Author/Authors :
Lu، نويسنده , , J.Z. and Zhong، نويسنده , , J.W. and Luo، نويسنده , , Cell K.Y. and Zhang، نويسنده , , L. and Dai، نويسنده , , F.Z and Chen، نويسنده , , K.M. and Wang، نويسنده , , Q.W. and Zhong، نويسنده , , J.S. and Zhang، نويسنده , , Y.K.، نويسنده ,
Abstract :
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 Fe3C granules, and dislocation movement made Fe3C 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.
Keywords :
Grain refinement , Plastic deformation , dispersion strengthening , Dislocation movement , Laser shock processing