Disappearance of the true threshold creep behaviour of an ODS Al–30SiCp composite at high temperatures

The creep behaviour of an oxide dispersion strengthened (ODS) Al–30SiCp composite has been investigated in a broad temperature interval ranging from 623 to 798 K. At temperatures up to 723 K true threshold creep behaviour occurs, while at temperatures above 723 K no true threshold stress has been found. Accepting the creep model of Rösler and Arzt (Acta Met. Mater. A150 (1992) 21), the creep behaviour of this composite at temperatures ranging from 748 to 798 K is interpreted in terms of the thermally activated detachment of dislocations from small alumina particles in the composite matrix. The disappearance of the true threshold stress at temperatures above 723 K is then due to a transition from athermal to thermally activated detachment of dislocations from alumina particles.