Recrystallization Processing of Cold-Rolled Nickel
- PDF / 7,261,610 Bytes
- 9 Pages / 612 x 792 pts (letter) Page_size
- 90 Downloads / 174 Views
N7.1.1
RECRYSTALLIZATION PROCESSING OF COLD-ROLLED NICKEL I. Baker, H. Chang and J. Li Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 ABSTRACT We have examined the effects of isothermal annealing, at a variety of temperatures, and directional annealing, under a range of conditions, on both primary recrystallization and secondary recrystallization in 90% cold-rolled 99.5% nickel of two different textures. The initial texture is shown to influence the rolling texture and, hence, the results of subsequent annealing. It was found that one alloy showed a cube texture after primary recrystallization, underwent abnormal grain growth upon annealing at high temperatures, and could be directionally (secondary) recrystallized to give large columnar grains. In contrast, the other alloy produce a weak cube texture after primary recrystallization, showed only normal grain growth upon annealing at higher temperatures, and could not be directionally annealed to produce columnar grains. The implications of these results are discussed for producing columnar grains. INTRODUCTION It is well known that many f.c.c. metals or alloys when heavily cold-rolled and annealed to allow primary recrystallization have a {100} texture, commonly know as the cube texture. That the cube texture forms in heavily cold-rolled and annealed nickel has been known for a long time [1], but has become of increasing interest recently [2-12] since cube-textured nickel can be used as a substrate for the growth of YBCO superconductors. Initially annealing at above the primary recrystallization temperature has been reported to strengthen the cube texture in nickel [3-6,10,11]. On the other hand, annealing either heavily cold-rolled nickel or cube-textured, primary-recrystallized nickel at high homologous temperatures often leads to secondary recrystallization (abnormal grain growth). This produces large grains with a completely different texture to the cube-texture observed in fine-grained, primary-recrystallized nickel [2,3,6-11]. The formation of the secondary recrystallization texture has been little studied in nickel [2,8], possibly since it may be viewed simply as a nuisance destroying the potentially-useful, cube-textured nickel [4-11]. The secondary recrystallization texture can be viewed as forming via oriented nucleation or oriented growth [12-15]. In oriented nucleation, some components of the deformation texture are favorably oriented for the nucleation of new grains, which grow to produce the secondary recrystallization texture. In contrast, in oriented growth, nuclei surrounded by boundaries with low energies or high mobilities consume other orientations during abnormal grain growth. Separating these two processes is not necessarily easy and in practice the formation of the secondary recrystallization texture is probably some combination of both process. There are two suggestions concerning which grains grow rapidly during secondary recrystallization textures. Some researchers [2,16,17] emphasize the role of grains with coincidence
Data Loading...
