单晶Cu纳米杆拉伸力学特性的尺寸依赖性模拟  

SIMULATION OF SCALE DEPENDENCY ON TENSILE MECHANICAL PROPERTIES OF SINGLE CRYSTAL COPPER NANO-ROD

作　　者：白清顺[1] 童振[1] 梁迎春[1] 陈家轩[1] 王治国[1] 

机构地区：[1]哈尔滨工业大学机电工程学院,哈尔滨150001

出　　处：《金属学报》2010年第10期1173-1180,共8页Acta Metallurgica Sinica

基　　金：国家杰出青年科学基金项目50925521;国家自然科学基金项目50705023;哈尔滨工业大学科研创新基金项目HIT.NSRIF.2009012;黑龙江省自然科学基金项目E200903资助~~

摘　　要：对圆形、方形截面形状的单晶Cu纳米杆拉伸变形过程进行了分子动力学模拟.通过中心对称参数方法并结合位错形核理论分析了截面形状、截面面积和长细比对纳米杆拉伸力学特性的影响,研究了单晶Cu纳米杆拉伸力学特性的尺寸依赖性.结果表明:首次屈服后,纳米杆在"位错形核-位错延伸与滑移-晶格原子交叉滑移"的交替循环作用机制下,产生塑性变形;截面形状对纳米杆拉伸变形的初始塑性影响较小,而对纳米杆拉伸力学特性的影响较大;随着截面面积的增大,两种截面形状的纳米杆都出现首次屈服点提前,屈服应力减小和弹性模量增大的现象;与方形截面形状纳米杆相比,圆形截面形状纳米杆的屈服应力的变化率较小,其弹性模量的变化率较大;当截面面积增大到500nm^2后,两种截面形状纳米杆的弹性模量趋于稳定,其值接近理论值84GPa.加大仿真规模后,长细比对纳米杆的拉伸力学特性略有影响.The tension process of single crystal Cu nano-rods with different cross section shapes were simulated by molecular dynamics at atomic scale.Based on centrosymmetry parameter method and combined with the dislocation nucleation theory,the effect of cross-section shape,cross-sectional area and slenderness ratio on the tensile mechanical properties of the nano-rods were analyzed,and the scale dependency of tensile mechanical properties of the single crystal Cu nano-rods has been studied.The results show that after first yield,the nano-rods produce plastic deformation under the ＂dislocation nucleation-extended dislocation and sliding-lattice atom cross-slip＂ mechanism of the alternating cycle.The geometry of cross-section has negligible effects on the tensile initial plasticity of the nano-rods,while it shows apparent effects on the tensile mechanical properties.With the increase of cross-sectional area,two types of nano-rods have the phenomenon of early yield point,yield strength decreases and Young＇s modulus increases.Compared with that of the square cross-sectional nano-rod, the variable rate of yield stress of the circular cross-sectional nano-rod is smaller and the variable rate of Young＇s modulus is larger.As the cross-sectional area increases to 500 nm^2,the Young＇s modulus of the two types of nano-rods become stable,and is close to the theoretical value of 84 GPa.Moreover, the slenderness ratio of the nano-rods has a slight effect on the tensile mechanical properties when the simulation size increased.

关 键 词：分子动力学 拉伸 纳米杆 位错形核 力学特性 

分 类 号：TG113.25[金属学及工艺—物理冶金] TB303[金属学及工艺—金属学]