(復(fù)旦大學(xué) 航空航天系，上海200433)
摘 要: 為了研究納米材料的微觀變形過(guò)程，采用橋域方法(Bridging domain method)對(duì)納米尺度下Cu薄膜表面摩擦過(guò)程進(jìn)行模擬，得到摩擦阻力和系統(tǒng)變形能隨摩擦距離的變化曲線，摩擦過(guò)程中存在靜-動(dòng)摩擦轉(zhuǎn)化點(diǎn)。微觀分析表明：摩擦初期Cu薄膜變形處于彈性階段，隨壓頭前方原子堆積，Cu薄膜進(jìn)入塑性變形階段，直接出現(xiàn)4層及以上原子的穩(wěn)定滑移，同時(shí)薄膜內(nèi)發(fā)射出沿非摩擦方向的斜向滑移帶。以中心對(duì)稱系數(shù)為度量捕捉到斜向滑移帶內(nèi)V形位錯(cuò)結(jié)構(gòu)的產(chǎn)生與演化過(guò)程，確定V形位錯(cuò)的運(yùn)動(dòng)對(duì)摩擦塑性階段的變形釋放起主導(dǎo)作用。此外，對(duì)位錯(cuò)原子數(shù)目的統(tǒng)計(jì)分析表明，宏觀下薄膜表面摩擦阻力的多次突跳是由微觀結(jié)構(gòu)下不全位錯(cuò)向全位錯(cuò)的發(fā)展所致；最后定量化分析位錯(cuò)、孿晶等不同變形機(jī)制對(duì)總應(yīng)變的貢獻(xiàn)比重，得到摩擦過(guò)程中位錯(cuò)滑移原子的應(yīng)變貢獻(xiàn)比重穩(wěn)定在10%左右，而孿晶遷移的應(yīng)變貢獻(xiàn)比重穩(wěn)定在2.5%左右。
關(guān)鍵字: 納米Cu薄膜；三維；橋域法；納米摩擦；位錯(cuò)
（Department of Aeronautics and Astronautics, Fudan University, Shanghai 200433, China）
Abstract:The scratch process of nano-Cu film has been investigated by using Bridging domain method. The friction force and system deformation energy vary with scratch distance in a similar trend, and there is a static-dynamic transition point in the scratch process. The microstructural analysis shows that the restorable strain occurs locally in Cu film at elastic stage, and then with the pile-up atoms in the front of indenter, the deformation of Cu film turns into plastic stage. The stable multilayer slip and a slanting slip zone along [1,0,1] are captured under the indenter.The generation and evolution of V shape dislocation in the slanting slip zone are analyzed via the centrosymmetry parameter, and the motion of V shape dislocation plays a leading role in the deformation release at plastic stage. In addition, statistical analysis for different dislocation atoms reveals that the development from partial dislocation to perfect dislocation leads to multiple jumps in friction force. The strain contribution analysis shows that the proportion of dislocation slip is finally about 10%, while twinning migration contributes less to the total strain, the proportion is finally about 2.5%.
Key words: nano-Cu film; three-dimension; bridging domain method; nano-friction; dislocation
