Laser Metal Deposition of Al-7050/Al50Mg50 Gradient Material
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INTRODUCTION
ADDITIVE manufacturing (AM) is a modern technique for building 3D components by layer-by-layer addition of material. It provides a lot of flexibility regarding customization and design freedom. Laser metal deposition (LMD) is an additive manufacturing process in which high power laser beam is used as a heat source to create melt pool on a substrate, into which powder is injected to build 3D components layer-bylayer. In the current era, LMD is being used for manufacturing, remanufacturing, and surface coating.[1–4] Until now, mostly the common engineering metals and alloys developed for conventional manufacturing process such as casting are being used for additive manufacturing applications. However, this conventionally available metal powder might not always be suitable for the additive manufacturing process. Especially, aluminum alloys are not suitable for laser deposition process because of high laser reflectivity and thermal conductivity. However, Al 4xxx series alloys have been successfully additively manufactured because of its superior castability,[5–11] but deposition of
A. SINGH, A. RAMAKRISHNAN, and G.P. DINDA are with the Department of Mechanical Engineering, Wayne State University, 5050 Anthony Wayne Dr., Rm 2115, Detroit, MI 48202. Contact email: [email protected] Manuscript submitted on January 31, 2019. Article published online June 11, 2019 METALLURGICAL AND MATERIALS TRANSACTIONS A
high-strength Al 7xxx series alloys via additive manufacturing processes remains a challenge. During LMD of Al 7050 alloy, the low boiling elements such as Mg and Zn partially evaporate.[12] Consequently, the deposited material contains less amount of desired strengthening elements (Mg and Zn) and results in poor mechanical properties. Hence, there is dire need to find out an optimized composition of LMD-friendly 7xxx series aluminum alloy. Alloy development has been an ever-ongoing process to enhance various material properties. Recently, Palm et al. developed a unique Al 4xxx series alloy with enhanced mechanical properties.[13] Effect of various alloying elements, e.g., Mg, Zr, Zn, etc., on the resulting properties of the deposited Al 7050 alloy has to be understood while processing via laser deposition for developing LMD-friendly Al 7xxx series alloys. However, the effect of various alloying elements on Al alloys via other processes such as casting, laser sintering is well reported.[14–19] The current alloy development process is one at a time practice, which is very time consuming and expensive. However, the LMD process has the potential to produce a series of alloy in a single coupon and expedites the new alloy development process. In this present investigation, a gradient Al-7050/Al50Mg50 specimen was fabricated by varying powder flow rates to develop a correlation between the Mg content in powder feed and the deposited specimen at various composition levels. The current study systematically demonstrates that instead of making separate samples, various compositions can be deposited
VOLUME 50A, AUGUST 2019—3
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