Effects of cerium and SiC mixed particles on nanoparticle strengthening activated TIG-welded AZ31 alloy joints
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ARTICLE Effects of cerium and SiC mixed particles on nanoparticle strengthening activated TIG-welded AZ31 alloy joints Fuxing Xie, Jun Shen,a) Huiyu Song, and Xiong Xie State Key Laboratory of Mechanical Transmission, School of Material Science and Engineering, Chongqing University, Chongqing 400044, People’s Republic of China (Received 28 June 2018; accepted 5 October 2018)
AZ31 magnesium alloy sheets were A-TIG-welded through a coating of flux, which contained different ratios of Ce powder and nano-sized SiC as reinforcement particles and equal mass of TiO2 as activating fluxes. The microscopic analysis results illustrated that relatively low content of Ce in the reinforcement particles caused the formation of Al3Ce precipitates and refined the grains of a-Mg phase together with b-Mg17Al12 and SiC particles. The increase in microhardness and ultimate tensile strength of the joints was 6.2% and 19.2%, respectively, when reinforcement particles contain 20 wt% Ce compared to the joints coated without Ce. By studying the electrochemical test results, when using 20 wt% Ce 1 80 wt% SiC as reinforcement particles, the corrosion current density was the lowest and the corrosion resistance reached the largest value, reflecting the improvement of corrosion property of the joint affected by Ce element.
I. INTRODUCTION
Magnesium (Mg) alloy, one of the lightest engineering materials, has low density, good thermal conductivity and damping vibration, high specific strength and stiffness, and excellent electromagnetic shielding and machinability.1,2 The joining methods of Mg alloys have always been an issue in many industrial fields. Therefore, highquality welding techniques are required for the manufacture of complex Mg alloy structures. Tungsten inert gas (TIG) welding is widely used for the production of magnesium alloy joints due to its practicability and economy. However, the shallow penetration of TIG welding in magnesium alloys is a problem. Although penetration can be increased by improving the heat input, coarse grains and poor joints properties induced by porosity and shrinkage porosity are also accompanied.3 Therefore, obtaining deep welds, refining crystalline structure, and removing defects were the main ways to achieve a high-quality, high-strength, and tenacious magnesium alloy welded joints. To solve the problems of the shallow penetration, a novel technique, called activating flux tungsten inert gas (A-TIG) welding, was invented by Paton Welding Institute. In the previous works,4 A-TIG welding successfully improved the penetration by coating the active powder on the surface of base metals before welding process. To achieve a higher quality level of the welds, Liu et al.5 and Shen et al.6,7 improved this technique by applying micron-sized and nano-sized SiC particles a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2018.404 J. Mater. Res., 2018
mixed with activated flux, respectively, and then conducted A-TIG welding to refine the Mg grains and strengthen the welds. The good wet
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