to the fatigue life of untreated specimens is gradually decreased as the mean stress σm increases, and when the σm is 67.3MPa, the fatigue life of specimens treated by LSP advances 719%, compared with that of untreated specimens.

Effects of multiple laser shock processing (LSP) impacts on mechanical properties and wear behaviors of AISI 8620 steel

The aim of this paper was to address the effects of multiple laser shock processing (LSP) impacts with different pulse energy on mechanical properties and wear behaviors of AISI 8620 steel. Wear analyses were conducted by means of calculation of volume loss and scanning electron microscope (SEM) of the wear surface. Surface profiles, roughness and micro-hardness were measured. The micro-structures in the surface layer of the untreated and LSPed samples (treated by multiple LSP impacts) were investigated by using transmission electron microscopy (TEM) observations. Experimental results and analyses indicated that multiple LSP impacts can remarkably improve the wear resistance of AISI 8620 steel, and the wear mechanism of multiple LSP impacts on AISI 8620 steel was also entirely revealed. The wear process of the unpolished sample subjected to multiple LSP impacts can be described as follows: the wear rate was big at the beginning of sliding dry wear, but then decreased after the micro-indention in the sample surface was polished to the disappear. This phenomenon can be attributed to the fact that multiple LSP impacts generate many micro-indents in the sample surface.

Micro-structural strengthening mechanism of multiple laser shock processing impacts on AISI 8620 steel

Micro-structural evolution in the near-surface region of AISI 8620 steel subjected to multiple laser shock processing (LSP) impacts were investigated by means of cross-sectional optical microscopy (OM) and transmission electron microscopy (TEM) observations. Micro-structural evolution process subjected to multiple LSP impacts can be described as follows: (i) the parallel lamellar pearlites are broken into bitty pearlites, and dislocation activities simultaneously led to the formation of dislocation lines (DLs) and dislocation pile-ups in original grains; (ii) bitty pearlites were all broken into Fe 3C granules, and dislocation movement made Fe 3C granules disperse near subgrain boundaries and led to subgrain boundaries separating individual cells, and (iii) subgrain boundaries were refined to grain boundaries. Multiple LSP impacts on AISI 8620 steel had dual-function: the refinement of coarse grains in the near-surface region by dislocation movement and dispersion strengthening of C atoms which cut cementite and diffused into the ferrite by moving dislocations.

Investigated on Residual Stress Field of Aluminum Alloy 7050T7451 with Fastener Holes by Laser Shock Processing

Laser shock processing (LSP) is a new technique for surface strengthening of fastener holes. The process of LSP before hole-drilling was adopted. A finite element model was established to study the effects of laser shock parameters on the residual stress field of aluminum alloy7050T7451 with Fastener Holes. The results indicate that increasing the laser power density until a fixed value results in a large peak in the hole-edge surface residual compressive stress. The hole-edge surface residual compressive stress and the depth of residual compressive stress are both increased with the increase of laser pulse width. Multiple laser shock processing can improve the residual compressive stress greatly, and with the increasing number of shot, the strengthening effect is gradually diminished.

Grain refinement mechanism of multiple laser shock processing impacts on ANSI 304 stainless steel

Micro-structural evolution and grain refinement in ANSI 304 stainless steel subjected to multiple laser shock processing (LSP) impacts were investigated by means of cross-sectional optical microscopy and transmission electron microscopy observations. The plastic strain-induced grain refinement mechanism of the face-centered cubic (fcc) materials with very low stacking fault energy was identified. The micro-structure was obviously refined due to the ultra-high plastic strain induced by multiple LSP impacts. The minimum grain size in the top surface was about 50–200 nm. Multidirectional mechanical twin matrix (MT)–MT intersections led to grain subdivision at the top surface during multiple LSP impacts. Furthermore, a novel structure with submicron triangular blocks was found at the top surface subjected to three LSP impacts. The grain refinement process along the depth direction after multiple LSP impacts can be described as follows: (i) formation of planar dislocation arrays (PDAs) and stacking faults along multiple directions due to the pile up of dislocation lines; (ii) formation of submicron triangular blocks (or irregularly shaped blocks) by the intersection of MT–MT (or MT–PDA or PDA–PDA) along multiple directions; (iii) transformation of MTs into subgrain boundaries; (iv) evolution by continuous dynamic recrystallization of subgrain boundaries to refined grain boundaries. The experimental results and analyses indicate that a high strain with an ultra-high strain rate play a crucial role in the grain refinement process of fcc materials subjected to multiple LSP impacts.