摘要
非晶合金因具有独特的无序结构、优异或独特的各种性能以及良好的应用前景,而受到专家学者的广泛关注.其中,制备过程中的冷却速率对非晶的结构与性能起着非常重要的调控作用.本文采用分子动力学的模拟方法,分别以4种冷却速率获得相同尺寸的Zr48Cu45Al7三元非晶合金的制备态原子结构模型,并模拟了各制备态模型的压缩变形过程.在此基础上系统地研究冷却速率对非晶微观结构及其变形行为的影响.研究表明:在施加大冷却速率时,非晶合金保留更多高温液态的结构特征,如五次对称性低的团簇数量较多,原子堆积较为松散,自由体积含量更多,并存在更多的"类液区".上述大冷却速率所对应的结构特征导致了非晶发生变形时,屈服强度降低,表现出软化行为,同时降低了剪切带形成与发生局域化变形的概率,从而提高了非晶的塑性.
Since the discovery of the first metallic glass(MG)in 1960,vast efforts have been devoted to the understanding of the structural mechanisms of unique properties,in particular,mechanical properties in MGs,which is helpful for the applications of such novel alloys.As is well known,the cooling rate during the quenching as well as the sample size,significantly affects the mechanical properties in MGs.In order to study the effect of cooling rate on microstructure and deformation behavior in MG by excluding the size effect,Zr48Cu45Al7 ternary composition with good glass-forming ability is selected as a research prototype in this work.The classical molecular dynamics simulation is utilized to construct four structural MG models with the same size under different cooling rates,and the uniaxial compressive deformation for each model is also simulated.It is found that an MG model prepared at a lower cooling rate has a higher yield strength and is more likely to form shear bands that lead the strain to be localized,resulting in a lower plasticity.The Voronoi tessellation,together with atomic packing efficiency and free volume algorithms that have been designed by ourselves,is used to analyze the four as-constructed models and high-temperature liquid model.It is found that the asconstructed model,which is prepared by quenching metallic melt at a higher cooling rate,can preserve more structural characteristics of the high-temperature liquid.In other words,the higher cooling rate leads to more clusters with relatively low five-fold symmetry,loose atomic packing and large fraction of free volumes in MG.By calculating the distribution of the free volumes,a new computational approach to detecting liquid-like regions in MG models is adopted.It is found that there are more liquid-like regions in the as-constructed model which is prepared by quenching metallic melt at a relatively high cooling rate.This should be the structural origin of the effect of cooling rate on the deformation behavior,in particular,the yield strength and the plasticity.This work provides an understanding of how the cooling rate during quenching affects the microstructure and deformation behavior,and will shed light on the development of new MGs with relatively large plasticity.
作者
周边
杨亮
Zhou Bian;Yang Liang(College of Materials Science and Technology,Nanjing University of Aeronautics and Astronautics,Nanjing 210016,China)
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2020年第11期170-178,共9页
Acta Physica Sinica
基金
国家自然科学基金(批准号:U1332112,51471088)
中央高校基本科研业务费专项资金(批准号:NE2015004)资助的课题.
关键词
非晶合金
冷却速率
微观结构与性能
分子动力学模拟
amorphous alloy
cooling rates
microstructures and mechanical properties
molecular dynamics simulation
