TiC/Inconel 718复合材料选区激光熔化成形的热物理机制

Thermal-Physical Mechanisms during Selective Laser Melting of TiC/Inconel 718 Composites

建立了Ti C/Inconel 718复合材料体系选区激光熔化三维有限元模型,在考虑了相变潜热,热传导/对流/辐射多重传热机制和随温度变化的热物性参数条件下,使用ANSYS二次开发语言APDL实现了高斯激光热源的移动,并利用"生死单元"完成了多层多道的能量加载,研究了其选区激光成形的热物理机制。结果表明:温度变化率与工艺参数(激光功率和扫描速度)存在正对应关系,最高可达7.03×10~6℃/s。当扫描速度过快(300 mm/s)或激光功率过低(50 W)时,获得的熔池温度低(1991℃),液相存在时间过短(0.29 ms),而且液相量少,粘度大,不利于液相金属在粉末间隙中的铺展和润湿,易于在制件中形成不规则孔洞,增加制件孔隙率;在优化的工艺参数P=100 W,v=100 mm/s下,重熔深度(15.1μm)、重熔宽度(35.0μm)、液相存在时间(1.2 ms)、熔池最高温度(2204℃)和温度变化率均较为合适,易于获得冶金结合良好的SLM制件。对Ti C/Inconel 718混合粉末进行了选区激光熔化实验,验证了模拟结果的正确性。

A three dimensional finite element model was established to simulate the selective laser melting（SLM） of Ti C/Inconel 718 composites.Latent heat of phase change,multiple heat transfer mechanisms and temperature-dependent thermal physical properties were considered.The movement of Gaussian laser source and the application of energy of multi-layers and multi-tracks were realized using APDL secondary development language.The results indicate that there is a positive corresponding relationship between the rate of temperature change and processing parameters（laser powers and scan speeds）.The maximum rate of temperature change is 7.03×10^6 °C/s.A high scan speed（300 mm/s） or a low laser power（50 W） yields an extremely short liquid lifetime（0.29 ms） and low temperature（1991 °C）,resulting in the formation of a small amount of liquid phase with a relatively high viscosity.This phenomenon is detrimental for the wettability of the liquid phase among the pores of powders,causing the appearance of irregular pores and the attendant high porosity in SLM-produced parts.The combination of a laser power of 100 W and a scan speed of 100 mm/s contribute to achieve a sound metallurgical bonding between the neighboring layers and tracks,due to the appropriate remelted depth（15.1 μm）,remelted width（35.0 μm）,the rate of temperature change,the liquid lifetime（1.2 ms） and maximum temperature（2204 °C） of molten pool.The selective laser melting experiments on a Ti C/Inconel 718 powder mixture were carried out and simulation results were verified to be correct.