Influence of Iron on the Size and Distribution of Metallic Lanthanum Particles in Free-Machining Titanium Alloys Ti 6Al 7Nb xFe 0.9La

Abstract

The addition of the rare earth metal Lanthanum to (α+β)-Titanium alloys like Ti 6Al 4V or Ti 6Al 7Nb improves their machinability as short chips form during machining. In related alloys, metallic Lanthanum is distributed as micrometer-size particles which are mainly located at the grain boundaries. In case Iron is present in Lanthanum containing (α+β)-Titanium alloys, a more homogeneous particle distribution is observed leading to improved ductility at room temperature and elevated temperature compared to Iron-free alloys. In the present study, the influence of Iron on the Lanthanum particle size and distribution was investigated in the system Ti 6Al 7Nb xFe 0.9La. First, the solidification behaviour was simulated. Afterwards, alloys with different amounts of Iron (0.25 %, 0.5 % and 1.0 %) were produced. The microstructure of these alloys as well as their deformability and mechanical properties at room temperature were analyzed which were improved compared to the Iron-free Ti 6Al 7Nb 0.9La and Ti 6Al 4V 0.9La alloys.