Study On Microstructure Evolution And Machining Surface Integrity In Single Crystal Silicon Nanomachining

Mono-crystalline silicon is widely used in aerospace,semiconductor and other industries due to its excellent properties.However,for brittle materials such as single crystal silicon,the brittle and plastic removal modes will occur as the cutting scale changes during processing.This cutting property of brittle materials is closely related to the evolution of micro-structure.At the same time,the evolution of micro-structures will not only result in different processing removal modes,but also affect the surface integrity of the processed work-pieces.Therefore,this article is starting from the perspective of micro-structure evolution,using the molecular dynamics simulation method and exploring the effects of micro-structure evolution and micro-structure evolution on the processing surface integrity under both the plastic and brittle removal modes.First of all,in order to observe the micro-structure evolution process intuitively,this paper focuses on Introducing the commonly micro-structural identification methods.By comparing the advantages and disadvantages of different micro-structure identification methods,at least three methods——atomic number method,energy method and dislocation extraction method,were chosen to study the micro-structure evolution during nano-cutting.Secondly,the micro-structure distribution and micro-structure evolution process which are in the process of single crystal silicon plastic removal are analyzed in detail.And the influence of micro-structure evolution on the processed surface integrity which is reflected by analyzing the change of the depth of metamorphic layer and the surface roughness is verified by experiment.The formation of chips and the forming process of the machined surface in the plastic removal mode were analyzed by means of the atomic snapshots and potential energy changes of the work-piece,and the area for the study of micro-structure evolution was selected.The atomic number method was used to analyze the micro-structure distribution and micro-structure evolution of the selected region.The nano-cutting process is revealing the regular pattern of micro-structure evolution.At the same time,the influence of cutting parameters on micro-structure distribution andmicro-structure evolution is illustrated by studying the micro-structural distribution and micro-structure evolution of the work-piece under the different cutting depths and cutting speeds.Finally,the micro-structural distribution and micro-structural evolution during the removal of single crystal silicon brittleness are described in detail,and the integrity of the processed surface is analyzed by the depth of the metamorphic layer and the surface roughness.The brittleness removal process was analyzed from the atomic transients and potential energy changes in the nano-cutting process,and compared with the macro-brittle removal process,indicating that the nano-cutting process under this condition is indeed performing brittle removal.At the same time,the evolution process of phase transitions and dislocations in the nano-cutting process was analyzed,and it was found that the nucleation and proliferation of dislocations were a major factor in the brittleness removal of single crystal silicon.