Figure 4 - uploaded by Manas Upadhyay
Content may be subject to copyright.
HAADF images and EDS line profiles for precipitates P1 1 and P9 1 along different paths. The points in the curves have been fitted using c-splines. The key for both HAADF images is presented below the HAADF image of P1 1 . HAADF images have been acquired using the TIA v4.2 (FEI https:// www. fei. com) software. Fiji v2.1.0/1.53c (https:// fiji. sc), gnuplot v5.4 (http:// www. gnupl ot. info) and Microsoft PowerPoint have been used to prepare this image.

HAADF images and EDS line profiles for precipitates P1 1 and P9 1 along different paths. The points in the curves have been fitted using c-splines. The key for both HAADF images is presented below the HAADF image of P1 1 . HAADF images have been acquired using the TIA v4.2 (FEI https:// www. fei. com) software. Fiji v2.1.0/1.53c (https:// fiji. sc), gnuplot v5.4 (http:// www. gnupl ot. info) and Microsoft PowerPoint have been used to prepare this image.

Source publication
Article
Full-text available
Precipitates in an austenitic stainless steel fabricated via any Additive Manufacturing (AM), or 3D printing, technique have been widely reported to be only Mn-Si-rich oxides. However, via Transmission Electron Microscopy (TEM) studies on a 316L stainless steel, we show that non-oxide precipitates (intermetallics, sulfides, phosphides and carbides)...

Context in source publication

Context 1
... (65.5%) are mixed. Figure 3 shows the HAADF images and EDS chemical maps for all non-oxide and mixed precipitates together with at most one oxide precipitate (if any) in L1-L3; Fig. S3 shows the HAADF images and EDS maps for nonoxide and mixed precipitates in L4 and L5. EDS line profile analysis (Methods) has been performed for each precipitate; Fig. 4 shows the EDS line profiles for two of the most complex mixed precipitates. Following this analysis, the chemical composition of all precipitates had been compared with the nominal composition of the 316LSS wrought alloy. Based on this comparison the elements in each oxide and non-oxide precipitate, and all the inclusions in each mixed ...

Similar publications

Conference Paper
Full-text available
AA7075 matrix bimetal composites reinforced with 304 stainless steel (SS) were manufactured by melt infiltration casting technique. A preform, made by assembling 304 SS shavings under 220 MPa pressure, was infiltrated by molten AA7075 alloy under vacuum atmosphere during this process. The preform was preheated for 10 min before infiltration to avoi...

