Diffusion of zirconium in aluminum

Abstract

Diffusivities of Zr in polycrystalline specimens of 99.999% pure aluminum, Al-0.063 at% Fe alloys and Al-0.18 at% Si alloys were determined by the residual-activity method with the radioactive tracer, Zirconium-95. The zirconium-95 tracer used in the present work was purified from a zirconium-95-niobium-95 mixture containing oxalic acid with a liquid-liquid extraction technique5). The zirconium-95 tracer was deposited onsamples in the form of the chloride ZrCl4. The metallic tracer was produced by the reaction of the chloride with Al in the initial stage of diffusion annealing. The chlorine gas produced in the above process acted as an etchant, removing a thin oxide film from the surface and thereby allowing the tracer to diffuse into the bulk without impediment by the surface oxide layer. The diffusivity of Zr in 99.999% pure aluminum in the temperature range between 531°C and 640°C was expressed as D=(7.28+10.4-4.29)×102exp{-(57.8±1.55)Kcal/mol/RT}cm2/sec. The diffusvities of Zr in Al-0.063 at% Fe alloys in the temperature range between 555°C and 640°C and that in Al-0.18 at% Si alloys in the temperature range between 531°C and 649°C were given by D=(3.43+8.78-2.47)×10exp{-(52.1±2.18)Kcal/mol/RT}cm2/sec and D=(5.48+75.1-5.11)×105exp{-(69.1±3.04)Kcal/mol/RT}cm2/sec, respectively. The pre-exponential factor and the activation energy for diffusion of zirconium in 99.999% Al, Al-0.063 at% Fe alloys and Al-0.18% Si alloys were very similar to those for diffusion of Fe, Mn and Cr in pure aluminum. © 1973, The Japan Institute of Light Metals. All rights reserved.