Size distribution of spray atomised aluminium alloy powders produced during linear atomisation

Abstract

Linear spray atomisation and deposition is an attractive technique for producing near net shape deposits, such as aluminium sheet and strip. In the present study, the influence of operating variables, such as atomising gas pressure and linear gas atomiser slit width, on the mass median diameter were investigated for linear spray atomisation and deposition of 3003 aluminium alloy (Al–1·12Mn–0·57Si–0·69Fe–0·15Cu, wt-%). The sieving results demonstrate that the mass median diameter decreases with increasing atomising gas pressure and linear gas atomiser slit width (gas flowrate) and that the size distribution becomes broader as the atomising gas pressure increases. Comparison of the influences of both atomising gas pressure and linear gas atomiser slit width on the mass median diameter reveals that atomising gas pressure has a more significant effect than linear gas atomiser slit width. In addition, the influence of atomising gas pressure on the averaged liquid mass flowrate was studied. The results indicate that the averaged liquid mass flowrate increases linearly with the atomising gas pressure differential over the range 262–379 kPa, suggesting that an aspiration effect is present. Laser diffraction was used to measure the size and distribution of the collected powders. Phase Doppler interferometry (PDI) was also used to characterise the droplet size and velocity distributions during linear spray atomisation and deposition of the aluminium alloy. The Sauter mean diameter (SMD) values were calculated based on the sieving results and compared with the SMD values measured by PDI and laser diffraction.