“Abnormal transient creep” in fine-grained Al-5356 alloy observed at low strain rates by high-resolution strain measurement

Transient creep at very low strain rates (less than 10−10s−1) is still unclear. The traditional uniaxial creep testing is less useful due to unsatisfied resolution strain ∼(10−6). To study transient creep behavior at such low strain rates, a high-resolution strain measurement using the helicoid spring specimen technique was employed in a fine-grained Al-5356 alloy at temperatures ranging from 0.47 Tm to 0.74Tm (Tm: melting point). To clarify transient creep mechanism at such low strain rates, transmission electron microscopy (TEM) was used in microstructure observation of crept specimens. The abnormal transient creep, high temperature strengthening at T>Tp(Tp: the phase transformation temperature, 0.58Tm) or intermediate temperature softening at 0.4Tm