摘要
A mesoscopic model has been established to investigate the thermodynamic mechanisms and densification behavior of nickel-based superalloy during additive manufacturing/three-dimensional （3D） printing （AM/3DP） by numerical simulation, using a finite volume method （FVM）. The influence of the applied linear energy density （LED） on dimensions of the molten pool, thermodynamic mechanisms within the pool, bubbles migration and resultant densification behavior of AM/3DP-processed superalloy has been discussed. It reveals that the center of the molten pool slightly shifts with a lagging of 4 ktm towards the center of the moving laser beam. The Mar- angoni convection, which has various flow patterns, plays a crucial role in intensifying the convective heat and mass transfer, which is responsible for the bubbles migration and densification behavior of AM/3DP-processed parts. At an optimized LED of 221.5 J/m, the outward convection favors the numerous bubbles to escape from the molten pool easily and the resultant considerably high relative density of 98.9 % is achieved. However, as the applied LED further increases over 249.5 J/m, the convection pattern is apparently intensified with the formation of vortexes and the bubbles tend to be entrapped by the rotating flow within the molten pool, resulting in a large amount of residual porosity and a sharp reduction in densification of the superalloy. The change rules of the relative density and the corresponding distribution of porosity obtained by experiments are in accordance with the simulation results.
A mesoscopic model has been established to investigate the thermodynamic mechanisms and densification behavior of nickel-based superalloy during additive manufacturing/three-dimensional(3D) printing(AM/3DP)by numerical simulation, using a finite volume method(FVM). The influence of the applied linear energy density(LED) on dimensions of the molten pool, thermodynamic mechanisms within the pool, bubbles migration and resultant densification behavior of AM/3DP-processed superalloy has been discussed. It reveals that the center of the molten pool slightly shifts with a lagging of 4 lm towards the center of the moving laser beam. The Marangoni convection, which has various flow patterns, plays a crucial role in intensifying the convective heat and mass transfer, which is responsible for the bubbles migration and densification behavior of AM/3DP-processed parts. At an optimized LED of 221.5 J/m, the outward convection favors the numerous bubbles to escape from the molten pool easily and the resultant considerably high relative density of 98.9 % is achieved. However, as the applied LED further increases over 249.5 J/m, the convection pattern is apparently intensified with the formation of vortexes and the bubbles tend to be entrapped by the rotating flow within the molten pool, resulting in a large amount of residual porosity and a sharp reduction in densification of the superalloy. The change rules of the relative density and the corresponding distribution of porosity obtained by experiments are in accordance with the simulation results.
基金
supported by the National Natural Science Foundation of China (51575267, 51322509)
the Top-Notch Young Talents Program of China
the Outstanding Youth Foundation of Jiangsu Province of China (BK20130035)
the Program for New Century Excellent Talents in University (NCET-13-0854)
the Science and Technology Support Program (the Industrial Part)
Jiangsu Provincial Department of Science and Technology of China (BE2014009-2)
the 333 high-level talents training project (BRA2015368)
the Science and Technology Foundation for Selected Overseas Chinese Scholar, Ministry of Human Resources and Social Security of China
the Aeronautical Science Foundation of China (2015ZE52051)
the Shanghai Aerospace Science and Technology Innovation Fund (SAST2015053)
the Fundamental Research Funds for the Central Universities (NE2013103, NP2015206 and NZ2016108)
the Priority Academic Program Development of Jiangsu Higher Education Institutions
