Laser shock processing of Ti-6Al-4V alloy

Abstract

Laser shock processing of Ti-6Al-4V alloy is considered. A mathematical model governing the laser non-conduction-limited heating is introduced and a numerical solution for the temperature distribution is presented. The pressure (recoil pressure) generated across the solid-vapour interface is determined and it is considered as an impact load for the elastic-plastic wave generation in the surface region of the substrate material. The depth of the plastic region is predicted from the elastic-plastic wave propagation analysis. An experiment is carried out to ablate the surface using a neodymium-doped yttrium aluminium garnet laser with 8 ns pulse length and 0.5 J energy content. Scanning electron microscopy is carried out to examine the surface morphology of the irradiated region. It is found that microhardness increases by 1.5 times the base hardness of the substrate material. The depth of the plastic region predicted extends 0.195 mm from the surface, which agrees well with the experimental findings. In addition, some localized microcracks are observed at the surface of the workpiece.

Laser Peening Process and Its Impact on Materials Properties in Comparison with Shot Peening and Ultrasonic Impact Peening

“…However, it was reported that the difference between the maximum for one and two shocks was 30 [53]. Therefore, it can be seen from Figure 14 and the ΔHV data from [53] that the difference between the minimum and maximum values are relatively close as compared to the ΔHV data from [93]. The variations observed by Yilbas et al [93] and Zhang et al [53] could be due to the initial conditions of the treated sample or processing parameters.…”

“…From this figure, it is evident that moving away from the shocked region results in hardness decrease to the base material, which has been attributed to the presence of tensile stresses [82]. Yilbas et al [93] also found that the microhardness of the Ti-6Al-4V after LSP was 1.5 times of the base material as shown in Figure 15. The hardness increase was attributed to the increased dislocation densities [49,76,85,128] and twinning deformation [82,96].…”

“…Recent LSP studies have shown that laser peening technique can be used for shaping and forming of metals [47] and inspection of coatings [80] as discussed in Section 4. The materials laser peened include titanium alloys [11,13,53,54,55,65,66,71,72,82,83,84,85,86,87,88,89,90], aluminum alloys [3,5,60,61,62,64,75,76,90,91,92,93,94,95,96,97,98,99,100,101,102,103,104], different steel grades [8,66,69,70,79,97,105,106,107,108,109,110,111,112,113,114,115,116,117,118,…”

“…For the TEM technique, typical information revealed are dislocation structure [ 11 , 79 , 91 , 141 , 142 ], dislocation entanglement [ 3 , 105 , 143 ], dislocation band [ 69 ] and precipitate structure [ 69 , 91 , 105 ]. SEM technique on the other hand, provides surface and subsurface features such as surface microcracks [ 82 , 83 ], macrocracks [ 144 ], fretting cracks [ 71 ], mild indentations [ 93 ], melting due to ablation [ 95 ] and other surface irregularities from the LSP process [ 54 ]. The measured compressive residual stress induced during the LSP is an important indicator of the effectiveness of the LSP process.…”

Effect of Multipath Laser Shock Processing on Microhardness, Surface Roughness, and Wear Resistance of 2024-T3 Al Alloy

“…One of the examples of the surface modification techniques is the laser shock processing. Laser shock processing (LSP) is an innovative surface treatment, with which mostly a Q-switched Nd:YAG laser with short pulses of several nanoseconds and with a power density, in the pulse peak, of as much as several tens of GW/cm 2 is used [ 1 , 2 ]. The high magnitude stress wave generated by the interaction between the high-power, short pulsed lasers and the materials can produce plastic deformation.…”