ABSTRACT
Differing from metal alloys produced by conventional techniques, metallic products prepared by additive manufacturing experience distinct solidification thermal histories and solid-state phase transformation processes, resulting in unique microstructures and superior performance. This review starts with commonly used additive manufacturing techniques in steel-based alloy and then some typical microstructures produced by metal additive manufacturing technologies with different components and processes are summarized, including porosity, dislocation cells, dendrite structures, residual stress, element segregation, etc. The characteristic microstructures may exert a significant influence on the properties of additively manufactured products, and thus it is important to tune the components and additive manufacturing process parameters to achieve the desired microstructures. Finally, the future development and prospects of additive manufacturing technology in steel are discussed.
ABSTRACT
We designed and generated gradient photonic moiré lattice fields comprising three varying periodic moiré wavefields. Because of the common twisted angles between periodic triangular and hexagonal moiré wavefields, gradient patterns can be easily obtained through coherent superposition of hexagonal-triangular-hexagonal photonic moiré lattice fields. In addition, two specific twisted angles of Δα|C=3 and Δα|C=5 are proposed, which not only guarantee the periodicity of moiré fields but also provide an additional degree of freedom to control the structural arrangement of the gradient photonic moiré lattice fields. Further study reveals the non-diffracting character of the gradient photonic moiré lattice field generated using the holographic method. This study proposes an easy way to generate and control the structures of gradient moiré lattice fields that can be used to fabricate photonic lattices in optical storage media for light modulation.