Machining of novel AA7075 foams containing thin-walled ceramic bubbles

Abstract

ABSTRACT Machining of novel light weight 7075 aluminum alloy reinforced with thin-walled hollow ceramic bubbles present a significant challenge to the manufacturing industry. The presence of hollow bubble phase causes poor surface finish and high machining cost. In this paper, an effort has been made to elucidate the mechanics of machining new grade AA7075 syntactic foams through an analytical force model which is the first of its kind for this material. Orthogonal cutting experiments carried out on different volume fraction and bubble size syntactic foams showed an increase in machining forces by up to 500 N with increasing feed (0.02 mm to 0.2 mm) and 200 N with decreasing cutting speed (100 m/min to 25 m/min). The hollow bubble size profoundly influences the plastic deformation behavior of the matrix. Decrease in average ceramic bubble size (0.6 mm to 0.3 mm) causes the machining forces to increase by margin of 65%. It is found that smaller the hollow bubble size and higher its volume fraction, higher will be the magnitude of machining forces. The causes of variation in machining forces is primary attributed to the characteristic bubble burst modes (Mode 1 and Mode 2) that alters the effective load transfer mechanism with 7075 matrix and its plasticity.