R.A. Rahman Rashid

Machinability of a near beta titanium alloy

In this paper, the machinability of a near beta Ti25Nb3Mo3Zr2Sn titanium alloy with different heat treatment histories has been investigated in terms of cutting force, chip temperature and chip formation. A solution treatment was performed followed by ageing at different temperatures for the near beta alloy. It has been shown that the same alloy behaves differently during machining at various cutting speeds after different heat treatments. The observations have been explained in terms of friction effects and the hardness of the materials. It has been concluded that the ductility of a workpiece plays a significant role in determining its machinability. High friction at the tool–chip interface in a ductile workpiece resulted in a higher degree of chip segmentation and a larger undeformed surface length in each chip.

Experimental evaluation of the effect of workpiece heat treatments and cutting parameters on the machinability of Ti-10V-2Fe-3Al β titanium alloy using Taguchi's design of experiments

This industry supported scientific investigation presented the steps taken to gain insight into the phenomena of machining β titanium alloy Ti10.2.3 using design of experiments approach. The influence of cutting parameters and workpiece heat treatments on the cutting forces and temperatures during turning of the aerospace grade Ti-10V-2Fe-3Al (Ti.10.2.3) alloy using Taguchis design of experiments is presented in this work. An L18 orthogonal array was designed and analysis of variance was performed on the tabulated results to investigate the effects of control variables (i.e., cutting speed, feed rate, and workpiece heat treatment) on the output parameters (i.e., cutting force, feed force, and the cutting temperature). The results showed that the feed rate was the most influential factor and the workpiece heat treatment was the least influential parameter which affected the response variables. Based on this observation, optimal cutting parameters and heat treatment conditions were calculated. This work minimised the number of experiments to be carried out to obtain the optimum machining parameters for this specific titanium alloy (Ti.10.2.3).

A case-study on the mechanism of flank wear during laser-assisted machining of a titanium alloy

In recent years, researchers have been investigating various technologies including laser-assisted machining (LAM) to improve the machinability of titanium alloys which is considered to be one of the difficult-to-cut materials. The LAM process involves heating the titanium workpiece with a laser beam of sufficient power to soften the material before it engages with the cutting tool. Benefits of LAM include significant reduction in cutting forces as well as better surface finish. However, as diffusion wear is the most dominant tool wear mechanism associated when machining titanium alloys, the effect of the additional heat from laser preheating on the cutting tool life is not clearly understood. Therefore, this paper aims at investigating the tool life of an uncoated carbide tool during LAM of Ti-6Al-4V alloy, as well as identifying the principal flank wear mechanisms involved during the cutting process. It was found that the tool life was reduced by about 8% when machining the workpiece with laser preheating. Moreover, it was found that the carbon from the cutting tool diffused into the titanium built-up edge formed in the vicinity of the cutting zone from where it was carried out through the chips. This considerably weakened the cutting edge of the tool resulting in accelerated tool wear.