Wire arc additive manufacturing method for Ti-6Al-4V alloy to improve the grain refinement efficiency and mechanical properties

Abstract

Wire and arc additive manufacturing (WAAM) technique has introduced a novel approach for producing complex Ti-6Al-4V parts with metric dimensions. However, the produced part leads to the development of a strong texture and anisotropic mechanical properties due to the formation of large columnar beta grains. To resolve this issue, the plastic deformation of each deposited track through hammer peening was developed as a means to refine these large beta grains. In this study, we have investigated an innovative approach to further enhance the efficiency of beta grain refinement by minimizing the arc heat input associated with previous deposited layer, which is achieved by employing a C-type filler wire. Our findings reveal a notable enhancement in grain refinement efficiency through the utilization of a C-type filler wire with peening process, as compared to available conventional commercial round shape filler wire. Specifically, the employment of the C-type filler wire results in a reduced melt pool penetration depth of WAAM Ti-6Al-4V (3.3 mm), compared to the commercially available round shape (R-Type) filler wire (4.48 mm). Within the plastically deformed region by peening, fine and randomly oriented beta grains are observed, extending to a depth of deformation reaching 844 +/- 32.65 mu m. Peening WAAM Ti-6Al-4V with the C-type filler wire leads to the development of isotropic mechanical properties in both horizontal and vertical directions, offering high strength due to the presence of small equiaxed beta grains and thin alpha laths (0.56 +/- 0.18 mu m), in contrast to the use of conventional commercial round shape filler wire.