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.
该论文的主要作者是Sibley机械和航空航天工程学院的助理教授Atieh Moridi。
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。
However, additive manufacturing is not without its own challenges. Foremost among them: Metallic materials need to be heated at high temperatures that exceed their melting point, which can cause residual stress buildup, distortion and unwanted phase transformations.
To eliminate these issues, Moridi and collaborators developed a method using a nozzle of compressed gas to fire titanium alloy particles at a substrate.
“It’s like painting, but things build up a lot more in 3D,” Moridi said.
颗粒的直径在45至106微米之间（微米为一百万米），以每秒600米的速度行驶，比声速快。为了透视这一点，另一个主流添加剂过程，直接的能量沉积，以每秒10米的速度以10米的速度通过喷嘴提供粉末，使Moridi的方法速度快60倍。
The particles aren’t just hurled as quickly as possible. The researchers had to carefully calibrate titanium alloy’s ideal speed. Typically in cold spray printing, a particle would accelerate in the sweet spot between its critical velocity – the speed at which it can form a dense solid – and its erosion velocity, when it crumbles too much to bond to anything.
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.”
尽管该过程在技术上称为冷喷雾剂，但确实涉及一些热处理。一旦颗粒碰撞并粘合在一起，研究人员就会加热金属，使组件将相互扩散并像均匀的材料一样沉降。
“We only focused on titanium alloys and biomedical applications, but the applicability of this process could be beyond that,” Moridi said. “Essentially, any metallic material that can endure plastic deformation could benefit from this process. And it opens up a lot of opportunities for larger-scale industrial applications, like construction, transportation and energy.”
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。
这项研究得到了MIT-Itity全球种子基金和Polimi International奖学金的部分支持。
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