Microstructure And Properties Of New Ti Alloy Fabricated By Heterogeneous Dual Wire Arc Additive Manufacturing

Ti-6Al-4V has advantages such as low density and high specific strength and is widely used in industries such as aviation and automotive.Using wire+arc additive manufacturing technology to fabricate Ti-6Al-4V components can achieve near-net shaping,greatly avoiding material waste and a large amount of secondary processing in the production of complex-shaped parts.However,Ti-6Al-4V parts produced by additive manufacturing have coarse columnar grains growing along the vertical direction,which reduces their property and limits their application.Therefore,this study uses dual-wire+arc additive manufacturing technology and in-situ alloying with Cu and Ni elements to suppress the growth of columnar grains and further improve the strength of the components.The specific research content is as follows:First,the study investigates the effect of adding Cu elements on the microstructure and properties of Ti-6Al-4V and prepares a new type of Ti-6Al-4V-xCu alloy.The study shows that adding Cu elements suppresses the cross-layer growth of the priorβgrains,eliminates the columnar shape of the priorβgrains,realizes the transformation from columnar to equiaxed grains,and significantly reduces the size of the grains and lath.With the increase of Cu content,theα-Ti morphology transforms from laths to acicular structures and equiaxed structures.The precipitation of the intermetallic compound Ti₂Cu significantly improves the strength of the component.Secondly,a new type of Ti-6Al-4V-yNi alloy is prepared using the Ni element with a larger growth restriction factor Q,and the effect of different Ni contents on the microstructure and properties of Ti-6Al-4V alloy is mainly studied.Adding Ni elements obtains equiaxed priorβgrains and further refines the size of grains and laths on the basis of Ti-6Al-4V-xCu alloy.With the increase of Ni content,theα-Ti in Ti-6Al-4V-yNi alloy maintains an acicular structure.The precipitation of the intermetallic compound Ti₂Ni significantly improves the strength of the component.Finally,a comparison is made between the two alloy elements to clarify the influence mechanism of Cu and Ni elements on the microstructure transformation and properties of Ti-6Al-4V alloy,as well as the differences in the influence of different alloy elements.Alloy elements promote nucleation by increasing undercooling at the solid-liquid interface,suppressing the cross-layer growth of columnar grains,and obtaining equiaxed grains while refining the priorβgrains.The higher the Q value,the more obvious the refining effect of the alloy elements.The enrichment of alloy elements and the precipitation of intermetallic compounds will hinder the growth ofα-Ti,refine its size,and change its morphology.The content of intermetallic compounds increases with the increase of element content,the hardness of the component gradually increases,and the tensile strength shows a trend of first increasing and then decreasing,while the elongation gradually decreases.