scholarly journals As-Built and Post-treated Microstructures of an Electron Beam Melting (EBM) Produced Nickel-Based Superalloy

2020 ◽  
Vol 51 (12) ◽  
pp. 6546-6559
Author(s):  
Sneha Goel ◽  
Hitesh Mehtani ◽  
Shu-Wei Yao ◽  
Indradev Samajdar ◽  
Uta Klement ◽  
...  
Keyword(s):  
Electron Beam ◽  
Hot Isostatic Pressing ◽  
Secondary Phase ◽  
Nickel Based Superalloy ◽  
Outer Periphery ◽  
Columnar Grains ◽  
Order Of Magnitude ◽  
Equiaxed Grains ◽  
Contour Region ◽  
Carbide Content

AbstractThe microstructures of an electron beam melted (EBM) nickel-based superalloy (Alloy 718) were comprehensively investigated in as-built and post-treated conditions, with particular focus individually on the contour (outer periphery) and hatch (core) regions of the build. The hatch region exhibited columnar grains with strong 〈001〉 texture in the build direction, while the contour region had a mix of columnar and equiaxed grains, with no preferred crystallographic texture. Both regions exhibited nearly identical hardness and carbide content. However, the contour region showed a higher number density of fine carbides compared to the hatch. The as-built material was subjected to two distinct post-treatments: (1) hot isostatic pressing (HIP) and (2) HIP plus heat treatment (HIP + HT), with the latter carried out as a single cycle inside the HIP vessel. Both post-treatments resulted in nearly an order of magnitude decrease in defect content in hatch and contour regions. HIP + HT led to grain coarsening in the contour, but did not alter the microstructure in the hatch region. Different factors that may be responsible for grain growth, such as grain size, grain orientation, grain boundary curvature and secondary phase particles, are discussed. The differences in carbide sizes in the hatch and contour regions appeared to decrease after post-treatment. After HIP + HT, similar higher hardness was observed in both the hatch and contour regions compared to the as-built material.

A controller for safe, convenient operation of LaB6 emitters on electron-beam instruments

1983 ◽  
Vol 41 ◽  
pp. 408-409
Author(s):  
W. J. Abramson ◽  
H. W. Estry ◽  
L. F. Allard
Keyword(s):  
Electron Beam ◽  
Control System ◽  
Thermal Shock ◽  
Appropriate Care ◽  
Electron Guns ◽  
Tungsten Filaments ◽  
Order Of Magnitude ◽  
Main Components

LaB6 emitters are becoming increasingly popular as direct replacements for tungsten filaments in the electron guns of modern electron-beam instruments. These emitters offer order of magnitude increases in beam brightness, and, with appropriate care in operation, a corresponding increase in source lifetime. They are, however, an order of magnitude more expensive, and may be easily damaged (by improper vacuum conditions and thermal shock) during saturation/desaturation operations. These operations typically require several minutes of an operator's attention, which becomes tedious and subject to error, particularly since the emitter must be cooled during sample exchanges to minimize damage from random vacuum excursions. We have designed a control system for LaBg emitters which relieves the operator of the necessity for manually controlling the emitter power, minimizes the danger of accidental improper operation, and makes the use of these emitters routine on multi-user instruments.Figure 1 is a block schematic of the main components of the control system, and Figure 2 shows the control box.

A Study of Electron Beam Irradiation Influence on Device Contact Junction Characteristics of Advanced DRAM Using Atomic Force Probing

2013 ◽  
Author(s):  
Wei-Chih Wang ◽  
Jian-Shing Luo
Keyword(s):  
Electron Beam ◽  
Electron Beam Irradiation ◽  
Forward Bias ◽  
Irradiation Damage ◽  
Beam Irradiation ◽  
Excess Current ◽  
Atomic Force ◽  
Order Of Magnitude ◽  
Voltage Contrast ◽  
Acceleration Voltage

