Texture Analysis of Additively Manufactured Ti-6Al-4V Deposited Using Different Scanning Strategies
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INTRODUCTION
A wide variety of additive manufacturing (AM) techniques are being adopted because of their many advantages over traditional manufacturing processes.[1] For example, AM can be used to achieve net or near-net shapes with a higher degree of complexity than through conventional techniques, thereby making topologically optimized designs practical.[2] In addition, depending upon the process and powder recycling practices, a very low buy-to-fly ratio can be achieved.[3] Beyond these design and manufacturing considerations, there are metallurgical benefits, including the possibility of producing compositionally graded structures[4,5] and potentially tailoring the composition and microstructure to achieve a certain site-specific property. Despite these advantages, there remains gaps in our understanding of the composition–microstructure–property relationships for additively manufactured materials.
MARIA J. QUINTANA is with the Materials Science and Engineering Department, Iowa State University, Ames, IA, 50011 and with the Facultad de Ingenierı´ a, Universidad Panamericana, Augusto Rodin 498, Mexico, 03920, Mexico. MATTHEW J. KENNEY and PETER C. COLLINS are with the Materials Science and Engineering Department, Iowa State University. Contact e-mail: [email protected] PRIYANKA AGRAWAL is with the Department of Materials Science and Engineering, University of North Texas, Denton, TX, 76203, USA. Manuscript submitted May 13, 2020; accepted September 22, 2020.
METALLURGICAL AND MATERIALS TRANSACTIONS A
These gaps exist due to at least three principal reasons. Firstly, the complex and cyclic time-temperature nature of these processes and the multi-scale physics that govern the evolution of the materials state* are *We are intentionally using the word ‘‘materials state’’ here to imply something broader than simply the microstructure. Materials state includes not only microstructure, but also preferential crystallographic orientations and the presence of defect structures, ranging from dislocation structures through macroscopic porosity and cracks, across a wide range of length scales (both spatial and temporal).
interrelated temporally and spatially in ways that our current physical relationships are ill-equipped to describe, let alone predict.[6–8] Secondly, the diverse nature of the processes themselves add to the difficulty in understanding the processing–composition–microstructure–property relationships. Fundamentally, the microstructure will be set by the solidification and subsequent phase transformations, which are governed by thermal gradients and time-temperature histories. As an example, the thermal gradients themselves vary considerably between large-scale and small-scale melt pools,[9–11] and the ratio of dominant heat transfer mechanisms varies between electron beam, laser, and plasma AM variants. Thirdly, some processes, including the electron beam powder bed ARCAM process, can be considered digital, in that the beam can be spatially and temporally controlled in discrete digital steps that are decouple
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