Recovery and ordering in cold-rolled boron-doped Ni 76 Al 24
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I. INTRODUCTION
RECOVERY
is a major phenomenon that occurs in those alloys that can be cold or hot deformed. However, information available on the recovery behavior of intermetallic compounds deformed by cold work is limited. Vidoz et al.[1] found that cold-rolled Ni3Fe annealed below the critical ordering temperature (Tc) led to substantial strain-age hardening before recrystallization. Roessler et al.[2] studied the effect of annealing on the restoration of order in Cu3Au. They observed hardness maxima with increase in order. Feller-Kniepmeier and Ruckert[3] examined recovery in Cu3Au after 10 and 90 pct deformation. It was found that at lower deformation, ordering was sluggish, whereas the heavily worked compound ordered rapidly. Hutchinson et al.[4] also studied recovery in Cu3Au. They found that the degree of recovery, as characterized by the line broadening at half-maxima width, increases linearly with the increase in temperature. However, they did not find any effect of order on recovery before recrystallization. Cahn et al.[5] reported on the recovery behavior of a (Co78Fe22)3V alloy and found that order was restored before recrystallization. They also found strain-age hardening with increase in order within the same temperature range. Early work on Ni3Al showed that the degree of order that was reduced by cold working was restored fully during annealing.[6–9] Baker et al.[8] found that order was restored during annealing and that there was extensive recovery before recrystallization. It is the aim of the present study to evaluate the recovery and ordering behavior during annealing of cold-rolled borondoped Ni76Al24. The effects of long-range order on dislocation, defect mobility, and diffusion kinetics will be considered.
S. GHOSH CHOWDHURY, Scientist, is with the Materials Characterization Division, National Metallurgical Laboratory, Jamshedpur, 831007, India. A.K. JENA, Director of Research, is with Porous Materials Inc., Cornell University Research Park, Ithaca, NY 14850-1298. R.K. RAY, Professor, is with the Department of Materials and Metallurgical Engineering, Indian Institute of Technology, Kanpur 208016, India. Manuscript submitted March 2, 1999.
METALLURGICAL AND MATERIALS TRANSACTIONS A
II. EXPERIMENTAL PROCEDURE The alloy used in the present investigation was Ni-24 at. pct Al-0.24 at. pct B. The alloy was homogenized by annealing at 1050 8C for 20 minutes. The homogenized alloy was cold rolled in steps of 25, 45, 65, and 85 pct. The coldrolled specimens were annealed isochronally by holding for 1 hour at temperatures between room temperature and 1000 8C, at intervals of 100 8C. Isothermal annealing was also carried out at a number of temperatures using 85 pct coldrolled samples. The order parameter was measured using an X-ray diffractometer. Microhardness was determined using 100 g load. The strain parameter (Bw /Br), where Bw and Br are the half-maximum width of cold-worked and recovered samples, respectively, was evaluated for samples subjected to isochronal annealing. Transmission electr
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