DEVELOPMENT AND EVALUATION OF DENSIFICATION MODELS FOR Al-Pb ALLOYS PRODUCED BY POWDER METALLURGY

Abstract

    The recent research into the alternate sliding bearing materials unequivocally point to the beneficial role of lead (Pb) in aluminum (Al).  But, these alloys offer a manufacturing challenge, due to wide immiscibility gap. For such applications, apart from homogeneous microstructure, porosity control is also equally important, as it influences the tribological performance through spreading of lead in aluminum matrix. These objectives can be achieved together by mechanical alloying through powder metallurgy (P/M). However, die compaction in P/M results in inhomogeneous density distributions leading to distortion during sintering process. In order to control the shape of final P/M parts, the appropriate models are necessary for densification of composite powders to simulate cold compaction responses. In the present work, the authors studied the effect of alloy composition and ball to charge ratio on densification behaviour of conventional ball milled Al-Pb alloys, with a view to develop non-linear regression models that can best describe the  densification behaviour of ball milled Al-Pb alloys from compressibility test data. Based on their validation, the study concludes that Richards model effectively predicts densification behaviour of P/M processed Al-Pb alloys. Such modeling will be of great significance in simulating the cold compaction response, especially in case of alloys where no historical data exists regarding effect of processing conditions on densification behaviour.