Session: 17-01-01: Research Posters

Paper Number: 149797

149797 - In-Situ Smelting of Discarded Urban Scrap Into Aluminum Alloys 

In recent years, the demand for critical materials has been continuously increasing, especially for aluminum-lithium-copper alloys. These materials are widely used in the aerospace industry due to their low density, high tensile strength, and fatigue strength. [1-3] However, recycling them is extremely complex due to high reactivity of Lithium. Lithium is highly prone to loss at high temperatures due to its reactivity with oxygen, nitrogen, and carbon dioxide. This project develops a manufacturing capability to Li-Cu transfer waste streams into Al-Li-Cu product streams. Two key issues to be addressed in the process of synthesizing the Al-Li-Cu alloys from waste metals are the high reactivity of lithium and micro segregation. In this project, fluxes were tested to provide a liquid protective layer during melting, and their effect in controlling oxidation and impurities was studied. Additionally, a “test work furnace” in a glove box was designed and assembled to synthesize samples in an argon atmosphere. Lithium-coated copper waste and commonly used aluminum (AA 1100) were supplied as the main feedstock materials. The structure and mechanical properties of the obtained samples were characterized and compared with the simulation predictions. LiCl, AlF₃, NaCl, and KCl have been used as fluxes for remelting experiments in atmosphere. Among them, LiCl resulted in the least lithium loss during remelting process due to its suitable melting point (605), density (2.068g/cm³), and good stability. However, it was observed that the distribution of lithium content in the samples obtained through this method was not uniform, with loss of lithium in the final product ranging from 20% to 98% in different areas of the final solidified alloy. The concentration at the edge of the sample was significantly lower than that at the center of the solidified product. One reason for this uneven distribution is the lack of mixing during melting. However, in this setup, stirring would break the protection layer formed by the flux, leading to accelerated lithium loss. Increasing the heating time and temperature may result in better mixing, but these two factors also significantly increase lithium loss. A test work furnace was set up in a glove box that provides argon protective atmosphere. This glove box system consisted of a modified casting furnace (CV11-3.5, Mellen Co. Ltd), a well-sealed glove box (HE-43/243, VAC Co. Ltd), a stirring system (BDC2002, Caframo Co. Ltd), and an oxygen purifier (VAC-109192, VAC Co. Ltd). The oxygen purifier ensures the oxygen concentration to be below 1 ppm to minimize oxidation of Li during the remelting process. Stainless steel 316 and graphite were tested as the stirring shaft and propeller due to their excellent high-temperature resistance, corrosion resistance, and stability. Pre-dried AA 1100 was first heated to 800°C until melted. The lithium containing waste material was then added to the molten bath. After fully melting, the mixture was thoroughly stirred at a rotation speed of 50-200 rpm to ensure effective mixing and uniform distribution of alloying elements. The composition and mechanical properties of obtained remelts were characterized by and will be discussed in this presentation.

references:

[1] T. J. Sanders Jr. and E. S. Balmuth, "Aluminum-Lithium Alloys: Low densities and High Stiffness," Metal Progress, vol. 113, p. 32, 1978.

[2] E. S. Balmuth and R. Schmidt, "Electrochemical Behavior of the T1 (Al2CuLi) Intermetallic Compound and Its Role in Localized Corrosion of Al-2% Li-3% Cu Alloys," in Proc. 1st Int. Conf. Al-Li Alloys, E. A. Strakes Jr. and T. H. Sanders Jr., Eds., Georgia, 1980, pp. 69.

[3] R. E. Lewis, D. Webster, and I. G. Palmer, "A Feasibility Study for Development of Structural Aluminum Alloys from Rapidly Solidified Powders for Aerospace Structural Applications," Air Force Materials Laboratory, Wright-Patterson AFB, OH, USA, Tech. Rep. AFML-78-102, Jul. 1978.

 

Presenting Author: Chuhao Li Worcester Polytechnic Institute

Presenting Author Biography: Chuhao Li is a PhD student from Worcester Polytechnic Institute. He has a bachelor’s in MTE from the Qingdao University of Science and Technology in China. After graduation, he undertook further study at WPI in 2021 and receive his Master's degree in May 2023. From 2023 to now, he has studied for a PhD degree at WPI in the field of processing methods and manufacturing of aluminum-lithium alloys.

Authors:

Chuhao Li Worcester Polytechnic Institute
Hyunsoo Jin Worcester Polytechnic Institute
Brajendra Mishra Worcester Polytechnic Institute
Jianyu Liang Worcester Polytechnic Institute