Artificial aging and creep of an Al–Ge–Si alloy

Abstract

Abstract The microstructural stability of a peak-aged (24 h at 160°C) Al–Ge–Si alloy, containing incoherent GeSi precipitates with high interfacial energy, has been examined under different creep conditions, with temperatures varying from 120 to 140°C and initial stresses varying from 65 to 85 MPa. A combination of transmission electron microscopy (TEM) and X-ray diffraction revealed that under all creep conditions, fresh nucleation of second-phase precipitates occurs in the alloy. TEM and quantitative image analysis demonstrated that exposure at 120°C with and without stress has no observable effect on the precipitate size, while increasing the creep temperature to 140°C coarsens the precipitates. Furthermore, prolonging the isothermal aging time at 160°C coarsens the second-phase precipitates considerably. These results are discussed in terms of the known factors responsible for the coarsening of precipitates in agehardenable alloy systems.