Brittle-ductile transition in monocrystalline silicon analysed by molecular dynamics simulation
Brittle-ductile transition in monocrystalline silicon analysed by molecular dynamics simulation
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DOI：
10.1243/095440604774202213
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发表时间：
2004-06
期刊：
影响因子：
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通讯作者：
H. Tanaka;S. Shimada;N. Ikawa
中科院分区：
文献类型：
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作者：
H. Tanaka;S. Shimada;N. Ikawa
为了更好地理解单晶硅材料在极小切深下的材料去除机理和材料去除过程中的脆韧转变，采用分子动力学（MD）计算机模拟方法对无缺陷单晶硅三点弯曲的非尺度变形行为进行了分析。MD模拟表明，塑性变形发生通过从金刚石到非晶结构的相变。八面体相变的临界剪切应力为12-14 GPa。在变形区，由于原子的热激活振动，可以产生原子尺度的裂纹核。裂纹成核后，在一定的应力场作用下发生扩展。当拉应力在裂纹核处达到约30 GPa的某一临界值时，裂纹开始萌生。塑性变形和裂纹萌生的临界值取决于晶体取向和静水压力。结果表明，也可以有临界准则的应力场，以确定是否塑性变形或裂纹萌生将占主导地位发生。当塑性变形进行到裂纹萌生时，可以实现延性模式加工。
For a better understanding of essential mechanisms of material removal at extremely small depth of cut and of the brittle-ductile transition in the material removal process of monocrystalline silicon, nonometric deformation behaviour in three-point bending of defect-free monocrystalline silicon is analysed by molecular dynamics (MD) computer simulation. MD simulations show that plastic deformation takes place through a phase transformation from diamond to amorphous structures. The critical octahedral shearing stress for phase transformation is estimated to be 12–14 GPa. In the deformed region, a crack nucleus on atomic scale can be generated owing to thermally activated vibration of atoms. After the crack nucleus, the crack extension takes place under a certain stress field. The crack initition takes place when a tensile stress reaches a certain critical value of about 30 GPa at the crack nucleus. The critical values for plastic deformation and crack initiation depend on crystal orientation and hydrostatic pressure. It is shown that there can also be critical criteria of the stress field to determine whether plastic deformation or crack initiation would predomiantly take place. When the plastic deformation proceeds to a crack initiation, ductile mode machining can be realized.