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The influence of decreased temperature of tensile testing on annealing-induced hardening (AIH) and deformation-induced softening (DIS) effects has been studied in an ultrafine-grained (UFG) Al–Zr alloy produced by high-pressure torsion. We show that the UFG Al–Zr alloy demonstrates a DIS effect accompanied by a substantial increase in the elongation to failure <i>δ</i> (up to <i>δ</i> ≈ 30%) depending on the value of additional straining. Both the AIH and DIS effects weaken with a decrease in the tensile test temperature. The critical deformation temperatures were revealed at which the AIH and DIS effects are suppressed. The activation energy <i>Q</i> of plastic flow has been estimated for the UFG Al–Zr alloy in the as-processed, subsequently annealed and additionally strained states. It was shown that the annealing decreases the <i>Q</i>-value from ~80 kJ/mol to 23–28 kJ/mol, while the subsequent additional straining restores the initial <i>Q</i>-value. Alloying with Zr results in the expansion of the temperature range of the AIH effect manifestation to lower temperatures and results in the change in the <i>Q</i>-value in all of the studied states compared to the HPT-processed Al. The obtained <i>Q</i>-values and underlying flow mechanisms are discussed in correlation with specific microstructural features and in comparison to the UFG Al.