The Thermo-Mechanical Coupling Effect in Selective Laser Melting of Aluminum Alloy Powder

Abstract

In the selective laser melting process, metal powder melted by the laser heat source generates large instantaneous energy, resulting in transient high temperature and complex stress distribution. Different temperature gradients and anisotropy finally determine the microstructure after melting and affect the build quality and mechanical properties as a result. It is important to monitor and investigate the temperature and stress distribution evolution. Due to the difficulties in online monitoring, finite element methods (FEM) are used to simulate and predict the building process in real time. In this paper, a thermo-mechanical coupled FEM model is developed to predict the thermal behaviors of the melt pool by using Gaussian moving heat source. The model could simulate the shapes of the melt pool, distributions of temperature and stress under different process parameters through FEM. The influences of scanning speed, laser power, and spot diameter on the distribution of the melt pool temperature and stress are investigated in the SLM process of Al6063, which is widely applied in aerospace, transportation, construction and other fields due to its good corrosion resistance, sufficient strength and excellent process performance. Based on transient analysis, the relationships are identified among these process parameters and the melt pool morphology, distribution of temperature and thermal stress. It is shown that the maximum temperature at the center point of the scanning tracks will gradually increase with the increment of laser power under the effect of thermal accumulation and heat conduction, as the preceded scanning will preheat the subsequent scanning tracks. It is recommended that the parameters with optimized laser power (P = 175–200 W), scanning speed (v = 200–300 mm/s) and spot diameter (D = 0.1–0.15 mm) of aluminum alloy powder can produce a high building quality of the SLM parts under the pre-set conditions.

Formation mechanism of pore defects and surface ripples under different process parameters via laser powder bed fusion by numerical simulation and experimental verification

“…The laser heat source adopts a Gaussian surface heat source, whose heat flux density q(r) follows the Gaussian distribution along the laser radius, as shown in Eq. ( 8) [26]:…”

“…In recent years, simulation studies of the LPBF process have been spewing out in the scope of the temperature field distribution of the melt pool and the influence of process parameters to predict the state and the surface morphology of the melt pool [23][24][25][26][27][28]. Gu et al [29] studied the characteristics of the melt pool with various laser power inputs, and analyzed the formation mechanism of defects such as balling effect, keyhole, surface ripples and interlayer fusion.…”

Adaptive Joint Multiobjective Operating Parameters’ Optimization for Active Direct Methanol Fuel Cells

“…[7,8] The operating parameters include methanol concentration, flow rate, temperature, and airflow rate. [9,10] The structural parameters include the physical parameters of the membrane electrode assembly (MEA) and the geometric parameters of the flow field structure. [11][12][13] Studies showed that optimizing the operating parameters and the cell structure are two effective ways to enhance DMFC performance.…”