Journal Article

SEM/EBSD Analysis on Globularization Behavior of Lamellar Microstructure in Ti-6Al-4V During Hot Deformation and Annealing

Ito, Yoshinori, Murakami, Shogo, Tsuji, Nobuhiro

2017

Overview

Scanning electron microscope/electron back-scattering diffraction was used to investigate local misorientation development within an individual α plate of a Ti-6Al-4V alloy with an α lamellar microstructure during hot deformation at 1223 K (950 °C) and a strain rate of 0.1 s −1 . The correlation between the local misorientation development and the globularization behavior of α plates during subsequent annealing at 1223 K (950 °C) was discussed. The misorientation profile along an individual α plate showed that not only a continuous and smooth change in orientation but also a discontinuous change in orientation was developed by the hot deformation. We assume that the points where discontinuous change in orientation occurs, P d , became α / α boundaries and resulted in splitting α plates the annealing. The mean length between adjacent discontinuous points, L I , was determined and compared with the actual mean length of the α plates after hot deformation and subsequent annealing, L a , as measured by optical microscopy. The two kinds of length parameters coincided at lower strains, but significant differences were observed at higher strains, i.e ., L I was larger than L a . Further analysis showed that rotation axes (R.A.s) changed even within regions where orientation changes were continuous. By taking into account the points where the R.A.s changed, P r and P d , the mean length between adjacent points, L II , appeared to coincide with L a at higher strains. A higher lattice distortion is expected near points P r at higher strains, which results in the formation of new α / α boundaries in subsequent annealing. Consequently, points P d already developed by hot deformation were considered to become α / α boundaries and led to splitting α plates in annealing. New α / α boundaries formed at points P r in subsequent annealing after a higher strain deformation, which led to a splitting of α plates as well.

• Publisher: Springer US,Springer Nature B.V
• Subject: Alloys / Annealing / Characterization and Evaluation of Materials / Chemistry and Materials Science / Deformation / Distortion / Electron backscatter diffraction / Materials Science / Metallic Materials / Metallurgy / Microstructure / Misalignment / Nanotechnology / Optical microscopy / Orientation / Plates / Scanning electron microscopy / Scattering / Splitting / Strain rate / Structural Materials / Surfaces and Interfaces / Thin Films / Titanium base alloys