The effect of Ni/Ti atomic ratios on residual stress and deformation in WAAM of dissimilar filler wire NiTi alloys
Rui Xiang, Jun Huang, Xiaoquan Yu, Huayu Zhao, Xueping Song, Ding Fan
Abstract
In the wire arc additive manufacturing (WAAM) process, differences in thermophysical properties among various filler materials can lead to stress concentration, increasing the risk of cracking in the parts. This study uses pure Ni and pure Ti filling wires and adjusts the wire feed ratio to control the Ni/Ti atomic ratio to fabricate NiTi alloy thin-walled parts. The phase compositions of NiTi alloys with different Ni/Ti atomic ratios are analyzed by the transmission electron microscope (TEM) and energy dispersive spectrometer (EDS). The influence of different Ni/Ti atomic ratios on the residual stress and deformation of thin-walled parts is studied by finite element method. Experimental validation is conducted using thermocouples, blind-hole method, and laser displacement sensors, allowing for a systematic analysis of the residual stress and deformation in both single-component and functionally graded thin-walled parts. The results indicate that, when the Ni/Ti atomic ratio is 1:1, the NiTi phase with two different orientations of twinned martensitic structures can be produced. When the Ni/Ti atomic ratio is 0.8:1, the risk of cracking the deposited layer can be effectively reduced. The interlaminar stress difference of NiTi alloy functional gradient materials prepared with Ni/Ti atomic ratios of 0.8:1 and 1:1 is small.