Microstructure and mechanical properties of an ultrafine Ti–Si–Nb alloy

Abstract

Nb-modified ultrafine Ti-Si eutectic alloy was made by cold crucible levitation melting, tested in compression at room temperature, and characterized by electron microscopy. Compression tests of (Ti 86.5 Si 13.5) 97 Nb 3 specimens measured an ultimate compressive strength of 1180 MPa and a compressive plastic strain of 12%, both of which are higher than in eutectic Ti 86.5 Si 13.5 alloy. Electron microscopy showed that the Ti-Si-Nb alloy had a bimodal microstructure with micrometer-scale primary α-Ti dendrites distributed in an ultrafine eutectic (α-Ti+Ti 5 Si 3) matrix. The enhanced ductility is attributed to the morphology of the phase constituents and to the larger lattice mismatches between α-Ti and Ti 5 Si 3 phases caused by the Nb addition. The crystallographic orientation relationship of Ti 5 Si 3 with α-Ti is (1100)[1126] Ti 5 Si 3 || (0111)[51 4 3 ] α-Ti.