Control of morphological and microstructural anisotropy through powder-based metal additive manufacturing

The utilization of "anisotropy" is becoming an important direction for realizing highly-functionalized products overcoming the current functional limits for materials with isotropic properties. In particular for the use in aerospace and biomedical industries, some products are exposed to anisotropic stress fields. Therefore, the products should be anisotropic along the functional axis. Additive manufacturing (AM) technology was originally specialized to fabricate the complicated structures in an arbitrary way. However, when it comes to metal AM, the control of material anisotropy has received an increasing attention in recent years. In this review article, the latest findings regarding the control of mechanical anisotropy through the modifications of macroscopic porous structure, microstructure, and crystallographic orientation by powder-based metal AM technologies are introduced. The powder-based metal AM is able to control a wide range of anisotropy from crystallographic texture to pore structure, however, their simultaneous control is yet challenging. Attainment of this heightens the value of metal AM technology and enhances the AM products' functions.