Additive manufacturing of metals and alloys to achieve heterogeneous microstructures for exceptional mechanical properties

Metals and alloys with heterogeneous microstructures exhibit an enhanced combination of strength and ductility, compared to their counterparts with homogeneous microstructures. Additive manufacturing (AM) techniques offers a new opportunity to induce heterogeneous microstructures in a wide range of metals and alloys, thereby optimizing their mechanical properties. In this review article, we focus on four types of heterogeneous microstructures induced by AM: lamellar, gradient, laminated, and harmonic ones. We will introduce (i) the tailored generation of heterogeneous microstructures, (ii) the effects of characteristic solidification conditions, and (iii) the intricate phase transformation in laser-based AM process. Furthermore, we discuss the features, advantages, and potential applications of the metals and alloys with heterogeneous microstructures made by AM. To conclude, we discuss current challenges and future opportunities in this field. Additive manufacturing offers the opportunity of creating heterogeneous microstructures that enhance the strength-ductility synergy in metals and alloys. We review generation methods, solidification effects, heat treatment, and potential applications.