Plastic deformation behavior of Ni3(Ti0.90Nb0.10) single crystals with the nine-layered ordered rhombohedral structure

The plastic deformation behavior of Ni3(Ti0.90Nb0.10) single crystals with a nine-layered ordered rhombohedral structure, called h h c T-structure, was investigated in compression tests. Two slip systems of {010}〈1¯01〉 and {111}〈11¯0〉 were operative depending on the crystal orientation. The plastic behavior by slip on {010}〈1¯01〉 was analogous to that by slip on {11¯00}〈1¯1¯20〉 in Ni3Ti single crystals although the geometry of slip system is different each other. A yield stress anomaly (YSA) clearly appeared by slip on {111}〈11¯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〈11¯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 L12 and D019, but also in other complex compounds with long stacking sequence of a close-packed plane.