Interdiffusion and reaction between Zr and Al alloys from 425° to 625 °C

Abstract Zirconium has recently garnered attention for use as a diffusion barrier between U–Mo nuclear fuels and Al cladding alloys. Interdiffusion and reactions between Zr and Al, Al-2 wt.% Si, Al-5 wt.% Si or AA6061 were investigated using solid-to-solid diffusion couples annealed in the temperature range of 425° to 625 °C. In the binary Al and Zr system, the Al 3 Zr and Al 2 Zr phases were identified, and the activation energy for the growth of the Al 3 Zr phase was determined to be 347 kJ/mol. Negligible diffusional interactions were observed for diffusion couples between Zr vs. Al-2 wt.% Si, Al-5 wt.% Si and AA6061 annealed at or below 475 °C. In diffusion couples with the binary Al–Si alloys at 560 °C, a significant variation in the development of the phase constituents was observed including the thick τ 1 (Al 5 SiZr 2 ) with Si content up to 12 at.%, and thin layers of (Si,Al) 2 Zr, (Al,Si) 3 Zr, Al 3 SiZr 2 and Al 2 Zr phases. The use of AA6061 as a terminal alloy resulted in the development of both τ 1 (Al 5 SiZr 2 ) and (Al,Si) 3 Zr phases with a very thin layer of (Al,Si) 2 Zr. At 560 °C, with increasing Si content in the Al–Si alloy, an increase in the overall rate of diffusional interaction was observed; however, the diffusional interaction of Zr in contact with multicomponent AA6061 with 0.4–0.8 wt.% Si was most rapid.