Frequent occurrence of discontinuous dynamic recrystallization in Ti-6Al-4V Alloy with α′ martensite starting microstructure

Hiroaki Matsumoto, Liu Bin, Sang Hak Lee, Yunping Li, Yoshiki Ono, Akihiko Chiba

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58 Citations (Scopus)

Abstract

The microstructural conversion mechanism in an α′ martensite starting microstructure during hot deformation (at 973 K (700 °C)-10 s -1) of the Ti-6Al-4V alloy is studied through detailed microstructural observations, kinetic analysis of deformation in the microstructure, and various theoretical models. After compressing the α′ starting microstructure at 973 K (700 °C)-10 s-1 and at a height strain of 0.8, it is observed that the α′ starting microstructure with acicular morphology evolved into an ultrafine-grained microstructure with an average grain size of 0.2 μm and a high fraction of high-angle grain boundaries. At the initial stage of deformation, subgrain formation in martensite variants and the formation of new grains with high-angle boundaries at interfaces of martensite variants, and {101̄1} twins are dominant. On increasing the height strain to 0.8, discontinuous dynamic recrystallization (DDRX) along with heterogeneous nucleation and fragmentation of grains with high-angle boundaries becomes dominant. In contrast, in the case of an (α + β) starting microstructure, continuous dynamic recrystallization (CDRX) is dominant throughout the deformation process. Thus, we found that DDRX becomes dominant by changing the starting microstructure from the conventional (α + β) to the acicular α′ martensite one. This behavior of the α′ martensite microstructure is attributed to the considerable number of nucleation sites such as dislocations, interfaces of martensite variants and {101̄1} twins, and the high-speed grain fragmentation along with subgrain formation in the α′ starting micro structure during the initial stage of deformation.

Original languageEnglish
Pages (from-to)3245-3260
Number of pages16
JournalMetallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
Volume44
Issue number7
DOIs
Publication statusPublished - 2013 Feb 20

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanics of Materials
  • Metals and Alloys

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