Bulk Amorphous Alloy Forming Ability And Stability

The bulk amorphous alloys have strong glass forming ability, but the micro-mechanism of this characteristic can not be understood at present time. In this dissertation, we have investigated the relationship between glass forming ability and negative mixing heat, elastic strain energy based on Miedema semiempirical model. The results show that the more negative the mixing heat is and the higher elastic strain energy is, the stronger the glass forming ability become in a certain range of composition. From these we can draw a conclusion that the key to control amorphous formation lies in the nature of bonding. At the same time, we also hoped to study this interaction between different atoms, which can influence amorphous formation in multi-component systems by means of Discrete-Variational Method and put forward an idea to the design of amorphous alloys by using this method.We prepared the Zr-based amorphous alloys of the binaiy, ternaiy and quatemaiy by means of vacuum arc melting plus simple spinning melting or anvil hammer method. It is shown from the curves of DTA and DSC that the disvitrification of amorphous of Zr65A175Cu275 and Zr65A175Ni10Cu175 take place beyond 4000C. After the disvitrification of ternary Zr65A175Cu275 alloy, both dispersed precipitation and small crystal can be seen on the BF photograph of TEM. By the further analysis of EDP, the main precipitation is tI-Zr2(Al,Cu). So we supposed that Al atoms dissolving in Zr2Cu could raise the swain energy of the system. On the other hand, the increasing of bonding between Al electron and Zr electron will decrease the interaction between Cu electron and Zr electron, which restrained the precipitation of Zr-,Cu and improved the formation of amorphous according to the theory of bonding.