Kiran Abhilash, Koukolíková Martina, Vavřík Jaroslav, Urbánek Miroslav, Džugan Jan
COMTES FHT a.s., Průmyslová 995, 33441 Dobřany, Czech Republic.
Materials (Basel). 2021 Sep 7;14(18):5129. doi: 10.3390/ma14185129.
The microstructural morphology in additive manufacturing (AM) has a significant influence on the building structure. High-energy concentric heat source scanning leads to rapid heating and cooling during material deposition. This results in a unique microstructure. The size and morphology of the microstructure have a strong directionality, which depends on laser power, scanning rate, melt pool fluid dynamics, and material thermal properties, etc. The grain structure significantly affects its resistance to solidification cracking and mechanical properties. Microstructure control is challenging for AM considering multiple process parameters. A preheating base plate has a significant influence on residual stress, defect-free AM structure, and it also minimizes thermal mismatch during the deposition. In the present work, a simple single track deposition experiment was designed to analyze base plate preheating on microstructure. The microstructural evolution at different preheating temperatures was studied in detail, keeping process parameters constant. The base plate was heated uniformly from an external heating source and set the stable desired temperature on the surface of the base plate before deposition. A single track was deposited on the base plate at room temperature and preheating temperatures of 200 °C, 300 °C, 400 °C, and 500 °C. Subsequently, the resulting microstructural morphologies were analyzed and compared. The microstructure was evaluated using electron backscattered diffraction (EBSD) imaging in the transverse and longitudinal sections. An increase in grain size area fraction was observed as the preheating temperature increased. Base plate preheating did not show influence on grain boundary misorientation. An increase in the deposition depth was noticed for higher base plate preheating temperatures. The results were convincing that grain morphology and columnar grain orientation can be tailored by base plate preheating.
增材制造（AM）中的微观结构形态对构建结构有重大影响。高能同心热源扫描会导致材料沉积过程中的快速加热和冷却。这会产生独特的微观结构。微观结构的尺寸和形态具有很强的方向性，这取决于激光功率、扫描速率、熔池流体动力学和材料热性能等。晶粒结构显著影响其抗凝固裂纹性能和机械性能。考虑到多个工艺参数，对增材制造来说，微观结构控制具有挑战性。预热基板对残余应力、无缺陷的增材制造结构有重大影响，并且还能使沉积过程中的热失配最小化。在本工作中，设计了一个简单的单道沉积实验来分析基板预热对微观结构的影响。在保持工艺参数不变的情况下，详细研究了不同预热温度下的微观结构演变。通过外部加热源将基板均匀加热，并在沉积前在基板表面设定稳定的所需温度。在室温以及200℃、300℃、400℃和500℃的预热温度下在基板上沉积单道。随后，对所得的微观结构形态进行分析和比较。使用电子背散射衍射（EBSD）成像在横向和纵向截面评估微观结构。观察到随着预热温度升高，晶粒尺寸面积分数增加。基板预热对晶界取向差没有影响。对于较高的基板预热温度，沉积深度增加。结果令人信服，即可以通过基板预热来调整晶粒形态和柱状晶粒取向。
