Study On Amorphous Phase Formation In Ti-Zr-Hf-M High Entropy Alloys

High entropy metallic glasses are the intersection of the high entropy alloys and metallic glasses. It has high degree of chemical disorder and close topological structure, and some better properties than that of high entropy and metallic glasses. The alloy design for high entropy metallic glasses is obviously different from that of traditional multicomponent metallic glasses. However, there were just a few reports that had released on high entropy metallic glasses and many relevant issues are still unresolved. Development new equal-atomic alloys and research which composition can be formed in amorphous phase have thus experimental and theoretical significance.In this thesis, 82 TiZrHf-based alloys were fabricated by arc-melting and their ribbons were fabricated by melt spinning method. The ribbon structures were analyzed by x-ray diffraction. The regularity of phase formation in TiZrHfCuM?M=Fe,Co,Ni,Ag,Al,V,Cr,Mn,Nb,Mo,Ta,Y,Lu,Er,Gd? system were firstly studied. The influence of element crystal structure, i.e. FCC element?Cu, Al, Ni Ag? and BCC element?Fe, Cr, Nb, V?, on the phase formation in quaternary, quinary and senary TiZrHf-based alloys were then studied. Finally, the validity of six parameters in distinguishing the formation of amorphous and crystalline phases was evaluated. There parameters, including two chemical parameters??, ?H? and four topology parameters??, ?, ?₂, ??, were calculated using computer program.The result shows that the larger topology parameter and smaller chemical order parameter favors the amorphous phase formation under the condition of rapid cooling. The addition of FCC elements favors the amorphous phase formation than BCC elements, and the more FCC content, the more probability of amorphous phase formation. This is because the more negative mixing heat between the HCP?Ti, Zr, Hf? and FCC element than that of BCC elements results in lower chemical order which benefits the amorphous phase formation.For amorphous phase formation in quaternary alloys, the effect of topology factor is more obvious than that of chemical factor. However, the effect of topology factor becomes weaker while the effect of chemical factor will become more important with the increase in component elements. For quinary and senary TiZrHf alloys, a small chemical parameter enough plays a decisive role in the formation of amorphous phase. The effectiveness of the four topology structural parameters has little difference when distinguishing the amorphous and crystalline phase. Relatively, ?₂ has the best effectiveness and ? has the worst. In addition, ?H is much better than ? in distinguishing the amorphous and crystalline phase.