Plastic deformation behavior of Ni 3(Ti 0.90Nb 0.10) single crystals with the nine-layered ordered rhombohedral structure

Abstract

The plastic deformation behavior of Ni 3(Ti 0.90Nb 0.10) single crystals with a nine-layered ordered rhombohedral structure, called h h c T-structure, was investigated in compression tests. Two slip systems of { 0 1 0 } 〈 1 ¯ 0 1 〉 and { 1 1 1 } 〈 1 1 ¯ 0 〉 were operative depending on the crystal orientation. The plastic behavior by slip on { 0 1 0 } 〈 1 ¯ 0 1 〉 was analogous to that by slip on { 1 1 ¯ 0 0 } 〈 1 ¯ 1 ¯ 2 0 〉 in Ni 3Ti single crystals although the geometry of slip system is different each other. A yield stress anomaly (YSA) clearly appeared by slip on { 1 1 1 } 〈 1 1 ¯ 0 〉 in a wide temperature range between room temperature and 700 °C. It was clarified that the YSA is caused by the Kear–Wilsdorf (K–W) locking of 1 / 2 〈 1 1 ¯ 0 〉 screw dislocations from the {1 1 1} slip plane onto the {0 0 1} plane. The result implies that the YSA by the K–W mechanism occurs not only in the GCP compounds with simple fcc or hcp unit cell such as L1 2 and D0 19, but also in other complex compounds with long stacking sequence of a close-packed plane.