Mohammad Ashfaq, Alahmari Abdulrahman M, Mohammed Muneer Khan, Renganayagalu Ravi Kottan, Moiduddin Khaja
Princess Fatima Alnijiris's Research Chair for Advanced Manufacturing Technology (FARCAMT Chair), Advanced Manufacturing Institute, King Saud University, Riyadh 11421, Saudi Arabia.
Industrial Engineering Department, College of Engineering, King Saud University, Riyadh 11421, Saudi Arabia.
Materials (Basel). 2017 Feb 21;10(2):211. doi: 10.3390/ma10020211.
Titanium aluminides qualify adequately for advanced aero-engine applications in place of conventional nickel based superalloys. The combination of high temperature properties and lower density gives an edge to the titanium aluminide alloys. Nevertheless, challenges remain on how to process these essentially intermetallic alloys in to an actual product. Electron Beam Melting (EBM), an Additive Manufacturing Method, can build complex shaped solid parts from a given feedstock powder, thus overcoming the shortcomings of the conventional processing techniques such as machining and forging. The amount of energy supplied by the electron beam has considerable influence on the final build quality in the EBM process. Energy input is decided by the beam voltage, beam scan speed, beam current, and track offset distance. In the current work, beam current and track offset were varied to reflect three levels of energy input. Microstructural and mechanical properties were evaluated for these samples. The microstructure gradually coarsened from top to bottom along the build direction. Whereas higher energy favored lath microstructure, lower energy tended toward equiaxed grains. Computed tomography analysis revealed a greater amount of porosity in low energy samples. In addition, the lack of bonding defects led to premature failure in the tension test of low energy samples. Increase in energy to a medium level largely cancelled out the porosity, thereby increasing the strength. However, this trend did not continue with the high energy samples. Electron microscopy and X-ray diffraction investigations were carried out to understand this non-linear behavior of the strength in the three samples. Overall, the results of this work suggest that the input energy should be considered primarily whenever any new alloy system has to be processed through the EBM route.
钛铝化合物完全有资格替代传统的镍基高温合金，应用于先进的航空发动机。高温性能和较低密度的结合赋予了钛铝化合物合金一定优势。然而，如何将这些本质上的金属间化合物合金加工成实际产品仍然存在挑战。电子束熔炼（EBM）作为一种增材制造方法，可以从给定的原料粉末制造出形状复杂的实心零件，从而克服了诸如机械加工和锻造等传统加工技术的缺点。在电子束熔炼过程中，电子束提供的能量对最终的成型质量有相当大的影响。能量输入由束电压、束扫描速度、束电流和轨迹偏移距离决定。在当前的工作中，改变束电流和轨迹偏移以反映三种能量输入水平。对这些样品的微观结构和力学性能进行了评估。微观结构沿成型方向从顶部到底部逐渐粗化。较高的能量有利于板条微观结构，而较低的能量则倾向于等轴晶粒。计算机断层扫描分析显示低能量样品中的孔隙率更高。此外，低能量样品拉伸试验中粘结缺陷的存在导致过早失效。将能量增加到中等水平在很大程度上消除了孔隙率，从而提高了强度。然而，这种趋势在高能量样品中并未持续。进行了电子显微镜和X射线衍射研究，以了解这三个样品中强度的这种非线性行为。总体而言，这项工作的结果表明，每当必须通过电子束熔炼路线加工任何新的合金系统时，都应首先考虑输入能量。
