Gradient plastic strain accommodation and nanotwinning in multi-pass laser shock peened 321 steel

Laser shock peening rounds influencing microstructural and mechanical properties of 300M steel

“…After one round of LSP, dislocations proliferated massively and interacted continuously, forming dislocation walls (Figure 10a). Meanwhile, the high strain rate PD also promoted the formation of mechanical twins (Figure 10b), similar to that LSP-treated AISI 321 steel, 420 steel and NiTi alloy [29][30][31]. With an increase in rounds of LSP, density of dislocation and mechanical twins gradually increased in the subsurface layer.…”

“…Continuous high strain rate deformation contributes to twin splitting and dislocation accumulation and annihilation to coordinate deformation to form LAGBs [13]. As deformation continues, LAGBs formed by lattice substructures gradually evolve into HAGBs [29], which eventually result in the formation nanocrystals in surface shown in Figure 8. Such extreme grain refinement makes it difficult for deformation twins to persist, explaining that no deformation twins were found in surface layer.…”

Bubble dynamic evolution, material strengthening and chemical effect induced by laser cavitation peening

“…Plastic deformation is one of the important strengthening mechanisms of material treated by LSP and CP, which introduces residual stress on the surface layer and improves the yield strength of material [34] , [35] , [36] . The plastic deformation of Q235 steel after the treatment of LCP was investigated, and the results are shown in Fig.…”

Laser shock peening: a promising tool for enhancing the aeroengine materials’ surface properties

“…The laser beam directly ablates the sample surface during the laser peening process in laser peening without a (absorbent) coating process. Due to high temperature, the laser beam interacts with the sample surface, leading to melting and resolidification of the peened surface [90,91]. In addition, this process induces tensile residual stress on the surface and causes an oxygen-rich layer.…”

“…The surface properties were observed to be further enhanced by repeated laser impacts [93]. Earlier investigations reveal that the increase in laser impact increases the magnitude and depth of induced CRS on titanium, steel, aluminium, and nickel alloys, as indicated in Table [79,91,93,94]. Masse and Barreau [95] investigated the effect of multiple laser peening on 0.55%C steel.…”