Mechanism of low-temperature superplastic deformation in aluminum alloys containing a dispersion of nanoscale Al_3(Sc,Zr) particles

摘要

The ultrafine grained (UFG) structure with an average size of ～0.8 μm was produced in an Al-Li-Mg-Sc alloy by equal-channel angular extrusion (ECAE) at 325℃ with a total strain of ～16. Superplastic behavior was examined in the temperature range 150-250℃ at strain rates ranging from 10~(-5) to 10~(-2) s~(-1). A maximum elongation-to-failure of 440% was recorded at 175℃ (～0.5 T_m, where T_m is the melting point) and a strain rate of 2.8 × 10~(-5) s~(-1) with the corresponded strain rate sensitivity of 0.32. Mechanisms of low-temperature superplasticity (LTSP) and high-strain-rate superplasticity (HTSP) are essentially the same. The difference between superplastic behaviors at low and high temperatures is attributed to what of applied stress.