The Simulation On Structure Evolution Duiing Crystallization And Compressive Behavior After Crystallization Of Zr₈₅Cu₁₅ Amorphous Binary

Amorphous alloys are relatively new materials that have excellent physical properties and mechnical properties. However, its plastic deformation capacity is poor at room temperature. Some scholars find that introducing nanocrystals to the amorphous matrix by nucleation or embedding the second phase particle is an effective way to improve its plasticity. In this paper, we investigate the crystallization process of Zr₈₅Cu₁₅ amorphous alloy and mechnical properties at room temperature after crystallization by using molecular dynamics simulation.When analysising the crystallization process of Zr₈₅Cu₁₅ amorphous alloy, we accidentally discover that TTT curves that obtained by isothermal annealing treatment of two amorphous configurations are shaped like double C and C curve respectively. Two amorphous configurations are obtained by relaxing in 300 K, relaxation time of the former is 500 ps, the later one is 2000 ps. The main reasons of this change are as follows: as relaxation time increases, the second peak of Cu-Cu pair distribution function splits off more obviously which shows the second-neighbors interaction of Cu-Cu pair varies from one relaxation time to another; Moreover, coordination number of Cu-centered clusters decreases which indicates that the structure of these clusters becomes more looser.We analyze and contrast the structure of these configurations which are successively obtained during isothermal annealing heat, cooling treatment and relaxation at room temperature of Zr₈₅Cu₁₅ amorphous alloy. Results show that crystallization phases on the structure of body-centered cubic generate in the process of isothermal annealing and cooling treatment. Furthermore, as the crystallization process continues, there is a big difference in variation trend between Cu-centered and Zr-centered coordination number, the average coordination number of the former reduces, but the latter increases. By means of pair analysis technique, we find that the pentagonal symmetry structure which remains in amorphous alloys is transformed into body-centered cubic structure whose characteristic bond pairs are 1441 and 1661 pairs. The increase in the number of 1441 pairs results in the reduction of average Cu-centered coordination number. In addition, the increase in the number of 1661 pairs accounts for the increasing of average Zr-centered coordination number.In the compression test of Zr₈₅Cu₁₅ amorphous plate with different crystallization volume fraction（Vcrys） at each strain rate, results indicate that more shear transformation zones（STZs） simultaneously start generating and the local strain distributes closer to the compression side with increasing strain rate. Furthermore, the plastic deformation capacity of amorphous plate when Vcrys is 13% gradually becomes worse, but the ductility is gradually strengthened when Vcrys is 40% as strain rate increases. In the compression test at lower strain rate, the stain localization of amorphous-nanocrystalline composites is more serious than Zr Cu amorphous alloy. However at higher strain rate, some amorphous-nanocrystalline composites deform more uniformly than amorphous alloy.