Mechanical Properties and Fracture Behaviors of GTA-Additive Manufactured 2219-Al After an Especial Heat Treatment
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JMEPEG (2017) 26:1808–1816 DOI: 10.1007/s11665-017-2627-5
Mechanical Properties and Fracture Behaviors of GTA-Additive Manufactured 2219-Al After an Especial Heat Treatment J.Y. Bai, C.L. Fan, S.B. Lin, C.L. Yang, and B.L. Dong (Submitted July 22, 2016; in revised form February 15, 2017; published online March 21, 2017) 2219-Al parts were produced by gas tungsten arc-additive manufacturing and sequentially processed by an especial heat treatment. In order to investigate the effects of heat treatment on its mechanical properties, multiple tests were conducted. Hardness tests were carried out on part scale and layer scale along with tensile tests which were performed on welding and building directions. Results show that compared to conventional casting + T6 2219-Al, the current deposit + T6 2219-Al exhibits satisfying properties with regard to strength but unsatisfying results in plasticity. Additionally, anisotropy is significant. Fractures were observed and the cracksÕ propagating paths in both directional specimens are described. The effects of heat treatment on the cracksÕ initiation and propagation were also investigated. Ultimately, a revised formula was developed to calculate the strength of the deposit + T6 2219-Al. The aforementioned formula, which takes into consideration the belt-like porosities-distributing feature, can scientifically describe the anisotropic properties in the material. Keywords
additive manufacturing, aluminum, fracture behaviors, GTA, mechanical properties
1. Introduction GTA-additive manufacturing, which uses the heat of GTAW (gas tungsten arc welding) to melt materials, is a low-cost and highly efficient technique to produce near-net structures directly from CAD files (Ref 1-6). So far, many materials can be produced using this technique, of which Ti alloys (Ref 7) and Ni alloys (Ref 8) are the most popular. Due to the low strength, little research has been conducted on Al alloys. However, some high-strength Al alloys are widely used in aviation and aerospace fields, such as the 2xxx, 6xxx and 7xxx series. Thus, it is necessary to give more attention to them. Since 6xxx welding wire and 7xxx welding wire are so far not available, current research is conducted on the 2xxx Al alloy (2219-Al). In earlier research of 2219-Al, Bai and Wang (Ref 9-11) found that the tensile strength of the as-deposited 2219-Al (GTA-additive manufactured 2219-Al) is only equal to 58% of the conventional casting + T6 2219-Al (under routinely used conditions). Because 2219-Al is a typical precipitationstrengthening material, heat treatment is an appropriate choice to improve the strength. However, due to the unconventional manufacturing method, the conventional heat treatment is ineffective in as-deposited materials. Fortunately, much research has been conducted on different materials. In 2012, an
J.Y. Bai, C.L. Fan, S.B. Lin, C.L. Yang, and B.L. Dong, State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, No. 92 West-Dazhi Street, Harbin 150001, China. Contact e-mails: baijiuyang
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