Recrystallization and grain growth in metastable beta III titanium alloy |
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Authors: | B B Rath R J Lederich C F Yolton F H Froes |
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Affiliation: | (1) Alloy Transformation and Kinetics Branch (Code 6320), Naval Research Laboratory, 20375 Washington, DC;(2) McDonnell-Douglas Research Laboratories, 63166 St. Louis, MO;(3) Colt Industries/Crucible Materials Research Center, 15213 Pittsburgh, PA;(4) Air Force Materials Laboratory, Wright-Patterson Air Force Base, 45433 Dayton, OH |
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Abstract: | The progress of recrystallization and subsequent grain growth has been systematically investigated in a metastable beta titanium
alloy (Ti-11.5 Mo-6 Zr-4.5 Sn). Quantitative evaluation of the kinetics of these processes over a wide range of temperature,
deformation, and initial grain sizes has been performed. For a given deformation, the average grain boundary velocity, decreasing
with the reciprocal of annealing time, suggests the occurrences of recovery with second order kinetics concurrent with the
recrystallization. The amount of deformation, varying from 20 to 80 pct cold reduction and proportional to the stored energy
of deformation in the alloy, increases the average grain boundary migration rate during recrystallization by three orders
of magnitude. The temperature dependence of the recrystallization rate, however, remains unaffected by the amount of deformation
at 83 kcal/mole (347 kJ/mole). The isothermal grain growth kinetics follow the power law such that the time exponent of the
process remains at a value of 0.35 at most annealing temperatures. The excellent agreement between the driving force exponent
of recrystallization and the time exponent of grain growth based on a model which relates the driving force dependence of
the rates of both processes, clearly suggests that the kinetics of these processes are controlled by a single mechanism,i.e. impurity dependent boundary migration.
This paper is based on a presentation made at a symposium on “Recovery, Recrystallization and Grain Growth in Materials” held
at the Chicago meeting of The Metallurgical Society of AIME, October 1977, under the sponsorship of the Physical Metallurgy
Committee. |
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