Recrystallization Behavior of Ni 3 AI(B)
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RECRYSTALLIZATION BEHAVIOR OF Ni3 AI(B) G. GOTTSTEIN AND W. KIM
Department of Metallurgy, Mechanics and Materials Science Michigan State University East Lansing, MI 48824 ABSTRACT The recrystallization kinetics, structure development, stored energy of cold work, and rolling and recrystallization textures were studied on boron doped Ni 76Al24 . The recrystallization kinetics were very slow compared to pure metals or disordered solid solutions, but similar to other intermetallic compounds. The development of the deformed and recrystallized microstructure is similar to metals with intermediate stacking fault energy. Despite a lack of massive deformation twinning the rolling texture is a typical brass type texture. The recrystallization texture is not a brass type recrystallization texture, but consists of components, which are related by a 25' rotation among each other and with the deformation texture. The observed phenomena are attributed to the constraints of grain boundary motion in long range ordered structures. It is further shown that Ni 3Al does undergo dynamic recrystallization during high temperature deformation. 1. INTRODUCTION The current study is aimed at the recrystallization behavior of ductilized Ni3Al. Interest in this topic arises from the fact that almost all structural materials undergo recrystallization during fabrication to their final product. Also, recrystallization may occur when fabricated components are subjected to elevated temperature service conditions. Previous investigations into the recrystallization of Ni3Al have been conducted on material without boron and analyzed mainly with regard to recrystallization and grain growth kinetics [1]. The current study used boron doped Ni76 A124 (referred to as Ni3A1 (B) in the following) and focussed in particular on the evolution of microstructure, and the rolling and recrystallization texture of heavily rolled and annealed Ni3Al (B). Also the liability of the material to dynamic recrystallization was investigated.
2. EXPERIMENTAL
The material was prepared by arc melting and drop casting of a composition 76 a/o Ni, 24 a/o Al and an addition of 0.24 a/o B. From this material samples of 7 mm thickness
were rolled at room temperature on a laboratory roll with 100 mm roll diameter. All specimens were rolled with a constant thickness reduction of 0.6 mm per pass. This produced rolling degrees of 90%, although local crack development was evident by optical inspection for degrees of rolling higher than 80%.
The recrystallization kinetics of specimens rolled 20%, 40%, 60%, and 80% were studied using isothermal annealing at temperatures between 600'C and 700'C. Also isochronal annealing for 15 min between 500*C and 1000*C in steps of 50TC were done for specimens rolled 85%. The progress of recrystallization was monitored by optical microscopy and by measuring the microhardness. All hardness indentations were made in the rol-
Mat. Res. Soc. Symp. Proc. Vol. 133.
1989 Materials Research Society
512
ling plane. The crystallographic texture of 90% roll
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