To investigate the thermal stress field and microstructure evolution of Ti-6Al-4V alloy component produced by laser engineerednet shaping (LENS), numerical simulations are performed at both macroscale and mesoscale. At the macroscale,a finite element model is developed and validated by comparing the simulated residual stress with the measured residualstress. Meanwhile, the effect of scanning strategies on residual stress is analyzed. At the mesoscale, a three-dimensional(3D) cellular automaton model is established to analyze the growth mechanism of β-columnar grains. The results show thatthe maximum residual stress locates at the surrounding area at the interface between the substrate and the cladding layer. Based on the results under the unidirectional and reciprocating scanning strategies, the residual stress of the component isminimized by using the reciprocating alternating scanning strategy. Due to the higher temperature gradient at the bottomof the molten pool, β-columnar grains grow epitaxially from the pre-existing grains in the substrate. When the direction ofdendritic growth is consistent with the direction of the temperature gradient, grain growth is faster and there is a clear preferredorientation, which ultimately forms β-columnar grain structures that tilt towards the scanning direction and penetratemultiple cladding layers.
To investigate the thermal stress field and microstructure evolution of Ti-6Al-4V alloy component produced by laser engineerednet shaping (LENS), numerical simulations are performed at both macroscale and mesoscale. At the macroscale,a finite element model is developed and validated by comparing the simulated residual stress with the measured residualstress. Meanwhile, the effect of scanning strategies on residual stress is analyzed. At the mesoscale, a three-dimensional(3D) cellular automaton model is established to analyze the growth mechanism of β-columnar grains. The results show thatthe maximum residual stress locates at the surrounding area at the interface between the substrate and the cladding layer. Based on the results under the unidirectional and reciprocating scanning strategies, the residual stress of the component isminimized by using the reciprocating alternating scanning strategy. Due to the higher temperature gradient at the bottomof the molten pool, β-columnar grains grow epitaxially from the pre-existing grains in the substrate. When the direction ofdendritic growth is consistent with the direction of the temperature gradient, grain growth is faster and there is a clear preferredorientation, which ultimately forms β-columnar grain structures that tilt towards the scanning direction and penetratemultiple cladding layers.