Citations

... The influence of other oxide inclusions (summarized in Table 2) on the corrosion performance of LPBF-316L is not discussed in the literature. Besides LPBF, researchers [225] had reported nano-inclusions with different compositions, including sulphur-rich inclusion in 316L manufactured by laser metal deposition (LMD). However, the influence of these inclusions on the corrosion performance of the alloy is not reported in the literature. ...
Article
Full-text available
The applications of laser-powder bed fusion (LPBF), an emerging additive manufacturing (AM) technique, are rapidly growing in various industries. The superior and consistent mechanical and corrosion properties of LPBF-printed components are essential for engineering applications. The 316L stainless steel (SS) is an essential alloy with widespread applications from household items to nuclear and aerospace industries. Extensive research is conducted to understand and improve the mechanical properties of LPBF printed 316L SS. Studying the corrosion behavior of LPBF printed 316L has attracted only limited attention. Additionally, a discrepancy in the corrosion performance of LPBF printed 316L has been reported due to the complex microstructure and defects introduced during LPBF. Therefore, understanding the influence of processing parameters and feedstock on defects and microstructure becomes critical in understanding the processing-corrosion relationships and producing LPBF printed 316L components with reproducible properties. This review presents the influence of feedstock, processing parameters, and post-processing techniques on manufacturing defects, microstructure, and corrosion performance of LPBF printed 316L. Strategies and hypotheses to improve the corrosion resistance of LPBF printed 316L are also presented.
... Vacuum melted argon gas atomised stainless steel AISI 316L powder (35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49)(50) μm) supplied by Mimete S.r.l. and nanometre sized (30-100 nm) hexagonal WC powder supplied by US Research Nanomaterials Inc. were used in this study. The morphology of these powders is shown in Fig. 1. ...
... The precipitated hard Fe 2 Si phase plays a crucial role in determining the material response. However, while improving hardness and wear, corrosion, fatigue and fracture resistance of the specimens could be compromised by the brittle intermetallic Fe 2 Si precipitates [46][47][48]. An evident diffraction peak of SiC was observed in the specimens' spectrum and confirmed by the JCPDS card 89-1396. ...
Article
Functionally grading material composition in laser-powder bed fusion grants the potential for manufacturing complex components with tailored properties. The challenge in achieving this is that the current laser-powder bed fusion machine technology is designed to process only powdered feedstock materials. This study presents a multi-feedstock material printing methodology for laser-powder bed fusion. Utilising colloid nebulisation, tungsten carbide nanoparticles were successfully deposited onto powder beds of stainless steel 316L during the laser-powder bed fusion process. By this means, a controlled volume of tungsten carbide nanoparticles was uniformly dispersed onto powder beds under the inert processing chamber atmosphere. As a result, specimens printed with this methodology showed an increase in strength. Similarly, the colloid medium played an important role in the resulting microstructures. It led to the formation of consistent and stable meltpools and a strong crystallographic texture. Recommendations are given for the successful dispersion of higher volumes of nanoparticles. Additionally, insights into application prospects for material nebulisation in laser-powder bed fusion are presented and discussed.
... Until recently, precipitates occurring in as-built LMD 316LSS or SLM 316LSS were reported to be only Mn-Si-rich oxide precipitates [22,[24][25][26][27][28][29]. However, in a recent TEM study on five lamellae extracted from an LMD 316LSS thin-wall, Upadhyay et al. [30] reported the presence of a large volume fraction of non-oxide precipitates including sulfides, carbides, phosphides and intermetallics, along with Mn-Si-rich oxide precipitates. The non-oxide precipitates were found to be smaller in their average size in comparison to the oxide precipitates. ...
... The non-oxide precipitates were found to be smaller in their average size in comparison to the oxide precipitates. An investigation into the origin of these non-oxide precipitates [30], with the help of finite element and precipitation kinetics simulations, revealed that non-oxide precipitates can indeed occur in LMD 316LSS but not in SLM 316LSS. The simulation results also suggested that precipitates could form/disappear and evolve in the solid-state. ...
... The material and most of the experimental setup used in this work has been described in detail in Upadhyay et al. [30]. In the following, only the essential details are recalled for the sake of completeness and self-sufficiency of this paper. ...
Article
Full-text available
During additive manufacturing of alloys, just after local heat-matter interactions, a molten material undergoes rapid solidification. Then, for the rest of the building time, it is subjected to cooling/heating cycles in the solid-state i.e., solid-state thermal cycling. The thermo-mechanical forces generated during solid-state thermal cycling can trigger a plethora of micro-mechanisms that can bring about significant microstructural changes that determine the eventual mechanical properties of as-built parts. In this work, the aim is to gain insight on solid-state thermal cycling-driven evolution of submicron-sized precipitates in an austenitic stainless steel using transmission electron microscopy. To that end, thin-film lamellae are extracted from a pre-built sample and subjected to different in-situ solid-state thermal cycles inside a transmission electron microscope. The solid-state thermal cycles are designed to understand the role of temperature amplitude and rates, number and type of thermal cycles, and post-process annealing on precipitate evolution. High angle annular dark field imaging and energy dispersive X-ray spectroscopy before and after each thermal cycle provide a deep insight on the contribution of different thermal cycling factors on the evolution of precipitate composition, size and morphology. Common trends include diffusion of Mn and Si from Mn-Si-rich oxides into the surrounding matrix, formation of Cr rings around oxide precipitates and S redistribution in non-oxide precipitates. Similar Cr rings and S distributions were also found in precipitates in as-built samples studied in (Upadhyay et al., Sci. Rep. 11 (2021) 10393), which strongly supports the representativeness of these results with respect to what occurs during additive manufacturing.
