Grindability of cast Ti–Cu alloys

Objectives. The purpose of the present study was to evaluate the grindability of a series of cast Ti–Cu alloys in order to develop a titanium alloy with better grindability than commercially pure titanium (CP Ti), which is considered to be one of the most difficult metals to machine. Methods. Experimental Ti–Cu alloys (0.5, 1.0, 2.0, 5.0, and 10.0 mass% Cu) were made in an argon-arc melting furnace. Each alloy was cast into a magnesia mold using a centrifugal casting machine. Cast alloy slabs (3.5 mm×8.5 mm×30.5 mm), from which the hardened surface layer (250 μm) was removed, were ground using a SiC abrasive wheel on an electric handpiece at four circumferential speeds (500, 750, 1000, or 1250 m/min) at 0.98 N (100 gf). Grindability was evaluated by measuring the amount of metal volume removed after grinding for 1 min. Data were compared to those for CP Ti and Ti–6Al–4V. Results. For all speeds, Ti–10% Cu alloy exhibited the highest grindability. For the Ti–Cu alloys with a Cu content of 2% or less, the highest grindability corresponded to an intermediate speed. It was observed that the grindability increased with an increase in the Cu concentration compared to CP Ti, particularly for the 5 or 10% Cu alloys at a circumferential speed of 1000 m/min or above. Significance. By alloying with copper, the cast titanium exhibited better grindability at high speed. The continuous precipitation of Ti2Cu among the α-matrix grains made this material less ductile and facilitated more effective grinding because small broken segments more readily formed.