Effect of the size distribution of alpha particles on microstructure evolution during heat treatment of an alpha/beta ti
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Effect of the Size Distribution of Alpha Particles on Microstructure Evolution during Heat Treatment of an Alpha/Beta Titanium Alloy J.D. MILLER and S.L. SEMIATIN (a)
A model was developed to describe the diffusional growth of a size distribution of alpha particles in Ti-6Al-4V during cooldown following alpha/beta solution treatment. Model results for initial microstructures with the same initial volume fraction of alpha but comprising either a distribution of particle sizes or a uniform particle size (equal to the average size of the distribution) yielded almost identical results in terms of final volume fraction and average particle size. The simulations quantified the narrowing of the size distribution associated with the different growth rates of small and large particles.
(b)
(c) Fig. 4—The difference in magnetic induction and direction distribution of the {110} grains after vacuum and hydrogen annealing: (a) magnetic induction and (b) and (c) direction distributions of the {110} grains.
REFERENCES 1. N.H. Heo and J.W. Yim: J. Kor. Phys. Soc., 2004, vol. 44, pp. 1547-51. 2. N.H. Heo, S.B. Kim, K.H. Chai, Y.S. Choi, and S.S. Cho: Mater. Sci. Forum, 2002, vols. 408–412, pp. 857-62. METALLURGICAL AND MATERIALS TRANSACTIONS A
Improvements in the performance of metallic structural materials for high-integrity applications have focused on both alloy design and microstructure control. Such improvements can have substantial impact for nickel- and titanium-base alloys used in the aerospace industry. For example, the development of a wide variety of wrought, powder-metallurgy, and single-crystal nickelbase superalloys and novel processes to manufacture them has led to substantial increases in the efficiency of jet engines. Significant, but perhaps less dramatic, breakthroughs have also been realized in the titanium industry. Recent advances for titanium alloys include the development of methods to manufacture ultrafine-particle-size alpha-beta alloys[1] and the introduction of advanced modeling techniques for system design.[2] In several recent efforts,[3,4] the heat-treatment response of two-phase, alpha/beta titanium alloys comprising globular, primary-alpha (hcp) particles in a matrix of beta (bcc) phase has been elucidated. In particular, the static-coarsening behavior of the alpha particles during heating cycles typical of those used during ingot breakdown, prior to forging, or during final heat treatment was established.[3] This work demonstrated that the average particle size increases measurably, but that the size distribution remains self-similar. In a related effort,[4] the growth kinetics of primary alpha during final heat treatments comprising soaking at a fixed, peak (solution) temperature in the two-phase field followed by cooling were quantified
J.D. MILLER, Research Engineer, is with UTC, Dayton, OH 45432. Contact e-mail: [email protected] S.L. SEMIATIN, Senior Scientist, Materials Processing/Processing Science, is with the Air Force Research Laboratory, Materials and Manufacturing Director
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