Two independent strain hardening mechanisms in single-crystal γ-Ti-56Al compound

The strain hardening of γ-Ti-56Al by superdislocations (b = [101]) occurs by two independent mechanisms in two different temperature ranges: from room temperature to approximately 623 K; and from 623 to 1073 K. The activation energy for the low temperature mechanism was found to be 0.014 eV, compared to 0.2–0.22 eV for the high temperature mechanism. The transition from the low temperature mechanism to the high temperature mechanism occurs near 623 K where a burst of double jogs is believed to occur through a thermally activated process. Many extended double jogs 15–20 nm wide were observed in the alloy deformed at 673 K. The beginning of the extended jog formation near 673 K in Ti-56Al is coincident with the near-zero value of the strain rate sensitivity parameter near 673 K in Ti-54Al.