Abstract In this paper, we revealed p+/n-well and n+/p-well junction characteristic changes caused by electron beam (EB) irradiation. Most importantly, we found a device contact side junction characteristic is relatively sensitive to EB irradiation than its whole device characteristic; an order of magnitude excess current appears at low forward bias region after 1kV EB acceleration voltage irradiation (Vacc). Furthermore, these changes were well interpreted by our Monte Carlo simulation results, the Shockley-Read Hall (SRH) model and the Generation-Recombination (G-R) center trap theory. In addition, four essential examining items were suggested and proposed for EB irradiation damage origins investigation and evaluation. Finally, by taking advantage of the excess current phenomenon, a scanning electron microscope (SEM) passive voltage contrast (PVC) fault localization application at n-FET region was also demonstrated.

scholarly journals Can Appropriate Thermal Post-Treatment Make Defect Content in as-Built Electron Beam Additively Manufactured Alloy 718 Irrelevant?

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 536 ◽  
Author(s):  
Sneha Goel ◽  
Kévin Bourreau ◽  
Jonas Olsson ◽  
Uta Klement ◽  
Shrikant Joshi
Keyword(s):  
Electron Beam ◽  
Process Optimization ◽  
Electron Beam Melting ◽  
Phase Distribution ◽  
Hot Isostatic Pressing ◽  
Alloy 718 ◽  
Proof Of Concept ◽  
Defect Content ◽  
Enhancing Production ◽  
Hardness Values

Electron beam melting (EBM) is gaining rapid popularity for production of complex customized parts. For strategic applications involving materials like superalloys (e.g., Alloy 718), post-treatments including hot isostatic pressing (HIPing) to eliminate defects, and solutionizing and aging to achieve the desired phase constitution are often practiced. The present study specifically explores the ability of the combination of the above post-treatments to render the as-built defect content in EBM Alloy 718 irrelevant. Results show that HIPing can reduce defect content from as high as 17% in as-built samples (intentionally generated employing increased processing speeds in this illustrative proof-of-concept study) to <0.3%, with the small amount of remnant defects being mainly associated with oxide inclusions. The subsequent solution and aging treatments are also found to yield virtually identical phase distribution and hardness values in samples with vastly varying as-built defect contents. This can have considerable implications in contributing to minimizing elaborate process optimization efforts as well as slightly enhancing production speeds to promote industrialization of EBM for applications that demand the above post-treatments.

The electron beam freeform fabrication of NiTi shape memory alloys. Part I: Microstructure and physical–chemical behavior

2020 ◽  
pp. 146442072097505
Author(s):  
RPM Guimarães ◽  
F Pixner ◽  
G Trimmel ◽  
J Hobisch ◽  
T Rath ◽  
...  
Keyword(s):  
Electron Beam ◽  
Additive Manufacturing ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Nickel Titanium ◽  
Freeform Fabrication ◽  
Austenitic Transformation ◽  
Columnar Grains ◽  
One Step ◽  
Niti Shape Memory Alloys

Nickel–titanium alloys are the most widely used shape memory alloys due to their outstanding shape memory effect and superelasticity. Additive manufacturing has recently emerged in the fabrication of shape memory alloy but despite substantial advances in powder-based techniques, less attention has been focused on wire-based additive manufacturing. This work reports on the preliminary results for the process-related microstructural and phase transformation changes of Ni-rich nickel–titanium alloy additively manufactured by wire-based electron beam freeform fabrication. To study the feasibility of the process, a simple 10-layer stack structure was successfully built and characterized, exhibiting columnar grains and achieving one-step reversible martensitic–austenitic transformation, thus showing the potential of this additive manufacturing technique for processing shape memory alloys.

