Molecular Dynamics Simulation of Deformation-Induced Nanocrystallization in an Amorphous Metal.
Molecular Dynamics Simulation of Deformation-Induced Nanocrystallization in an Amorphous Metal.
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非晶金属变形诱导纳米结晶的分子动力学模拟。
DOI：
10.2472/jsms.52.235
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发表时间：
2003
期刊：
影响因子：
--
通讯作者：
A. Nakatani
中科院分区：
文献类型：
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作者：
R. Matsumoto;H. Kitagawa;A. Nakatani
采用大规模分子动力学模拟方法研究了非晶态金属形变诱导纳米晶化的基本过程。采用Finnis-Sinclair势表示α-Fe。通过加热-快淬模拟建立了非晶金属模型。拉伸变形施加到具有512026个原子的非晶块。初始温度为300 K。当变形剧烈时，在与拉伸方向成45度角的剪切带周围观察到大量的晶团形核点。晶体的成核温度约为1200 K，约为玻璃化转变温度的一半。任何两个成核位置之间的平均距离约为6 nm。这些集群迅速增长，直到它们相互撞击。在此过程中，变形局限于剩余的非晶相，因为晶粒很少变形。一些大颗粒通过吸收小颗粒而变大，因此颗粒总数减少。纳米晶化后，在一些晶粒中观察到形变孪晶。在变形的最后阶段，空隙在晶界处成核。结晶相的发展是由结晶潜热引起的，即使在断裂之后也是如此。晶粒中的位错立即向晶界或非晶相移动。（111）方向与拉伸方向相反的晶粒很少形核。一些晶粒具有长形，这是因为它们在剪切带旁形核并向低温区生长。
A large-scale molecular dynamics simulation is performed to obtain fundamental knowledge of deformation-induced nanocrystallization in an amorphous metal. The Finnis-Sinclair potential is adopted to represent α-iron. The model amorphous metal is created by a heating-rapid quenching simulation. Tensile deformation is applied to the amorphous block with 512 026 atoms. The initial temperature is 300K. As it is deformed severely, a lot of nucleationsites of crystal-clusters are observed around the shear bands which develop in the direction of about 45 degrees from tensile direction. The nucleation temperature of crystal is about 1200K which is about a half of glass transition temperature. The average distance between any two nucleation sites is about 6nm. Those clusters grow up rapidly until they strike each other. In the process, deformation is localized at the remaining amorphous phase, because the grains are rarely deformed. Some large grains grow bigger by absorbing small grains, therefore the total number of grains decreases. After the nanocrystallization, deformation twins are observed in some grains. At the final stage of deformation, a void is nucleated at a grain boundary. The crystalphase develops by latent heat of crystallization even after a break. Dislocations which are packed in the grain are moved out to the grain boundary or amorphous phase immediately. Grains whose (111) directions turn on the tensile direction are rarely nucleated. Some grains have long shape, because they nucleate beside the shear bands and grow toward low temperature regions.