| DENG Yansheng,CAO Changhong,TAO Yanhui,SUN Cong,WANG Yanyan.Aluminum Nitride Surface Modification Mechanism by Laser Ultrasonic-assisted Grinding[J],53(22):141-148, 160 |
| Aluminum Nitride Surface Modification Mechanism by Laser Ultrasonic-assisted Grinding |
| Received:June 04, 2024 Revised:September 25, 2024 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2024.22.012 |
| KeyWord:molecular dynamic laser-ultrasound assisted grinding aluminum nitride alumina reinforced phases |
| Author | Institution |
| DENG Yansheng |
Jihua Laboratory, Guangdong Foshan , China |
| CAO Changhong |
Xinjiang Institute of Technology, Urumchi , China |
| TAO Yanhui |
Xinjiang Institute of Technology, Urumchi , China |
| SUN Cong |
Northeastern University, Shenyang , China |
| WANG Yanyan |
Centre for Vision, Speech and Signal Processing CVSSP, University of Surrey GU2 7XH, UK |
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| Abstract: |
| Aluminium nitride (AlN), as a covalently bonded compound with a fibrillar zincite-type crystal structure, has excellent properties such as super bandgap width (6.20 eV), high thermal stability (melting point of 3 214 ℃), high breakdown field (1.2-1.4 mV/cm), and good ultraviolet penetration. Single-crystal AlN as an epitaxial substrate can significantly reduce the defect density in the device and effectively improve the performance of the device. In addition, aluminum nitride ceramics are versatile, mainly used in electronic heat dissipation, microwave communications, aerospace, heat exchangers, functional materials and other fields. However, the AlN meets the brittle fracture during the manufacture process and the using process. Therefore, a number of surface enhancement methods are applied in the machining of brittle materials, such as laser-assisted grinding (LAG), ultrasound-assisted grinding (UVAG), magnetic-field-assisted grinding (MFAG), chemical-mechanical polishing (CMP) process, and electrolytic internal dressing (ELID) grinding process. However, existing processing technologies are limited on improving mechanical properties and strengthening mechanisms of AlN ceramics. To fill these gaps, an efficient laser ultrasonic-assisted grinding (LUAG) was proposed and the molecular dynamic was applied, combining laser heating and ultrasonic vibration with abrasive grain processing technology. The AlN surface generation mechanism was investigated by LUAG. With the help of molecular dynamic, the microscopic material removal evolution process of AlN surface was studied from grinding force field, atomic phase transition, and subsurface damage depth field. The traditional grinding (TG), the LAG, the UVAG and the LUAG were used to machine the AlN surface. The specific AlN surface material removal mechanism and the surface material evolution mechanism were discussed respectively. The primary cause of the material transformation was that the stability of the transformed cubic AlN was smaller than the close-packed hexagonal AlN. The softened surface material caused by the high temperature and the high pressure resulted from the combination effect between the laser and ultrasonic. Meanwhile, the abrasive vibration of the wheel decreased the local high temperature region and formed a more uniform thermal distribution. To be specific, the laser energy is utilized to cause the atomic phase transition of the surface and the ultrasonic is used to decrease the surface material accumulation, which presents a smaller grinding force in LUAG processing technology. Therefore, the blank space is efficiently restrained. Furthermore, a small quantity of the generated Al2O3 is beneficial for the dispersion strengthening of the machined surface. It is the decreased grinding force that weakens the movement of the material dislocation. Compared to TG, LUAG produces 50% lower grinding forces and 28.4% lower surface roughness. The surface hardness of AlN is up to 1 298.6HV, which is 25% higher than that of TG. The wear marks and subsurface damage depth on the surface of AlN are reduced by 50% and 33%, respectively. The small amount of alumina produced by LUAG is used as a reinforcing phase for diffusion strengthening to achieve material hardening and improve wear resistance of the substrate. The results of this research deepen the understanding of material removal and damage under the coupled effects of laser, ultrasonic, and abrasive processing while facilitating and enabling high-performance fabrication of AlN substrate surfaces. |
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