... The addition of manganese also proves suitable only to a limited extent. When active gas is used as a shielding gas, the alloying elements of silicon and manganese have an affinity to react with oxygen, act as getters and form detrimental silicon and manganese oxides [63][64][65][66][67][68]. Non-metallic inclusions and oxides form especially on a large scale in AM-manufactured components and have a detrimental effect on the mechanical properties of these components [69]. ...
Article
Full-text available
In the present study, the application and tailoring of the alloy composition of chromium martensitic hot-work steels using metal cored wires (MCW) for wire arc additive manufacturing (WAAM) in a modified short-circuit metal transfer process is demonstrated. The nickel content was varied and the alloys were fabricated as tubular-cored wires with various powder fillings. By recording the material transfer at high speed during processing, evidence was gathered indicating the suitability of the fabricated cored wires for WAAM. Optimized process parameters were identified by taking a Design of Experiment (DoE) approach and additive manufacturing (AM) structures were fabricated from the chromium martensitic hot-work tool steel alloys. The microstructure and mechanical properties of the parts were subsequently characterized. The phase fraction of the polygonally shaped delta ferrite could be reduced and microstructural refinement could be achieved by adding nickel to the investigated hot-work tool steel. In addition to molybdenum-enriched precipitates that covered the grain boundaries, randomly scattered non-metallic inclusions and oxides were observed. Modifying the microstructure by adding nickel also affects the mechanical properties of the product: an increase in hardness, impact toughness and yield strength as the nickel content increased in the AM structures fabricated by WAAM was observed.
Article
Full-text available
New developments at synchrotron beamlines and the ongoing upgrades of synchrotron facilities allow the possibility to study complex structures with a much better spatial and temporal resolution than ever before. However, the downside is that the data collected are also significantly larger (more than several terabytes) than ever before, and post-processing and analyzing these data is very challenging to perform manually. This issue can be solved by employing automated methods such as machine learning, which show significantly improved performance in data processing and image segmentation than manual methods. In this work, a 3D U-net deep convolutional neural network (DCNN) model with four layers and base-8 characteristic features has been developed to segment precipitates and porosities in synchrotron transmission X-ray micrograms. Transmission X-ray microscopy experiments were conducted on micropillars prepared from additively manufactured 316L steel to evaluate precipitate information. After training the 3D U-net DCNN model, it was used on unseen data and the prediction was compared with manual segmentation. A good agreement was found between both segmentations. An ablation study was performed and revealed that the proposed model showed better statistics than other models with lower numbers of layers and/or characteristic features. The proposed model is able to segment several hundreds of gigabytes of data in a few minutes and could be applied to other materials and tomography techniques. The code and the fitted weights are made available with this paper for any interested researcher to use for their needs (https://github.com/manasvupadhyay/erc-gamma-3D-DCNN).
Article
Additive manufacturing exhibits great potentials for the fabrication of novel materials due to its unique non-equilibrium solidification and heating process. In this work, a novel nano-oxides dispersion strengthened Co28Cr9W1.5Si (wt.%) alloy, fabricated by laser powder bed fusion (LPBF), was comprehensively investigated. During the layer-by-layer featured process, in-situ formation of Si rich, amorphous, nano-oxide inclusions was observed, whose formation is ascribed to the high affinity of Si to oxygen. Meanwhile, distinctive body-centered cubic (BCC) Co5Cr3Si2 nano-precipitates with an 8-fold symmetry were also confirmed to appear. The precipitates, rarely reported in previous studied Co-Cr alloys, were found to tightly bond with the in-situ oxidization. Furthermore, the morphologies, the size distributions as well as the microstructure of the interface between the matrix and the inclusions were investigated in detail and their influence on the tensile deformation was also clarified. The existence of transition boundaries between these inclusions and the matrix strongly blocked the movement of dislocations, thereby increasing the strength of the alloy. It was understood that when the plastic deformation proceeds, the fracture occurs in the vicinity of the oxide inclusions where dislocations accumulate. A quantitative analysis of the strengthening mechanism was also established, in which an additional important contribution to strength (∼ 169 MPa) caused by the effects of in-situ formed oxide inclusions was calculated.