Optimization of Sintering Parameters for Ti-6Al-4V Density Enhancement Using Response Surface Methodology

The use of solvent dilution during debonding in the Ti-MIM field has now attracted the interest of practitioners in the field. Therefore, the binding material used in this study is composed of 60% by weight of palm stearin (PS) binding material and 40% by weight of polyethylene (PE) mixed with Ti-Al-4V powder. PS binding material has the potential to be used because it is cheap and easy to obtain in Malaysia. The suitable powder loading for this injection is at 65% volume. This study aims to optimize the parameters of the sintering process involved in MIM through the central composite design (CCD) of the response surface methodology (RSM) to produce the highest density of Ti-Al-4V. Using the sintering temperature, sintering time, heating rate and cooling rate as the focused parameters in this study as well as the interaction between these parameters. Analysis of variance (ANOVA) was done with Design Expert Software for each optimization process to evaluate the influence of each factor. Through this ANOVA, it was found that the sintering temperature gave the biggest contribution since its F value is the highest which is 32.75. Cooling rate, sintering time and heating rate contribute 11.19%, 3.66% and 2.46% respectively. As far as the sintering process is concerned, the optimal parameters are sintering temperature 1237.3°C, sintering time 62.6 minutes. heating rate 3.8°C/min and cooling rate 9.5°C/min. Scanning electron micrograph (SEM) is another validation test that being carried out beside ANOVA. By examining the morphology of the Ti-Al-4V sintered part through the scanning, the presences α-phase and β-phase can be seen. The balance of a + ß structure helps increase the elongation of titanium alloy as well. Because the optimal parameter through the validation test applying a cooling rate of 9.5°C/min allows the presence of more α lamella than β layers which causes the elongation of the sinter body to increase even though its strength can be decreased. This situation causes the strength to decrease while density and the elongation of the sinter body increases.