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Subsurface damage and phase transformation in laser-assisted nanometric cutting of single crystal silicon
摘要： Single crystal Si subsurface damage and phase transformation caused by laser-assisted nanometric cutting were investigated in this paper through the ultraprecision cutting experiments and molecular dynamics simulation. Post-cutting examination of a crystal’s subsurface revealed a distorted Si-I layer and an amorphous Si with embedded nanocrystalline Si-III and Si-XII. As a result of insufficient contact pressure during laser-assisted cutting, the amorphous Si was directly generated from the Si-I through the collapse of the crystal lattice rather than from the intermediate high-pressure phase Si-II. The newly-formed amorphous Si crystallized partially during the laser-assisted cutting and transformed into metastable Si-III and Si-XII phases caused by the laser annealing effect. In comparison to machining without laser assistance, it was found that dislocation activity was increased by a factor of ~8×1014 when laser assistance was applied. This gave rise to enhancement of plastic deformability of the material, with the critical ductile-brittle transition depth of cut increasing from 150 nm to 395 nm and the thickness and extent of stress in the distorted Si-I subsurface layer being reduced.
关键词： single crystal silicon,laser assisted,phase transformation,nanometric cutting,subsurface damage
更新于2025-09-16 10:30:52
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Effects of laser-assisted grinding on surface integrity of zirconia ceramic
摘要： Zirconia ceramics has an important position in the field of biomaterials because of excellent mechanical properties. Because of abrasive resistance and hardness, conventional machining of zirconia ceramic is difficult and time-consuming. A nontraditional hybrid laser-assisted grinding (LAG) system combining laser and cubic boron nitride (CBN) grinding wheel was developed for machining zirconia ceramic. This hybrid system utilizes the outstanding thermostability of zirconia ceramic: The material present on the cutting path is rapidly removed by local laser heating and grinding wheel. A combined theoretical and experimental study was performed to evaluate different modes of machining of zirconia ceramic. The machining parameters were predicted by numerical analysis. The surface quality, surface morphology, and subsurface damage of zirconia ceramic specimens were analyzed and compared. The results show that LAG can easily achieve ductile regime grinding in the same machine tool. Compared with conventional grinding, the surface integrity of zirconia ceramic was significantly improved by the LAG process. LAG could achieve ductile regime grinding with a large depth-of-cut. It changes the machinability of zirconia ceramic.
关键词： Surface quality,Surface morphology,Laser-assisted grinding,Zirconia ceramic,Subsurface damage
更新于2025-09-11 14:15:04