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 (250μm) 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 0.98N (100gf). Grindability was evaluated by measuring the amount of metal volume removed after grinding for 1min. 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.