Recrystallization kinetics in copper: Comparison between techniques
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I.
INTRODUCTION
IN studying recrystallization kinetics, it is necessary to determine the volume fraction of recrystallized material X in partially recrystallized samples. The most direct way to determine X is by microscopy using a series of partially recrystallized samples, and often optical microscopy is used. v] However, for example, in heavily deformed copper, it is difficult to distinguish deformed material from recrystallized material by optical microscopy. Other, more indirect methods have also been used to determine the recrystallized fraction. Hardness indentations, calorimetry measurements, neutron diffraction texture data, electrical resistivity, and measurements of magnetic parameters have been employed for this purpose in the pasty 5j The aim of the present article is to compare the results obtained by various techniques. As a basis for this comparison, data obtained by the electron backscattering pattem (EBSP) techniqueE6,71in the scanning electron microscope (SEM) are used. This method has the advantage of being a direct measurement of the traces of grains on a prepared external surface combined with orientation information, and not an indirect measurement like the other previously mentioned techniques. By EBSP, it is possible to determine almost objectively whether an area is recrystallized. The material studied was copper cold-rolled to 92 pct reduction and annealed at 121 ~ The recrystallization in this material is very inhomogeneous, and it is therefore a good test material for the various techniques. The results of calorimetry, hardness (micro and macro), orientation contrast determination in the SEM, and neutron diffraction are related to the EBSP results and the agreements and disagreement are discussed.
E. WOLDT, Senior Scientist, is with the Institut flJr Werkstoffe, Technische Universit~it Braunschweig, D-38106 Braunschweig, Germany. D. JUUL JENSEN, Senior Scientist, is with the Materials Department, Riso National Laboratory, DK-4000 Roskilde, Denmark. Manuscript submitted June 29, 1994. METALLURGICAL AND MATERIALS TRANSACTIONS A
II.
EXPERIMENTAL
The material was copper of 99.96 pct purity, the main impurities being Pb, As, Ni, Ag, Co, and Fe. Initially the material was in the form of cold-drawn bars of square cross section (12 mm). These were cut into 20-cm-long pieces, each of which was sealed in a glass tube under 5N Argon gas and annealed at 450 ~ for 1.5 hours. The average grain size after this treatment was 35/xm. Subsequently, the pieces were deformed by rolling in steps of 1-mm reduction (12-, 2 7 mm), 0.5-mm reduction (7~ 2 2 mm), and 0.2-mm reduction (242 1 mm). This is equivalent to a total deformation of 92 pct. The choice of the reduction steps ensured that the condition for homogeneous deformationt81 during rolling was fulfilled apart from the first reduction step. In the next step, samples of 6-mm and 10-mm diameters were punched out of the rolled sheet and stored at 6 ~ Before any experiments, all disks were e~ched in 50 pct nitric acid to remove surface contamination a
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