Numerical And Experimental Investigations On Selective Laser Sintering Of Multi-component Metal Powder

As an important branch of Rapid prototyping (RP), Selective Laser Sintering (SLS) is attractive to many researchers in manufacturing for its wide use of metal, polymer, ceramic and other powder in the sintering. However,"balling", warping and cracking problems associated with metallic SLS have presented serious obstacles that restrict the more extensive applications of SLS technique. To alleviate the defects in metallic SLS, numerical and experimental studies were carried out detailed on the features of temperature field as well as thermal elastic-plastic stress and strain during metallic SLS process.By using the ANSYS software, a finite element model which simulates a real SLS process of a multi-component Ni-CuSn metal powder system was established to calculate the 3D transient temperature field. In the model, the latent heat, convection and temperature-dependent thermal properties were taken into account. A moving Gaussian laser beam was simulated using the ANSYS parametric design language. Comparisons were made between the numerical and experimental results. The results show that, the distribution of temperature during laser sintering process has a great effect on"balling"phenomena of the laser sintered metal part. Optimizing the distribution of temperature, which can be realized by changing laser processing parameters, is an effective way to decrease the"balling"effects.Based on the results of temperature field, a finite element model for analyzing the stress field in SLS process of a multi-component metal powder system was established by using an indirect thermal-mechanical coupling method. A successive transformation of the sintering material from powder morphology to high-temperature liquid phase and, afterwards, to continuous solids was simulated by using a"birth and death"element technique of the ANSYS software. The analysis results show that, the warping and cracking of sintered part which is induced by thermal stress can be efficiently alleviated by optimizing the geometrical structure of the part to be built, enhancing the pre-heating temperature, and well choosing the building substrate.