THE INFLUENCE OF GRAIN SIZE ON THE ROUGHENING BEHAVIOR OF AL-MG ALLOYS

摘要

The discontinuous plastic flow exhibited by numerous aluminum alloys presents significant challenges to the use of aluminum alloys in automotive applications. The inhomogeneous morphology of the surface asperities generated during metal forming causes strain localization resulting in tearing during metal forming, and increasing friction between mating die surfaces that results in accelerated die wear and in progressively reduced shape accuracy in metal stampings. Before forming models that account for changes in friction can be developed, the relationships between plastic strain, grain size, and surface roughness need to be better understood. To accomplish this objective, the roughening behavior of a commercial Al alloy was examined with different heat treatments and grain sizes. The results of this evaluation indicate that the standard roughness measures increase with strain in a manner that can be represented by a simple linear model with the slope a function of heat treatment and grain size. However, optical microscopy indicates that the roughening process may be more complex than suggested by this simple model.