Effect of intermediate annealing on texture evolution and plastic anisotropy in an Al-Mg autobody alloy
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I. INTRODUCTION
ALUMINUM alloys are currently widely investigated for substitution of steels in automobiles in order to manufacture lighter cars and thus reduce energy consumption. Specially, the age-hardening Al-Mg alloys of the 5xxx series seem to be particularly suitable for autobody applications. They have a good combination of strength and formability. The formability is closely related to plastic anisotropy, which is intrinsically caused by crystallographic textures. The last step in thermomechanical processing of the age-hardening Al-Mg sheets is usually a solution heat treatment so that a recrystallization texture is present. In contrast to rolling texture, there is a larger variety in recrystallization texture, which can be influenced by alloy addition and constitution.[1,2] The texture evolution during the processing therefore becomes more complicated and has given rise to many related investigations. However, most of these studies were focused on the influence of the conditions during preheating, hot rolling, cold rolling, and final heat treatment.[3–6] The present work aims to extend this kind of study to another important process, intermediate annealing (IA). This process is usually employed in the processing of Al alloys and has been demonstrated to be of importance in controlling microstructures and textures. In this article, the texture evolution during the thermomechanical processing of an Al-Mg alloy, with and without IA, respectively, is studied by use of orientation distribution functions (ODFs). Then, the effect of IA on the formation of final annealing textures is analyzed with the aid of differential ODFs (DODFs) and microstructural characterization. Its effect on the plastic anisotropy is discussed from the viewpoint of improving the formability of the alloy. SAIYI LI, formerly Research Associate with the Department of Materials Science and Engineering, Central South University of Technology, Changsha 410083, People’s Republic of China, is Postdoctoral Research Fellow, Department of Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, B-3001 Leuven, Belgium. SUK-BONG KANG, Director, and HUNG-SUK KO, Engineer, are with the Department of Materials Engineering, Korea Institute of Machinery and Materials, Changwon 641010, Korea. Manuscript submitted March 23, 1999. METALLURGICAL AND MATERIALS TRANSACTIONS A
II. EXPERIMENTAL A. Material Processing The chemical composition of the Al-Mg alloy investigated is given in Table I. The alloy was air melted in a graphite crucible in an induction furnace and then cast in a cast iron mold at 700 8C. The ingot was homogenized at 480 8C for 24 hours and hot rolled at 400 8C from 23 to 3 mm. Then, the hot band was divided into two sets. One set was cold rolled down to the 1-mm final thickness. Another set was annealed at 400 8C for 1 hour and then cold rolled to the same final gage. The samples with and without IA are hereafter referred to as IA and non-IA samples, respectively. The cold-rolled samples were given two kinds of typical final h
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