Residual lattice strain and phase distribution in Ti-6Al-4V produced by electron beam melting

DOI: 10.3390/ma12040667

Authors: Tuerdi Maimaitiyili (Paul Scherrer Institute (PSI); Malmö Universitet) , Robin Woracek (European Spallation Source ERIC; Nuclear Physics Institute of the CAS) , Magnus Neikter (Luleå University of Technology) , Mirko Boin (Helmholtz-Zentrum Berlin für Materialien und Energie) , Robert Wimpory (Helmholtz-Zentrum Berlin für Materialien und Energie) , Robert Pederson (University West) , Markus Strobl (European Spallation Source ERIC; Nuclear Physics Institute of the CAS; Paul Scherrer Institute) , Michael Drakopoulos (Diamond Light Source) , Norbert Schäfer (Helmholtz-Zentrum Berlin für Materialien und Energie) , Christina Bjerkén (Malmö Universitet)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Materials , VOL 12

State: Published (Approved)
Published: February 2019
Diamond Proposal Number(s): 7858

Abstract: Residual stress/strain and microstructure used in additively manufactured material are strongly dependent on process parameter combination. With the aim to better understand and correlate process parameters used in electron beam melting (EBM) of Ti-6Al-4V with resulting phase distributions and residual stress/strains, extensive experimental work has been performed. A large number of polycrystalline Ti-6Al-4V specimens were produced with different optimized EBM process parameter combinations. These specimens were post-sequentially studied by using high-energy X-ray and neutron diffraction. In addition, visible light microscopy, scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD) studies were performed and linked to the other findings. Results show that the influence of scan speed and offset focus on resulting residual strain in a fully dense sample was not significant. In contrast to some previous literature, a uniform α- and β-Ti phase distribution was found in all investigated specimens. Furthermore, no strong strain variations along the build direction with respect to the deposition were found. The magnitude of strain in α and β phase show some variations both in the build plane and along the build direction, which seemed to correlate with the size of the primary β grains. However, no relation was found between measured residual strains in α and β phase. Large primary β grains and texture appear to have a strong effect on X-ray based stress results with relatively small beam size, therefore it is suggested to use a large beam for representative bulk measurements and also to consider the prior β grain size in experimental planning, as well as for mathematical modelling.

Journal Keywords: residual stress/strain; electron beam melting; diffraction; Ti-6Al-4V; electron backscattered diffraction; X-ray diffraction

Subject Areas: Materials, Engineering


Instruments: I12-JEEP: Joint Engineering, Environmental and Processing

Other Facilities: HZB

Documents:
materials-12-00667-v2 (1).pdf