Influence of Heat Treatment on the Machinability of Titanium Alloys

Orthogonal cutting force measurements and single-point tool life tests were conducted in order to analyze the sensitivity to heat treatment on the machinability of three titanium alloys: Ti6Al4V, Ti-5Al-4V-0.6Mo-0.4Fe (TIMETAL (R) 54M), and Ti6246. The Ti6246 alloy showed the highest tool wear rates and the higher cutting forces in all the heat treatment conditions which could be related to its higher mechanical properties. TIMETAL (R) 54M alloy, a newly developed alloy with similar mechanical properties to the more commonly used Ti6Al4V, showed the lowest wear rates. Microstructural changes due to heat treatment have some influence in the machinability of the alloys. The beta annealed samples of the Ti6Al4V and TIMETAL (R) 54M alloys, with a very coarse lamellar microstructure, showed considerably shorter tool life and higher cutting forces. The rest of the heat treatments showed no significant influence in the machining behavior of the analyzed alloys as they do not cause important microstructural changes.