Laser Wire Deposition of Thick Ti-6Al-4V Buildups: Heat Transfer Model, Microstructure, and Mechanical Properties Evalua
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INTRODUCTION
TI-6AL-4V is an attractive alloy for the aerospace industry due to its unique combination of strength-toweight ratio and excellent corrosion resistance.[1] However, its high manufacturing cost, in part associated with the generation of substantial material waste during conventional subtractive processing, makes it a niche product to large manufacturing industries such as aerospace, medical, and oil and gas industries.[2–4] Additive manufacturing (AM) is then commonly seen as an attractive solution to reduce material waste generation but also lead times. There are two big AM families for metals: powder bed fusion (PBF) and directed energy deposition (DED) processes. The latter and particularly laser wire deposition (LWD) have had only slight coverage within the commonly used AM processes.[5–14] The lower geometrical complexity of the printed parts can account for the
N. CHEKIR, Y. TIAN, R. GAUVIN, N. BRODUSCH, and M. BROCHU are with the Department of Mining and Materials Engineering, McGill University, Montreal, QC, H3A 0C5, Canada. Contact e-mail: [email protected] J.J. SIXSMITH is with Liburdi Automation Inc., Dundas, ON, L9H 7K4, Canada. Manuscript submitted April 10, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS A
lower interest of LWD as an AM option. LWD, however, often yields to a better structural integrity of the printed components.[15] Other advantages of the DED processes include higher deposition rates and the possibility of printing large components.[16–18] Optimizing the materials properties of the printed Ti-6Al-4V components is of great interest to make AM a viable option for the aerospace industry. Researchers are still facing many challenges such as the anisotropy in the developed microstructure and the subsequent anisotropy in tensile properties.[7,18–21] Another great challenge is the repeatability of the generated results. As pointed out by Keist and Palmer,[19] AM of Ti-6Al-4V is commonly associated with a wide range of properties for which tensile properties can for example either hardly meet minimum cast requirements as set by ASTM F1108 or sometimes exceed the minimum wrought requirements as set by AMS4911. This variability in properties can be associated with the use of different deposition parameters inducing different thermal histories. These deposition parameters include laser power, laser spot size diameter, travel speed, wire feed speed, wire diameter, and deposition strategy among others.[16,22] Changing them results in a change of the thermal history of the printed component affecting in turn the developed microstructure and eventually the material properties.[16,22]
Many finite element analysis simulations have been proposed in order to predict thermal history, induced distortion, and final phase distribution of the printed components to reduce the variability of the results.[16,23–28] However, most of these studies focus on the buildup of thin components. Denlinger et al.[23] investigated the deposition of larger components with an evolving mesh that reduces t
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