加工参数对单晶γ-TiAl表面质量和亚表层损伤的影响机理

Influence mechanism of machining parameters on surface quality and subsurface damage of single crystalγ-TiAl

为研究加工工艺参数对纳米切削单晶γ-TiAl合金表面质量和亚表层损伤的影响机理,以分子动力学(molecular dynamics,MD)为基础理论,采用非刚性金刚石刀具建立三维纳米切削模型,通过研究切屑体积、表面粗糙度、静水压分布、位错密度、位错演化、相变原子数,详细分析不同切削速度和切削深度对表面和亚表面结构的影响。结果发现:随着切削速度的增加,切屑体积增大,加工效率提升,且存在切削速度为100 m/s的临界值。表面粗糙度先减小后增大,同样存在切削速度为100 m/s的临界值。位错的复杂程度降低,位错密度减小,塑性变形程度增加;随着切削深度的增加,切屑体积增大,加工效率提升,表面粗糙度、位错密度以及塑性变形程度显著增加。在切削过程中,发现位错主要分布在刀具前方和下方,在刀具前方45°方向存在V形位错和梯杆位错以及位错间的相互反应,且切削完成后残留下空位和原子团簇等稳定缺陷。

To study the influence mechanism of machining process parameters on surface quality and subsurface dam-age of nano-cutting single crystalγ-TiAl alloy,molecular dynamics(MD)was used as the basic theory.Using a non-ri-gid diamond tool,a three-dimensional nano-cutting model was established,and the influence of different cutting speeds and depths of cut on the surface and subsurface structure were analyzed in detail by studying chip volume,surface roughness,workpiece hydrostatic pressure distribution,dislocation density,dislocation evolution,and phase transitions atomic number.The results showed that with the increase of cutting speed,the chip volume increases,the machining ef-ficiency improves and there is a critical value of the cutting speed of 100 m/s,the surface roughness first decreases and then increases and there is also a critical value of the cutting speed of 100 m/s,the complexity of dislocations reduces,the density of dislocations decreases,and the degree of plastic deformation increases.However,with the increase of cut-ting depth,the chip volume increases,the machining efficiency improves,the surface roughness,the density of disloca-tions and the degree of plastic deformation increase significantly,and it was found that the dislocations were mainly dis-tributed in front of and below the tool during cutting process,and there were V-shaped dislocations and stair rod disloca-tions in the direction of 45o in front of the tool,as well as dislocations reacting with each other,and stable defects such as vacancies and atomic clusters remained after the cutting process.