Effect of heat input on microstructure and mechanical properties of pulsed TIG-based wire arc additive manufactured Ti6Al4V alloy
Due to the high heat input of wire arc additive manufacturing,it is easy to produce coarse microstructure in the titanium alloy,resulting in lower mechanical properties.In this study,the effects of heat input and duty cycle on the process,microstructure and mechanical properties of Ti6Al4V titanium alloy fabricated by wire arc additive manufacturing were investigated by applying plused currents during the wire arc additive manufacturing Ti6Al4V.The results indicate that,with the base current and peak time ratio decreasing,the heat input reduces from 988 J/mm to 414 J/mm.This reduction is accompanied by a decrease in the temperature gradient(G)and an increase in the solidification rate(R),which leads to the transformation of coarse β columnar grains into equiaxed grains.At the same time,with the decrease of the heat input,the cooling rate increases from 7.27℃/s to 44.08℃/s.The high cooling rate promotes the refinement of the α laths,the width of the α laths reduces from 1.07 μm to 0.49 μm.The formation of β equiaxed grains and the refinement of α laths improve the tensile strength from 914 MPa to 1049 MPa,and the strain remains at about 8%.
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