Formation of Grain Structures of Thermal Sprayed Nickel Coatings and the Coating Properties

2005 ◽  
Vol 502 ◽  
pp. 517-0
Author(s):  
Kenji Murakami
Keyword(s):  
Steel Substrate ◽  
Nickel Coatings ◽  
Grain Structures ◽  
Heat Treated ◽  
Columnar Grains ◽  
Different Temperatures ◽  
Plasma Sprayed ◽  
Equiaxed Grains ◽  
Sprayed Coatings ◽  
Lamellar Interfaces

Pure nickel powder was low pressure plasma sprayed onto a steel substrate held at different temperatures during spraying. The as-sprayed coatings consist of columnar grains whose axes are nearly perpendicular to the lamellae composing the coatings. As the coating temperature becomes higher, the length of the columnar grains increases and is longer than the thickness of the lamellae, indicating the growth of the grains across the lamellar interfaces during spraying. On the other hand, the coatings that were heat treated after spraying consist of coarse equiaxed grains. The coatings that experienced high temperatures during spraying or the heat treated coatings have large porosity and contain large globular pores. The hardness, apparent density and the tensile strength of the coating itself were the highest for the coating prepared at a low temperature and became low on heat treatment. The thermal conductivity in the direction perpendicular to the coating was the largest for the coating that consisted of long columnar grains.

Effect of Cu-Excess on the Microstructure and Microwave Dielectric Properties of CaCu3Ti4O12 Ceramics

2015 ◽  
Vol 1087 ◽  
pp. 50-54 ◽  
Author(s):  
Mohamad Johari Abu ◽  
Julie Juliewatty Mohamed ◽  
Mohd Fadzil Ain ◽  
Zainal Arifin Ahmad
Keyword(s):  
Dielectric Constant ◽  
Microwave Dielectric Properties ◽  
Secondary Phase ◽  
Solid State Reaction Method ◽  
Lattice Parameter ◽  
Tangent Loss ◽  
Conventional Solid State Reaction ◽  
Microwave Dielectric ◽  
Order Of Magnitude ◽  
Grain Growth Behavior

CaCu(3+x)Ti4O12 (CCTO) ceramics with different Cu-excess (x = 0 – 0.6) were prepared by conventional solid-state reaction method. Characterization of the prepared ceramics with XRD and FESEM showed that lattice parameter and grain size are slightly increased, indicating Cu-excess to have the big impact on the both phase structure and microstructure. The XRD profiles indicated that the secondary phase (CuO or Cu2O) existed at edge/corner of CCTO grain, which promoted inhibited grain growth behavior. The CCTO ceramics exhibited two trends of dielectric constant related to frequency, which showed a flatter curve about ~50 in 1 – 25 GHz regions, and it’s dropped rapidly to ~35 in 25 – 50 GHz region. With Cu-excess, the dielectric constant of the ceramics was increased for an average of a quarter-order of magnitude, while the tangent loss also increased up to triple times than x = 0, for the same frequency range. Despite enormous increase of dielectric constant related to varying Cu-excess, the tangent loss also increased.

scholarly journals Corrosion Resistance of 2060 Aluminum–Lithium Alloy LBW Welds Filled with Al-5.6Cu Wire

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1988 ◽  
Author(s):  
Fencheng Liu ◽  
Xiaoguang Wang ◽  
Baosheng Zhou ◽  
Chunping Huang ◽  
Feiyue Lyu
Keyword(s):  
Intergranular Corrosion ◽  
Laser Beam Welding ◽  
Electrochemical Corrosion ◽  
Corrosion Current ◽  
Equiaxed Dendrite ◽  
Al2cu Phase ◽  
Immersion Corrosion ◽  
Aluminum Lithium ◽  
Columnar Grains ◽  
Equiaxed Grains

Alloy sheets of type 2060 aluminum–lithium were welded by laser beam welding (LBW) filled with ER2319 Al-5.6Cu wire. Microstructural observations showed the uneven distribution of columnar grains, equiaxed grains and equiaxed dendrite grains in the weld. The θ′(Al2Cu) phase and other phases precipitated in the weld. The θ′(Al2Cu) phase centrally distributed at the grain boundaries. During the immersion corrosion, the pitting corrosion first occurred and then gradually expanded and transformed to intergranular corrosion and exfoliation corrosion. The electrochemical corrosion test showed a higher corrosion tendency of the base metal and heat-affected zone for the lower corrosion potential, but the corrosion current density of the weld was relatively larger. The segregation of Cu, Mg and other elements at the grain boundary aggravated the occurrence of intergranular corrosion.

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