Interdiffusion and Reaction Between Al and Zr in the Temperature Range of 425 to 475 °C

Abstract

Interdiffusion and reaction between Al and Zr was investigated as functions of Zr purity, temperature, and time, using Al versus Zr solid-to-solid diffusion couple annealed in the temperature range from 425 °C to 475 °C. All diffusion couples were observed to develop two intermetallic layers, i.e., Al3Zr and Al2Zr. The Al3Zr phase grew with planar morphology, while the Al2Zr phase developed a non-planar interfacial morphology. Growth rate and integrated interdiffusion coefficients were determined using Wagner’s approach for each phase. Purity of Zr had a significant effect on the development of Al3Zr and Al2Zr phases. Diffusion couples with low-purity Zr (i.e., 99.2%) exhibited a higher growth rate for the Al3Zr, at the expense of Al2Zr growth. Couples with low purity Zr also resulted in a higher degree of non-planarity for Al2Zr phase. In general, degree of non-planarity increased with an increase in anneal time, while it decreased with an increase in temperature. Non-planar morphology was simulated based on 3-D anisotropic diffusion using diffusivity tensor (quadric), and needle-like growth, similar to that observed by experiments were simulated.