Additive Manufacturing of Titanium Alloys

JOM, Oct 2017

M. Qian, D. L. Bourell

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Additive Manufacturing of Titanium Alloys

JOM Additive Manufacturing of Titanium Alloys M. QIAN 0 D.L. BOURELL 0 0 1.-Centre for Additive Manufacturing, School of Engineering, RMIT University , Melbourne, VIC 3000 , Australia. 2.-Mechanical Engineering and Materials Science and Engineering, University of Texas , Austin, TX, USA. 3.- - Titanium alloys are among the most extensively studied metallic materials in the broad context of metal additive manufacturing (AM), and the last decade has seen increased niche applications of additively manufactured titanium products. Additive manufacturing of titanium alloys continues to attract significant research attention today. Invited by the JOM editorial office, we have organized 13 solicited papers for the December 2017 issue of JOM under the topic ‘‘Additive Manufacturing of Titanium Alloys’’. The key features of each accepted contribution are summarized as follows. In the first article titled ‘‘New Development in Selective Laser Melting of Ti-6Al-4 V: A Wider Processing Window for the Achievement of Fully Lamellar a + b Microstructures’’, Lui and co-workers investigated selective laser melting (SLM) of Ti6Al-4 V alloy with the less commonly used layer thickness of 90 lm, with a view to broadening the flexibility of the SLM process. Fully lamellar a b microstructures were produced in the as-built state through control of the interlayer time. As a result, the as-built Ti-6Al-4 V with a 90-lm layer thickness achieved tensile ductility of 11% and a tensile yield strength of 980 MPa. The second article, ‘‘Defect, Microstructure, and Mechanical Property of Ti-6Al-4 V Alloy Fabricated by High-Power Selective Laser Melting’’, by S. Cao et al. discusses the use of a high laser power (350 W, 800 W, and 1000 W) together with the accordingly adjusted parameters to improve the SLM productivity for Ti-6Al-4 V. The resultant microstructures and defects were characterized. Increasing laser power increased the build rate, but the formation of defects needs to be properly managed. Further systematic research appears necessary to fully identify and understand the influence of high laser power on the defect, microstructure, and mechanical property of SLM-fabricated Ti-6Al-4 V. Ma Qian and David Bourell are the guest editors for the invited topic Additive Manufacturing of Titanium Alloys in this issue. The third article by O. A. Quintana and W. Tong deals with the ‘‘Effects of Oxygen Content on Tensile and Fatigue Performance of Ti-6Al-4 V Manufactured by Selective Laser Melting’’. The oxygen content assessed was in the range of 0.110–0.164%. As-built Ti-6Al-4 V samples containing 0.162%O exhibited very high tensile strengths (1360.9 ± 5.5 MPa). After hot isotactic processing (HIP), samples containing 0.164%O exhibited a fatigue strength of 645 MPa compared with 595 MPa for samples containing 0.118%O. The increase in oxygen content from 0.118% to 0.164% did not show a noticeable impact on the fatigue strength of notched specimens, which was in the range of 175–180 MPa. In the fourth article, B. Torries and N. Shamsaei report on the ‘‘Fatigue Behavior and Modeling of Additively Manufactured Ti-6Al-4 V Including Interlayer Time Interval Effects’’. They investigated the influence of different cooling rates, as achieved by varying the interlayer time interval, on the fatigue behavior of Ti-6Al-4 V specimens fabricated via Laser Engineered Net Shaping (LENSTM) and modeled the fatigue behavior using a calibrated microstructure sensitive fatigue (MSF) model. It was shown that the MSF model satisfactorily predicted the fatigue behavior of Ti-6Al-4 V specimens. The fifth article by J. Gockel et al. focuses on the ‘‘Trends in Solidification Grain Size and Morphology for Additive Manufacturing of Ti-6Al-4 V’’. Using analytical, numerical, and experimental approaches, the authors provide a holistic view of the trends in the solidification grain structure of Ti6Al-4 V across a wide range of AM process input variables. They concluded that within certain processing ranges, it is possible to indirectly control prior beta grain size through direct control of melt pool size. The sixth article is concerned with how to manage powder bed fusion challenges including porosity, surface finish, distortions, and residual stresses of the as-built material. In this contribution, the authors present a ‘‘Numerical and Experimental Qian and Bourell

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M. Qian, D. L. Bourell. Additive Manufacturing of Titanium Alloys, JOM, 2017, 2677-2678, DOI: 10.1007/s11837-017-2630-1