Comparison of Ni-based alloys with extreme values of antiphase boundary energies:: dislocation mechanisms and mechanical properties

Dislocation properties have been Studied in several L1(2) nickel-based alloys with high (Ni74Al26). medium (Ni-3(Al, 0.25%Hf)), and low (Ni3Ga) antiphase boundary (APB) energies respectively, deformed in the temperature domain of the yield-stress anomaly. Several APB enemies have be en measured and compared with those found in the literature. The peak in the temperature variation of the strain-hardening coefficient has been correlated with the unlocking of incomplete Kear-Wilsdorf locks. The corresponding unlocking stresses. as well as the frequencies of octahedral-cube and cube-octahedral cross-slip, are strongly correlated with the respective fault energies. The local pinning of near-edge dislocations in cube planes appears essential for the observation of the yield-stress anomaly in alloys with high APB energies.