On Reversibility Of Liquid Transition In Sn-based Alloys

The existence of liquid-liquid structural change (L-LST) has attracted more and more attention to the researchers, which enriches the phenomenology in liquid physics and shed light on the structure and property of liquid materials.Owing to the limitations of different experimental method, most of attentions have been played on the only heating process in the researche field of L-LST. And it is thought that temperature-induced L-LST is irreversible in liquid alloys. Then, what is the behavior of the melt in several heating and cooling process. Whether temperature induced liquid-liquid structure transitions is likely to appear in certain alloy features reversible? What are the conditions and rules? Prove up these questions, it no doubt has a important significance on depth knowledge of the structure of liquid substances and the rule of L-LST.In this paper, the temperature dependence of electrical resistivity (ρ-T), differential thermal analysis (DTA) of some liquid Sn-based alloys (Sn-Bi,Sn-Sb,Ga-Sn and so on) was investigated, in order to research the reversibility of liquid-liquid structural change. The major contents and conclusions are as follows:First the electrical resistivities (ρ) of some liquid Sn-based alloys have been measured continuously in several heating and cooling cycles, The results show that there are two kinds of transitions in Sn-Bi and Sn-Sb alloys. Moreover the character of L-LST in Sn-Bi alloys in first cycle heating is different from that of the subsequent cooling and heating cycles. One is the irreversible transition in the first heating process. The other is the reversible transition in the subsequent cooling and heating cycles. But only the irreversible transition occurs in the Ga-Sn and no structure transition occurs in Zn-Sn alloys.With electrical resistivity method, the kinetics of temperature-induced liquid-liquid structure transition process in Sn-Bi40wt%and Sn-Bi70wt%melt was investigated in isothermal and continuous heating experiments. Also the characteristic and mechanism of the transition are discussed using kinetic theory of phase transition and thermodynamics. In addition, the relationship between melt structure transition and solidified structure was further investigated through solidification experiments in Sn-Sb alloys. In conclusion, The experiment investigations of the several Sn-based alloy systems suggest that the reversibility of the L-LST doesn't exist in all of Sn-based alloys system, and the irreversible L-LST affects the solidification remarkably. The new phenomena, results and regulations reflected in this paper provide a new basis for deeper understanding the essence of liquid structure transitions, and are also of significance for promoting the innovation of material processing.