Theoretical motivation of caUses of structral transfarmations in liquid metals and alloys

Considered have been structural transitions in liquid pure metals In, Ga, Bi, Pb, Sn, Ge, Al, Fe and in InSb compound appearing at T1, T2, T3 ..., at a temperature increase over the melting point. Structural transitions proceed according to two mechanisms of phase transitions: according to the type of melting, when thermal volume of expansion reaches the volume of the characteristic cell, and according to the hcp → bcc type of high-temperature transiition, when the cell volume of the former phase together with the volume of thermal expansion reach the cell volume of the new phase. From 1. the metal boiling condition at Tsub(boil):vsup(s.p.)=ΔVsub(boil) the average statistic number of the nearest atoms (Ksub(s.p.)) has been found in s.p. micromedium (of statistically packed atoms). For Al at 89O-970 deg C the hcp → bcc transition in groupings and in the s.p. micromedium was found; for Fe the transition at 1670 deg C is connected with Fe2+ → Fe3+ without coordination change in the groupings (K=8). Structural changes in the alloys proceed according to the mechamism of high-temperature hcp → bcc transition. Principles of initiation of structural transitions in the Fe-Ni, Ni-Cr, Ni-Mo, Al-Ge, Fe-S and Fe-P systems are analyzed