Effects of processing conditions on powder particle.pdf

P u b li s h e d b y M a n e y P u b li s h in g ( c ) I O M C o m m u n ic a ti o n s L td Effects of processing conditions on powder particle size and morphology in centrifugal atomisation of tin J. W. Xie, Y. Y. Zhao and J. J. Dunkley expressions for some specific liquids in a certain range of atomising conditions.5 As the atomising mode dependsThis paper investigates the effects of atomiser design critically upon the liquid flow conditions on the atomiser,and processing parameters on the morphology and it is critical to understand the behaviour of the liquid flowsize distribution of centrifugally atomised tin powder. on the disc in order to obtain powders with the desiredPremature solidification of the melt on the atomiser properties. The flow behaviour of the melt in centrifugaland poor wetting of the atomiser by the melt were atomisation is usually complicated. Mathematical model-found to be the main causes of unsuccessful atomis- ling can be used to calculate the thickness and velocityation. The particle size distributions of the powders profiles of the liquid metal film and thus to predict orfollow a lognormal distribution. The median particle explain the experimental results, such as particle shape andsize increased with decreasing atomiser rotation speed size distribution.6–8 However, these models need to beand with increasing melt flowrate. Cups with a high experimentally validated before they can be used withincluded angle made significantly finer powders than confidence.flat discs under the same operating conditions. Sufficient wetting of the atomiser by the molten metal isPM/1053 essential for rapid acceleration and consequently effective disintegration of the melt. In the centrifugal atomisation ofDr Xie ( jxie@liv.ac.uk) and Dr Zhao are in the Mg alloys, poor wetting of the atomising disc or cup byDepartment of Engineering, The University of the Mg alloys was found to be a major cause of failure ofLiverpool, Liverpool L69 3BX, UK. Mr Dunkley i