Complexity and Anisotropy of Plastic Flow of α-Ti Probed by Acoustic Emission and Local Extensometry.

Mikhail Lebyodkin,Thiebaud Richeton,Kékéli Amouzou,Tatiana Lebedkina,Amandine Roth

doi:10.3390/ma11071061

Abstract

Current progress in the prediction of mechanical behavior of solids requires understanding of spatiotemporal complexity of plastic flow caused by self-organization of crystal defects. It may be particularly important in hexagonal materials because of their strong anisotropy and combination of different mechanisms of plasticity, such as dislocation glide and twinning. These materials often display complex behavior even on the macroscopic scale of deformation curves, e.g., a peculiar three-stage elastoplastic transition, the origin of which is a matter of debates. The present work is devoted to a multiscale study of plastic flow in α-Ti, based on simultaneous recording of deformation curves, 1D local strain field, and acoustic emission (AE). It is found that the average AE activity also reveals three-stage behavior, but in a qualitatively different way depending on the crystallographic orientation of the sample axis. On the finer scale, the statistical analysis of AE events and local strain rates testifies to an avalanche-like character of dislocation processes, reflected in power-law probability distribution functions. The results are discussed from the viewpoint of collective dislocation dynamics and are confronted to predictions of a recent micromechanical model of Ti strain hardening.

Highlights

The scope of this paper is two-fold
The following aspects should be noted:. Both deformation curves (Figure 2a) show a tendency to a concave shape at the elastoplastic transition
High resolution techniques based on the acoustic emission (AE) and local applied, on the one hand, to verify the hypothesis of dislocation mechanism of the non-monotonous polycrystals deformed investigate work hardening of α-Ti polycrystals deformed by tension [9,10,11,12] and, on the other hand, to investigate on on finer scales relevant to the to so-called collectivecollective processesprocesses in the dislocation the deformation deformationprocesses processes finer scales relevant the so-called in the dynamics

Summary

Introduction

The scope of this paper is two-fold. First, despite intensive investigations of plasticity of materials with a hexagonal close-packed (hcp) structure during last time, many aspects of their mechanical behavior are still poorly understood. Materials 2018, 11, 1061 stages II and III [1,2]), hcp materials often display three-stage strain hardening behavior associated with the elastoplastic transition and resulting in a concave shape of the deformation curve at small strains [3,4,5,6,7,8,9,10,11]. To distinguish such behavior from the generic work-hardening stages observed in materials with various structures [1,2], these specific stages are usually designated as A, B, and C

Methods

Results

Discussion

Conclusion