Creep and Tensile Behaviors of Fe-Cr-Al Foils and Laser MicroWelds at High Temperature

El Kadiri, H., Bienvenu, Y., Solanki, K.N., Horstemeyer, M., & Wang, P. (2006). Creep and Tensile Behaviors of Fe-Cr-Al Foils and Laser MicroWelds at High Temperature. Materials Science and Engineering A, A421. 168-181.

We examine a Fe-Cr-Al foil-based material and a continuous-wave laser weld generated in ultra-fine "keyhole" mode undergoing tensile and creep-tension tests over a temperature range of 25-1000 °C. At all temperatures, the bead exhibits superior tensile resistance than the base material due to a homogenous reprecipitation of fine aluminum nitrides, AlN, but creeps faster at 900 °C, because of a finer-grained microstructure scarcely undergoing secondary recrystallization. Under tensile loading, the base material ductility is higher than that of the weld and increases with increasing temperature, but drops above 900 °C due to faster grain growth and chromium carbide precipitation. The base material stress-strain curves exhibit concomitant decrease of the yield point effect magnitude and increase of the strain hardening rate with the temperature, but only up to a critical value, which decreases with increasing the strain rate. After vanishing at this critical temperature, the yield point effect reappears upon the onset of sample necking responsible for the ensuing continuous decrease of the engineering stress. The strain-stress curves of laser welds show no yield point effect and the work hardening persists at all temperatures. Under creep-tension, the weld shows a strong anisotropic behavior, and the highest flow rate is recorded for welds oriented parallel to the loading direction, because of a more important cavity nucleation. © 2006 Elsevier B.V. All rights reserved.