Microstructure regulation of titanium alloy functionally gradient materials fabricated by alternating current assisted wire arc additive manufacturing

Abstract

Using wire arc additive manufacturing (WAAM), an alternating current (AC)-assisted WAAM method was proposed to fabricate a Titanium alloy functionally gradient material. The AC was added at the Ti6Al4V filling wire to regulate the microstructure variation from bottom to top during the deposition process. In this study, scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) were used to analyze the microstructure change. Transmission electron microscopy (TEM) was used to study the micro-mechanism. The mechanical performance was tested by Vickers hardness and tensile experiments. Results were obtained for the microstructures of different deposition layers with gradient changes. The results showed that β-lath accumulated around the dislocations, which were hindered by the β phase. Grain size and grain character distributions were remarkably different as the AC increased. The maximum hardness was 480 HV when the value of AC was 20 A, and the highest elongation of the deposited layer was 10.22% with a strength of 650.2 MPa when the AC value was 30 A. The effect of the magnetic field generated by the AC on the flow behavior of the molten pool, the gradual change in microstructure, and the solidification behavior of the molten pool are also discussed.

Keywords

• Wire arc additive manufacturing
• Alternating current
• Functionally gradient material
• Electromagnetic stirring