整体高温辅助激光定向能量沉积TiAl4822合金开裂抑制机理及组织性能研究OA

The TiAl4822(Ti-48Al-2Cr-2Nb)alloy,renowned for its exceptional high-temperature mechanical properties and low density,stands out as a highly promising candidate for critical aerospace components.However,its high chemical reactivity and inherent room-temperature brittleness pose significant challenges to the conventional manufacturing of large and complex geometries.Laser directed energy deposition(LDED),characterized by its high fabrication efficiency and remarkable process flexibility,has emerged as a crucial approach for preparing TiAl4822 alloy components.Nevertheless,the rapid melting-solidification cycle during LDED induces a substantial temperature gradient and residual stress,which results in component cracking.Currently,there is no well-established method to completely prevent crack formation.In this study,a dense and crack-free thin-walled TiAl4822 alloy component with dimensions of 30 mm×25 mm×6 mm is successfully fabricated using the whole high-temperature-assisted LDED technique.An investigation is conducted on their macro-morphology,microstructure,porosity,and microhardness.The results reveal that the thin-walled TiAl4822 alloy specimen prepared by LDED at room temperature is prone to brittle fracture primarily through cleavage,and its microstructure mainly comprises fine equiaxed grains.After implementing whole high-temperature assistance at an integral temperature of 800℃,the grains in the deposited layer transform from bottom to top into inclined columnar grains.The porosity is significantly reduced from 0.05%to 0.008%,accompanied by a more uniform pore-size distribution,and no macroscopic cracks are observed on the surface.Concurrently,the microhardness decreases from 390.46HV0.2 to 354.94HV0.2,which can be attributed to grain coarsening,a decrease in grain-boundary density,and precipitate evolution under high-temperature conditions.Overall,the integral high-temperature-assisted LDED effectively inhibits crack initiation and the formation of large pores while homogenizing the microstructure,providing a novel pathway for high-density,high-performance TiAl4822 preparing.