重复纳米切削对γ-TiAl合金表面质量及亚表面损伤的影响

Effect of Repeated Nanocutting on Surface Quality and Subsurface Damage of γ-TiAl Alloy

本研究运用分子动力学方法对单晶γ-TiAl合金重复纳米切削过程进行了模拟,研究了重复纳米切削过程中的切削力和微观缺陷演化,分析了已加工表面的粗糙度和残余应力,讨论了重复纳米切削和单次切削之间的差异。结果表明:重复纳米切削伴随着位错的形成和湮灭,第2次切削过程中的位错线长度波动小于第1次切削,切削状态更稳定;加工初始阶段的切削力迅速增大,随后切削力进入稳定加工阶段,同时发现,第2次切削的切削力小于第1次切削;二次切削后,残余应力分布更加均匀,且刀具的二次挤压作用使得加工表面层残余压应力增大;两次切削加工可以提高表面质量和降低亚表面损伤,而残余压应力的增大及加工所需能量的增加降低了已加工表面的可塑性,使得第3次切削加工对表面和亚表面没有明显改善。

In this paper,the repeated nanocutting process of single crystal γ-TiAl alloy was simulated by molecular dynamics method.The evolution of cutting force and microstructure defects in the repeated nanocutting process was studied.The roughness and residual stress of the machined surface were analyzed,and the difference between the repeated nanocutting and the single cutting was discussed.The results show that the repeated nano-cutting process is accompanied by the formation and annihilation of dislocations,and the fluctuation of dislocation line length in the second cutting process is less than that in the first cutting process,and the cutting state is more stable.The cutting force increases rapidly in the initial stage of machining,and then the cutting force enters the stable machining stage.At the same time,it is found that the cutting force of the second cutting is less than that of the first cutting.After the second cutting,the residual stress distribution is more uniform and the residual compressive stress of the machined surface increases due to the twice extrusion of the tool.Secondary machining can improve surface quality and reduce subsurface damage,while the increase in residual compressive stress and energy required for machining reduces the plasticity of the machined surface,so that the third machining has no obvious improvement in surface and subsurface quality.