Zr-based Amorphous Alloy, Plastic Deformation And Numerical Simulation

The metallic glasses possess of a series of excellent properties, which is metastable in thermodynamics, crystallization will occur when heated up to certain temperature, nanocrystallite distribute uniformly in the amorphous matrix after crystallization will improve the mechanical properties and soft magnetic properties greatly. Therefore, the crystallization kinetics become one of the hottest fields in research of amorphous alloys.It is found that plastic deformation can also lead to crystallization in amorphous alloy. It is expected to become an effective means to prepare new amorphous matrix composites. The plastic deformation inevitably occurs when amorphous alloys are applied in engineering. Microstructure transformation of amorphous alloys will influence various properties greatly. Accordingly, study of crystallization mechanism in amorphous alloys induced by plastic deformation has great importance in scientific research and engineering application.Commonly, we observe the transformation of microstructure in the region of plastic deformation by dint of experimental apparatus, but we can not see the distribution of inner force just discribe it by expressions, the expressions are computed with mathematics and mechanics complexly. The stress value and distribution can be observed vividly by finite elements simulation, therefore it is necessary to use finite elements simulation means in the research of metallic glasses.The transformation of matellic glass microstructure after indentation deformation and rolling deformation at room temperature are observed by X-ray diffraction (XRD), scanning electronic microscopy(SEM) and high-resolution transmission electron microscopy(HREM), evolution of free volume are investigated by differential scanning calorimetry(DSC). And we use the Finite Element Simulation software DEFORM 3D to simulate the vickers indentation deformation of Zr65Al7.5Ni10Cu12.5Ag5 matellic glass and rolling deformation of Zr60Al15Ni25 matellic glass, the simulation process consists of creating model, defining material and appending boundary condition and so on. Distribution of stress and strain in the deformational region can be gained by this simulation. Then we combine the experimental results and discuss the microcosmic mechanism of crystalization induced by plastic deformation. The vickers indentation choose 500 gram force load, sustain 15 seconds and then uninstall. The experimental results indicate that crystalization occurs in vickers indentation region, There are different microstructure transformation in tip region, edge region and other regions. The simulative results indicate the effective stress and strain in tip region and edge region are larger than those in other regions apparently, effective stress and strain are larger in tip reguon than those in edge region. The rolling is successive, that is to say, workpiece is rolled based on last transmutative extent, with 10 percentage transmutative extent until 90 percentage. Similarly, the rolling deformation also induced microstructure transformation, inhomogenenous plastic deformation occurs with shear band. The rolling simulative results indicate that stress at x, y and z direction exceed yield strength, plastic deformation occurs, the effective stress and strain distribution under roller and those at transverse section present different rules.Combine the experimental results and simulative results, it is easy to find out that there are consanguineous relation between microstructure variety and stress, this phenomenon supports the viewpoint that power supply of crystalization is force effect but not heat effect.