Volume and Grain Boundary Diffusion of Al in β-Ti by Laser Induced Breakdown Spectrometry (LIBS)

摘要

The impurity diffusion coefficients of Al in β-Ti have been determined in the temperature range between 1223 and 1573 K by means of Laser Induced Breakdown Spectrometry (LIBS). The volume diffusion coefficients for Al impurity diffusion found in this study are significantly larger than those found in previous investigations, and show a non-linear behavior with a distinct upward curvature with increasing temperature. It is evident that such unusual experimental values resulted from the impurities, especially Fe, Si, O in the Ti specimen during annealing, as shown in the results of chemical analyses. Such impurities are supposed to accelerate the Al impurity diffusion in the matrix. The grain boundary diffusivity sδD_(gb) was also calculated by using the volume diffusivities and processing the tails of the measured profiles. The temperature dependence of the gram boundary diffusion coefficients can be expressed by linear Arrhenius equations. The values of pre-exponential factor and the activation energy for grain boundary diffusion were 4.13X10~(-6) m~3s~(-1) and 258 kJmol~(-1), respectively. The value of the activation energy is about 77 kJmol~(-1) smaller than that previously found for volume diffusion.