Fabrication of Copper-Rich Cu-Al Alloy Using the Wire-Arc Additive Manufacturing Process
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INTRODUCTION
THE Cu-Al series alloys have been desired continuously for application in fossil energy pipelines and certain parts (such as propellers, valves, and laminated plates) in shipbuilding industries, due to their outstanding wear and corrosion resistance.[1] As the solid solution element in the Cu-Al alloy, the Al element mainly helps to increase the formation of deformation twins and dislocation density during the deformation twinning process,[2] which intrinsically refines the grain size and optimizes the mechanical properties, such as hardness and yield strength (YS) of the Cu-Al alloy.[3] To date, research on Cu-Al alloys has mainly focused on improving the strength of the material through optimizing the crystal structures using microalloying elements such as Ni, Zr, Cr, and Ag.[4] Severe plastic deformation processes, such as cold rolling, equal-channel angular pressing, and high-pressure torsion, can also improve the strength and hardness of alloys, as they can refine the grains significantly through generating twins in materials with low stacking fault energy.[5]
BOSHENG DONG, ZENGXI PAN, CHEN SHEN, YAN MA, and HUIJUN LI are with the Faculty of Engineering & Information Sciences, University of Wollongong, Wollongong, 2522, Australia. Contact email: [email protected] Manuscript submitted February 20, 2017. Article published online September 5, 2017. METALLURGICAL AND MATERIALS TRANSACTIONS B
In recent years, a-phase Cu-Al alloy has gained considerable attention,[6,7] since the deformation twinning mechanism in this alloy generates a special phenomenon that the ductility of gradient structured Cu-Al first increases then decreases with the decrease of stacking fault energy.[8] This phenomenon has been demonstrated as follows. Along with the stacking fault energy decrease, the increase of ductility, which comes first, is attributed to the low dynamic recovery and sufficient twin boundaries, while the following decrease of ductility is mainly limited by the refined grains with high strength. Also, this solid solution a-phase Cu-Al alloy is popular for use as the material to further investigate the relationship between deformation twinning and stacking fault energy.[9] It has been reported that lower stacking fault energy material would generate more twins during SPD and the refined grains would lead to higher YS and ultimate tensile strength (UTS). Therefore, reducing the stacking fault energy would result in enhanced strength in the following deformations.[10] Currently, the Cu-Al alloys are mainly produced using powder metallurgy processes such as induction vacuum melting,[8] furnace arc melting,[6] and ball milling.[10,11] Although powder-based technology is capable of fabricating small sized components with good accuracy,[12] the metallic powder should be melt or mixed in a sealed chamber with shielding gas or vacuum, which requires expensive hardware. In addition, these processes lack the flexibility of producing complex
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geometries and tend to generate defects, such as unmel
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