The Effects of Processing Variables on Formability of Aluminium Sheets : 1st Report, The Effect of Cold Reduction

Abstract

This investigation aims to clarify the optimum processing conditions of a commercially pure aluminium sheet for press-formability, in correlation with the tensile properties and the crystallographic orientation. The process variables dealt with are the cold reduction and the annealing temperature after hot working. In the first report, the effects of the cold reduction are examined in as-rolled conditions. Plastic strain ratio γ of the tensile specimens taken at 45° and 90° to rolling direction shows the maximum in the 80% cold-reduced sheet. But, the γ-value at 0° to rolling direction decreases monotonously with an increasing cold reduction and is the least among those three directions at any amounts of cold reduction. From observation of the location where a fracture initiates during drawing, it is confirmed that the drawability is governed by the minimum γ-value in planar directions. As the cold reduction increases, the stretch-formability always lowers, but the drawability does not always lower. The former is well correlated with the variation of the n-value obtained from a bulge test and the latter is correlated with that of the minimum γ-value.