Surface formation mechanism in ultraprecision diamond turning of coarse-grained polycrystalline ZnSe
Surface formation mechanism in ultraprecision diamond turning of coarse-grained polycrystalline ZnSe
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DOI：
10.1016/j.ijmachtools.2020.103554
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发表时间：
2020-06-01
影响因子：
14
通讯作者：
Yan, Jiwang
中科院分区：
文献类型：
--
作者：
Huang, Weihai;Yan, Jiwang
硒化锌是一种优良的红外光学材料。在这项研究中，超精密金刚石车削实验进行了各种条件下的粗晶粒多晶ZnSe（p-ZnSe）和相应的表面形成机制进行了研究，通过检查的表面形貌，芯片形态，材料微观结构的变化，和切削力。观察到两种类型的表面缺陷（即犁削诱导的微米级解理坑和撕裂诱导的亚微米级撕裂坑）。据确定，犁诱导的微米级解理坑可以通过减少未变形的芯片厚度来抑制。此外，它被确定，撕裂引起的亚微米级撕裂坑可以通过使用具有零前角的切削刀具来抑制。最小的表面粗糙度占主导地位的晶界台阶时，形成的切削工具在一个大的角度跨越孪晶界。提出了一个模型，表面缺陷和边界台阶与晶体取向和切削方向。通过使用大刀尖金刚石刀具进行切削，获得了1.5nm Sa的光滑表面。此外，在切削切屑中观察到锌的氧化物到朱砂的相变，并且切削切屑的金属化发生在极小的未变形切屑厚度（类似于20 nm）处。此外，还发现工件内部的相变取决于刀尖半径。研究结果为脆性多晶材料的超精密加工提供了重要参考。
Zinc selenide is an excellent infrared optical material. In this study, ultraprecision diamond turning experiments were carried out on coarse-grained polycrystalline ZnSe (p-ZnSe) under various conditions and the corresponding surface formation mechanisms were investigated by examining the surface topography, chip morphology, material microstructural change, and cutting forces. Two kinds of surface defects were observed (i.e. plowing-induced micron-scale cleavage craters and tearing-induced submicron-scale tearing pits). It was determined that plowing induced micron-scale cleavage craters could be suppressed by reducing undeformed chip thickness. Furthermore, it was ascertained that tearing-induced submicron-scale tearing pits could be restrained by using a cutting tool with a zero rake angle. The minimal surface roughness was dominated by grain boundary steps formed when the cutting tool crossed twin boundaries at a large angle. A model was proposed for correlating surface defects and boundary steps with crystal orientations and cutting directions. By using a large-nose diamond tool for cutting, a smooth surface of 1.5 nm Sa was obtained. In addition, a zinc blende to cinnabar phase transformation was observed in the cutting chips, and metallization of cutting chips occurred at an extremely small undeformed chip thickness (similar to 20 nm). Moreover, it was discovered that phase transformation inside the workpiece depends on the radius of the tool nose. The findings of this study provide an important reference for ultraprecision machining of brittle polycrystalline materials.