Effect of superimposed low frequency oscillations on the static creep behaviour of Al-1 wt% Si and Al-1 wt% Si-0.1 wt% Zr-0.1 wt% Ti alloys

Torsional oscillations of increasing frequencies with constant torsional strain amplitude, theta, of 3.1x10(-4) were superimposed on wires of Al-1 wt% Si and Al-1 wt% Si-0.1wt% Zr-0.1 wt% Ti alloys, while being crept under constant stress (52.3 MPa) and different testing temperatures. It was found that increasing the frequency of oscillations resulted in an increase of both transient and steady state creep. In the transient stage, while the exponent n is increasing with frequency v, the parameter beta decreases. Zirconium and titanium addition generally reduced the rate of creep. A value of 20 kJ/mol was found for the activation energy of the mechanism operating in the transient and steady state stages which was ascribed as being due to dislocation intersection.