| Tensile deformation and fracture behavior of ultrafine grain sized, dispersion-strengthened 8009 (Al-8.5% Fe-1.3%V-1.7%Si) plate were examined, within the temperature range between 25 and 300℃. Both tensile strength and ductility gradually decrease with increasing temperature and/or decreasing strain rate. SEM fractographs indicate that 8009 fails by dimpled rupture, regardless of test conditions. The size and distribution of dimples, however, differ significantly with different testing temperatures. At 25℃, bimodal distribution of dimples are evidenced, while equal size of shallow dimples are observed at elevated temperatures. TEM micrographs indicate that at 25℃, both silicide and oxide particles are highly decorated with dislocations. At elevated temperatures, on the other hand, particles are free of dislocations and overall dislocation density is extremely lower than that at 25℃. Most of remaining dislocations are neatly arranged into arrays after high temperature deformation. The enhanced dynamic recovery appears to reduce work hardening and enhance plastic instability and flow localization, leading to reduced tensile ductility at elevated temperature. |
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