Spatter is an inherent, unpreventable, and undesired phenomenon in laser powder bed fusion (L-PBF) additive manufacturing. Spatter behavior has an intrinsic correlation with the forming quality in L-PBF because it leads to metallurgical defects and the degradation of mechanical properties. This impact becomes more severe in the fabrication of large-sized parts during the multi-laser L-PBF process. Therefore, investigations of spatter generation and countermeasures have become more urgent. Although much research has provided insights into the melt pool, microstructure, and mechanical property, reviews of spatter in L-PBF are still limited. This work reviews the literature on the in situ detection, generation, effects, and countermeasures of spatter in L-PBF. It is expected to pave the way towards a novel generation of highly efficient and intelligent L-PBF systems.

A new single phase Aurivillius structured ceramic shows room temperature multiferroic behavior.

Multiferroics that simultaneously exhibit ferroelectricity and ferromagnetism have recently attracted great attention due to their potential application in next generation electronic devices. However, only a few single-phase multiferroic materials exhibit ferroelectric and ferromagnetic orders at room temperature. Recently, some bismuth layer-structured Aurivillius compounds were reported as multiferroics at room temperature, but the origin of their magnetic property is still under debate because the net magnetization may originate from the presence of secondary phases that are not easily detected by laboratory XRD diffractometers. Here, textured Aurivillius phase Bi 5.25 La 0.75 FeCoTi 3 O 18 ceramics were prepared by Spark Plasma Sintering. The ferromagnetic character of the ceramics was indicated by the magnetic field-induced reversible intensity changes of a certain set of crystalline planes belonging to the Aurivillius phase, as measured by in situ neutron diffraction under the applied magnetic field. The first principles calculations indicate that the ferromagnetism originates from double exchange interactions Fe 3þ -O-Fe 3þ , Co 3þ -O-Co 3þ , and Fe 3þ -O-Co 3þ in the ferro-toroidal main phase. The magnetic-controlled ferroelectric domain switching was observed by piezoelectric force microscopy at room temperature. The prepared Aurivillius phase ceramics, with Co/Fe contributing to magnetization and polarization at the same time, can be considered an intrinsic room-temperature multiferroic.

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Ag and Cu have different advantages and are widely used in key fields due to their typical highly electrical and thermal conductive (HETC) properties. Laser powder bed fusion (LPBF), an innovative technology for manufacturing metallic multi-material components with high accuracy, has expanded the application of Ag–Cu in emerging high-tech fields. In this study, the multi-material sandwich structures of Ag7.5Cu/Cu10Sn/Ag7.5Cu were printed using LPBF, and the formation mechanism, interface characteristics, and molten pool behavior of the Ag7.5Cu/Cu10Sn (A/C) and Cu10Sn/Ag7.5Cu (C/A) interfaces were studied to reveal the influence of different building strategies. At the A/C interface, pre-printed Ag7.5Cu promoted Marangoni turbulence at a relatively low energy density (EA/C = 125 J/mm3). Due to the recoil pressure, the molten pool at the A/C interface transformed from a stable keyhole mode to an unstable keyhole mode. These phenomena promoted the extensive migration of elements, forming a wider diffusion zone and reduced thermal cracking. At the C/A interface, the molten pool was rationed from the conduction mode with more pores to the transition mode with fewer defects due to the high energy density (EC/A = 187.5 J/mm3). This work offers a theoretical reference for the fabrication of HETC multi-material structures via LPBF under similar conditions.

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