Strengthening effect of blocky phases and ?/? interface in the directionally solidified high-Nb-containing TiAl alloy

Herein, a TiAl alloy containing a high Nb concentration with a composition of Ti-45.5Al-7Nb-(W, Cr, B) was prepared by electromagnetic cold crucible zone melting (ECCZM) using a ceramic mould. The microstructure, tensile properties and fracture morphology were analyzed by means of SEM, EDS and TEM. As results, there were three blocky phases, namely alpha(b)(2), gamma(b), and TiB, and two types of gamma/gamma interfaces. The tensile tests at room temperature showed that the ultimate tensile strength of the alloy reached a maximum value of 645 MPa. The primary strengthening mechanism of the alloy was the interfacial strengthening of the gamma/gamma interfaces. The two types of gamma/gamma interfaces can hinder dislocation movement and allow the dislocations to move under high tensile stress, thus strengthening the alloy without increasing stress concentration. Moreover, the three blocky phases can hinder dislocations through the interface between them and gamma lamellae, thereby strengthening the lamellae. Among them the gamma(b) phase plays a coordinated role in controlling the deformation of the lamellar colony.

Automated summary

A TiAl alloy with a high Nb concentration was prepared using electromagnetic cold crucible zone melting (ECCZM) and analyzed for its microstructure, tensile properties, and fracture morphology. The alloy exhibited three blocky phases and two types of interfaces. Tensile tests showed that the ultimate tensile strength of the alloy reached a maximum of 645 MPa. The primary strengthening mechanism of the alloy was through interface strengthening and hindering dislocation movement.