Forget glue, screws, heat or other traditional bonding methods. A Cornell-led collaboration has developed a 3D printing technique that creates cellular metallic materials by smashing together powder particles at supersonic speed.
这种称为“冷喷雾”的技术形式导致机械强大的多孔结构比传统制造工艺制成的类似材料强40％。结构的小尺寸和孔隙率使它们特别适合构建生物医学组件，例如替换关节。万博平台盘口
The team’s paper, “Solid-State Additive Manufacturing of Porous Ti-6Al-4V by Supersonic Impact,” published Nov. 9 in Applied Materials Today.
The paper’s lead author is Atieh Moridi, assistant professor in the Sibley School of Mechanical and Aerospace Engineering.
Moridi说：“我们专注于制造细胞结构，这些细胞结构在热管理，能量吸收和生物医学中有很多应用。”“与其仅使用热量作为键合的输入或驱动力，我们现在使用塑性变形将这些粉末颗粒粘合在一起。”
Moridi的研究小组专门通过增材制造工艺创建高性能金属材料。添加剂制造不是用大块的材料雕刻出几何形状，而是按一层构建产品层，而是一种自下而上的方法，可以使制造商在其创造物品中更大的灵活性。
但是，增材制造并非没有自己的挑战。其中最重要的是：金属材料需要在高温超过其熔点的高温下加热，这可能会导致残留的应力积累，失真和不需要的相变。
为了消除这些问题，Moridi和合作者使用压缩气体喷嘴开发了一种方法，以在底物处发射钛合金颗粒。
“It’s like painting, but things build up a lot more in 3D,” Moridi said.
The particles were between 45 and 106 microns in diameter (a micron is one-millionth of a meter) and traveled at roughly 600 meters per second, faster than the speed of sound. To put that into perspective, another mainstream additive process, direct energy deposition, delivers powders through a nozzle at a velocity on the order of 10 meters per second, making Moridi’s method sixty times faster.
颗粒不仅会尽快投掷。研究人员必须仔细校准钛合金的理想速度。通常，在冷喷雾印刷中，粒子在其临界速度之间的最佳位置会加速，即它可以形成浓密的固体的速度 - 及其侵蚀速度，当它崩溃过多以至于无法与任何东西结合。
Instead, Moridi’s team used computational fluid dynamics to determine a speed just under the titanium alloy particle’s critical velocity. When launched at this slightly slower rate, the particles created a more porous structure, which is ideal for biomedical applications, such as artificial joints for the knee or hip, and cranial/facial implants.
“If we make implants with these kind of porous structures, and we insert them in the body, the bone can grow inside these pores and make a biological fixation,” Moridi said. “This helps reduce the likelihood of the implant loosening. And this is a big deal. There are lots of revision surgeries that patients have to go through to remove the implant just because it’s loose and it causes a lot of pain.”
While the process is technically termed cold spray, it did involve some heat treatment. Once the particles collided and bonded together, the researchers heated the metal so the components would diffuse into each other and settle like a homogeneous material.
莫里迪说：“我们只专注于钛合金和生物医学应用，但是这一过程的适用性可能超出了这一点。”“从本质上讲，任何可以忍受塑性变形的金属材料都可以从此过程中受益。它为大规模的工业应用（例如建筑，运输和能源）打开了很多机会。”
合着者包括博士生Akane Wakai和麻省理工学院，米兰理工大学，伍斯特理工学院，伦敦布鲁内尔大学和赫尔米特·施密特大学的研究人员。
The research was supported, in part, by the MIT-Italy global seed fund and Polimi International Fellowship.
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