Microstructural Mechanisms during Dynamic Globularization of Ti-6Al-4V Alloy

Abstract

The microstructural mechanisms during dynamic globularization were investigated for ELI grade Ti-6Al-4V alloy with initial martensite microstructure. For this purpose, compression tests were carried out isothermally at 1073 K up to the strains of 1.0 and 1.4 with the strain rates ranging from 10 À3 s À1 to 1 s À1 . Fully dynamically globularized specimen exhibited higher Vickers hardness values due to the finer grain size and higher dislocation density compared to the conventionally produced one, i.e., partial dynamic globularization by subsequent annealing. The strain rate sensitivity (m) values of the flow stresses at initial stage (" % 0:05) and final stage (" % 1:4) of deformation were %0:15 and %0:36, respectively, leading to the conclusion that deformation was controlled by dislocation glide/climb at low strains and grain boundary sliding at high strains. Also, microstructural evolution during dynamic globularization was rationalized by examining the microstructures associated with kinking and fragmentation of lamellar plates.

Softening Behavior of Ti6Al4V Alloy during Hot Deformation

“…The constants n and α were estimated to be 5.65 and 0.005 MPa -1 respectively. The calculated activation energy for all deformation conditions revealed a good agreement with the reported values in the literature [11][12][13], (Table 1). The wide range of activation energy values reported can be attributed to the difference in the initial microstructure and the deformation condition resulting in different deformation mechanisms.…”

Constitutive analysis of hot deformation behavior of a Ti6Al4V alloy using physical based model

“…continuous dynamic recrystallization, CDRX) [37], conventional/discontinuous dynamic recrystallization (i.e. nucleation and growth) [38,39] and the globularization upon straining [1,30,40]. These mechanisms are related to a wide range of activation energy values due to the difference in the initial microstructure and processing condition.…”

Martensite Formation and Decomposition during Traditional and AM Processing of Two-Phase Titanium Alloys—An Overview

“…Zherebtsov et al [11] observed that in Ti-6Al-4V billets processed by warm severe plastic deformation, the formation of a homogeneous UFG microstructure is promoted by initial microstructure which is either fully martensitic or globular. Park et al [57,58] analyzed high-temperature deformation behavior and microstructural evolution process of ELI Ti-6Al-4V alloy having martensite microstructure. Hot compression tests were carried out at the temperature range of 700-950 • C. Fully dynamically globularized material exhibited high hardness due to the fine grain size and high dislocation density.…”