Some mechanical properties of Al-Zr alloys

Abstract

Some mechanical properties of Al-Zr alloys (-0.3wt%Zr)were investigated by the static tensile test at -30-150°C and by the creep test at 150°C.
The results obtained are summarized as follows:
(1) Any fundamental difference between Al-Zr alloys and pure aluminum was not observed by the static tensile test. In all cases, tensile strength is higher by about 3kg/mm² at-30°C than 150°C, and elongation value of cold rolled specimens is also higher at lower temperature, except the case of pure aluminum in which it increases again at 150°C due to recrystallization softening.
(2) The general tendencies above mentioned are hardly changed by pre-aging treatment before cold working. But it is interesting that age-hardened alloys do not show a decrease of ductility and their elongation values increase somewhat.
(3) Pre-aging treatment for a very short time is most effective to decrease the steady-state creep rate at 150°C for cold rolled specimens. Treatment at higher temperature for a long time is not effective but detrimental, even if under age-hardened conditions.
(4) Creep-resistance properties at 150°C of Al-Zr alloys are governed by thermal stability of the cold worked structure and different somewhat from recrystallization behaviors at higher temperature, where some stable precipitates are necessary for prohibiting subgrain boundary migration. In the former case, slight segregation of Zr atoms on the dislocations seems to be sufficient for decreasing the steady-state creep rate.