الفهرس 
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Abstract
Morphology, growth kinetics and diffusion for Cu-Ag alloys AlZn/SiC, composite materials and HPSN/steel joint have been investigated by light and scanning electron microscopy Also, the effect of diffusion on the mechanical properties such as; Brinell hardness, Vicker hardness, tensile strength, bending strength and tribological parameters (test duration, applied pressure and rotational speed). At all investigated aging temperatures under the solvus lines the Cu-5&88 wt.% Ag alloys and AIZn 12.5/SiCp composite materials were observed to decompose by discontinuous precipitation reactions. The resulted is a fine lameller structure of depleted phase. The migration rates for discontinuous precipitation reaction are found to be approximately one to two orders of magnitude The kinetics of transformation had been analyzed with the assumption that the process is limited only by cell boundary diffusion of the solute. The analysis leads to some simplifications of that presented by Zener’s, Tu &Turnbull Aaronson&Liu, Cahn’s, Sundquist, Petermann&Hornbogen and Shapiro&Kirkaldy theories due to the new growth behaviour mechanisms as the results of diffusion Also, the interfacial diffusion is investigated at aging temperatures ranging from 873 to I 033K for HPSN/steel brazed joint. The analysis of the growth rates of the grain boundary movement into both directions of brazed alloys due to the diffusion of inter layer elements, showed that they were controlled by grain boundary diffusion only at the steel side The early stage of diffusion induced grain boundary migration (DIGM) mechanism for the formation of cells was developed by Fournelle and Clark mechanisms in the side of steeL.