Effect of preheating on the thermal, microstructural and mechanical properties of selective electron beam melted Ti-6Al-4V components

Research output: Contribution to journalArticle

  • External authors:
  • Chu Lun Alex Leung
  • Riccardo Tosi
  • Emmanuel Muzangaza
  • Sara Nonni
  • Peter D. Lee

Abstract

Two-stage preheating is used in selective electron beam melting (SEBM) to prevent powder spreading during additive manufacturing (AM); however, its effects on part properties have not been widely investigated. Here, we employed three different preheat treatments (energy per unit area, EA) to a Ti-6Al-4V powder bed. Each standalone build, we fabricated a large block sample and seven can-shaped samples containing sintered powder. X-ray computed tomography (XCT) was employed to quantify the porosity and build accuracy of the can-shaped samples. The effective thermal conductivity of the sintered powder bed was estimated by XCT image-based modelling. The microstructural and mechanical properties of the block sample were examined by scanning electron microscopy and microhardness testing, respectively. The results demonstrate that increasing EA reduces the anisotropy of tortuosity and increases the thermal conductivity of the sintered powder bed, improving the heat transfer efficiency for subsequent beam-matter interaction. High preheat has a negligible effect on the porosity of large AM components; however, it decreases the microhardness from 330 ± 7 to 315 ± 11 HV0.5 and increases the maximum build error from 330 to 400 μm. Our study shows that a medium EA (411 kJ m−2) is sufficient to produce components with a high hardness whilst optimising build accuracy.

Bibliographical metadata

Original languageEnglish
Article number107792
JournalMaterials and Design
Volume174
Early online date12 Apr 2019
DOIs
Publication statusPublished - 15 Jul 2019