Plastic flow and microstructure evolution during thermomechanical processing of laser-deposited Ti-6Al-4V preforms

S. L. Semiatin, P. A. Kobryn, E. D. Roush, D. J. Furrer, T. E. Howson, R. R. Boyer, D. J. Chellman

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Abstract

Plastic flow behavior and microstructure evolution during hot working and heat treatment of Ti-6Al-4V synthesized via a laser-deposition, Laser Engineered Net Shaping (LENSTM), process were established. To this end, isothermal, hot compression tests were conducted on samples in either a deposited + stress relieved condition or a deposited + hot isostatically pressed (hipped) condition. The starting microstructures consisted of columnar grains with fine or coarse Widmanstätten (basketweave) alpha platelets. At subtransus temperatures, the flow curves of both microstructural conditions exhibited a peak stress at low strains followed by extensive flow softening; these curves were almost identical to previous measurements on ingot-metallurgy (IM) Ti-6Al-4V with similar transformed microstructures. In addition, the kinetics of globularization of the alpha phase during subtransus deformation or subsequent static heat treatment were found to be the same as for IM Ti-6Al-4V with comparable alpha-platelet thicknesses. During supertransus heat treatment, moderately fine beta-grain microstructures were developed in samples that had been predeformed below the beta transus. Such a heat treatment for samples previously deformed above the transus gave rise to a nonuniform distribution of coarse beta grains, an effect attributed to critical grain growth.

Original languageEnglish
Article number156
Pages (from-to)1801-1810
Number of pages10
JournalMetallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
Volume32
Issue number7
DOIs
Publication statusPublished - 1 Jan 2001
Externally publishedYes

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