4H-SiC热辅助纳米切削机理的分子动力学研究

Study on the Material Removal Mechanism of 4H-SiC in Thermally Assisted Nanometric Cutting

摘要:

4H-SiC因其优异的热导率、高击穿电压和良好的高温稳定性，在功率电子与高频器件等领域具有重要应用。然而，其极高的硬度和较低的断裂韧性导致在纳米尺度切削加工面临亚表面损伤严重、刀具磨损严重等问题。研究表明热辅助加工能显著改善材料的加工性能，调控不同的切削温度有益于促进塑性变形和提高加工效率，因此探究温度对4H-SiC纳米切削过程中材料去除机理的影响具有重要意义。本研究采用分子动力学模拟方法，系统研究了不同切削温度(100-1000?K)下4H-SiC的切削力学行为、表面形貌、亚表面损伤、应力分布及位错演变规律。结果表明：随着切削温度升高，平均切削力显著降低，在1000?K时切向与法向切削力较常温(300?K)分别下降15.4%和29.3%；中高温(500-600?K)切削能有效抑制亚表面损伤、缓解应力集中并减少位错密度；但温度过(≥800?K)则会因位错增殖与缠结加剧而导致损伤加深、应力分布范围扩大。本研究揭示了温度调控下4H-SiC的塑性去除机制与损伤演化规律，为其高效低损伤纳米切削加工提供了理论依据。

Abstract:

Owing to its excellent thermal conductivity, high breakdown voltage, and high-temperature stability, 4H-SiC is a promising material for power electronics and high-frequency devices. However, its extreme hardness and low fracture toughness cause severe subsurface damage and rapid tool wear during nanoscale cutting. Thermally assisted machining can improve machinability by promoting plastic deformation and enhancing efficiency; therefore, understanding the temperature-dependent material removal mechanism in nanometric cutting of 4H-SiC is essential. This study employs molecular dynamics simulations to systematically investigate the cutting mechanical behavior, surface morphology, subsurface damage, stress distribution, and dislocation evolution of 4H-SiC under different cutting temperatures (100–1000 K). The results show that the average cutting forces decrease markedly with increasing temperature. At 1000 K, the tangential and normal forces are reduced by 15.4% and 29.3%, respectively, compared with those at room temperature (300 K). Cutting at intermediate temperatures (500–600 K) effectively suppresses subsurface damage, alleviates stress concentration, and reduces dislocation density. However, excessively high temperatures (≥800 K) aggravate damage and broaden the stress distribution due to enhanced dislocation multiplication and tangling. This work reveals the plastic removal mechanism and damage evolution of 4H-SiC under different temperatures, offering a theoretical basis for efficient, low-damage nanometric cutting.