Scanning speed is a critical parameter for laser process,which can play a key role in the microstructure evolution of laser melting.In the laser melting of single crystal superalloy,the effects of scanning speed were ...Scanning speed is a critical parameter for laser process,which can play a key role in the microstructure evolution of laser melting.In the laser melting of single crystal superalloy,the effects of scanning speed were investigated by experimental analysis and computational simulation.The laser was scanning along710 direction on(001) surface in different speeds.Solidification microstructures of dendrites growth direction and the primary dendritic spacing were analyzed by metallograph.Besides,a planar interface during solidification was taken into attention.Experiment results indicated that the primary dendritic spacing and thickness of planar interface decrease with the increase of speed.Through simulation,distribution of dendrites growth velocity and thermal gradient along dendrite growth direction were calculated,and the simulation of dendrites growth direction agreed with the experiment results.Additionally,a constant value was acquired which can be used to predict the primary dendritic spacing.Moreover,according to curve-fitting method and inequality relation,a model was proposed to predict the thickness of planar interface.展开更多
Laser welding and laser-based powder-bed fusion additive manufacturing in the deep penetration(keyhole)mode are promising technologies for the synthesis of metal components.The significant potential of these technolog...Laser welding and laser-based powder-bed fusion additive manufacturing in the deep penetration(keyhole)mode are promising technologies for the synthesis of metal components.The significant potential of these technologies remains latent because of structural defects(porosity),which significantly degrade the structural integrity and performance of the end products.Practical strategies for reducing those defects are addressed through fundamental understanding of their formation.In this study,pore formation of hydrodynamic origin is investigated,including the dynamics and mechanisms of the formation based on the above mentioned technologies.The pore volume and frequency of pore appearance,depending on the amplitude and frequency of capillary vibrations,are considered.Physical analysis is performed to obtain the scanning velocity values for the maximum and zero amplitudes and the frequency of capillary waves.A comparison between calculated curves and experimental data confirms both the capillary origin of the pores and the estimated scanning speeds at which the parameters of the pores exhibit their maximum values or vanish.The results obtained may facilitate in the selection of the optimal scanning speed when designing a pore-free technology.展开更多
基金financially supported by the National Natural Science Foundation of China (NSFC) under grant Nos.51401210 and 51271186
文摘Scanning speed is a critical parameter for laser process,which can play a key role in the microstructure evolution of laser melting.In the laser melting of single crystal superalloy,the effects of scanning speed were investigated by experimental analysis and computational simulation.The laser was scanning along710 direction on(001) surface in different speeds.Solidification microstructures of dendrites growth direction and the primary dendritic spacing were analyzed by metallograph.Besides,a planar interface during solidification was taken into attention.Experiment results indicated that the primary dendritic spacing and thickness of planar interface decrease with the increase of speed.Through simulation,distribution of dendrites growth velocity and thermal gradient along dendrite growth direction were calculated,and the simulation of dendrites growth direction agreed with the experiment results.Additionally,a constant value was acquired which can be used to predict the primary dendritic spacing.Moreover,according to curve-fitting method and inequality relation,a model was proposed to predict the thickness of planar interface.
基金Ministry of Science and Higher Education within the State Assignment to Federal Research Centre≪Crystallography and Photonics≫Russian Academy of Science.
文摘Laser welding and laser-based powder-bed fusion additive manufacturing in the deep penetration(keyhole)mode are promising technologies for the synthesis of metal components.The significant potential of these technologies remains latent because of structural defects(porosity),which significantly degrade the structural integrity and performance of the end products.Practical strategies for reducing those defects are addressed through fundamental understanding of their formation.In this study,pore formation of hydrodynamic origin is investigated,including the dynamics and mechanisms of the formation based on the above mentioned technologies.The pore volume and frequency of pore appearance,depending on the amplitude and frequency of capillary vibrations,are considered.Physical analysis is performed to obtain the scanning velocity values for the maximum and zero amplitudes and the frequency of capillary waves.A comparison between calculated curves and experimental data confirms both the capillary origin of the pores and the estimated scanning speeds at which the parameters of the pores exhibit their maximum values or vanish.The results obtained may facilitate in the selection of the optimal scanning speed when designing a pore-free technology.
