摘要
根据EAM多体势,利用分子动力学方法模拟了Ni压头压入Al基体的纳米压痕全过程.包括压头接近和离开基体时的原子组态;压入和上升时的载荷-位移曲线以及位错的发射和形变带的产生和变化;同时模拟了纳米尺度的应力弛豫行为.结果表明,当压头尚未接触基体时就能吸引基体原子,通过缩颈而互相连接.当压入应力Ts为1.9 MPa时,基体Al开始发射位错;当分切应力Td=6.4 MPa时,出现形变带.压头上升过程出现反向的拉应力,使基体反向屈服,在卸载过程中基体残留位错的组态不断改变.当压头上升离开基体后能拉着基体通过缩颈而相连,当压头和基体分离后仍粘有基体原子.在纳米尺度也存在应力弛豫现象,其原因是热激活引起的位错发射和运动.
The plastic deformation process during nanoindentation of Ni tip into Al substrate, including loading, unloading and stress relaxation has been studied by using molecular dynamics simulation with EAM potential. Results showed that a connective neck between the indenter and the substrate will be formed when the indenter approaches and leaves the substrate surface. During nanoindentation, the first dislocation is emitted at a critical shear stress tau(s)=1.9 MPa, and shear bands appear at partial shear stress tau(d)=6.4 MPa. When the indenter moves upwards, a reverse tensile stress appears and results in reverse yield of the substrate and continuous change in dislocation configuration. When the indentation tip is retracted and passed through its initial indentation position, it connects to the substrate by necking, and when the tip broke away from the substrate finally, there still exist some substrate atoms on the tip. Stress relaxation has been observed on the nanoscale, which attributes to heat activated dislocation emission and motion.
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2004年第12期1238-1242,共5页
Acta Metallurgica Sinica
基金
国家自然科学基金项目50325209
50232030
50172006
50171012国家重大基础研究规划项目19990650资助
关键词
纳米压痕
分子动力学模拟
位错发射
形变带
应力弛豫
nanoindentation
molecular dynamics simulation
dislocation emission
shear band
stress relaxation
