How to control the crystallization of metallic glasses during laser powder bed fusion? Towards part-specific 3D printing of in situ composites

This paper describes a strategy for creating highly oriented crystalline-amorphous composites using the laser powder bed fusion (LPBF) process. The strategy involves using a novel two-stage melting approach and ultrahigh-pressure hot isostatic pressing (HIP) on well-known AMZ4 (Zr59.3Cu28.8Al10.4Nb1.5) and equiatomic CuZr amorphous alloys.The experiments demonstrate that by the fine-tuning laser parameters, allowed to obtain parts with purely amorphous material and to create geometry-specific microstructural design composites based on laminate amorphous-crystalline structure. This approach also provides novel opportunities for nonequilibrium phase distribution design by controlling local crystallization in the heat-affected zone (HAZ) and avoiding heat accumulation. Additionally, the porous amorphous material can be densified without crystallization using HIP at a temperature near the supercooled liquid region.The distribution of the crystalline phase created during LPBF and crystallization on pre-induced nuclei during HIP was proven to be a critical factor for composite properties. Wear and bending tests reveal the influence of crystalline-amorphous layers orientation on mechanical properties. The functional demonstrators were manufactured to show the possibilities in the design for additive manufacturing (DfAM) with a microstructuredesigned composites.