Amorphous Alloy Plastic Deformation Based On Ansys Finite Element Numerical Simulation

In this thesis, the deformation during rolling and Vickers indentation of Zr6oAl15Ni25and Zr6sAl7.5Cu12.sNi10Ag5bulk metallic glasses (BMGs) is investigated by experiments and numerical simulation by using ANSYS/LS-DYNA dynamic explicit finite element analysis (FEA) software. The microstructures of the as-cast and deformed Zr-based BMGs have been investigated by using X-ray diffractometer (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED).We have systematically studied the plastic deformation and stress distribution of the deformation zones due to rolling and Vickers indentation.In rolling experiment at room temperature, the rolling reduction of Zr60Al15Ni25BMG is obtained up to95%without fracture. A large number of shear bands are observed in the rolling deformation zones, indicating that the inhomogeneous plastic deformation occurs in the BMG during rolling. According to the STZ (Sheer Transformation Zone) theory, when the maximum shear stress reaches the material yield stress in the rolling process, the local shear transformation occurs, resulting in the shear expansion of alloy structure and a large number of excess free volume. The finite element simulation results shows that as the rolling reduction is greater than10%, the maximum shear stress in the most regions exceeds the yield stress. According to the Tresca yield criteria, the inhomogeneous plastic deformation occurs in the BMG. The stress distribution in the deformation zones has a critical role in promoting the formation of shear bands in the plastic deformation process of BMG, which coincides with the experimental results.In the Vickers interfacial indentation experiment, a large number of semi-circular shear bands and a small number of ray-like shear bands are found blow the interfacial indentation of the Zr65Al7.5Cu12.sNi10Ag5BMG, indicating that the interfacial indentation deformation is inhomogeneous plastic deformation. The spherical crystals with the diameter abut60nm and quasi-crystals about5nm are observed below indentation tip (region B) by HRTEM. This shows that the crystallization of BMG occurs in the process of Vickers indentation, and that the crystallization kinetics is different in different deformation regions, being due to the different stress distribution, which is confirmed by the finite element simulation results.