Analysis of a free machining α+β titanium alloy using conventional and ultrasonically assisted turning

Rapid advancements in power generation and aviation industries have witnessed a widespread use of titanium and its alloys in many applications. This is primarily due to their excellent mechanical properties including, amongst other, high strength-to-density ratio, outstanding fatigue properties and corrosion resistance with the ability to withstand moderately high temperatures. However, this combination of properties results in poor machinability of the material, increasing the cost of components machined with conventional cutting techniques. Recently, Ti 6Al 2Sn 4Zr 6Mo, a modern titanium alloy with improved mechanical properties, has been introduced as a possible replacement of Ti 6Al 4V in aerospace industry. However, its poor machinability and formation of long chips in conventional turning are main limitations for its wide-spread application. Therefore, a new alloy based on Ti 6Al 2Sn 4Zr 6Mo, namely Ti 6Al 7Zr 6Mo 0.9La, was developed; it shows enhanced machinability generating short chips during metal cutting, which prevents entanglement with cutting tools improving productivity. To further enhance the machinability of this material, a novel hybrid machining technique called ultrasonically assisted turning (UAT) was used. Experimental investigations were carried out to study the machinability, chip shapes, cutting forces, temperature in the process zone and surface roughness for conventional and ultrasonically assisted turning of both alloys. UAT shows improved machinability with reduced nominal cutting forces, improved surface roughness of the machined workpiece and generation of shorter chips when compared to conventional machining conditions.