Study On The Correlation Between Properties Of Electrical Transportation And Melt Of CuZr-based Amorphous Alloy

The amorphous alloys have been considered as the promising structural and functional materials owing to their superior mechanical properties, the excellent corrosion resistance and the magnetic properties. They are generally obtained through rapidly cooling, resulting in that the short-range order and long-range disorder of amorphous alloys has similarity with the melt. So the amorphous alloys might be considered as the solids with the frozen-in liquid structure. Therefore, the research of the structure change of the melt is significant for exploring the methods to improve the amorphous alloy’s glass forming ability（GFA） and optimize relevant properties. In the present work, by the methods of differential scanning calorimetry（DSC） and electrical resistance（ER）, and combining the XRD electron diffraction as well as transmission electron microscopy scanning, the influence of melt temperature on the microstructure、forming ability and crystallization behavior of the amorphous alloys is systematically studied. The main results of this paper are summarized as follows:（1）The crystallization kinetics of CusoZrso and Cu₃₆Zr₄₈Al₈Ag₈ ribbons were researched by the DSC method. The results indicate that the Tg、Tx and Tp increase with the elevating melt temperature, showing obvious dynamic behavior. Furthermore, the activation energy of Tx and Tp calculated by applying the Kissinger equation also enlarges as the melt temperature increases, that reveals it’s more difficult to overcome the energy barrier for nucleation and growth, on behalf of the higher thermal stability.（2）The Cu₃₆Zr₄₈Al₈Ag₈ ribbons prepared under different molten current were tested by resistivity experiment with four different heating rates. Comparing to the DSC method, it reveals more crystallization behavior on higher temperature and indicates multi-stage crystallization of the samples. On the one hand, the increase of crystallization activation energy and peak activation energy calculated through resistivity method shows that the larger the current, the better the thermal stability. On the other hand, the supercooled liquid region ΔTx and parameter γ show the decrease of GFA with the increasing molten current. It is because of the high-temperature oxidation, which will generate some oxide inclusions, and promote the crystallization as the nucleation points.（3）Some annealing experiments of CusoZrso ribbons were carried out under the same condition. The phenomenon shows the amorphous samples fabricated at 1323K precipitate Cu₁₀Zr₇ phase prior to the 1623K ones. It is due to the existing heterogeneous clusters in the melt of 1323K, which will site into the amorphous matrix during subsequent quenching process. These clusters will act as heterogeneous nucleation sites and lead the ribbons to precipitate crystalline phases preferentially. The results state there is a correlation between the melt temperature and the microstructure of Cu₅₀Zr₅₀.（4）Studies of the precipitation phases of Cu₃₆Zr₄₈Al₈Ag₈ ribbons on the first-step crystallization indicate that the samples prepared with different currents have the same type of crystallization phases, but different quantity. As the competitive priority phase, the CuZr phase is precipitated at first and then broken down into Cu₁₀Zr₇ phase accompanied with some AgZr phase. With the increasing temperature, there precipitate some eutectic phases of CuZr and AlCu2Zr, along with small amount of CuAl2. Particularly, the ribbons prepared with 30.6A precipitate some quasi crystal phases in the initial stage of crystallization. It is because of the high-temperature oxidation of the alloy system. Some octahedral gap location surrounded by Zr atoms is dominated by oxygen, and then form some stable clusters. Further, these clusters will act as nucleation points and promote the precipitation of quasi crystal phase.