Vovchok O. Influence of alloying elements on the relaxation resistance and thermal stability of alloy systems with HCP structure

By using differential scanning calorimetry, electroresistivity and internal friction data including mechanical spectroscopy and hysteretic damping as well as by applying / employing the electro-hydro-pulsed advanced technique for a melt treatment there has been proved an opportunity of principle to form the short-range cluster compounds AmBn such as MgmBan, AlmTin and MgmGdn in liquid alloys of Mg-Ba and Mg-Al-Ca-Ti(Gd) systems and their HCP primary a-solid solutions with elastic relaxation. A physical interpretation of the cluster compounds is given based on a concept of the co-operative (self-organized) interactions as to the solutes and defects which are intrinsic in mesoscopic regions of pre-and post melting. According to isothermal kinetic data and discrete temperature spectra findings the observed deflections from classical (Arrhenius) behaviour and from the Cottrell-Bilby law t^2/3 to be suitable for long-range solute diffusion to dislocations are attributed to the local (short-range) ordering which should consider as a mode of local clustering embedded into crystalline structure of solid solutions with partly destroyed long-range order. Methods of increasing the relaxation strength and thermal resistance of metal alloy systems with cluster-forming structure are proposed to provide much higher long-term strength of hypoeutectic magnesium alloys as well as microyield resistance of a-titanium at cryogenic temperatures.