Investigation Of The Glass Forming Ability Of Ti-Based Alloys

In this dissertation, ab-intio energy calculation combined with thermody-namic methods, such as, ground state convex hull and CALPHAD (Calculation of Phase Diagrams) method was used to investigate the GFA (Glass Forming Ability) of Ti-based alloys, especially the Ti-Cu binary alloys. Meatastable phases were investigated, and also their effects during the crystallization of amorphous alloys. A brief introduction to our work on the GFA of Ti-Cu binary system was also given at end of this article.First principle calculations were introduced in the research of the ground state energy of the stable compound of Ti-Cu binary system as well as the lattice constants and the bulk modulus. There is little discrepancy between these data and the experimental one obtained in other articles, which means both the method and the parameters used in the method are perfect. And after calculated the energy of the metastable phase CuTi and CuTi3, a ground state convex hull was produced. And it can be inferred from the ground state convex hull the products of the crystallization of Ti55Cu45 amorphous alloy.With the results of the First Principle calculations, CALPHAD method was used to reoptimise the thermodynamic parameters of Ti-Cu binary system and a reoptimised phase diagram was thus obtained.Three compositions was selected and got 50-70μm melt spun by arc-melting. Peaks in DSC curves corresponding to the crystallization of the amorphous alloy indicate that there is much more amouphous phase in the sample than crystalline phase. XRD was used to investigate the crystalline phase arisen with the formation of amorphous phase. At last, three alloys whose compositions are near the eutectic point were used to make a research on the GFA of Ti-Cu binary system. Both theγparameter and the Trg parameter were calculated, it can be seen from these data, that it is possible to get bulk metallic glasses in multicomponent systems developed from the this binary system.