摘要
采用分子动力学模拟了纳晶β-SiC材料在不同晶粒尺寸和应变率下的力学行为以及β-SiC纳米多层复合结构的增韧特性.模拟中分别采用Nosé-Hoover方法和Berendsen方法控制温度和压力,采用Tersoff多体原子势函数描述β-SiC中碳、硅原子间的相互作用.结果表明:在低应变率条件下,小晶粒的纳晶β-SiC的主要破坏方式为晶粒破裂成非晶团簇,非晶团簇和晶界的相互作用提高了纳晶的延展性;而大晶粒的纳晶β-SiC以晶界断裂为主,表现为脆性破坏.在高应变率条件下,不同晶粒尺寸的纳晶β-SiC均能表现出延展性.对于非晶夹层复合结构,厚度较小的纳米非晶层能有效地提高复合结构的屈服应变,并出现类似于塑性流动的性质,有利于增强材料的韧性.
The mechanical properties of nano-crystalline β-SiC with different grain sizes and strain rates,as well as the toughing characteristics of β-SiC nano-laminates were studied with the molecular dynamics method.The Nosé-Hoover and Berendsen methods were adopted for controlling temperature and pressure respectively.The Tersoff potential function was used for describing the interaction of the Si and C atoms. For nano-crystalline β-SiC with small-sized grains,the fracture strain can be enhanced by breaking grains into amorphous clusters.The main failure mechanism for nano-crystalline β-SiC with large-sized grains is intergranular breakage which will lead to brittle fracture in the entire material.For β-SiC nano-laminates,the amorphous layer with smaller thickness can improve the yield strain and show behavior similar to that of plastic flow.
基金
国家自然科学基金(10632080)资助
关键词
纳晶β-SiC陶瓷材料
增韧机制
分子动力学
应变率效应
非晶夹层复合结构
nano-crystalline β-SiC material
toughness mechanism
molecular dynamics method
effect of strain rate
amorphous layered composite structure
