Chen Furong, Yang Yihang, Feng Hualong
School of Materials Science and Engineering, Inner Mongolia University of Technology, Hohhot 010051, China.
Materials (Basel). 2021 Feb 24;14(5):1061. doi: 10.3390/ma14051061.
Wire arc additive manufacturing (WAAM) of aluminum-magnesium (Al-Mg) ER5356 alloy deposits is accomplished by cold metal transfer (CMT). During the process, the temperature change of the alloy deposits has a great influence on molding quality, and the microstructure and properties of alloy deposits are also affected by the complex thermal history of the additive manufacturing process. Here, we used an inter-layer cooling process and controlled the heat input process to attempt to reduce the influence of thermal history on alloy deposits during the additive process. The results showed that inter-layer cooling can optimize the molding quality of alloy deposits, but with the disadvantages of a long test time and slow deposition rate. A simple and uniform reduction of heat input makes the molding quality worse, but controlling the heat input by regions can optimize the molding quality of the alloy deposits. The thermophysical properties of Al-Mg alloy deposits were measured, and we found that the specific heat capacity and thermal diffusivity of alloy deposits were not obviously affected by the temperature. The microstructure and morphology of the deposited specimens were observed and analyzed by microscope and electron back-scatter diffraction (EBSD). The process of controlled heat input results in a higher deposition rate, less side-wall roughness, minimum average grain size, and less coarse recrystallization. In addition, different thermal histories lead to different texture types in the inter-layer cooling process. Finally, a controlled heat input process yields the highest average microhardness of the deposited specimen, and the fluctuation range is small. We expect that the process of controlling heat input by model height region will be widely used in the WAAM field.
采用冷金属过渡（CMT）工艺实现了铝镁（Al-Mg）ER5356合金熔敷层的电弧增材制造（WAAM）。在此过程中，合金熔敷层的温度变化对成型质量有很大影响，且合金熔敷层的微观组织和性能也受增材制造过程复杂热历史的影响。在此，我们采用层间冷却工艺并控制热输入过程，试图减少增材过程中热历史对合金熔敷层的影响。结果表明，层间冷却可优化合金熔敷层的成型质量，但存在试验时间长和沉积速率慢的缺点。简单且均匀地降低热输入会使成型质量变差，但按区域控制热输入可优化合金熔敷层的成型质量。对Al-Mg合金熔敷层的热物理性能进行了测量，我们发现合金熔敷层的比热容和热扩散率受温度的影响不明显。通过显微镜和电子背散射衍射（EBSD）对沉积试样的微观组织和形貌进行了观察与分析。控制热输入的工艺可实现更高的沉积速率、更小的侧壁粗糙度、最小的平均晶粒尺寸以及更少的粗大再结晶。此外，不同的热历史在层间冷却过程中会导致不同的织构类型。最后，控制热输入工艺使沉积试样的平均显微硬度最高，且波动范围小。我们期望通过模型高度区域控制热输入的工艺能在WAAM领域得到广泛应用。
