Recrystallization in Commercially Pure Aluminum
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I.
INTRODUCTION
THEinitial stages of recrystallization in commercial purity aluminum have been studied in detail ~by techniques such as in situ annealing in a high voltage electron microscope, 100 kV transmission electron microscopy, and light microscopy. The main sample parameters varied in that work were the initial grain size (370 and 19 microns) and the degree of prior deformation being 50 and 90 pct reduction by cold-rolling. Steps in the recrystallization process such as formation of nuclei and their growth are influenced by many parameters of which the degree of deformation is very important. To characterize more completely the recrystallization of commercial purity aluminum, the former study ~ was therefore extended by examining the effect of lower degrees of deformation, i.e., 5 to 30 pct reduction in thickness by cold-rolling. The purity of the aluminum was 99.4 pct and samples of two different grain sizes were examined. The material was studied by the same techniques as in Reference 1, and the results are therefore comparable. This allows a discussion in the present paper of the effect of the degree of deformation varied over a wide range on the recrystallization behavior of commercial purity aluminum.
II.
EXPERIMENTAL TECHNIQUES
A. Materials
The chemical composition of the aluminum used is given in Table I. To reduce the amount of iron in supersaturated solution the starting material was heat treated at 600 ~ in high vacuum for 24 hours followed by slow cooling in the furnace. Fine-grained material was produced by coldBENT BAY is Senior Lecturer, Engineering Academy of Denmark, Department of Mechanical Engineering, 2800 Lyngby, Denmark; and NIELS HANSEN is Head of the Metallurgy Department, Rise National Laboratory,4000 Roskilde, Denmark. Manuscript submittedJune 28, 1983. METALLURGICALTRANSACTIONSA
rolling by 80 pct followed by annealing for 30 minutes at 400 ~ At this stage the specimen thickness was 2 mm. Coarse-grained material was produced by cold-rolling the fine-grained, soft material by 10 pct and annealing for 30 minutes at 550 ~ followed by slow cooling. The grain sizes obtained were 290 and 24 ~m. The final cold deformations prior to the recrystallization treatments were 5, 15, and 30 pct reduction in thickness by cold-rolling. " The material contained large plate-shaped intermetallic FeA13 particles of a mean diameter given in Table I. B. Microscopy
High voltage electron microscopy (HVEM), 100 kV transmission electron microscopy (TEM), and light microscopy were used in this study. These experimental techniques and details about sample preparation are described in Reference 1. The in situ HVEM-annealing-technique used with success in the earlier study] however, appeared to be unsuitable in this study. The reasons were that the number of nucleation sites decreased and the nucleation temperature increased when the degree of deformation prior to recrystallization was decreased. The relatively small number of nucleation sites in the present samples made it difficult to identify potential
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