Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA.
School of Mechanical and Materials Engineering, Washington State University, Pullman, WA, USA.
Nat Commun. 2023 May 9;14(1):2667. doi: 10.1038/s41467-023-38142-z.
Sintering theory predicts no long-range mass transport or distortion for uniformly heated particles during particle coalescence. However, in sintering-based manufacturing processes, permanent part distortion is often observed. The driving forces and mechanisms leading to this phenomenon are not understood, and efforts to reduce distortion are largely limited to a trial-and-error approach. In this paper, we demonstrate that distortion during sintering results from mass-transport driven by nonhomogeneous temperature distribution. We then show that hitherto unknown mass transport mechanisms, working in the direction opposite to temperature gradient are the likely cause of distortion. The experimental setup, designed for this purpose, enables the quantification of distortion during sintering. Two possible mass transport mechanisms are defined, and the continuum model applicable to both is formulated. The model accurately predicts the transient and permanent distortion observed during experiments, including their size dependence. Methods to control distortion that can give rise to 4D printing are discussed.
烧结理论预测在颗粒团聚过程中，均匀加热的颗粒不会发生长程质量传输或变形。然而，在基于烧结的制造工艺中，通常会观察到永久的零件变形。导致这种现象的驱动力和机制尚不清楚，减少变形的努力在很大程度上仅限于反复试验的方法。在本文中，我们证明了烧结过程中的变形是由非均匀温度分布驱动的质量传输引起的。然后我们表明，到目前为止未知的质量传输机制，朝着与温度梯度相反的方向工作，是导致变形的可能原因。为此目的设计的实验装置能够量化烧结过程中的变形。定义了两种可能的质量传输机制，并制定了适用于两者的连续体模型。该模型准确预测了实验过程中观察到的瞬态和永久变形，包括它们的尺寸依赖性。讨论了可以实现 4D 打印的控制变形的方法。
