CAJ | 학술논문

本文用分子动力学模拟研究了Ni熔体以不同冷速凝固后微观结构的演变规律,并通过理论计算确定出了Ni熔体凝固后获得理想非晶的临界条件.模拟结果发现冷速小于1011 K/s时, Ni熔体凝固后形成晶态组织;冷速在1011 K/s到1014.5 K/s之间时, Ni熔体凝固后形成由晶态结构与非晶态结构组成的混合组织.冷速小于1010 K/s, Ni熔体凝固后形成的晶态组织具有fcc结构;冷速在1010 K/s到1014.5 K/s之间时, Ni熔体凝固后组织中的晶态由fcc和hcp结构层状镶嵌排列构成.通过分析模拟结果和计算结果,确定出了Ni熔体凝固后形成理想非晶的临界冷速为1014.5 K/s.并发现Ni熔体中临界晶核(冷速等于1014.5 K/s)和亚临界晶核(冷速大于1014.5 K/s)均由fcc和hcp组成层状偏聚结构,这表明Ni熔体中生长的晶体、临界晶核和晶胚的结构是相同的.
본문용분자동역학모의연구료Ni용체이불동랭속응고후미관결구적연변규률,병통과이론계산학정출료Ni용체응고후획득이상비정적림계조건.모의결과발현랭속소우1011 K/s시, Ni용체응고후형성정태조직;랭속재1011 K/s도1014.5 K/s지간시, Ni용체응고후형성유정태결구여비정태결구조성적혼합조직.랭속소우1010 K/s, Ni용체응고후형성적정태조직구유fcc결구;랭속재1010 K/s도1014.5 K/s지간시, Ni용체응고후조직중적정태유fcc화hcp결구층상양감배렬구성.통과분석모의결과화계산결과,학정출료Ni용체응고후형성이상비정적림계랭속위1014.5 K/s.병발현Ni용체중림계정핵(랭속등우1014.5 K/s)화아림계정핵(랭속대우1014.5 K/s)균유fcc화hcp조성층상편취결구,저표명Ni용체중생장적정체、림계정핵화정배적결구시상동적.
The microstructures of nickel solidified at different cooling rates are studied by using molecular dynamics simulation and the critical condition for nickel melt to form ideal metallic glass is calculated. The simulation results show that the crystal structure is obtained after the nickel melt has been solidified at a cooling rate that is lower than 1011 K/s;while a mixture is composed of crystal structure and amorphous structure when the cooling rate is in a region from 1011 K/s to 1014.5 K/s. The solidified crystal of nickel is of fcc structure when the cooling rate is lower than 1010 K/s, while it changes into crystal structure composed of fcc and hcp when the cooling rate is between 1010 K/s and 1014.5 K/s. By analyzing the calculation and simulation results, it is determined that the critical cooling rate for nickel melt to form ideal metallic glass is 1014.5 K/s. Moreover, it is found that the structures of the subcritical nuclei (the cooling rate is higher than 1014.5 K/s), critical nuclei (the cooling rate is 1014.5 K/s), and the growing crystal (the cooling rate is lower than 1014.5 K/s) are the lamellar structures composed of fcc and hcp atoms, which indicates that the subcritical nuclei, critical nuclei and the growing crystal have the same structures.