Microstructure and mechanical properties of Ti44Al6Nb alloys with different cerium contents

Ti44Al6Nb-based alloy ingots with different cerium (Ce) contents (0, 0.05, 0.10, 0.15, 0.20; at%) were prepared by non-consumable vacuum arc smelting furnace (WK-II). The surface quality, macrostructure, microstructure, compressive properties and fracture morphology of these ingots were studied. The results show that Ce has few influences on the surface quality. Ce can refine grain size and the average grain size decreases from 0.50 to 0.19 mm with the increase of Ce content. Meanwhile, the microstructure morphology of these ingots changes from large lamellar microstructure to dual-phase microstructure. With addition of Ce, CeO and AlCe3 are formed during melting and solidifying, which act as the core of heterogeneous nucleation and refine the grain. The compressive testing results show that Ce can improve strength and ductility. The ultimate compressive strength increases from 1156.2 to 1472.2 MPa with Ce content increasing from 0 at% to 0.20 at%. The compression ratio is improved from 10.2 % to 15.3 % with Ce content increasing from 0 at% to 0.10 at%. The refined crystalline strengthening and grain boundary strengthening are the main reasons for the improvement of compressive property.