Crystallographic Texture and Substructural Phenomena in 316 Stainless Steel Printed by Selective Laser Melting

Abstract

There is a fast-growing interest in the use of selective laser melting (SLM) for metal/alloy additive manufacturing. Our current knowledge of SLM-printed 316 stainless steel (SS316) is limited and sometimes appears sporadic, presumably due to the complex interdependent effects of a large number of process variables of the SLM processing. This is reflected in the discrepant findings in the crystallographic textures and microstructures in this investigation compared to those reported in the literature, which also vary among themselves. The as-printed material is macroscopically asymmetric in terms of both structure and crystallographic texture. The <101> and <111> crystallographic directions align parallel with the SLM scanning direction (SD) and build direction (BD), respectively. Likewise, some characteristic low-angle boundary features have been reported to be crystallographic, while this investigation unequivocally proves them to be non-crystallographic, since they always maintain an identical alignment with the SLM laser scanning direction, irrespective of the matrix material’s crystal orientation. There are also 500 ± 200 nm columnar or cellular features, depending on the cross-section, which are generally found all over the sample. These columnar or cellular features are formed with walls made of dense packing of dislocations entangled with Mn-, Si- and O-enriched amorphous inclusions. They remain stable after ASM solution treatments at a temperature of 1050 °C, and therefore, are capable of hindering boundary migration events of recrystallization and grain growth. Thus, the nanoscale structures can be retained at high temperatures. Large 2–4 μm inclusions form during the solution treatment, within which the chemical and phase distribution are heterogeneous.

Design Guidelines and Performance Analysis of a Wideband Coaxial Horn Antenna Fabricated via Additive Manufacturing

“…The disparities observed between the measurement and simulation results can be attributed to variations in the fabrication process, such as the different roughness values on the surfaces according to the building fabrication direction or crystallographic textures, i.e., roughness between 1-17 µm have been reported for the 316L processed by L-PBF [27]. Also, crystallographic textures, that are normally generated during additive manufactured metals [28], can affect the acoustic wave speeds [29]. The roughness was measured using a confocal microscope, resulting in an average roughness of R a = 3.27 µm with a standard deviation of 0.21 µm.…”

“…It offers the advantage of providing omnidirectional high gain with a wideband behavior with a steady-frequency vertical radiation pattern. The simulations results in [10] reveal that the geometric optics (GO)-shaped reflector shows a frequency bandwidth larger than 45% (25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40) for |S 11 | ≤ −20 dB with a maximum directivity of approximately 14 dBi. The gain of these antennas is directly linked to the electrical size of the antenna aperture.…”

Inclusions and Segregations in the Selective Laser-Melted Alloys: A Review

“…Some important defects in the SLM-manufactured alloys. (a) Gas pores [32], (b) Cr [33], (c) Roughness [34], (d) LOF [35], (e) Keyhole [32], (f) Balling [32], (g) Melt pool [36], (h) Seg gation [37], (i) Inclusion [38].…”

“…These values are higher than those of 316L steel that was traditionally cast. 31 [32], (b) Crack [33], (c) Roughness [34], (d) LOF [35], (e) Keyhole [32], (f) Balling [32], (g) Melt pool [36], (h) Segregation [37], (i) Inclusion [38].…”

In Situ Observations of the Strain Competition Phenomenon in Aluminum Alloy Resistance Spot Welding Joints during Lap Shear Testing

“…The mechanics of large-scale heterogeneous materials remain a significant challenge in the field of science and engineering materials [1][2][3]. Particularly, for a fusion-welded joint, the microstructure distribution is uneven, resulting in its heterogeneous mechanical properties.…”