Improving microstructure and mechanical properties of Ti43Al5Nb0.1B alloy by addition of Fe

Abstract

Alloying additions of 0 at%–1.1 at% Fe were added into Ti43Al5Nb0.1B alloys for increasing the room-temperature strength and ductility, and the microstructure and mechanical properties were systematically studied. The results show that the lattice tetragonality (c/a) of γ phase and the average width of columnar grains of alloys decrease with Fe content increasing. Fe addition brings about the formation of Fe-rich B2 phase both in the dendrites and in interdendritic regions, and its content increases with Fe contents increasing. Furthermore, Fe addition aggravates the Al segregations in the interdendritic regions. The alloy with 0.7 at% Fe exhibits higher combined mechanical properties with the ultimate compression strength and fracture strain of 1958.4 MPa and 29.8%, respectively. The grain refinement strengthening and solid-solution strengthening of Fe are responsible for the improvement in the strength and the strain. However, excessive Fe addition results in the decrease in the strength and strain, which is attributed to the severe Al segregations in the interdendritic regions that cause the premature fracture during compression.