Diffusion of 65Zn in AZ91 and in QE22 reinforced by Saffil fibers

Effective diffusion coefficients Deff of radioisotope 65Zn in Mg-based alloys AZ91 and QE22 with short Saffil fibers were measured by serial sectioning method in the temperature interval 648–728 K. The results were compared with 65Zn volume diffusion coefficients Dv obtained with the same materials without the reinforcement. This enabled to assess the influence of the interfaces between the matrix and the fibers upon the effective diffusion coefficients and to estimate the diffusion coefficients Di of Zn in Saffil/matrix interphase boundaries. It was observed that temperature dependence of both Deff and Di is significantly concave in the studied temperature interval, which was ascribed to relaxation of thermo-elastic stresses present in the composite as a consequence of considerable differences between the coefficients of thermal expansion (CTE) of both the constituents. Deff and Di tend to higher values close to 693 K, where the CTE is in a local minimum – i.e., where the maximum dislocation density by the phase interface can be expected.