Hot deformation behavior and process optimization of TC4-DT alloy fabricated by wire and arc additive manufacturing with in-situ forging

Abstract

The near net shape forging of a preform fabricated using additive manufacturing (AM) technique has attracted significant attention due to its exceptional material utilization rate. However, the complexity of the parts hinders its further development. This study investigated the hot deformation behavior of TC4-DT titanium alloy fabricated by wire and arc additive manufacturing (WAAM) with in-situ forging. The isothermal compression samples underwent homogenizing treatment to eliminate layer bright lines before being subjected to deformation at temperatures ranging from 800 to 950 °C and strain rates ranging from 0.01 to 1 s−1 with the height reduction of 60%. Subsequently, the hot deformation constitutive equations and hot processing map were established to analyze the characteristics of hot deformation and microstructure evolution. The results demonstrate that the hyperbolic sine constitutive equation considering strain can accurately predict flow stress under arbitrary deformation conditions, with an average relative error of 7.23%. Furthermore, microstructure analysis under different deformation conditions validated the applicability of the hot processing map, which identified preferable and easily achievable in-situ hot forging regions at temperatures between 900 and 950 °C and strain rates between 0.05 and 1 s−1 with the strain exceeded 0.4. Finally, WAAM combined with optimized in-situ hot deformation processing enables the production of macrostructures consisting of fully equiaxed prior-β grains while maintaining isotropy in mechanical properties, thereby providing a solid foundation for direct additive manufactured complex forgings featuring uniformly fine equiaxed grains and highly comprehensive properties.