超精密磨削YAG晶体的脆塑转变临界深度预测  

Prediction of brittle-to-ductile transition depth in ultra-precision grinding YAG crystals

作　　者：敖萌灿 黄金星 曾毓贤 吴跃勤 康仁科[1] 高尚[1] AO Mengcan;HUANG Jinxing;ZENG Yuxian;WU Yueqin;KANG Renke;GAO Shang(State Key Laboratory of High-performance Precision Manufacturing,Dalian University of Technology,Dalian 116024,China;Institute of Manufacturing Engineering,Huaqiao University,Xiamen 361021,China)

机构地区：[1]大连理工大学高性能精密制造全国重点实验室,辽宁大连116024 [2]华侨大学制造工程研究院,福建厦门361021

出　　处：《光学精密工程》2024年第1期84-94,共11页Optics and Precision Engineering

基　　金：国家重点研发计划资助项目(No.2022YFB3605902);国家自然科学基金资助项目(No.51975091,No.51991372)。

摘　　要：钇铝石榴石(YAG)晶体是制造固体激光器的重要材料,超精密磨削是加工YAG晶体等硬脆材料零件的重要方法,研究硬脆材料加工表面的微观变形、脆塑转变机理对超精密磨削加工具有重要的指导作用。为了实现YAG晶体低损伤磨削加工,获得高质量表面,基于弹塑性接触理论和压痕断裂力学,通过分析单磨粒划擦作用下材料表面的变形过程,考虑材料的弹性回复、微观下力学性能的尺寸效应,建立了脆塑转变临界深度的预测模型,并计算得到YAG晶体的脆塑转变临界深度为66.7 nm。在此基础上,通过不同粒度砂轮超精密磨削YAG晶体试验对建立的脆塑转变临界深度预测模型进行验证,并计算不同粒度砂轮在相应工艺条件下的磨粒切深。结果表明,磨粒切深高于脆塑转变临界深度时,YAG晶体磨削表面材料以脆性方式被去除,磨削表面损伤严重;磨粒切深低于脆塑转变临界深度时,磨削表面材料以塑性方式被去除,能够获得高质量磨削表面,加工表面粗糙度达到1 nm。建立的脆塑转变临界深度预测模型能够为YAG晶体的低损伤超精密磨削加工提供理论指导。Yttrium aluminum garnet(YAG)crystals are widely used for manufacturing solid-state lasers,and ultraprecision grinding is critical for machining hard and brittle material parts,such as YAG crystals.The investigation of microdeformation and brittle-to-ductile transition mechanisms of hard and brittle mate⁃rial-machined surfaces is necessary for ultraprecision grinding.Based on the elastic-plastic contact theory and indentation fracture mechanics,a model for predicting the critical depth of brittle-to-ductile transitions was established to achieve low-damage grinding of YAG crystals and obtain high-quality surfaces.The de⁃formation process of the material surface under the action of a single abrasive scratch was analyzed,considering the elastic recovery of the material and the size effect of micromechanical properties.The critical depth of the brittle-to-ductile transition of the YAG crystal is 66.7 nm.The proposed prediction model of the critical depth of the brittle-to-ductile transition was verified by ultraprecision grinding of YAG crystals with grinding wheels of different grain sizes.In addition,the grit-cutting depths of different grain-size grinding wheels under the corresponding process conditions were calculated.The results show that when the grit-cutting depth is more extended than the critical depth of the brittle-to-ductile transition,the surface material of the YAG crystal is removed in a brittle manner,and the grinding surface is severely damaged.However,when the grit-cutting depth is less than the critical depth of the brittle-to-ductile transition,the grinding surface material is removed in a ductile manner,high-quality grinding surface can be obtained,and the machined surface roughness can reach 1 nm.The proposed model for predicting the critical depth of the brittle-to-ductile transition provides theoretical guidance for low-damage ultraprecision grinding of YAG crystals.

关 键 词：超精密磨削 YAG晶体 纳米压痕 纳米划痕 脆塑转变 

分 类 号：TN305.2[电子电信—物理电子学] O786[理学—晶体学]