Onuike Bonny, Bandyopadhyay Amit
W. M. Keck Biomedical Materials Research Lab, School of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164-2920, USA.
Addit Manuf. 2020 Jan;31. doi: 10.1016/j.addma.2019.100931. Epub 2019 Nov 1.
Bimetallic structures provide a unique solution to achieve site-specific functionalities and enhanced-property capabilities in engineering structures but suffer from bonding compatibility issues. Materials such as titanium alloy (Ti6Al4V) and stainless steel (SS410) have distinct attractive properties but are impossible to reliably weld together using traditional processes. To this end, a laser-based directed energy deposition (DED) system was used to fabricate bimetallic joint of Ti6Al4V and SS410 keeping niobium (Nb) as a diffusion barrier layer. Both shear and compression tests were used to characterize the joint's strength, and compared with the base materials. The bimetallic-joint shear and compressive yield strengths were 419± 3 MPa (~ 114 % of SS410) and 560 ± 4 MPa (~ 169 % of SS410), respectively. The increase in interfacial shear and compressive yield strengths over the base material indicates strong metallurgical bonding between the base materials and the interlayer, Nb. Proof-of-concept part for direct application of the bimetallic joint was demonstrated by welding base metals, end-to-end, to the joint. The interfacial microstructures, elemental diffusion and phases, including failure modes were examined using secondary and backscatter electron imaging, X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS). The bimetallic-joint interfaces were free from brittle intermetallic compounds such as FeTi and FeTi that are generally responsible for weak bond strength.
双金属结构为在工程结构中实现特定部位功能和增强性能提供了独特的解决方案，但存在键合兼容性问题。钛合金（Ti6Al4V）和不锈钢（SS410）等材料具有明显吸引人的特性，但使用传统工艺无法可靠地焊接在一起。为此，使用基于激光的定向能量沉积（DED）系统制造Ti6Al4V和SS410的双金属接头，将铌（Nb）作为扩散阻挡层。通过剪切和压缩试验来表征接头的强度，并与母材进行比较。双金属接头的剪切屈服强度和压缩屈服强度分别为419±3 MPa（约为SS410的114%）和560±4 MPa（约为SS410的169%）。与母材相比，界面剪切屈服强度和压缩屈服强度的提高表明母材与中间层Nb之间存在强烈的冶金结合。通过将母材端对端焊接到接头上，展示了双金属接头直接应用的概念验证部件。使用二次电子成像、背散射电子成像、X射线衍射（XRD）和能量色散光谱（EDS）对接头的微观结构、元素扩散和相，包括失效模式进行了研究。双金属接头界面没有诸如FeTi和FeTi等通常导致结合强度较弱的脆性金属间化合物。
