Deformation of Al-Si and Al-Fe high purity alloys in the presence of precipitation of varying amounts

Abstract

Al-0.1 Si, Al-0.1 Fe, Al-0.5 Si and Al-0.5 Fe (all wt.%) alloys were tensile tested in a supersaturated condition in the temperature range 298 to 698 K. The tested specimens corresponding to different experimental conditions were subjected to transmission electron microscopy. In the Al-Si alloys a ductility minimum, due to the precipitation of Si, was seen in the range 348 to 398 K. In the Al-0.5 Si alloy additionally there was a drastic decrease in ductility in the range 450 to 573 K due to the copious precipitation of ultra-fine, structurally unidentifiable particles. In the AI-Fe alloys the ductility minimum was present at 473 K, regard less of grain size and solute content. This minimum could be clearly associated with the precipitation of FeAl₆ in the Al-0.5 Fe alloy; in the Al-0.1 Fe alloy atom clusters and/or very fine FeAl₆ preclpltates could have been responsible. The ductility and strength variations seen in the four alloys could be qualitatively understood in terms of the combined effect of precipitation, work hardening, thermal softening, subgrain formation and the subsequent re­dissolution of the precipitates and subgrains.