Texturing and Phase Evolution in Ti-6Al-4V: Effect of Electron Beam Melting Process, Powder Re-Using, and HIP Treatment

Vladimir V Popov,Mikhail L Lobanov,Stepan I Stepanov,Elena N Popova,Gary Muller-Kamskii,Artemiy A Popov,Alexander Katz-Demyanetz,Yuanshen Qi

doi:10.3390/ma14164473

Abstract

The research demonstrates microstructural changes and development of specific texture in Ti-6Al-4V specimens produced by electron beam melting (EBM) under different conditions. The effect of two factors, namely, raw material (powder) recycling and hot isostatic pressing (HIP), on the EBM produced samples structure and properties, has been explored. The as-printed and treated samples were investigated using electron backscattered diffraction (EBSD) analysis. Modification of mechanical properties after the EBM and HIP are explained by the EBSD data on microstructural phenomena and phase transformations. The work is devoted to assessing the possibility of reusing the residual titanium alloy powder for the manufacture of titanium components by the combination of EBM and HIP methods.

Highlights

Received: 29 May 2021Accepted: 6 August 2021Published: 10 August 2021Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.Ti-6Al-4V alloy is one of the most widely used alloys for metal additive manufacturing by electron beam melting (EBM) and selective laser melting (SLM) techniques
We showed the process of phase recrystallization occurring during EBM and hot isostatic pressing (HIP), and analyzed texture of solidification and phase transformations formed during primary melting
The prior work [18] showed that application of HIP for the titanium components additively manufactured from non-ideal powder radically improves their fatigue resistance [18]

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Wang et al investigated the effect of beam speed on the Vickers hardness and elastic modulus of Ti-6Al-4V specimens produced by EBM process [23] They concluded that the speed function 50 resulted in highest values of these mechanical characteristics. The effect of powder degradation/oxidation (due to recycling) and effect of HIP treatment on the phase distribution and texture was investigated. To contribute to the understanding of the physical dependencies related to powder-bed additive manufacturing and post-processing, the mechanisms and fundamental microstructural features of phase transformation need to be studied and characterized. Systematic microstructural investigation and analysis of phase distribution and phase formation mechanism is a possible alternative or valuable addition to the high-cost mechanical properties testing in the evaluation or prediction of the mechanical performance of the printed parts.

Materials and Methods

Results

Pole figures

Conclusions