Morphological and microstructural investigation of the non-planar interface formed in solid-state metal additive manufacturing by additive friction stir deposition
Morphological and microstructural investigation of the non-planar interface formed in solid-state metal additive manufacturing by additive friction stir deposition
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DOI：
10.1016/j.addma.2020.101293
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发表时间：
2020-10-01
影响因子：
11
通讯作者：
Yu, Hang Z.
中科院分区：
文献类型：
--
作者：
Perry, Mackenzie E. J.;Griffiths, R. Joey;Yu, Hang Z.
添加剂搅拌摩擦沉积(AFSD)是一种新兴的固态金属添加剂制造技术，以界面结合力强、力学性能各向同性而著称。这被认为是由界面附近的物质流动现象造成的，但实验证实仍然缺乏。在这里，我们试图通过形态和微观结构的研究来了解AFSD中形成的界面，其中非平面界面的形态是用X射线计算机层析技术在轨道尺度(厘米尺度)上表征的，而材料的变形历史是通过界面区域的微观结构图来探索的。X射线计算机层析成像显示了界面上独特的3D特征，具有显著的宏观材料混合。在平面外方向，沉积的材料插入进给杆区的初始基板表面下方，而基板表面在刀具突出影响区向上涌动。在前进侧形成了复杂的三维结构，如鳍片和锯齿，导致结构互锁；在后退侧，界面表现为光滑的斜面。显微组织图显示了沉积材料统一的热机械历史，形成了均匀的、几乎完全再结晶的组织。衬底表面形成了与位置有关的部分再结晶微结构；在远离沉积轨迹中心线的区域发现了更多的晶内取向梯度。通过这些观察，我们讨论了AFSD过程中界面物质流动和界面形态形成的机制。
Additive friction stir deposition (AFSD) is an emerging solid-state metal additive manufacturing technology renowned for strong interface adhesion and isotropic mechanical properties. This is postulated to result from the material flow phenomena near the interface, but experimental corroboration has remained absent. Here, we seek to understand the interface formed in AFSD via morphological and microstructural investigation, wherein the non-planar interfacial morphology is characterized on the track-scale (centimeter scale) using X-ray computed tomography and the material deformation history is explored by microstructure mapping at the interfacial regions. X-ray computed tomography reveals unique 3D features at the interface with significant macroscopic material mixing. In the out-of-plane direction, the deposited material inserts below the initial substrate surface in the feed-rod zone, while the substrate surface surges upwards in the tool protrusion-affected zone. Complex 3D structures like fins and serrations form on the advancing side, leading to structural interlocking; on the retreating side, the interface manifests as a smooth sloped surface. Microstructure mapping reveals a uniform thermomechanical history for the deposited material, which develops a homogeneous, almost fully recrystallized microstructure. The substrate surface develops partially recrystallized microstructures that are location-dependent; more intra-granular orientation gradients are found in the regions further away from the centerline of the deposition track. From these observations, we discuss the mechanisms for interfacial material flow and interface morphology formation during AFSD.