TC4电子束熔炼的XRD分析

Evaluating the Effect of Processing Parameters on Porosity in Electron Beam Melted Ti-6Al-4V via Synchrotron X-ray Microtomography

ROSS CUNNINGHAM,1,3SNEHA P.NARRA,2TUGCE OZTURK,1

JACK BEUTH,2and A.D.ROLLETT1

1.—Department of Materials Science and Engineering,Carnegie Mellon University,Pittsburgh,

PA,USA.2.—Department of Mechanical Engineering,Carnegie Mellon University,Pittsburgh,

PA,USA.3.—e-mail:rwcunnin@

Electron beam melting(EBM)is one of the subsets of direct metal additive

manufacturing(AM),an emerging manufacturing method that fabricates

metallic parts directly from a three-dimensional(3D)computer model by the

successive melting of powder layers.This family of technologies has seen

significant growth in recent years due to its potential to manufacture complex

components with shorter lead times,reduced material waste and minimal

post-processing as a‘‘near-net-shape’’process,making it of particular interest

to the biomedical and aerospace industries.The popular titanium alloy Ti-6Al-

4V has been the focus of multiple studies due to its importance to these two

industries,which can be attributed to its high strength to weight ratio and

corrosion resistance.While previous research has found that most tensile

properties of EBM Ti-6Al-4V meet or exceed conventional manufacturing

standards,fatigue properties have been consistently inferior due to a signifi-

cant presence of porosity.Studies have shown that adjusting processing

parameters can reduce overall porosity;however,they frequently utilize

methods that give insufficient information to properly characterize the

porosity(e.g.,Archimedes’method).A more detailed examination of the result

of process parameter adjustments on the size and spatial distribution of gas

porosity was performed utilizing synchrotron-based x-ray microtomography

with a minimum feature resolution of1.5l m.Cross-sectional melt pool area

was varied systematically via process mapping.Increasing melt pool area

through the speed function variable was observed to significantly reduce

porosity in the part.

INTRODUCTION

Electron Beam Melting(EBM)Additive Manufacturing(AM)

Additive manufacturing(AM)encompasses a wide range of technologies that utilize a layer-wise approach to manufacture near-net-shape parts from a computer generated three-dimensional(3D)model.1One subset of these,the powder bed-based systems,have gener-ated significant interest due to the recent availability of commercial systems,and their potential to manu-facture complex parts with high resolution and dimensional tolerance.1,2These machines utilize an energy beam to selectively melt areas on a uniformly spread powder bed,sequentially building parts layer by layer.These types of systems are distinguished by their energy source,which is either a laser in selective laser melting(SLM)systems,or an electron beam in electron beam melting(EBM)systems.While SLM and EBM systems share many properties and challenges,there are some defining differences between the two:for example,EBM systems operate in a vacuum,whereas SLM systems use an inert atmosphere.This study focuses on the EBM systems,specifically an Arcam A2.

JOM,Vol.68,No.3,2016

DOI:10.1007/s11837-015-1802-0

Ó2016The Minerals,Metals&Materials Society (Published online January19,2016)

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